epa-402r-10003 federal guidance report no. 14 …€¦ · 4 this document is federal guidance...
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EPA-402R-10003
FEDERAL GUIDANCE REPORT NO. 14
Radiation Protection Guidance for Diagnostic and Interventional X-Ray Procedures
Interagency Working Group on Medical Radiation
U.S. Environmental Protection Agency
Washington, D.C. 20460
2012
1
I
PREFACE 2
3 This document is Federal Guidance Report No. 14 (FGR 14), “Radiation Protection Guidance for 4
Diagnostic and Interventional X-ray Procedures.” It replaces Federal Guidance Report No. 9 5
(FGR 9) (EPA 1976), “Radiation Protection Guidance for Diagnostic X-rays,” which was 6
released in October 1976. Federal Guidance reports were initiated under the Federal Radiation 7
Council (FRC), which was formed in 1959, through Executive Order 10831. A decade later its 8
functions were transferred to the Administrator of the newly formed Environmental Protection 9
Agency (EPA) as part of Reorganization Plan No. 3 of 1970 (Dunn et al. 2012). Under these 10
authorities it is the responsibility of the Administrator to “advise the President with respect to 11
radiation matters, directly or indirectly affecting health, including guidance for all Federal 12
agencies in the formulation of radiation standards and in the establishment and execution of 13
programs of cooperation with States.” (EPA 2012) 14
15
FGR 9 provided constructive guidance on the use of diagnostic film radiography, for which there 16
was an incentive to deliver appropriate radiation doses and avoid retakes resulting from under- or 17
over-exposing the film. This report, Federal Guidance Report No. 14, focuses on the transition 18
to digital imaging, extends the scope (to include computed tomography (CT), interventional 19
fluoroscopy, bone densitometry, and veterinary practice), and updates sections on radiology and 20
dentistry that were covered in FGR 9. It also addresses adequate imaging through justification of 21
the procedure and optimization, and features an expanded section on occupational exposure. 22
23
FGR 9 was developed out of a growing concern in the 1970s among medical practitioners, 24
medical physicists, and other scientists that medical uses of ionizing radiation represented a 25
significant and growing source of exposure for the U.S. population. Human exposures to 26
medical radiation were neither controlled by law nor covered by consensus guidance. In 1972, 27
the Federal Radiation Council released a report concluding that “...medical diagnostic radiology 28
accounts for at least 90% of the total man-made radiation dose to which the U.S. population is 29
exposed.” In response, the Environmental Protection Agency (EPA) and the Department of 30
Health, Education, and Welfare (predecessor of the Department of Health and Human Services 31
(DHHS)) developed and issued FGR 9, which was approved by President Carter (Carter 1978) 32
and published in the Federal Register on February 1, 1978. 33
34
According to EPA (Carter 1980), FGR 9 was the first Federal Guidance Report to provide a 35
framework for developing radiation protection programs for diagnostic uses of x-rays in 36
medicine. It introduced into Federal guidance the concepts of: 37
• Conducting medical x-ray studies only to obtain diagnostic information, 38
• Limiting routine or elective screening examinations to those with demonstrated benefit 39
over risk, 40
• Considering possible fetal exposures during examinations of pregnant or potentially 41
pregnant patients, 42
• Ensuring diagnostic equipment operators meet or exceed the standards of credentialing 43
organizations, and 44
• Specifying that standard x-ray examinations should satisfy maximum numerical exposure 45
criteria. 46
47
II
Much of FGR 9 has stood the test of time, but other parts have become obsolete. In particular, 48
the advent of digital x-ray image acquisition has eliminated film blackening as a built-in 49
deterrent to over-exposing patients. 50
51
Digital imaging methodologies have improved medical care by increasing the quality of 52
diagnostic images and significantly decreasing the need for exploratory surgeries. However, in 53
some cases, the use of this newer technology was accompanied by a significant increase in 54
patient radiation dose (Seibert et al. 1996). Some newly introduced technologies, e.g., CT, 55
yielded higher patient doses than the radiographic procedures they replaced. Finally, increased 56
utilization of imaging studies resulted in a greater radiation dose to the population. 57
58
The U.S. Food and Drug Administration’s (FDA) performance standards for radiation emitting 59
products address radiography, fluoroscopy, and CT equipment, and are codified at 21 CFR Part 60
1020 (FDA 2012e). The FDA revised these performance standards in 2005, in part to address 61
some of the radiation dose issues. 62
63
The National Council on Radiation Protection and Measurements (NCRP) reports that medical 64
radiation exposure to the average member of the US population has increased rapidly and 65
continues to do so. Their previous estimate, based on 1970’s and early 1980’s data, was that 66
medical exposure accounted for 0.53 millisievert (mSv) or 53 millirem (mrem) per year, which 67
was 15% of the total annual average (per capita) dose (NCRP 1989a). Based on 2006 data, this 68
estimate was increased to 3 mSv (300 mrem) per year or 48% of the total (NCRP 2009). 69
70
Concerns continue to be raised about the risks associated with patients’ exposure to radiation 71
from medical imaging (Amis et al. 2007; FDA 2010b; FDA 2012e). Because ionizing radiation 72
can cause damage to DNA, exposure may increase a person’s lifetime risk of developing cancer. 73
Although the risk to an individual from a single exam may not itself be large, millions of exams 74
are performed each year, making radiation exposure from medical imaging an important public 75
health issue (Brenner 2007). Berrington de González et al. estimate that approximately 29,000 76
future cancers could be due to CT scans performed in the U.S. in 2007 (Berrington de González 77
et al. 2009). Smith-Bindman et al. estimate that 1 in 270 women and 1 in 600 men who undergo 78
CT coronary angiography at age 40 will develop cancer from that CT scan; the risks for 20-year-79
olds are estimated to be roughly twice as large, and those for 60-year-olds are estimated to be 80
roughly half as large (Smith-Bindman et al. 2009). Although experts may disagree on the extent 81
of the risk of cancer from medical imaging, there is uniform agreement that care should be taken 82
to weigh the medical necessity of a given level of radiation exposure against the risks. 83
84
Given these changes in the available technologies, the reported increase in annual dose from 85
medical imaging, and concerns addressed above, EPA has decided to issue this new guidance to 86
the Federal medical community. Also, it is suitable for use by the broader medical community. 87
This guidance creates no binding legal obligation; rather, it offers recommendations for the safe 88
and effective use of x-ray imaging modalities. Federal agencies that adopt these 89
recommendations (e.g., into orders or standard operating procedures) should, at their discretion, 90
strengthen these statements where appropriate. EPA believes that the information contained in 91
this guidance will help users of diagnostic imaging equipment ensure that any given procedure is 92
justified for the patient being examined and that the dose delivered to that patient is optimized. 93
III
EPA also believes that the information contained in this guidance will provide for radiation 94
protection of medical workers. The goal of radiation management is to keep patient and worker 95
radiation doses as low as reasonably achievable consistent with the use of appropriate equipment 96
and the imaging requirements for specific patients and specific procedures. 97
98
FGR 14 establishes guidance for digital x-ray imaging that addresses protection aspects that were 99
not envisioned in FGR 9. These include: 100
• Reference levels and dose optimization 101
• Newer dose metrics 102
• Introduction of positron emission tomography/computed tomography (PET/CT) 103
• Computed tomography (CT), fluoroscopy (including interventional fluoroscopy), bone 104
densitometry, and veterinary imaging as modalities additional to radiography and 105
dentistry 106
107
In carrying out its federal guidance responsibilities, EPA works closely with other federal 108
agencies through its participation on the Interagency Steering Committee on Radiation Standards 109
(ISCORS). Moreover, EPA recognizes, as it did in 1976, that the expertise needed to make 110
sound recommendations for reducing unnecessary radiation exposure due to the medical use of 111
x-rays in diagnostic and interventional procedures resides in several agencies. Therefore, this 112
report was prepared by the interagency Medical Work Group of the ISCORS Federal Guidance 113
Subcommittee that included physicians, medical physicists, health physicists, and other scientists 114
and health professionals from the Department of Defense, the Department of Veterans Affairs, 115
the Department of Health and Human Services, the Department of Labor, and the EPA. 116
117
As in FGR 9, the recommendations contained in this report represent consensus judgment of the 118
Medical Work Group for the practice of diagnostic and interventional imaging by Federal 119
agencies. Since the body of knowledge on both the radiation exposure and efficacy of x-ray 120
examinations is rapidly changing, comments and suggestions on the areas addressed by this 121
report will assist EPA to conduct periodic reviews and to make appropriate revisions. 122
123
124
125
126 127
128
129
IV
RECOMMENDATIONS FOR AGENCY ACTIONS 130 131
1. Patient safety requires that infrastructure exists for collecting, storing, and analyzing patient 132
dosimetry data. Federal facilities should plan for longitudinal tracking of patient radiation 133
doses. This planning should address the data acquisition, networking, storage, analysis, and 134
security requirements of existing and planned future diagnostic devices. 135
2. All uses of radiation in diagnostic medical imaging should be justified and optimized. This 136
is the responsibility of all involved providers and technologists. Dose management begins 137
when a patient is considered for a procedure involving ionizing radiation, involves 138
equipment setup before the exam begins, and ends when any necessary radiation-related 139
follow-up is completed. 140
3. It is strongly recommended that the justification of medical exposure for an individual 141
patient be carried out by the Referring Medical Practitioner, in consultation with the 142
Radiological Medical Practitioner when appropriate. Each health care facility should 143
establish a formal mechanism whereby Referring Medical Practitioners have sources of 144
information available at the time of ordering regarding appropriate diagnostic imaging 145
methods to answer the clinical question and to optimize ionizing radiation dose to the 146
patient. 147
4. For each type of examination, Federal facilities and agencies should promote the 148
development of national reference levels for use as quality assurance and quality 149
improvement tools. 150
5. For each type of examination there exists, within available technology, an optimal 151
combination of imaging equipment and technique factors to produce adequate images at 152
doses below the reference level. Federal facilities should evaluate each imaging system’s 153
performance to optimize dose, and maintain this by establishing appropriate procedures and 154
conducting periodic monitoring. 155
6. Agencies should only adopt screening programs that have been submitted to rigorous 156
scientific evaluation of efficacy, as has been done for mammography, to ensure that the risk 157
posed to the population screened does not outweigh the benefits in detection of disease. 158
7. Agencies should use methods for estimating individual occupational doses based on the 159
goal of assigning accurate doses rather than overly conservative estimates of doses. NCRP 160
Report No. 122 provides recommended methods for determining effective dose (E) and 161
effective dose equivalent. The various Federal regulatory agencies should establish 162
consistent methods and procedures for this purpose. 163
V
TABLE OF CONTENTS 164
165
PREFACE I 166
RECOMMENDATIONS FOR AGENCY ACTIONS IV 167
TABLES IX 168
INTERAGENCY WORKING GROUP ON MEDICAL RADIATION X 169
INTRODUCTION 1 170
RADIATION SAFETY STANDARDS AND GENERAL CONCERNS 4 171
GENERAL PRINCIPLES OF RADIATION PROTECTION 4 172
GENERAL STANDARDS FOR PROTECTION AGAINST RADIATION 6 173 Minors as Workers 6 174 Embryo or Fetus of Pregnant Workers 6 175 Members of the Public 7 176
GENERAL CONCEPTS FOR RADIATION PROTECTION 7 177
RADIATION SAFETY PROGRAM 8 178 Radiation Safety Officer 8 179 Qualified Physicist 9 180 Personnel and Area Monitoring 9 181 Patient Safety 10 182 Radiation Safety Procedures for Fluoroscopy 10 183 Special Patient Populations 11 184
Pregnant patients 11 185 Pediatric patients 12 186 Patients enrolled in a research protocol 12 187
Analysis of Risk from Radiation 13 188 Informed Consent for Research Involving Radiation 14 189 Occupational Radiation Safety Training 14 190 Notification and Reporting Requirements 14 191
STRUCTURAL SHIELDING AND DOOR INTERLOCK SWITCHES 15 192
REQUESTING AND PERFORMING STUDIES INVOLVING X-RAYS 15 193
REQUESTING STUDIES: REFERRING MEDICAL PRACTITIONERS (REQUESTING HEALTH 194 PROFESSIONALS) 15 195
Qualifications to Request X-ray Examinations 17 196
PERFORMING AND SUPERVISING STUDIES: RADIOLOGICAL MEDICAL PRACTITIONERS AND 197 TECHNOLOGISTS 17 198
Radiological Medical Practitioners 18 199
VI
Radiologists 18 200 Medical Radiologic Technologists 19 201
SCREENING AND ADMINISTRATIVE PROGRAMS 19 202 Chest Radiography 20 203 Mammography 20 204
REFERRAL AND SELF-REFERRAL EXAMINATIONS 20 205 Patients Requesting Imaging on Themselves without a Referral from a Licensed Independent Practitioner 206 (Referring Medical Practitioner) 20 207 Physician Self-Referral 20 208
COMMUNICATION AMONG PRACTITIONERS 21 209
TECHNICAL QUALITY ASSURANCE IN MEDICAL IMAGING WITH X-RAYS 23 210
TECHNIQUE FACTORS 23 211
TESTING BY A QUALIFIED PHYSICIST 24 212
EQUIPMENT FAILURE 25 213
DEFICIENCY CORRECTION VERIFICATION 25 214
DOSIMETRY 25 215
REFERENCE LEVELS 26 216
GUIDANCE BY DIAGNOSTIC AND INTERVENTIONAL MODALITY 28 217
INTRODUCTION 28 218
RADIOGRAPHY 30 219 Equipment 30 220 Testing and Quality Assurance 31 221 Personnel 32 222
Radiological Medical Practitioner 32 223 Technologist 32 224 Other personnel 33 225
Procedures 33 226
FLUOROSCOPY 37 227 Equipment 37 228 Testing and Quality Assurance 40 229 Personnel 40 230 Procedures 42 231
Dose measurement 42 232 Recordkeeping 42 233 Patient management 43 234 Quality process 44 235 Staff safety 46 236
COMPUTED TOMOGRAPHY 47 237 Equipment 48 238 Testing and Quality Assurance 49 239 Personnel 49 240 Procedures 49 241
VII
BONE DENSITOMETRY 52 242 Equipment 52 243 Testing and Quality Assurance 53 244 Personnel 55 245 Procedures 56 246
DENTAL 58 247 Equipment 58 248 Testing and Quality Assurance 60 249 Personnel 61 250 Procedures 62 251
VETERINARY 64 252 Equipment 64 253 Testing and Quality Assurance 65 254 Personnel 66 255 Procedures 66 256
Veterinary clinic setup 66 257 Personal protective equipment 67 258 Animal restraint 67 259 Use of x-ray equipment 67 260 Personal dosimetry 68 261 Special procedures for portable hand-held systems 68 262
MEDICAL IMAGING INFORMATICS 69 263
SUMMARY AND RECOMMENDATIONS FOR FACILITY ACTION 71 264
GENERAL 71 265
BONE DENSITOMETRY 71 266
CHILDREN AND PREGNANT WOMEN 72 267
DENTISTRY 72 268
FLUOROSCOPY 72 269
VETERINARY 73 270
INFORMATICS 73 271
INFORMED CONSENT 73 272
PRESCRIPTION 73 273
REFERENCE LEVELS 74 274
ACRONYMS AND ABBREVIATIONS 75 275
GLOSSARY 78 276
APPENDIX A – NIH INFORMED CONSENT TEMPLATES A-1 277
MINIMAL RISK A-2 278
VIII
MINOR TO INTERMEDIATE RISK A-3 279
REFERENCES REF-1 280
281
282
IX
TABLES 283
284 Table 1. Testing Frequency of Imaging Equipment that Produces X-Rays ................................. 24 285
Table 2. Quality Assurance Measures for Film and Digital Modalities ....................................... 34 286
287
288
289
X
INTERAGENCY WORKING GROUP ON MEDICAL RADIATION 290
291 292 293
Department of Health and Human Services 294
L. Samuel Keith, MS, CHP, CO-CHAIR 295
John L. McCrohan, MS (retired) 296
Donald L. Miller, MD, FSIR FACR 297
Petro Shandruk (retired) 298
299
Department of the Air Force 300
Cindy L. Elmore, Ph.D., DABR 301
LTC Scott Nemmers, BSC 302
303
Department of the Army 304
COL Mark W. Bower, CHP, Ph.D. 305
COL Erik H. Torring, DVM, MPH 306
307
Department of Labor, 308
Occupational Safety and Health Administration 309
Doreen G. Hill, MPH, Ph.D. 310
311
Department of the Navy 312
CAPT Stephen T. Sears, MC, CO-CHAIR 313
CAPT Michael A. Ferguson, MC 314
CDR Douglas W. Fletcher, MSC 315
CDR Chad A. Mitchell, MSC 316
317
Department of Veterans Affairs 318
Ronald C. Hamdy, MD, FRCP, FACP 319
Edwin M. Leidholdt, Jr., Ph.D. 320
Eleonore D. Paunovich, DDS, MS 321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
Environmental Protection Agency 342
Michael A. Boyd, MSPH 343
344
Commonwealth of Pennsylvania 345
John P. Winston 346
347
Expert Consultants/Other Contributors 348
Kimberly Applegate, MD, MS, FACR 349
Charles E. Chambers, MD, FACC FSCAI 350
Steven Don, MD 351
Marilyn Goske, MD 352
Fred A. Mettler, MD, MPH, FACR 353
Terrence J. O’Neil, MD, FACP 354
S. Jeff Shepard, MS 355
Dana M. Sullivan, RT(R)(M) , DVA 356
357
358
359
360
Acknowledgements 361 362
Environmental Protection Agency 363
Helen Burnett (retired) 364
Jessica Wieder 365
366
Department of Health and Human Services 367
J. Nadine Gracia, MD 368
Sandra Howard 369
370
1
INTRODUCTION 371
372
There are a few commonalities that are integrated throughout this document. 373
374 1. This guidance was written without regard to specific models of equipment 375
2. It is intended to be a practical and appropriately prescriptive tool. 376
3. A balance was struck between being sufficiently specific and keeping the document generic 377
enough to remain current. 378
4. Dose reduction has been offset by increased utilization (number and type of procedures) 379
5. Dose reduction technology should be incorporated into the equipment. 380
6. Dose reduction technology only works when it is used. 381
7. Operators need initial and periodic refresher training, easy to use tools (e.g., checklists), 382
and motivation. 383
8. Dose reduction strategies should be integrated into protocols, where possible. 384
9. Improvements in imaging and equipment will continue. 385
386
The fundamental objective in performing an x-ray examination is to obtain the required 387
diagnostic information with only as much radiation dose as is required to achieve adequate image 388
quality. Achievement of this objective requires: 1) assuring equipment is functioning properly 389
and calibrated, 2) assuring equipment is operated only by competent personnel, 3) appropriately 390
preparing the patient, and 4) selecting appropriate equipment and using appropriate protocols. 391
392
Even more so than when the original FGR 9 (EPA 1976) was published in 1976, imaging in 2012 393
plays a critical role in medical care within the United States. In the approximately thirty years 394
that have elapsed since the early 1980s, medical imaging has grown rapidly in utilization and 395
capability (NCRP 1989a; NCRP 2009). Computed tomography (CT) provided a new cross 396
sectional imaging method, initially for evaluating the contents of the skull and then for other 397
body cavities and organs, for assessing tissues and organs that previously required surgery for 398
evaluation. This resulted in fewer exploratory surgical procedures and permitted more accurate, 399
non-invasive diagnoses. The number of CT procedures is growing at a rate greater than 10% per 400
year. 401
402
Smaller image detector elements increased the spatial resolution of CT imaging. Other 403
technological improvements have included improved mechanical function, multi-row detector 404
CT scanners, more capable computer technology, and improved x-ray tubes. As a result CT now 405
permits evaluation of physiologic characteristics as well as anatomy, and permits pediatric exams 406
previously limited by motion artifact. Indications for imaging have increased as have use of 407
multi-sequence studies that allow organs to be evaluated during several phases of contrast 408
enhancement. 409
410
Improvements in fluoroscopy detector systems and improvements in techniques and equipment 411
(catheters, stents, embolic agents) facilitated an increase in the number and variety of image-412
guided interventions. These procedures replaced many open surgical procedures and now 413
provide new therapy options for many diseases. 414
415
With the vast information available through imaging and the increased availability of CT and 416
2
fluoroscopy systems, there has been a marked increase in the contribution of radiation dose from 417
x-ray based medical studies to the overall radiation dose to the US population. CT imaging 418
studies increased from 3 million in 1980 to 62 million in 2006, at which time, scans were 419
increasing at the rate of 10% per year (ACR 2007d; NCRP 2009). During this period, the 420
estimated effective dose from all x-ray-related medical procedures other than radiation therapy 421
increased from 0.39 to 2.23 millisievert per year (mSv/y) (39 to 223 millirem per year (mrem/y)), 422
or from 11% to 36% of the total US population dose. By 2006, the annual x-ray effective dose in 423
the U.S. virtually equaled that from radon as well as the worldwide collective dose resulting 424
from the Chernobyl disaster (ACR 2007d; NCRP 2009). 425
426
Human epidemiological studies have demonstrated the potential of ionizing radiation to induce 427
cancer at an effective dose greater than 0.1 Sv. It is prudent to consider that lower doses might 428
also carry a risk. National and international organizations have classified ionizing radiation 429
(including x-rays) as a known human carcinogen (NTP 2011). These groups include the 430
National Toxicology Program and the World Health Organization’s International Agency for 431
Research on Cancer (IARC 2012). 432
433
Technological advances have improved diagnostic capabilities and image quality. Some of these 434
advances entail increases in patient dose. However, some have provided new and effective 435
methods for reduction of radiation exposure. Improvements in film and film-screen technology 436
permitted reduction in the amount of radiation dose necessary to obtain standard images like the 437
chest radiograph. Improvement in image intensifiers and digital image receptors decreased the 438
amount of radiation necessary for fluoroscopic studies and the advent of pulsed fluoroscopy 439
permits even further reduction in the radiation required for a given imaging study. Simple 440
advances such as “last image hold” that cause the last image acquired to remain on the video 441
display screen after the fluoroscopy is stopped markedly reduce the dose of radiation involved in 442
these studies. Transition to improved systems also markedly reduced the radiation dose 443
necessary for mammography. In CT, improvements in detector composition and function, dose 444
modulation based on the patient’s size and body part examined, advanced reconstruction 445
algorithms, and prospective acquisition gating during the cardiac cycle have all provided 446
methods to significantly reduce the radiation dose from imaging studies. 447
448
Research has demonstrated that these dose-reduction techniques are not always employed or 449
used to best advantage in medical imaging, and medical education does not typically provide 450
focus on the effects of and protection from radiation exposure (ICRP 2000b). Seemingly simple 451
and obvious items, like altering the energy and amount of radiation used in imaging children as 452
compared with adults, have not been adopted universally. Some units with pulsed fluoroscopy 453
capability have never been used in that mode. This document is intended to assist the reader in 454
appreciating the need for understanding doses from procedures and maximizing the benefit-risk 455
ratio in the use of medical imaging systems. 456
457
The primary goal of medical imaging is to answer a clinical question or guide an intervention. 458
When performing medical imaging with ionizing radiation, using only as much radiation dose as 459
is required to achieve adequate image quality should be the second goal. There are several ways 460
to reduce radiation dose that will be discussed specifically in the sections dedicated to each 461
imaging modality. 462
3
463
Important ways to reduce radiation exposure to patients are to avoid duplicate studies and to 464
avoid any study that does not contribute effectively to the primary goal of answering the clinical 465
question. Sharing digital images among facilities reduces patient radiation doses by precluding 466
unnecessary duplicative imaging. The individual requesting the imaging examination should 467
have sufficient knowledge of the radiation doses associated with imaging examinations to be 468
able to request the most effective imaging study that provides the necessary information at the 469
lowest radiation dose. When appropriate, examinations not involving ionizing radiation are 470
preferable. Organizations, such as the American College of Radiology (ACR) and American 471
College of Cardiology (ACC), have published guidance that can help health professionals choose 472
the most appropriate examinations to answer their clinical questions. 473
474
As an example, in the evaluation of a patient with cough and fever, a standard two view chest x-475
ray series may provide adequate information for the diagnosis and treatment of pneumonia at a 476
small fraction of the radiation dose that would be delivered by a chest CT. Similarly, a CT 477
angiogram may provide visualization of a large vascular distribution in a single imaging run with 478
a lower radiation dose than the multiple digital subtraction angiographic sequences that may be 479
required to adequately visualize the same area. 480
481
Once a specific imaging study is selected, technical aspects of the image acquisition become the 482
most critical influence on radiation dose delivered to the patient and quality of the resulting 483
images. Although reduction of radiation exposure overall should be a goal, reduction of dose to 484
a level that results in an increased number of unsatisfactory examinations requiring repeat 485
imaging will actually increase patient dose overall and should be avoided as much as excessive 486
dose should be. In the use of film-screen technology, over and under exposure were evident on 487
the resulting image, but with digital based imaging, these conditions are not as apparent. One 488
reason is that image quality may continue improving with increasing dose, even beyond what is 489
needed or adequate. As a result, good clinical practices include effective quality control 490
programs, optimized imaging protocols providing only the necessary sequences, adjustment of 491
technical factors and dose of radiation for patient size and age, and employment of the best 492
available dose reduction technologies existing in the equipment in use. 493
494
This document is intended to assist the reader in validating their efforts and maximizing the 495
benefit:risk ratio in requesting and performing medical diagnostic and interventional procedures 496
involving x-rays. The document is divided into sections based on imaging modality. 497
498
499
500
4
RADIATION SAFETY STANDARDS AND GENERAL CONCERNS 501 502
GENERAL PRINCIPLES OF RADIATION PROTECTION 503 504
The International Commission on Radiological Protection (ICRP) has formulated a set of three 505
fundamental principles for radiation protection (ICRP 2007a; ICRP 2007c). These principles are 506
justification, optimization of protection, and application of dose limits. The first two principles 507
apply to a source of exposure, and thus are intended to support protection for all individuals who 508
may be exposed to that source. The third principle applies to occupational and public exposure, 509
but explicitly excludes medical exposure of patients. 510
511
The principle of justification states that, in general, “any decision that alters the radiation 512
exposure situation should do more good than harm. This means that by introducing a new 513
radiation source, by reducing existing exposure, or by reducing the risk of potential exposure, 514
one should achieve sufficient individual or societal benefit to offset the detriment it causes” 515
(ICRP 2007a; ICRP 2007c). With regard to medical exposures specifically, “the principal aim of 516
medical exposures is to do more good than harm to the patient, subsidiary account being taken of 517
the radiation detriment from the exposure of the radiological staff and of other individuals” 518
(ICRP 2007a). 519
520
The ICRP (ICRP 2007a) addresses justification in medicine as follows: 521
522
“The principle of justification applies at three levels in the use of radiation in medicine. 523
At the first level, the use of radiation in medicine is accepted as doing more good than 524
harm to the patient. This level of justification can now be taken for granted. 525
526
“At the second level, a specified procedure with a specified objective is defined and 527
justified (e.g., chest radiographs for patients showing relevant symptoms, or a group of 528
individuals at risk to a condition that can be detected and treated). The aim of the second 529
level of justification is to judge whether the radiological procedure will usually improve 530
the diagnosis or treatment or will provide necessary information about the exposed 531
individuals. 532
533
“At the third level, the application of the procedure to an individual patient should be 534
justified (i.e., the particular application should be judged to do more good than harm to 535
the individual patient). Hence all individual medical exposures should be justified in 536
advance, taking into account the specific objectives of the exposure and the 537
characteristics of the individual involved.” 538
539
The principle of optimization of protection states that “the likelihood of incurring exposures, the 540
number of people exposed, and the magnitude of their individual doses should all be kept as low 541
as reasonably achievable, taking into account economic and societal factors. This means that the 542
level of protection should be the best under the prevailing circumstances, maximizing the margin 543
of benefit over harm” (ICRP 2007a; ICRP 2007c). 544
545
5
The principle of application of dose limits states that “the total dose to any individual from 546
regulated sources in planned exposure situations other than medical exposure of patients should 547
not exceed the appropriate limits recommended by the Commission” (ICRP 2007a; ICRP 548
2007c). It is important to note this definition explicitly excludes medical exposure of patients. 549
Dose limits do not apply to medical exposure, which is defined by the ICRP as “the exposure of 550
persons as part of their diagnosis or treatment (or exposure of a patient’s embryo/fetus or breast-551
feeding infant) and their comforters and carers (other than occupational)” (ICRP 2007c). As the 552
ICRP has stated, “Provided that the medical exposures of patients have been properly justified 553
and that the associated doses are commensurate with the medical purpose, it is not appropriate to 554
apply dose limits or dose constraints to the medical exposure of patients, because such limits or 555
constraints would often do more harm than good” (ICRP 2007c). This recommendation against 556
establishing absolute dose limits should not discourage a facility from implementing threshold 557
guidelines for diagnostic procedures that trigger a review of practice at the facility, or from 558
establishing dose notification and alert values for CT (NOTE:cite NEMA standard XR25-2010 to 559
be provided by Ed 2012-08-17). 560
561
When an interventional procedure is indicated, the medical condition being treated and the non-562
radiation risks of the procedure typically present a substantially greater risk of morbidity and 563
mortality than do the radiation risks (Miller 2008). 564
565
While dose limits do not apply to medical exposures, each physician must always strive to 566
minimize patient irradiation to the dose that is necessary to perform the procedure. Therefore, 567
radiation doses to patients should always be optimized. 568
569
The concept of patient radiation dose optimization is used throughout this document. Dose 570
optimization means delivering a radiation dose to the organs and tissues of clinical interest no 571
greater than that required for adequate imaging and minimizing dose to other structures (e.g., the 572
skin (FDA 1994)). Patient radiation dose is considered to be optimized when imaging is 573
performed with the least amount of radiation required to provide adequate image quality and, for 574
fluoroscopy, adequate imaging guidance (NIH NCI SIR 2005). The goal of every imaging 575
procedure is to provide images adequate for the clinical purpose. What constitutes adequate 576
image quality depends on the modality being used and the clinical question being asked. 577
Imaging requirements depend on the specific patient and the specific procedure. Reducing 578
patient radiation dose to the point where images are inadequate is counterproductive; it results in 579
radiation dose to the patient without answering the clinical question, ultimately resulting in the 580
need for additional radiation dose. Improving image quality beyond what is clinically needed 581
subjects the patient to additional radiation dose without additional clinical benefit. The goal of 582
patient radiation management is to keep patient radiation dose as low as reasonably achievable 583
consistent with the use of appropriate equipment and the imaging requirements for a specific 584
patient and a specific procedure. 585
586
Ideally, dose would be accurately measured or estimated in relevant tissues and organs in real 587
time. As of 2012, this is not possible. Currently, radiation dose is measured differently for CT, 588
fluoroscopically-guided procedures, and radiography due to the endpoint health effect of interest 589
(cancer or acute tissue damage), the way radiation is detected, and the way dose is calculated. 590
The dose metrics and units of measurement used for patient radiation dose measurement are 591
6
necessarily dependent on the equipment and modality being used. Different dose metrics are 592
managed in different ways. For example, during fluoroscopically-guided procedures, it is 593
desirable to optimize kerma area product and reference air kerma (indicators of patient dose) 594
while also minimizing peak skin dose. The most appropriate dose metrics available should be 595
used. 596
597
598
GENERAL STANDARDS FOR PROTECTION AGAINST RADIATION 599 600
Federal facilities must have safety programs in place to protect workers, as required by Public 601
Law 91-596, Section 19 entitled Federal Agency Safety Programs and Responsibilities (Congress 602
2004) and Executive Order 12196 entitled Occupational Safety and Health Programs for Federal 603
Employees (Carter 1980). For medical imaging the standards for protection against ionizing 604
radiation are promulgated by the Nuclear Regulatory Commission (NRC) for radioactive 605
materials in 10CFR20 (USNRC 2012c), and the US Occupational Safety and Health 606
Administration (OSHA) for x-rays in 29CFR1910 (OSHA 2012). If both radioactive materials 607
and x-rays are utilized, then NRC regulations generally take precedence. Portions of the NRC 608
and OSHA regulations, when considered together, establish dose limits for staff and members of 609
the public; requirements for the wearing of dosimeters; requirements for the posting of warning 610
signs; periodic employee training and hazard communication; comprehensive record keeping for 611
exposure monitoring results, periodic facility medical physicist assessments, and preventive 612
interventions; and timely reporting of results of exposure monitoring and exposure incidents to 613
individual employees, including exposures to staff or members of the public that exceed 614
regulatory limits. It is important to note that these dose limits are for occupational, incidental, 615
and public exposure and do not specifically limit the exposure that a patient may receive as a 616
result of medical evaluation or treatment in the process of their personal health care. As of 2012, 617
and consistent with recommendations from ICRP, there is no regulatory limit on the amount of 618
radiation a patient may receive. 619
620
Minors as Workers 621 622
Readers of this document should be aware that the Federal Regulations cited above also provide 623
direction concerning occupational radiation exposure to individuals below the age of 18. Dose 624
limits for these individuals are generally 10% of the occupational dose limits for adults. 625
626
Embryo or Fetus of Pregnant Workers 627 628
As of 2012, the occupationally received dose equivalent to the embryo or fetus of a radiation 629
worker who has voluntarily declared her pregnancy in writing shall not exceed 5 mSv (0.5 rem) 630
during the remainder of the pregnancy, or an additional 0.5 mSv (0.05 rem) if the gestation limit 631
has been or is within 0.5 mSv (0.05 rem) of being exceeded when the declaration is made 632
(USNRC 2012b). This limit does not pertain to the exposure of an embryo or fetus resulting 633
from a medical procedure to the pregnant worker. When a radiation worker informally advises 634
the facility that she is, might be, or is attempting to become pregnant, her past and current 635
exposure values should be evaluated and risks associated with radiation exposure to the fetus 636
should be discussed. If she formally declares her pregnancy (i.e., becomes a “declared pregnant 637
7
woman” per 10CFR20.1003 (USNRC 2012a)), she should be issued a dosimeter to be worn on 638
the lower abdomen, under the apron, at the level of the fetus, and exchanged monthly, unless 639
such a dosimeter is already being worn. The facility should avoid substantial variation above a 640
uniform monthly exposure rate of 0.5 mSv/month. 641
642
Members of the Public 643 644
The total effective dose equivalent to an individual member of the public should not exceed 645
1 mSv (100 mrem) in a year from occupancy in uncontrolled areas in or near medical radiation 646
facilities (NCRP 2004a). In health care facilities, all non-radiation workers (e.g., janitorial staff, 647
secretaries) should be afforded protection consistent with that afforded members of the public. 648
This is relevant to the design of radiation shielding and occupancy limits. 649
650
651
GENERAL CONCEPTS FOR RADIATION PROTECTION 652 653
There are several principles by which workers can minimize their exposure to x-rays. Most of 654
them are based on certain fundamental concepts concerning x-rays: (1) limiting the time of 655
exposure reduces the dose, (2) except at short distances, radiation intensity is inversely 656
proportional to the square of the distance from the radiation source (Inverse Square Law), and (3) 657
x-rays travel in straight lines from their source and can be attenuated by shielding. Those who 658
are exposed to radiation should judiciously use time, distance, and shielding to limit their 659
radiation dose. 660
661
Humans should be exposed to the unattenuated primary radiation beam(s) of x-ray imaging 662
equipment in federal medical facilities only for medical purposes. For this definition, “medical 663
purposes” include research involving the exposure of human subjects conducted in accordance 664
with the Federal Policy for the Protection of Human Subjects (OSTP et al. 1991). In particular, 665
humans may not be exposed to these unattenuated beams solely for training, to test equipment, or 666
to obtain images for accreditation. The only exception to this requirement is that precision 667
assessments may be made in dual energy x-ray bone densitometry in accordance with the 668
guidelines of the International Society for Clinical Densitometry (ISCD 2007a; ISCD 2007b). 669
670
Optimization of protection is at the heart of a successful radiation control program. It involves 671
evaluating and, where practical to do so, incorporating measures to reduce collective dose and 672
minimize the number of people exposed. In accordance with the ICRP’s principle of 673
optimization of protection, each facility should use, to the extent practicable, procedures and 674
engineered controls to achieve occupational doses and doses to members of the public that are as 675
low as reasonably achievable (ALARA), with economic and social factors being taken into 676
account. The ALARA approach is applied after it has been determined that a proposed activity 677
will not exceed any mandatory dose limit. 678
679
The ALARA approach requires that only people whose presence is necessary are permitted in the 680
room while images are acquired. For radiation protection purposes, it is strongly recommended 681
that these people be shielded from radiation by means such as protective aprons and/or portable 682
shields and maintain as much distance as possible from the point where the x-ray beam intersects 683
8
the patient. To limit worker dose, it is strongly encouraged that the operator be behind a shielded 684
barrier when observing the patient during image acquisition. 685
686
687
RADIATION SAFETY PROGRAM 688 689
A radiation safety program is the mechanism for an institution to ensure that: 690
• the use of ionizing radiation within its purview is performed in accordance with existing 691
laws and regulations, 692
• individual health professionals and technologists are equipped with knowledge of the 693
options available to them as they make benefit:risk determinations and prescribe the 694
appropriate examination for each individual patient, and 695
• x-ray equipment users and the surrounding public receive adequate protection from this 696
radiation. 697
The primary objective is to obtain necessary diagnostic information or interventional results with 698
minimum irradiation of the patient. This also helps keep exposure to staff and members of the 699
public at a minimum. The key personnel and activities involved in managing a radiation safety 700
program are: 701
702
Radiation Safety Officer 703 704
The Radiation Safety Officer (RSO) is responsible for radiation safety. The RSO may be the 705
same person designated for radiation safety for NRC purposes under Title 10, Code of Federal 706
Regulations, Part 35 (USNRC 2012d). An RSO should be designated for each facility that uses 707
ionizing radiation for medical imaging, and should be appointed in writing by the facility 708
director or agency. The RSO shall be permitted to directly communicate with facility executive 709
management. The RSO, whenever possible, should be a qualified expert as defined in this 710
document. The RSO should be a person having knowledge and training in ionizing radiation 711
measurement and evaluation of safety techniques and the ability to advise regarding radiation 712
protection needs (for example, a person certified in diagnostic medical physics by the American 713
Board of Radiology, or in health physics by the American Board of Health Physics, or those 714
having equivalent qualifications). The RSO has the following specific responsibilities: 715
716
1. Establish and implement radiation safety procedures and review them periodically to assure 717
their conformity with regulations and good radiation safety and medical physics practices. 718
2. Instruct personnel in regulatory requirements and proper radiation protection practices 719
before they begin working with radiation and periodically thereafter to maintain and update 720
that knowledge. 721
3. Conduct or supervise radiation surveys where indicated and keep records of such surveys 722
and tests, including summaries of corrective measures recommended and/or instituted. 723
4. Assure that area monitoring and personnel monitoring devices are used as required and 724
records are kept of the results of such monitoring. This function requires reviewing the 725
monitoring reports promptly to ensure that public and personnel doses do not exceed 726
regulatory limits and are ALARA, making dosimetry records available to each worker at 727
any time, and periodically informing workers of their dose record. These records will be 728
9
kept in a suitable organized file (readily retrievable but not necessarily on site) for the life 729
of the facility or as legally required. 730
5. Assure that any warning signals on imaging equipment and suites are regularly checked for 731
proper function and that required signs are properly posted. 732
6. Monitor compliance with the requirements of regulations and the requirements specified in 733
the facility’s standard operating procedures. 734
7. In conjunction with a qualified physicist, promptly investigate each known or suspected 735
case of excessive or abnormal exposure, determine the causes, take steps to prevent its 736
recurrence, monitor such corrective actions, and make appropriate reports. 737
8. Ensure that required notifications and reports in the case of personnel overexposures and 738
radiation medical events are submitted as required by regulations. 739
9. Promptly notify facility executive management of significant safety hazards, significant 740
violations of regulations, exposures of staff or members of the public that exceed regulatory 741
requirements, and radiation medical events. 742
10. Review or have a qualified expert review, prior to construction or modification, plans for 743
rooms in which x-ray producing equipment is to be installed, including room layout, 744
shielding (AAPM 2006c; NCRP 2004a), and viewing and communications systems, and 745
verify that the shielding is installed according to plan and functions as designed before 746
clinical use of the equipment. 747
748
Qualified Physicist 749 750
The services of a qualified physicist are essential for the optimal use of medical imaging. The 751
following services should be performed by or under the supervision of a qualified physicist: 752
753
1. Participate in evaluation and selection of equipment 754
2. Conduct acceptance testing of new equipment 755
3. Monitor imaging systems at least annually 756
4. Evaluate, in conjunction with the RSO, unexpected radiation events 757
5. Oversee the technical QA program 758
6. Investigate the root causes of image quality issues and identify appropriate solutions. 759
7. Design or review and approve x-ray room radiation shielding 760
8. Perform verification surveys of x-ray room shielding 761
9. Periodically review existing imaging protocols 762
10. Assist with development and evaluation of new and revised imaging protocols 763
11. Perform patient-specific radiation dose calculations (e.g., fetal dose calculations) 764
12. Provide training on quality control and radiation safety 765
13. Ensure that instruments used to monitor x-ray imaging systems are appropriate for the task, 766
appropriately calibrated for the task (e.g., energy and dose rate measurements), and 767
maintained 768
14. Evaluate the radiation-related aspects of research protocols 769
770
Personnel and Area Monitoring 771 772
Each worker who is expected to receive more than 10% of the applicable dose limit should be 773
required to wear one or more dosimeters. There shall be a procedure for regular issuance and 774
10
replacement of dosimeters for exposure evaluation, and records of the doses received shall be 775
retained as required by NRC in 10CFR20 (USNRC 2012c) and OSHA in 29CFR1910.1096 776
(OSHA 2012). When a protective apron is worn, one dosimeter should be worn at the collar 777
outside the apron. A second dosimeter may be worn on the abdomen under the apron. The two 778
dosimeter method provides a more accurate method of assessing effective dose (NCRP 1995). 779
When multiple dosimeters are issued to an employee, each dosimeter should be labeled to 780
indicate the location on the body where it is to be worn. Facilities should ensure that workers 781
wear dosimeters as required, and in the designated locations; failure to do so can result in 782
incorrect dose assessments. Periodic assessments and feedback to employees regarding their 783
exposures are particularly important. If there is a question, the facility can also post dosimeters 784
in public areas adjacent to rooms where x-rays are produced in order to quantify the amount of 785
radiation a person in those areas might receive. Facilities/agencies should use methods for 786
estimating individual doses based on the goal of assigning accurate doses. Federal regulatory 787
agencies should adopt methods and procedures consistent with NCRP Report No. 122, which 788
provides recommended methods for determining effective dose (E) (NCRP 1995). 789
790
Patient Safety 791
792
As with all medical procedures, there are critical elements of patient safety that must be 793
observed. The first critical element is ensuring that the correct patient undergoes the specified 794
diagnostic test or interventional procedure, and that the examination is performed on the 795
appropriate body part. To that end, each facility should have in place a specified method for 796
verification of patient identity prior to events such as administration of medication or surgical 797
procedures. These precautions should also be extended to diagnostic and interventional imaging. 798
If the medical procedure involves intervention or a specific side of the patient’s anatomy, the 799
specific body part should be confirmed prior to the procedure. The precautions should be 800
commensurate with the risk from the examination or procedure, with greater precautions being 801
taken for procedures of greater risk. 802
803
Radiation Safety Procedures for Fluoroscopy 804 805
It is strongly recommended that, other than for the patient being examined, only staff and 806
ancillary personnel required for the procedure, or those in training, be in the room during the 807
fluoroscopic examination (AAPM 1998; ACR 2008c). No body part of any staff or ancillary 808
personnel involved in a fluoroscopic examination should be in the primary beam. However, if 809
primary beam exposure is unavoidable, it should be minimized. It is essential that all personnel 810
in the room during fluoroscopic procedures be protected from scatter radiation by either whole-811
body shields or protective aprons. For procedures performed using microampere fluoroscopy 812
systems, a qualified physicist should determine if aprons are required. 813
814
Aprons should provide the desired protection at an acceptable weight, because the apron weight 815
itself can pose a substantial ergonomic risk to its wearer. Apron weight can be reduced by using 816
thinner lead or by replacing lead, completely or partially, with a combination of one or more 817
other materials that have the same or better attenuation for the scattered radiation from 818
fluoroscopic beams. Though 0.5 mm lead-equivalent aprons are considered the standard as of 819
11
2012, an apron with thinner lead equivalence may provide adequate protection. Based on the 820
calculation of effective dose (E) from dual monitors, a 0.3 mm lead-equivalent apron will result 821
in a value of E that is only moderately higher (7 to 16 %) than a 0.5 mm lead-equivalent apron 822
(NCRP 1995). The two-dosimeter method described above under PERSONNEL AND AREA 823
MONITORING may be preferable for monitoring personnel in the room during high dose 824
interventional procedures. Monthly dose monitoring can also be implemented to ensure that staff 825
members who use garments with < 0.5 mm lead equivalent thickness continue to maintain an 826
occupational dose below the required dose limits. With these precautions in place, it is quite 827
possible to provide adequate protection with a 0.35 mm or less lead equivalent thickness. 828
829
Thyroid and eyes should be protected if the potential exposure to the worker will exceed 25% of 830
the annual regulatory dose limits for those organs. It is strongly recommended that lead 831
personnel protective equipment (e.g., aprons, gloves, thyroid collars) be evaluated at least 832
annually for lead protection integrity using visual and manual inspection (Miller et al. 2010b; 833
NCRP 2010). If a defect in the attenuating material is suspected, radiographic or fluoroscopic 834
inspection may be performed as an alternative to immediately removing the item from service. 835
Protective aprons, gloves and thyroid shields should be hung or laid flat and never folded, and 836
manufacturer’s instructions should be followed. Consideration should be given to minimizing 837
the radiation exposure of inspectors by minimizing unnecessary fluoroscopy. 838
839
Special Patient Populations 840 841
Specific special populations addressed here include: 842
843
1. Pregnant patients 844
2. Pediatric patients 845
3. Patients enrolled in a research protocol 846
847
Occupational radiation exposure to minors and to the fetus of a pregnant worker is discussed in 848
the section General Standards for Protection Against Radiation. 849
850
Pregnant patients 851 852
Because of the special risk that radiation exposure poses to the embryo or fetus, each facility 853
should establish and implement procedures to determine, before conducting an examination or 854
procedure, whether a female patient of childbearing age may be pregnant. 855
856
Signs should be posted in suitable locations, such as patient reception areas and procedure 857
rooms, asking female patients to notify staff if they might be pregnant. Consideration should be 858
given to alternate tests or procedures, such as ultrasound, that would not expose the embryo or 859
fetus to ionizing radiation, or to modifying the examination or procedure to reduce the radiation 860
dose to the embryo or fetus. 861
862
Evaluation of the benefit:risk ratio in relation to the radiation dose from medical imaging in a 863
pregnant woman is very complex. In instances where a study using ionizing radiation is deemed 864
necessary, every effort should be made to avoid exposing the fetus to the direct radiation beam. 865
12
If a patient is pregnant, a radiologist, radiation oncologist, or other physician knowledgeable in 866
the risk from the radiation exposure should work with the patient in making the decision whether 867
to perform the examination or procedure. There should be a discussion of the benefits and risks 868
with a pregnant patient prior to the imaging unless an emergent need for the imaging or her 869
condition precludes this. If a previously unrecognized pregnancy is identified after a procedure, 870
the referring physician should be notified and the patient counseled as appropriate. 871
872
The precautions should be commensurate with the risk from the examination or procedure to be 873
performed, with greater precautions being taken for procedures imparting larger radiation doses 874
to the abdomen or pelvic region of the patient. The physician might consider delaying the 875
procedure until after pregnancy so as to avoid exposing the embryo or fetus. For procedures that 876
may impart a dose to this region, and especially for those exceeding 0.05 Gy (5 rad), the 877
anticipated dose and associated risks should be included as part of informed consent and a serum 878
pregnancy test should be obtained, unless a physician determines that the delay caused by 879
performing the test would harm the patient. A confirmatory pregnancy test would not be 880
necessary if pregnancy can be excluded by documented surgical or medical history. Procedures 881
that may impart a dose to the embryo or fetus exceeding 0.05 Gy (5 rad) are prolonged 882
fluoroscopic procedures to the abdomen or pelvis and CT imaging involving two or more scans 883
of the abdomen or pelvis. 884
885
The dose to a fetus should be estimated. If the dose to the embryo or fetus could exceed 0.05 Gy 886
(5 rad), a formal dose assessment should be performed by a qualified physicist and provided with 887
consultation to the referring physician so that the patient can be advised accordingly. Doses at or 888
above 0.1 Gy (10 rad) warrant discussions between the patient and her physician of potentially 889
adverse fetal effects, and the fetal dose assessment should be included in the medical record. 890
891
Pediatric patients 892 893
Children are more sensitive to radiation and also have greater expected remaining life spans than 894
adults. As such, children represent a population at greater risk for subsequent development of 895
radiation induced cancer than adults. This difference in the benefit:risk ratio should be 896
considered in the prescription of medical imaging requiring ionizing radiation. Alternative 897
imaging modalities that do not use ionizing radiation, such as ultrasound or MRI, should be 898
considered for imaging children. 899
900
Protocols for all ionizing radiation imaging should be “child-sized” or optimized so that the dose 901
is appropriate for the size of the infant or child (FDA 2001; Strauss et al. 2010). For 902
radiography, fluoroscopy, and CT, this key principle holds true. For example, unlike abdominal 903
CT studies performed in adults, pediatric CT studies usually do not require multiple passes 904
through the child’s body. This reduces the radiation dose to the child without compromising 905
diagnosis. 906
907
Patients enrolled in a research protocol 908 909
All research involving human subjects that is conducted, supported, or otherwise subject to 910
regulation by any Federal department or agency must conform to the most current version of the 911
13
Federal Policy for the Protection of Human Subjects (FPPHS) (OSTP et al. 1991). This policy 912
requires approval of research protocols by a properly constituted institutional review board (IRB) 913
and obtaining informed consent from the patient. 914
915
Many protocols use radiation that is medically indicated (also referred to as “standard-of-care”). 916
Medically-indicated radiation is used to diagnose or guide treatment as a non-research medical 917
procedure for clinical management of the research subject. The radiation dose from a medically-918
indicated procedure done as part of a research study should not require additional justification, 919
review, and approval by an IRB. When the radiation exposure is described as indicated for 920
research (the radiation use does not meet the criteria of “medically indicated”) it must be 921
reviewed and approved. IRBs have responsibility for oversight of research involving human 922
subjects, but usually seek the advice of the institution’s Radiation Safety Committee regarding 923
the radiation risk from any non-medically indicated radiation use that is a component of the 924
research. 925
926
Analysis of Risk from Radiation 927 928
An analysis of risk to the human research subjects, including that from radiation exposure, must 929
be performed prior to preparation of the information to be provided to the subjects to seek 930
informed consent and prior to review of the research study by the IRB. The risks of both 931
deterministic and stochastic effects from the radiation exposure should be considered. For 932
consideration of the risk of deterministic effects, the maximal doses to individual organs and 933
tissues should be estimated, although dose rate and dose fractionation may also be considered. 934
935
The risk from stochastic effects, particularly cancer, should also be considered. Ideally, this risk 936
should be calculated from estimating doses to individual organs and tissues and using organ and 937
tissue specific risk coefficients that account for the age and gender of the subject. The 938
International Commission on Radiation Units and Measurements (ICRU) provides useful 939
information for determining patient dose (ICRU 2005, or most current version). However, for 940
many imaging procedures, this approach would consume considerable resources and requiring it 941
would discourage many research studies from being performed. 942
943
The ICRP developed the quantity effective dose (E) for radiation protection purposes to assess 944
the risk of detriment to workers from stochastic effects caused by occupational exposure to 945
ionizing radiation (Harrison and Streffer 2007; ICRP 1991a). This quantity was intended to be 946
applied to a population of working-age adults of both genders. Although effective dose was not 947
intended to be used for assessing risk from medical exposures, it is commonly used to convey the 948
potential risk from radiation exposure for subjects participating in investigational protocols 949
(Martin 2007). For many imaging procedures, the effective dose can be estimated easily. 950
Furthermore, effective dose provides a single quantity from participating in a research study that 951
can be compared to other sources of radiation exposure (e.g., medical procedures and natural 952
background radiation). From the research subject’s perspective, this comparison is simple and 953
expresses the risk in a meaningful way. The effective dose may be used for estimating risk from 954
stochastic effects to human research subjects, but should not be used without considering its 955
appropriateness in light of the characteristics of the study population, including their ages and 956
genders, the body parts being irradiated, and their expected life-spans. ICRP Publication 62 957
14
(ICRP 1991b) provides guidance on the use of effective dose in estimating risk to human 958
subjects. 959
960
Informed Consent for Research Involving Radiation 961
962
To enroll in any research study using human subjects, participants must be knowledgeable about 963
the risks, benefits, privacy considerations and other matters. They must participate voluntarily 964
and must provide written informed consent using an IRB-approved consent form. Requirements 965
for human research in x-ray imaging facilities are addressed in the Federal Register (OSTP et al. 966
1991) and are specified in the current Code of Federal Regulations sections that apply to 967
individual facility operations (e.g., 32CFR219 for DoD, 45CFR46 for DHHS, 40CFR26 for 968
EPA, and 38CFR16 for VA). Appendix A contains sample informed consent templates for the 969
research use of radiation, adapted from those used by NIH in 2012 (NIH 2008a; NIH 2008b; 970
NIH 2010). 971
972
These consent documents have been developed for use when patients are irradiated for research 973
purposes as opposed to being irradiated for clinical care. These documents explain risk based on 974
effective dose. The maximum level of radiation risk should be expected to be minimal, minor to 975
intermediate, or moderate when the respective societal benefit is minor, intermediate to 976
moderate, or substantial (ICRP 1991b). The specific values of numerical dose for each of these 977
ranges may vary according to the specific IRB and the specific research population. The sample 978
consent templates in Appendix A may be considered as a starting point for IRB consideration for 979
the general adult population. These consent templates should be modified as appropriate to meet 980
the particular requirements or needs of a given study. 981
982
Occupational Radiation Safety Training 983 984
Each facility should train staff who operate x-ray producing equipment or who are routinely 985
exposed to radiation by the equipment. Training should be provided initially prior to utilization 986
of the equipment and at least annually thereafter. The training should be commensurate with risk 987
to the staff and to the patient. It should include the risks from exposure to ionizing radiation, 988
regulatory requirements, recommendations of this guidance document, facility requirements, 989
proper operation of the equipment, methods for maintaining doses to staff within regulatory 990
limits and as low as reasonably achievable, and guidance for protecting the patient and embryo 991
or fetus. 992
993
Notification and Reporting Requirements 994
995 If radiation exposures to staff or members of the public exceed regulatory limits, the facility shall 996
make notifications and reports as required by the NRC or OSHA (OSHA 2012; USNRC 2012c). 997
998
999
15
STRUCTURAL SHIELDING AND DOOR INTERLOCK SWITCHES 1000 1001
To prevent inadvertent patient injury or the need to repeat exposures of patients, it is strongly 1002
recommended that interlock switches that terminate x-ray production not be placed on doors to 1003
any diagnostic or interventional x-ray room (NCRP 2004a). 1004
1005
For the structural shielding of rooms containing x-ray imaging or x-ray-producing devices, the 1006
shielding design goal should be 5 mGy in a year to any person in controlled areas. For 1007
uncontrolled areas, the shielding design goal should be a maximum of 1 mGy to any person in a 1008
year (0.02 mGy per week) (NCRP 2004a). Shielding design for and acceptance testing surveys 1009
of imaging rooms should be performed or reviewed by a qualified physicist using appropriate 1010
methodology such as is provided in NCRP reports. Whenever room modifications are performed 1011
or the assumed shielding parameters change (e.g., new equipment, increased workload, or altered 1012
use of adjacent spaces), the suitability of the design should be reviewed by a qualified physicist. 1013
The shielding design calculations, as-built shielding plans, and the report on the acceptance 1014
testing of the structural shielding should be kept for the duration of use of the room for x-ray 1015
imaging. The American Association of Physicists in Medicine guidance should be used as 1016
appropriate, for modalities not covered in NCRP reports. At the time of this writing, this 1017
includes guidance for PET/CT shielding (AAPM 2006c). 1018
1019
Mobile radiographic equipment is frequently used for bedside examinations. Effective radiation 1020
protection in these circumstances is normally provided through exposure time and distance 1021
(NCRP 1989b; NCRP 2000; NCRP 2004a). When mobile radiographic or fluoroscopic 1022
equipment is used in a fixed location, or frequently in the same location, it is strongly 1023
recommended that a qualified expert evaluate the need for structural shielding (NCRP 2004a). 1024
When radiographic or fluoroscopic equipment is used in a temporary facility (e.g., field 1025
hospital), the effective use of distance, exposure time, or non-structural shielding may eliminate 1026
the need for structural shielding. 1027
1028
1029
REQUESTING AND PERFORMING STUDIES INVOLVING X-RAYS 1030
1031 The following section uses the terms Referring Medical Practitioner and Radiological Medical 1032
Practitioner. The Referring Medical Practitioner is a health professional who, in accordance with 1033
state and federal requirements, may refer individuals to a Radiological Medical Practitioner for 1034
medical exposure (IAEA 2011b). The Radiological Medical Practitioner is a health professional, 1035
with education and specialist training in the medical uses of radiation, who is competent to 1036
independently perform or oversee procedures involving medical radiation exposure in a given 1037
specialty (IAEA 2011b). 1038
1039
REQUESTING STUDIES: REFERRING MEDICAL PRACTITIONERS (REQUESTING 1040
HEALTH PROFESSIONALS) 1041 1042
A medical procedure should only be performed on a patient if it is appropriately justified and 1043
optimized for that particular patient. In this context, “appropriateness” is generally defined in 1044
terms of benefit and risk. The RAND corporation has developed a definition of “appropriate” 1045
16
that is widely used: the expected health benefit (i.e., increased life expectancy, relief of pain, 1046
reduction in anxiety, improved functional capacity) exceeds the expected negative consequences 1047
(i.e., mortality, morbidity, anxiety of anticipating the procedure, pain produced by the procedure, 1048
misleading or false diagnoses, time lost from work) by a sufficiently wide margin that the 1049
procedure is worth doing (NHS 1993; Sistrom 2008). In other words, the anticipated clinical 1050
benefits should exceed all anticipated procedural risks, including radiation risk. This implies that 1051
radiation should be included in the benefit:risk evaluation for each patient both before and during 1052
any procedure. 1053
1054
As with any medical procedure, the requesting or “ordering” provider (i.e., the Referring 1055
Medical Practitioner) should have adequate knowledge of the patient, understand the nature of 1056
the proposed and alternative imaging procedures, and fully comprehend the medical diagnostic 1057
and treatment options available in order to be able to assess the benefit:risk ratios for the imaging 1058
procedures. These ratios balance the benefit of the diagnostic examination being requested 1059
against the stochastic and deterministic risks to the patient from radiation exposure during 1060
imaging, as well as the benefits and risks from alternative radiological and non-radiological 1061
procedures. The Referring Medical Practitioner (with privileges at the facility/within the 1062
healthcare network for the ordering of radiographic studies) should have determined that 1063
sufficient clinical history, symptoms, signs, or findings exist to necessitate the examination. All 1064
exposures to radiation should involve a benefit:risk analysis, in order to ensure that the expected 1065
benefits of the examination outweigh the potential risks, and that the most appropriate 1066
radiological or non-radiological procedure is selected on the basis of its benefit:risk ratio. In all 1067
cases, the use of radiation in diagnostic medical imaging should be justified and optimized. This 1068
is the responsibility of all involved providers and technologists. Dose management begins when 1069
a patient is considered for a procedure involving ionizing radiation, involves equipment setup 1070
before the exam begins, and ends when any necessary radiation-related follow-up is completed. 1071
1072
Physicians and licensed independent practitioners (Referring Medical Practitioners) who have 1073
the legal authority and privileges to request diagnostic imaging studies involving ionizing 1074
radiation should have a basic understanding of radiation effects and protection methods. Also, 1075
they should have an appreciation for the radiation dose involved in a study and the potential 1076
effects of this dose over the lifetime of the patient to properly assess the benefit:risk ratio. The 1077
justification of medical exposure for an individual patient should be carried out by the Referring 1078
Medical Practitioner, in consultation with the Radiological Medical Practitioner when 1079
appropriate. Each health care facility should establish a formal mechanism whereby Referring 1080
Medical Practitioners have sources of information available at the time of ordering regarding 1081
appropriate diagnostic imaging methods to answer the clinical question and to optimize ionizing 1082
radiation dose to the patient. These may include decision support software or appropriateness 1083
criteria. A mechanism for consultation with Radiological Medical Practitioners should also be 1084
made available. 1085
1086
One of the most important methods for reducing radiation exposure is the elimination of 1087
clinically unproductive examinations. This continues to be a significant, but largely unrealized 1088
opportunity. Appropriate education of the requesting physician, utilization of existing current 1089
recommendations (such as the ACR Appropriateness Criteria (ACR 2012)) and consultation with 1090
a Radiological Medical Practitioner prior to generation of the examination request can all 1091
17
improve the probability that the most appropriate examination is performed relative to the 1092
clinical question. Automated algorithms integral to electronic ordering systems have the 1093
capability to alert the referring provider to more appropriate examinations, and can alert them to 1094
unnecessary repeat examinations. 1095
1096
Follow-up examinations are commonly done so that significant changes in clinical information 1097
are obtained for making proper decisions on continuation or alteration of the management of the 1098
patient. These examinations may result in unnecessary patient exposure if repeated before 1099
significant changes in patient status occur; therefore, it is recommended that they be done only at 1100
time intervals long enough to make proper decisions concerning continuation or alteration of 1101
treatment. 1102
1103
Qualifications to Request X-ray Examinations 1104 1105
Requests for imaging examinations involving the use of x-rays in Federal health care facilities 1106
should be made only by physicians or other Referring Medical Practitioners who are licensed in 1107
the United States or one of its territories or possessions and privileged within the healthcare 1108
facility or network. Properly trained individuals such as physician assistants and persons in 1109
postgraduate medical training status do not have to meet the above requirements, but should be 1110
under the general supervision of a licensed physician who does. 1111
1112
It is recognized that medical students, interns, residents, and some physician assistants may not 1113
have developed medical judgment as to which test would be most efficacious. Such lack of 1114
experience is remedied by work under conditions where there is sufficient expert supervision and 1115
radiology providers available for consultation who can monitor the appropriateness of 1116
examinations based on the clinical history and can provide assistance. 1117
1118
In addition to the privileges for which broad qualifications are needed, there are a number of 1119
specialties which require only limited types of x-ray examinations. For example, Doctors of 1120
Dental Surgery or Dental Medicine may request appropriate examinations of the head, neck, and 1121
chest, although such requests are normally confined to the oral region. 1122
1123
Variances to the above qualification requirements should occur only for emergency or life-1124
threatening situations, such as natural disasters. Also, non-peacetime operations in the field or 1125
aboard ship could require such variances. Equipment designed for field use might need to be 1126
operated by those personnel available to assist in the performance of necessary medical, dental, 1127
and veterinary services. 1128
1129
PERFORMING AND SUPERVISING STUDIES: RADIOLOGICAL MEDICAL 1130
PRACTITIONERS AND TECHNOLOGISTS 1131 1132
Responsible use of medical, dental, and veterinary x-ray equipment involves restricting its 1133
operation to properly qualified and supervised individuals. Such a policy should be established 1134
for each x-ray facility by the responsible authority upon the recommendations of medical, dental, 1135
and veterinary staff. Eligible radiological medical practitioners include those who are granted 1136
privileges for equipment use on the basis of the needs of patients served by the facility. These 1137
18
are privileges to use radiation-emitting equipment and are separate from privileges to perform 1138
procedures. Such privileges might include, as part of their practice, the use of CT equipment by 1139
radiologists and cardiologists; the use of fluoroscopes by cardiologists, radiologists, urologists, 1140
and others; and the use of dental x-ray equipment by dentists. Before radiological medical 1141
practitioners are granted equipment use privileges, it is strongly recommended that they receive 1142
adequate training in equipment use and radiation protection. However, specific protocols 1143
limiting equipment use privileges to specified types of radiological medical practitioners should 1144
be part of the written policy statement. 1145
1146
After completion of an accredited educational program and certification by a state or voluntary 1147
credentialing organization, radiologic technologists should be able to produce radiographic 1148
images with lower average patient doses than incompletely-trained or non-credentialed 1149
operators. Non-credentialed operators may have little or no formal training in anatomy, patient 1150
positioning, or radiation protection practices. Inadequately trained operators are likely to 1151
irradiate patients and themselves unnecessarily (EPA 2000). Personnel responsible for image 1152
acquisition should be trained in patient preparation and positioning, selection of technique 1153
factors and acquisition parameters, radiation protection measures, routine equipment QC, digital 1154
image post-processing and image processing. They should also be able to reduce to a minimum 1155
the number of repeat examinations. Performance of imaging examinations by incompletely 1156
trained personnel is not justified except for emergent circumstances. 1157
1158
In order to achieve lower patient doses, the operator’s manual should be readily available to the 1159
user, and equipment operation should be guided by the manufacturer’s instructions, including 1160
any appropriate adjustments for optimizing dose and ensuring adequate image quality. 1161
1162
Radiological Medical Practitioners 1163
1164 A Radiological Medical Practitioner is a health professional, with education and specialist 1165
training in the medical uses of radiation, who is competent to independently perform or oversee 1166
procedures involving medical exposure in a given specialty. Within the Radiology department, 1167
this individual is typically a radiologist. Other individuals who use ionizing radiation for 1168
imaging, usually outside the Radiology department (e.g., cardiac catheterization or fluoroscopy 1169
in the operating room), are also considered Radiological Medical Practitioners. These 1170
individuals, when acting as a Radiological Medical Practitioner, have the same responsibilities 1171
for imaging protocols and for supervising equipment operation that would otherwise be assigned 1172
to a radiologist. The Radiological Medical Practitioner is also responsible for optimizing the 1173
dose of ionizing radiation. 1174
1175
Radiologists 1176 1177
A radiologist is a licensed physician or osteopath who is certified in Radiology or Diagnostic 1178
Radiology by the American Board of Radiology or the American Osteopathic Board of 1179
Radiology (AOBR), or has completed a diagnostic radiology residency program approved by the 1180
Accreditation Council for Graduate Medical Education (ACGME) or the American Osteopathic 1181
Association (AOA). Within the Radiology department, the radiologist generally serves as the 1182
19
Radiological Medical Practitioner. In addition to interpreting imaging studies, radiologists set 1183
protocols for examinations involving x-ray systems and play a critical role in the performance of 1184
studies. Imaging protocols should be devised for each imaging system and each imaging study. 1185
These protocols should provide adequate image and study quality while optimizing the radiation 1186
dose, particularly to radiosensitive tissues. Considerations include identifying the appropriate 1187
area of coverage, collimation, number of views to be acquired, and image quality needs (which 1188
dictates the required x-ray beam energy and intensity). For CT, this includes CT-specific 1189
technique factors, area of coverage, and the number of CT examination phases. Radiologists are 1190
a source of knowledge on the advantages and disadvantages of different imaging modalities and 1191
should be consulted when that expertise is needed. 1192
1193
Medical Radiologic Technologists 1194 1195
Medical Radiologic Technologists (MRTs) and Registered Cardiovascular Invasive Specialists 1196
(RCIS) having appropriate radiation and other training are the personnel who operate the 1197
imaging equipment, deliver the radiation to the patients and capture the diagnostic images. As 1198
such, they are extremely important in the optimized use of diagnostic imaging. Operator 1199
competence is normally achieved by successful completion of a training program which provides 1200
both a didactic base and sufficient practical experience. The training program should be 1201
accredited by a mechanism acceptable to the appropriate credentialing organization, e.g., the 1202
American Registry of Radiologic Technologists or Cardiovascular Credentialing International 1203
(CCI). Continuing competence and professional growth should be encouraged with specific 1204
opportunities to further the technologist's knowledge and skills through attendance at workshops 1205
or by other means of training. 1206
1207
The radiologic technologist should be familiar with and facile at utilizing the imaging systems 1208
and the techniques and technology available to them to reduce patient radiation dose while 1209
producing clinically adequate images. As a critical part of the healthcare team, they should be 1210
empowered to question techniques and requests when alternatives which would deliver lower 1211
doses are available. 1212
1213
SCREENING AND ADMINISTRATIVE PROGRAMS 1214
1215 Screening programs using ionizing radiation should be justified, and the doses should be 1216
optimized for screening. It is important to keep requirements current with technological 1217
advances. There are several reasons why individuals without known disease or symptoms may 1218
be referred for imaging examinations. Some are specifically for administrative or occupational 1219
safety programs such as the annual postero-anterior chest radiograph acquired to evaluate for 1220
pneumoconiosis in coal, silica and asbestos workers. Self-referral by patients for screening 1221
imaging to evaluate for disease in the absence of symptoms is an increasingly common 1222
occurrence whose appropriateness should be weighed and the individual counseled on the 1223
benefits and risks. If screening has been shown to have a positive benefit:risk ratio, it is 1224
generally warranted. As an example, in 2012, one accepted screening program is mammography 1225
(ACR 2009b). Generally, neither screening nor elective x-ray examinations should be performed 1226
on pregnant women. 1227
1228
20
Chest Radiography 1229
1230 Screening for tuberculosis is no longer performed in the United States with chest radiography, 1231
although this technique may still be required during disaster relief and humanitarian operations 1232
in other parts of the world. 1233
1234
“Routine” radiographs without specific indications or symptoms should not be performed on 1235
admission to the hospital or while an inpatient. 1236
1237
Standard postero-anterior chest radiographs are performed periodically to evaluate certain 1238
populations with high occupational risk for lung disease. These populations include coal miners, 1239
asbestos workers, silica workers and a few other specific populations. There are typically 1240
specific requirements for these images; yet, as with all other images, it is important to optimize 1241
the radiation dose delivered to the individual. 1242
1243
Mammography 1244 1245
Breast cancer is a common and significant health risk in the United States. Because of the 1246
importance of early detection in control and survival, mammography is an important screening 1247
modality. This technique has improved considerably since the publication of Federal Guidance 1248
Report 9 (EPA 1976), especially with respect to reducing radiation dose per examination. 1249
Women and their health care providers are encouraged to refer to the most current NCI 1250
recommendations when deciding upon breast cancer screening examinations. Mammography 1251
facilities must comply with the Mammography Quality Standards Act (MQSA) regulations 1252
(FDA 2012c). 1253
1254
REFERRAL AND SELF-REFERRAL EXAMINATIONS 1255 1256
There are two types of self-referral. One is patient self-referral, where patients refer themselves 1257
for an imaging procedure without having a physician request (referral). The other is physician 1258
self-referral where physicians see patients, decide to perform imaging procedures on those 1259
patients, and then refer the patients to themselves or their own medical practice for the 1260
procedure. 1261
1262
Patients Requesting Imaging on Themselves without a Referral from a Licensed 1263
Independent Practitioner (Referring Medical Practitioner) 1264 1265
With the increased capabilities of imaging systems and particularly with CT imaging, there has 1266
been an increased interest in and demand for use of this technology to screen for pre-clinical 1267
disease in the general population. Such screening programs should be subjected to rigorous 1268
scientific evaluation, as has been done for mammography, to ensure that the risk posed to the 1269
population screened does not outweigh the benefits in detection of disease. 1270
1271
Physician Self-Referral 1272 1273
In this context, self-referral examinations are examinations requested or ordered by the same 1274
21
physician who subsequently performs or interprets them. They are frequently performed by 1275
equipment operators lacking adequate training and having supervision by health professionals 1276
with inadequate radiologic experience. Some examinations performed by non-radiologists may 1277
occur because of the convenience of having the x-ray unit and the patient in the same location, 1278
or, in the case of civilian contract services, need to justify the equipment purchased or 1279
maintenance costs. 1280
1281
Unnecessary radiation exposure caused by self-referral practices that are not diagnostically 1282
relevant generally need not occur in Federal health care institutions where facilities staffed by 1283
radiologists are normally provided. Exceptions could be small operational units, such as ships, 1284
field units, or isolated stations where the normal workload does not justify a staff radiologist. 1285
Thus, the conduct of self-referral x-ray examinations should be permitted only by a physician 1286
whose qualifications to supervise, perform, and interpret diagnostic radiologic procedures have 1287
been demonstrated to the appropriate authorities. 1288
1289
It is recognized that limited self-referral type examinations are performed in Federal medical 1290
centers in certain clinical specialties. The use of such self-referral x-ray examinations should, 1291
however, be limited to studies unique to and required by the specialty of the physician 1292
performing them and be consistent with a peer review policy. 1293
1294
Self-referral practices in federal facilities are expected to be immune to economic considerations 1295
for the referring physician. Self-referral practices in contract civilian facilities can lead to 1296
overutilization due to economic incentives for the referring physician and should be prohibited. 1297
Exception may be made in remote areas where no practicable alternative exists. 1298
1299
COMMUNICATION AMONG PRACTITIONERS 1300 1301
Optimal medical care requires appropriate interaction between the Referring Medical Practitioner 1302
and the Radiological Medical Practitioner. The information technology system also plays an 1303
important role. Requests for x-ray examinations should be considered as medical consultations 1304
between the Referring Medical Practitioner and the Radiological Medical Practitioner. A request 1305
should state the diagnostic objective of the examination and should detail relevant medical 1306
history including results of previous diagnostic x-ray examinations and other relevant tests. 1307
1308
Whenever possible the Radiological Medical Practitioner should review all examination requests 1309
requiring fluoroscopy, CT, or other complex or high-dose studies before the examination is given 1310
and preferably before it is scheduled. For this reason, it is important that a thorough and accurate 1311
patient history be included with each examination request. Based upon the clinical question, 1312
history, and relevant available previous studies, the Radiological Medical Practitioner should 1313
direct the examination using standard protocols, with any appropriate addition, substitution, or 1314
deletion of views or sequences. It is preferable that changes in the examination be done in 1315
consultation with the Referring Medical Practitioner. 1316
1317
Effective communication of the findings is an essential component of imaging studies. Facilities 1318
are strongly encouraged to have policies on the communication of findings that are consistent 1319
with the guidelines of accrediting organizations and professional societies (ACR 2010). 1320
22
1321
The provision of care by more than one medical facility may result in duplication of imaging 1322
studies. To prevent this, and as technology permits, the Referring Medical Practitioner should 1323
review the patient’s medical record to determine whether the proposed imaging study would 1324
duplicate a previous study. This requires that the reports and images from all studies are 1325
accessible through the patient’s Electronic Health Record (EHR) (Congress 2007). 1326
1327
When referral from one facility to a second is anticipated, only the studies needed for proper 1328
referral should be performed in the first facility. Those imaging studies should be made 1329
available to the second medical facility concurrent with the transfer, either electronically or in 1330
hard copy format. 1331
1332
23
TECHNICAL QUALITY ASSURANCE IN MEDICAL IMAGING WITH X-RAYS 1333 1334
Quality assurance refers to those steps that are taken to make sure that a facility consistently 1335
produces images that are adequate for the purpose with optimal patient exposure and minimal 1336
operator exposure. Quality assurance may be divided into two major categories: quality 1337
administration and quality control. 1338
1339
Quality administration refers to the management aspect of a quality assurance program. It 1340
includes those organizational steps taken to make sure that testing techniques are properly 1341
performed and that the results of tests are used to effectively maintain a consistently high level of 1342
image quality. An effective program includes assigning personnel to determine optimum testing 1343
frequency of the imaging devices, evaluate test results, schedule corrective action, provide 1344
training, and perform ongoing evaluation and revision of the quality assurance program. 1345
1346
Quality control comprises the procedures used for the routine physical testing of the primary 1347
components of the imaging chain from the x-ray source, through processing, to the viewing of 1348
images, as addressed in Table 1. Each facility, through its radiation quality control team (e.g. 1349
qualified physicist and biomedical maintenance personnel), needs to track maintenance and 1350
monitoring procedures. 1351
1352
Each facility performing medical imaging with x-rays should establish in writing and implement 1353
a technical quality assurance, quality administration, and quality control program that conforms 1354
to the most recent version of the “ACR Technical Standard for Diagnostic Medical Physics 1355
Performance Monitoring of Radiographic and Fluoroscopic Equipment” (ACR 2006b) and the 1356
“ACR Technical Standard for Diagnostic Medical Physics Performance Monitoring of Computed 1357
Tomography (CT) Equipment” (ACR 2007b). The program should include all aspects of the 1358
imaging process from image acquisition through image display. For film-screen imaging, it 1359
should include film and chemical expiration dates and storage requirements, monitoring of film 1360
processing, dark-room conditions, cleaning of intensifying screens, the cleaning and performance 1361
of view boxes, the ambient viewing conditions in rooms used for image interpretation, and image 1362
repeat analysis. For imaging with solid state image receptors such as computed radiography and 1363
direct radiography, it should include testing calibration of the CR plate readers and direct digital 1364
detectors, cleaning and inspection of CR plates, image repeat/reject analysis, calibration of 1365
detector exposure indices, monitoring of doses to the image receptors(exposure indices), 1366
uniformity of the sensitivity of the image receptor inventory, cleaning and monitoring of the 1367
luminance and calibration of video monitors used for initial image QC and interpretation, and the 1368
ambient viewing conditions in rooms used for image interpretation. Monitors for interpretation 1369
of grayscale images should be calibrated to the DICOM Grayscale Standard Display Function 1370
(NEMA 2009). These quality assurance measures are addressed in the Radiography section 1371
under Testing and Quality Assurance. 1372
1373
TECHNIQUE FACTORS 1374 1375
Technique factors should be established for each imaging procedure. For radiographic 1376
examinations, these include kV, mAs and exposure time if automatic exposure control is not 1377
used, and perhaps choice of image receptor. For CT examinations, these include kV, mA, 1378
24
rotation speed, pitch, selection of a mode in which mA is modulated during the scan (if 1379
available), and degree of noise reduction (if available). Technique factors may be programmed 1380
into the imaging device, or they may be manually selected. If they are programmed in, 1381
programming should be consistent across all similar devices at a facility. Technique factors 1382
should be chosen that produce a clinically-adequate image at the least dose to the patient, not an 1383
ideal image. Whenever possible, technique factors should be adjusted to the thickness of the 1384
patient. 1385
1386
If the review of technique factors used clinically or the comparison of dose indices indicates that 1387
an optimum balance has not been achieved between patient dose and image quality or that 1388
patient doses exceed national standards, the technique factors, whether posted in a chart or 1389
programmed into the imaging device, and/or selection of image receptor, should be modified as 1390
necessary. 1391
1392
TESTING BY A QUALIFIED PHYSICIST 1393 1394
It is strongly recommended that the technical quality assurance program includes testing by a 1395
qualified physicist of all imaging equipment producing x-rays. The equipment should be tested 1396
after installation but before first clinical use, annually thereafter, and after each repair or 1397
modification that may affect patient dose or image quality. Testing after repair or modification 1398
should be performed before clinical use of the equipment. The testing, including a summary of 1399
methods, instruments used, measurements and deficiencies identified, should be documented in a 1400
written report signed by the qualified physicist. The testing should include the items in Table 1 1401
below: 1402 1403
Table 1. Testing Frequency of Imaging Equipment that Produces X-Rays
TASK INITIAL AFTER
MODIFICATION
OR REPAIR (a)
ANNUAL
Measure radiation output parameters, including
beam intensity and beam quality
X X X
Test modes of operation used clinically, such as
automatic control systems (e.g., automatic
exposure controls of radiographic systems,
automatic exposure rate controls of fluoroscopy
systems.)
X X X
Assess image quality X X X
Determine Detector Exposure Index Accuracy
(b)
X X X
Evaluate the accuracy of patient dose or dose
rate indicators
X X X
Assess the typical patient dose delivered for
various examinations for comparison to national
reference levels
X X X
Perform an acceptance test X X
25
Table 1. Testing Frequency of Imaging Equipment that Produces X-Rays
TASK INITIAL AFTER
MODIFICATION
OR REPAIR (a)
ANNUAL
Review the overall technical quality control
program
X
Perform a periodic review of all CT protocols (c) X X
(a) Testing following repairs or modifications may be limited to features and parameters that
would be affected by the repairs or modification.
(b) Determine accuracy of detector exposure indices according to AAPM TG116 methodology
(AAPM 2009) and manufacturer’s recommendations if available.
(c) The review of CT protocols should be performed together by the radiologist, CT technologist,
and medical physicist. Consider staggering annual reviews throughout the year to maintain
momentum without impacting schedules.
1404
The qualified physicist may be assisted by other properly trained persons in obtaining test data 1405
for performance monitoring. These persons should be trained by the qualified physicist in the 1406
techniques for performing the tests, the function and limitations of the imaging equipment and 1407
test instruments, the reasons for the tests, and the importance of the test results. The qualified 1408
physicist should be present at the facility for the initial and annual testing and should promptly 1409
review, interpret, and approve all data measurements and test results. 1410
1411
EQUIPMENT FAILURE 1412 1413
When x-ray imaging equipment fails to meet the performance specifications, the equipment 1414
should be promptly adjusted or repaired to correct the deficiency or should be removed from 1415
clinical use. A written or electronic record should be kept of the correction of such deficiencies 1416
in accordance with the organization’s record keeping policy. The record should include the date 1417
of correction and the action taken to correct the deficiency. 1418
1419
DEFICIENCY CORRECTION VERIFICATION 1420 1421
After correction of deficiencies that affect patient dose or image quality, the equipment should be 1422
tested promptly, by or under the supervision of a qualified physicist, to verify that the deficiency 1423
was corrected and that the correction did not cause other deficiencies. 1424
1425
DOSIMETRY 1426 1427
Patient dose indices, measured at clinically-used technique factors by or under the supervision of 1428
a qualified physicist, should be available for review. For radiography, entrance skin exposures 1429
for common projections should be listed for a patient of typical thickness. For fluoroscopy 1430
systems that have appropriate dosimetry measurement capabilities (e.g., air kerma or dose area 1431
product), the accuracy should be measured and recorded. For fluoroscopy systems that do not 1432
have dosimetry indicators, the typical and maximal entrance skin exposure estimates should be 1433
measured and recorded for each fluoroscopic mode of operation for small, average, and large 1434
patient thicknesses. 1435
26
REFERENCE LEVELS 1436 1437
The primary purpose of an imaging study using ionizing radiation is to answer a clinical question 1438
or assist in making a diagnosis. Production of such a study results in two determinants: the 1439
qualitative evaluation by the health professional of the clinical value of the study, and the amount 1440
of radiation exposure required to conduct it. Each study should be evaluated for acceptable 1441
quality by a qualified individual (technologist or Radiological Medical Practitioner). A 1442
representative sampling and assessment of exposure indicators from each modality should be 1443
performed at least annually, but preferably quarterly, by a radiologic technologist under the 1444
guidance of a qualified physicist. 1445
1446
Reference levels (RLs) are values used as quality assurance and quality improvement tools. 1447
Quality improvement uses quantitative and qualitative methods to improve the safety, 1448
effectiveness, and efficiency of health care delivery processes and systems. Left unchanged, a 1449
system will produce the same results it has been achieving or degenerate. To achieve a higher 1450
level of performance, the system must be changed. 1451
1452
RLs were first introduced in the 1990s (ICRP 2003; Wall and Shrimpton 1998). RLs are used to 1453
help avoid radiation dose to the patient that does not contribute to the medical imaging task 1454
(ICRP 2003). They are intended to provide guidance on what is achievable with current good 1455
practice rather than optimum performance, and help identify unusually high radiation doses or 1456
exposure levels (ACR 2008b; IAEA 1996). RLs are a guide to good practice, but are neither 1457
dose limits nor thresholds that define competent performance of the operator or the equipment 1458
(Vañó and Gonzalez 2001). For assessments where the dose metric is determined using a 1459
phantom, a value above the reference level requires investigation. On the other hand, for 1460
interventional procedures, if the mean dose metric for a number of cases of a procedure exceeds 1461
the reference level, it does not always mean that the procedure has been performed improperly. 1462
Similarly, a mean dose metric for a procedure that is less than the reference level does not 1463
guarantee that the procedure is being performed optimally (Vañó and Gonzalez 2001). 1464
1465
These levels are based on exposure to a standard phantom or actual patient dose metrics for 1466
specific procedures measured at a number of representative clinical facilities. RLs are set at 1467
approximately the 75th
percentile (third quartile) of these measured data. The use of RLs is 1468
supported by national and international advisory bodies (Amis et al. 2007; ICRP 2000a). These 1469
and other organizations have provided guidelines on measuring radiation dose metrics and 1470
setting reference levels (IAEA 1996; ICRP 1991a; ICRP 1996; ICRP 2007c; Wall and Shrimpton 1471
1998). RLs can be specific to the country or region, and may be derived from multinational, 1472
national or local data (ICRP 2003; ICRP 2007b). As of 2012, U.S. reference levels are not 1473
available for most imaging studies. In order to generate national RLs for the U.S., it is essential 1474
that institutions where these procedures are performed submit radiation dose metrics to a central 1475
dose registry. 1476
1477
Each institution or individual practitioner should use reference levels as a quality improvement 1478
tool by collecting and assessing radiation dose data. Standard phantoms are used where the 1479
procedure is standardized (e.g., chest radiograph or head CT). Patient dose metric data are 1480
collected if the procedure is individualized for each patient (such as fluoroscopically guided 1481
27
interventions) and should be collected for standardized procedures as well. The mean radiation 1482
dose for the examination is then compared to the reference level for that examination (ICRP 1483
2003). If the mean radiation dose at the facility exceeds the reference level, equipment and 1484
clinical practices should be investigated in order to reduce radiation doses (NRPB 1990; Wall 1485
2001). Equipment function should be investigated first, followed by review of the clinical 1486
protocol (Vañó and Gonzalez 2001). Investigations are also appropriate where local values are 1487
substantially below the RLs, as excessively low doses may be associated with poor image quality 1488
(Balter et al. 2008; IAEA 2009). As appropriate, operator performance may be assessed if no 1489
other cause is found. The development of reference levels requires consideration of the 1490
technique factors which most affect patient exposure. The Nationwide Evaluation of X-ray 1491
Trends (NEXT) is a program conducted by the Food and Drug Administration (FDA) in 1492
conjunction with the States and the Conference of Radiation Control Program Directors 1493
(CRCPD) (FDA 2010a). The NEXT data provide a profile of aspects of medical and dental 1494
imaging using ionizing radiation in the United States at the time of survey. These data provide a 1495
window into clinical practice because they reflect the myriad of combinations of imaging 1496
equipment, technique factors, and the skills of equipment operators. Therefore, regardless of the 1497
specific details of technique or combinations of all these factors, the frequency distributions of 1498
dose derived from the NEXT data were assumed to be sufficiently representative of the complex 1499
interaction of Referring Medical Practitioner preference, Radiological Medical Practitioner 1500
preference, operator technique, and x-ray equipment performance for each of the selected 1501
standard examinations. Thus, NEXT data, when available and current, serve as a useful source 1502
for the development of national reference levels in the U.S. (ACR 2008b). 1503
1504
Professional organizations in the U.S., such as the American College of Radiology (ACR 2008b) 1505
and the American Association of Physicists in Medicine (Gray et al. 2005), support the use of 1506
third quartile values of particular dose indices. It is important, however, to emphasize that with 1507
good technique, practicable levels of exposure for most patients will be below these levels. 1508
1509
The ICRP considers RLs a useful tool to help optimize patient radiation dose in fluoroscopically 1510
guided interventional (FGI) procedures (ICRP 2007c). As of 2012, some studies have presented 1511
RLs for cardiovascular procedures (Balter et al. 2008; D'Helft et al. 2009; Neofotistou et al. 1512
2003; Peterzol et al. 2005) and a limited number of interventional radiology procedures (Aroua 1513
et al. 2007; Brambilla et al. 2004; Hart et al. 2009; Miller et al. 2009; Tsalafoutas et al. 2006; 1514
Vano et al. 2008a; Vano et al. 2009; Vano et al. 2008b; Verdun et al. 2005). Unfortunately, the 1515
observed distributions of patient doses for most types of FGI procedures are very wide, because 1516
the dose for each instance of a procedure is strongly dependent on individual clinical 1517
circumstances. A potential approach is to include the ‘complexity’ of the procedure in the 1518
analysis (Balter et al. 2008; IAEA 2009; ICRP 2007c). Since, as of 2012, complexity cannot be 1519
quantified (with the exception of some interventional cardiology procedures), this adjustment is 1520
not possible for FGI procedures (Balter et al. 2008; IAEA 2009). Because of the high individual 1521
variability of patient dose in cases of FGI procedures, the number of cases recommended in the 1522
literature as sufficient to provide adequate radiation dose data for a single facility varies from 10 1523
to >50 (Vano et al. 2008a; Wall and Shrimpton 1998). 1524
1525
It is expected that U.S. reference levels will decrease over time as outlier institutions improve 1526
their equipment and practices. In the United Kingdom, reference levels derived from data in the 1527
28
2000 review were approximately 20% lower than those derived from data in the 1995 review and 1528
approximately half of those determined in the mid-1980s (Hart et al. 2009). 1529
1530
For each type of examination there exists, within available technology, an optimal combination 1531
of imaging equipment and technique factors to produce adequate images at doses below the 1532
reference level. Hence, it is important to evaluate each system’s performance to determine 1533
whether dose is optimized and to maintain this by establishing appropriate procedures and 1534
conducting periodic monitoring. 1535
1536
1537
GUIDANCE BY DIAGNOSTIC AND INTERVENTIONAL MODALITY 1538
1539
INTRODUCTION 1540 1541
Except in emergency situations, informed consent should be obtained from the patient or the 1542
patient’s legal representative and appropriately documented prior to the initiation of any 1543
procedure that is likely to expose the patient, or fetus if the patient is pregnant, to significant 1544
risks and potential complications. When obtaining informed consent for image-guided 1545
procedures using ionizing radiation that are known to be potentially high dose, an estimation of 1546
the anticipated risks from the radiation dose should be communicated to the patient as part of the 1547
overall discussion of risks (NCRP 2010). When a delay in treatment would jeopardize the health 1548
of a patient and informed consent cannot be obtained from the patient or the patient’s legal 1549
representative, an exception to obtaining informed consent is made (ACR 2006a). 1550
1551
Once the physician or dentist determines that the prescription of an x-ray examination is 1552
warranted for diagnostic purposes, other factors become important in limiting patient exposure. 1553
Optimization of patient dose may not be accomplished, even when well-designed equipment is 1554
used, unless appropriate quality assurance programs exist to keep it functioning properly and 1555
those who operate it are properly qualified to use the features of the equipment. These latter 1556
considerations are discussed in the chapter on Technical Quality Assurance in Medical Imaging 1557
with X-Rays. To ensure that x-ray equipment used is justifiably representative of present day 1558
technological advances, authorities should develop and periodically review a planned 1559
replacement schedule for all types of diagnostic x-ray equipment used in their programs. 1560
1561
All x-ray equipment used for the imaging of humans for medical purposes should be maintained 1562
so that it conforms, throughout its useful lifetime, to applicable FDA regulations (FDA 2012g). 1563
Furthermore, users should be aware of upgrades to software and hardware that enhance safety. 1564
These should be evaluated and considered for implementation. 1565
1566
The qualifications of x-ray imaging equipment operators should be defined by the responsible 1567
authority in a written protocol which details: 1) who may operate x-ray imaging equipment and 1568
the supervision required, 2) the education, training, and proficiency requirements for x-ray 1569
imaging equipment operators, and 3) requirements for continuing education and demonstration 1570
of proficiency. This policy should be reviewed and revised as required. 1571
1572
Prior to each examination requiring ionizing radiation, there should be a pre-procedure 1573
29
“verification” that patient identity, intended procedure and positioning, and equipment are 1574
correct. Also, the technologist should confirm that the patient, if female, is not pregnant and 1575
that, if contrast media is to be used, the patient is not allergic to it. Invasive procedures and CT 1576
examinations require both pre-procedure “verification” and “time-out” processes. Those 1577
processes should be as specified by The Joint Commission for invasive procedures under the 1578
Universal Protocol (The Joint Commission 2012a; The Joint Commission 2012b). 1579
1580
30
RADIOGRAPHY 1581 1582
General radiography is a service usually provided by a Radiology Department, either in a central 1583
department or satellite facilities. Requests (orders) for general radiography services are 1584
performed based on protocols for standard views of each anatomic area, modified, if needed, to 1585
suit special requests or circumstances. Authorized variations to these protocols should be made 1586
for patient age and body habitus. Each medical center should have a written policy for the safe 1587
use of radiographic equipment. This policy should apply to all radiographic equipment, whether 1588
fixed or portable. This policy should: 1589
1590
1. require testing of the radiographic equipment by a qualified physicist (or under their 1591
guidance for facilities or locations where it is not practicable to provide such staffing), 1592
2. require training and credentialing of persons operating or directing the operation of 1593
radiographic equipment, and 1594
3. specify procedures for the safe use of the equipment, including dose management and 1595
recordkeeping. 1596
1597
Equipment 1598 1599
Beginning in the 1990s, a transition occurred from film-screen radiography to digital 1600
radiography (radiography using other image receptors). These newer image receptor 1601
technologies include storage phosphor plates and several direct-image-capture technologies. All 1602
of these digital radiography technologies produce digital images that are most commonly viewed 1603
on video monitors, although the images may be printed on film using a laser printer, chemically 1604
developed, and examined on a view box. 1605
1606
With film-screen radiography, there is feedback to the technologist if technique factors, primarily 1607
mAs, result in an excessive exposure to the patient. The pertinent measure of the response to 1608
radiation exposure is the optical density of the film. Optical density is a non-linear function of 1609
radiation exposure. In film-screen radiography, when imaging a specific projection of a 1610
particular patient, only a narrow range of patient exposures will produce an adequate image. An 1611
exposure greater than this range produces an “overexposed” film with excessive optical density 1612
and inadequate image contrast, and an exposure below this range produces an “underexposed” 1613
film with excessively low optical densities and inadequate image contrast. Thus, provided that 1614
an appropriate x-ray tube voltage is used and the film is properly developed, the choice of film-1615
screen combination largely determines the radiation exposure to a patient of a given size. 1616
1617
There are advantages and disadvantages to digital image receptors in comparison to film-screen 1618
receptors. Digital receptors respond to radiation over a wide range of exposures. The statistical 1619
noise in the image varies with the exposure, with higher exposures producing images with 1620
relatively less statistical noise. One of the many advantages is that the wide range of exposures 1621
permits the exposure for a particular image to be matched to the clinical task – for an imaging 1622
procedure in which more statistical noise can be tolerated, a lower exposure can be used. 1623
Another advantage is that images acquired with overly high exposures and some of those 1624
acquired with overly low exposures may still be useful, avoiding retakes. An image acquired 1625
31
with an excessively low exposure will have excessive statistical noise, but this may not render 1626
the image uninterpretable. 1627
1628
There are also disadvantages to digital radiography. Digital image receptors facilitate acquiring 1629
multiple images, which may encourage the acquisition of more images than are clinically 1630
necessary. As of 2012, radiography with storage phosphor plates may require significantly 1631
larger patient exposures, by a factor of 1.5 to 2, than rare-earth phosphor film-screen systems to 1632
produce images of equivalent quality (Compagnone et al. 2006; Seibert et al. 1996). In digital 1633
radiography, an excessive exposure decreases statistical noise and will likely produce an image 1634
that is of higher quality than needed for the clinical task. Furthermore, it may not be apparent to 1635
either the technologist or the Radiological Medical Practitioner that the exposure was excessive. 1636
Thus, there may be a tendency for technologists to routinely use unnecessarily high exposures, a 1637
phenomenon called “dose creep” or “exposure creep” (Freedman et al. 1993; Seibert et al. 1996; 1638
Willis and Slovis 2005). Excessive exposures are especially likely when using manually selected 1639
technique factors instead of automatic exposure control. Examinations made using storage 1640
phosphor plates and mobile radiographic machines are particularly susceptible to excessive 1641
exposures. Excessive exposures can also occur due to improper calibration of the automatic 1642
exposure control system, the incorrect configuration of protocols, or the use of an inappropriate 1643
protocol when automatic exposure control is used. Deliberate use of a protocol that provides an 1644
excessive exposure to avoid retakes or criticisms due to underexposure should be avoided. 1645
1646
Testing and Quality Assurance 1647 1648
Quality assurance measures for radiographic imaging using film-screen image receptors are well 1649
established, and are described in several publications (AAPM 2006b; ACR 2006b; NCRP 1650
1989b). These measures include, among others, cleaning of image intensifying screens; 1651
establishing technique charts for exposures; and monitoring film processing, darkroom 1652
conditions, film storage, retakes, inadequate images, view boxes, and viewing conditions. 1653
Digital radiography retains some of the quality assurance issues seen with film screen image 1654
receptors, eliminates others, and adds new ones (AAPM 2005; AAPM 2006a; ICRP 2004). 1655
1656
Storage phosphor image receptor systems and many direct image capture systems provide the 1657
capability to monitor the exposure to the image receptor from each individual imaging exposure, 1658
with a quantity termed the exposure indicator. The exposure indicator relates to receptor 1659
exposure, and not directly to patient dose. As of 2012, each manufacturer of these systems 1660
defines, calculates, and names their exposure indicator differently. These proprietary exposure 1661
indicators are not consistent. Some are proportional to the exposure and others are proportional 1662
to the logarithm of the exposure. Some increase as the exposure to the image receptor increases 1663
and others decrease as the exposure increases. A standard indicator of exposure to the image 1664
receptor (called the Exposure Index) for adoption by all manufacturers was developed and 1665
published in 2009 and adopted by the International Electrotechnical Commission (AAPM 2009; 1666
IEC 2008). Each facility should have a program for monitoring indices of exposure to image 1667
receptors, and work toward adopting the standard index when feasible after it is adopted. 1668
Facilities should work with their Radiological Medical Practitioners and qualified physicists to 1669
develop procedures and establish target Exposure Index values and respective Deviation Index 1670
ranges by category of examination and patient population. 1671
32
1672
Quality assurance measures should be adopted for digital radiography (ACR 2007a). Table 2 1673
below in the procedures section lists these measures. 1674
1675
It is strongly recommended that radiographic technique factors be established for common 1676
procedures. These either should be programmed into the x-ray machine or a technique chart 1677
should be immediately available to the operator. Because of the phenomenon of dose creep, the 1678
use of appropriate technique factors is especially important in digital radiography. The technique 1679
factors for imaging protocols should be optimized for the age and size of the patient, and for the 1680
imaging task. Although a qualified physicist can assist with this process, protocol optimization 1681
also requires the efforts of a Radiological Medical Practitioner. This process can benefit from 1682
the involvement of a technologist and the vendor, as well. It is particularly important to optimize 1683
the technique factors for radiographic imaging protocols performed on infants and children since 1684
the preset vendor protocols may result in unnecessary radiation dose. 1685
1686
Pediatric imaging imposes additional concerns. It is strongly recommended that particular 1687
attention be paid to dose optimization for pediatric patients. For pediatric patients the operator 1688
should determine the need for an anti-scatter grid (if removable) and patient immobilization. 1689
Collimation should be adjusted appropriately and technique charts should be used for those body 1690
parts that do not cover the sensor of the automatic exposure control device. 1691
1692
Personnel 1693 1694
Each person who directs the operation or operates radiographic equipment should be trained in 1695
the safe use of radiographic equipment, in order to ensure adequate image quality and optimize 1696
patient dose. Also see the section on PERFORMING AND SUPERVISING STUDIES: 1697
RADIOLOGICAL MEDICAL PRACTITIONERS AND TECHNOLOGISTS. 1698
1699
Radiological Medical Practitioner 1700 1701
Radiographic equipment should be operated under the general supervision of a physician. This 1702
individual fulfills the responsibilities of the Radiological Medical Practitioner. Depending on the 1703
study, the responsible physician may be a radiologist, a surgeon, a cardiologist, a 1704
gastroenterologist, or another medical specialist. This individual should be appropriately trained 1705
in the imaging modality, should be familiar with the principles of radiation protection, and 1706
should have a sufficient understanding of the medical imaging modality’s features to determine 1707
the appropriate protocol to evaluate the patient’s clinical symptoms. 1708
1709
Technologist 1710 1711
The technologist is responsible for using facility-approved imaging protocols and radiation 1712
protection measures. Technologists should be trained to produce adequate quality radiographic 1713
images and to assist in the quality assurance program. They should also be able to optimize 1714
various technique factors of the x-ray equipment to produce an adequate radiographic image at 1715
the lowest practicable patient dose and to use optimal procedures in working with patients and 1716
ancillary equipment to reduce to a minimum the number of repeat examinations. Some operators 1717
33
have little or no formal training in anatomy, patient positioning, or radiation protection practices. 1718
Performance of x-ray examinations by these inadequately trained individuals is not justified 1719
except for emergencies. 1720
1721
Other personnel 1722
1723
Only personnel with specific, appropriate training should be permitted to operate x-ray 1724
equipment. The use of x-ray equipment by other individuals is warranted only in an urgent or 1725
emergent situation when qualified personnel as specified above are not available to perform the 1726
examination in a timely fashion. 1727
1728
Procedures 1729
1730 It is strongly recommended that a radiologist provide general supervision in facilities performing 1731
radiography. A board certified radiologist is preferred. Periodic review of the radiographic 1732
images should be performed as part of the routine quality assurance process. 1733
1734
X-ray examinations should be performed in accordance with approved imaging protocols. The 1735
technologist should not perform any examination which has not been requested by an authorized 1736
person. 1737
1738
Collimation restricts the useful beam to the clinical area of interest. Collimation to exclude body 1739
areas not being examined should be used to minimize unnecessary exposure. Masking portions 1740
of a digital image is not a substitute for collimation. 1741
1742
If it does not interfere with the examination, contact or shadow shielding, using leaded aprons or 1743
other shields, should be employed to shield those parts of the patient that are particularly 1744
radiosensitive and are within the primary beam. Gonadal shielding should be used as 1745
appropriate. It is strongly recommended that breast shielding be used for scoliosis examinations 1746
on girls and young women. All shields should be placed between the x-ray source and the tissue 1747
to be shielded. When shielding is used, an automatic exposure control sensor should be selected 1748
that is not within the shadow of the shield, or manual exposure control should be used. 1749
1750
A written outline containing the minimum number of views to be obtained and the equipment to 1751
be used for each requested examination should be made available to each Radiological Medical 1752
Practitioner and equipment operator in every radiology facility. Beyond the specified minimum 1753
views, the examination should be individualized according to a patient's needs. 1754
1755
The outline of procedures should indicate who may authorize deviations from the standard set of 1756
views for any examination. Every effort should be made to reduce to a minimum the number of 1757
standard views for any examination. The necessity of additional views, such as comparison 1758
views, should be determined by the Radiological Medical Practitioner. 1759
1760
A periodic review of all standard examination procedures should be performed to determine if 1761
the established routine is achieving the objectives and whether modifications are warranted. 1762
34
Continuation of a standardized examination procedure should be predicated on satisfying the 1763
following criteria: 1764
1765
1. the efficacy of the examination is sufficiently high to assure that the diagnosis could not 1766
have been made with less risk by other non-radiological means or a smaller number of 1767
views, 1768
2. consideration of previous similar examinations performed with multiple views established 1769
that in a significant number of the cases all views were necessary for the diagnoses 1770
rendered, and 1771
3. the yield or outcome of the examinations offsets the radiation exposure delivered. 1772
1773
A periodic review should be performed at least annually by experts designated by departmental 1774
leadership, and with the input of referring physicians. These reviews should consider applicable 1775
regulations as well as the consensus and advice of professional societies concerning the efficacy 1776
of radiologic examinations. 1777
1778
Other quality assurance measures are listed in Table 2 below. The specifics of these measures 1779
may change over time. The user should consult the relevant AAPM testing protocols. 1780
Table 2. Quality Assurance Measures for Film and Digital Modalities
Film-Screen
Radiography
Task Frequency Methodology
Physicist testing See Table 1 See section on Technical Quality Assurance in Medical
Imaging with X-Rays.
Processor Monitoring Daily Clean crossover racks and perform sensitometry test.
Darkroom Cleaning Weekly Check for dust, clutter, etc.
Processor Preventive
Maintenance
Monthly Perform deep cleaning and evaluate darkroom chemicals as
recommended by the manufacturer.
Screen Cleaning Monthly Clean all screens in inventory according to manufacturer’s
recommendations
Repeat Analysis Quarterly Track the repeat/reject rate and ensure it is less than or
equal to 7% (NCRP 1988). Trends indicating deterioration
in performance or increase in patient dose should be
investigated.
Darkroom Fog Annually Lightly expose a film (image a step wedge at 70 kVp, 5
mAs). In the darkroom with safelight on, cover half the
latent image with an opaque material for at least 2 minutes
then develop the film. A visible line between the two parts
of the image indicates a darkroom fog problem.
Film-Screen Contact Test Annually Follow film-screen contact test tool instructions.
Review Local Radiation
Protection and Quality
Control Operating
Instructions
Annually Revise as needed.
35
1781
Computed Radiography
Task Frequency Methodology
Physicist testing See Table 1 See section on Technical Quality Assurance in Medical
Imaging with X-Rays.
Image Plate Erasure Weekly, or
daily if
unsure of
status
Perform primary erasure of each plate following
manufacturer’s instructions. This should be performed
before use if the status of the plate is unknown or fogging is
anticipated. Plates in storage do not require erasing until
used (AAPM 2006a).
Quality Control Phantom
Image Acquisition
Monthly Follow manufacturer’s recommendations.
Transmit Phantom Image
to Interpreting Medical
Treatment Facility (MTF)
Monthly For Teleradiology Sites Only: After acquisition of QC
image, transmit to interpreting MTF for verification of
image quality.
Operator Console At least
Monthly
View and evaluate QC pattern (AAPM 2005), clean
monitors.
Repeat Analysis Quarterly Track the repeat/reject rate and ensure it is less than or
equal to 7% (NCRP 1988). Trends indicating deterioration
in performance or increase in patient dose should be
investigated.
Dose Monitoring Quarterly Review patient dose indices according to manufacturer’s
recommendations.
Detector Exposure Index
Monitoring
Quarterly Review exposure indicators according to AAPM TG116
methodology (AAPM 2009) and compare with guidance
levels. One source for appropriate guidance levels may be
the manufacturer.
Image Plate Inspection
and Cleaning
Quarterly Follow manufacturer’s recommendations for proper
cleaning technique using approved cleaning solution and
proper safety precautions.
Review Local Radiation
Protection and Quality
Control Operating
Instructions
Annually Revise as needed.
1782
Direct Digital
Radiography
Task Frequency Methodology
Physicist testing See Table 1 See section on Technical Quality Assurance in Medical
Imaging with X-Rays.
Quality Control Phantom
Image Acquisition
Weekly Follow manufacturer’s recommendations.
Operator Console At least
Monthly
View and evaluate QC pattern (AAPM 2005), clean
monitors.
36
Direct Digital
Radiography
Task Frequency Methodology
Transmit Phantom Image
to Interpreting MTF
Monthly For Teleradiology Sites Only: After acquisition of QC
image, transmit to interpreting MTF for verification of
image quality.
Repeat Analysis Quarterly Track and trend the repeat/reject rate and ensure it is less
than or equal to 7% (NCRP 1988).
Dose Monitoring Quarterly Review patient dose indices according to manufacturer’s
recommendations.
Detector Exposure Index
Monitoring
Quarterly Review exposure indicators according to AAPM TG116
methodology (AAPM 2009) and compare with guidance
levels. One source for appropriate guidance levels may be
the manufacturer.
Review Local Radiation
Protection and Quality
Control Operating
Instructions
Annually Revise as needed.
1783
Interpretation and QC
Display Monitors
Task Frequency Methodology
User task: Visual
assessment using QC test
pattern
Daily AAPM TG-18 Online Report 3, table 8a or equivalent
(AAPM 2005)
Physicist, technologist
tasks: Display system
performance
Monthly/
Quarterly AAPM TG-18 Online Report 3, table 8b or equivalent
(AAPM 2005)
Physicist tasks: display
system calibration
verification
Initially
and
Annually
AAPM TG-18 Online Report 3, table 8c, or equivalent
(AAPM 2005)
Monitor cleaning Monthly
and as
needed
Clean monitors with cleaner approved by manufacturer
1784
Other External
Equipment
Task Frequency Methodology
Printer quality control See
methodology
Follow manufacturer’s recommendations
Digitizer quality control See
methodology
Follow manufacturer’s recommendations
1785
1786
1787
37
FLUOROSCOPY 1788 1789
Fluoroscopy may be employed by a variety of services in a medical facility to guide procedures, 1790
including imaging. It can be performed with fixed, mobile or portable fluoroscopy systems. 1791
Some fluoroscopically guided procedures can deliver a large radiation dose to the patient, even 1792
when used properly. Prolonged procedures may result in injury, including non-healing ulcers, 1793
and other tissue injuries (FDA 1994). Because staff must remain with the patient in the 1794
procedure room during fluoroscopy, their potential occupational radiation dose is non-trivial. 1795
Each medical center should have a written policy for the safe use of fluoroscopic equipment. 1796
This policy should apply to all fluoroscopy equipment, whether fixed, mobile, or portable, e.g., 1797
mobile C-arm systems and mini C-arm systems. This policy should 1798
1799
1. require testing of the fluoroscopic equipment by or under the direction of a qualified 1800
physicist, 1801
2. require training and credentialing of persons operating or directing the operation of 1802
fluoroscopic equipment, 1803
3. specify procedures for the safe use of the equipment, including dose management and 1804
recordkeeping, and 1805
4. require a clinical QA/QI program for fluoroscopy. 1806
1807
Although the aggregate population effective dose is larger from the use of general purpose 1808
diagnostic equipment and CT, the highest organ doses (especially skin doses) to individuals, 1809
other than in radiation oncology, generally result from interventional fluoroscopic procedures. 1810
These procedures may require high exposure rates for long periods of time; thus, it is of utmost 1811
importance that Federal health care facilities give particular attention to fluoroscopic 1812
examinations. Even for simple and low-dose fluoroscopic examinations, proper training is 1813
required to perform the procedure with the optimal radiation dose. Therefore, x-ray equipment 1814
capability should not exceed the medical mission of the facilities, i.e., fluoroscopy should not be 1815
available in facilities where qualified medical personnel are not assigned. Equipment, physicians 1816
and staff should all meet current guidelines of the American College of Radiology Technical 1817
Standard for Management of the Use of Radiation in Fluoroscopic Procedures and its successors 1818
(ACR 2008c). 1819
1820
Equipment requirements and training requirements for operators differ depending on whether the 1821
procedures to be performed will be relatively low dose or potentially high dose. 1822
Fluoroscopically guided procedures should be classified as potentially high radiation dose if 1823
more than 5% of cases of that procedure result in an air kerma at the interventional reference 1824
point exceeding 3 Gy or a kerma-area product (KAP) exceeding 300 Gy-cm2. Low dose 1825
procedures are below these levels (NCRP 2010). 1826
1827
Equipment 1828 1829
If the medical mission requires fluoroscopy, only image-intensified units (with image intensifiers 1830
or flat panel detectors) should be used. As of mid-2006, all fluoroscopic equipment sold in the 1831
United States provides a final indication of air kerma (proportional to radiation dose) at a 1832
reference point at the completion of the examination. This simplifies the process of measuring 1833
38
and recording radiation dose in the medical record. 1834
1835
Some operative procedures, both minimally invasive and open surgical, performed both inside 1836
and outside the operating room, (e.g., hip replacement, transsphenoidal hypophysectomy, some 1837
endoscopic procedures) may require fluoroscopic assistance. In general, these procedures tend to 1838
be relatively low-dose. For these procedures, to the fullest extent practicable, only equipment 1839
with features such as last-image-hold and reduced dose pulsed fluoroscopy, or equipment with 1840
similar dose-reducing features, should be used. The advantage of this technology is that the 1841
radiation exposure can be reduced compared to continuous fluoroscopy, while adequate image 1842
quality is maintained. 1843
1844
For procedures with a potential for high patient doses (this includes most interventional 1845
radiology, interventional cardiology, interventional neuroradiology and endovascular surgical 1846
procedures), additional requirements apply for both equipment and personnel (Hirshfeld et al. 1847
2004; Lipsitz et al. 2000; Miller et al. 2003a; Miller et al. 2003b; Padovani and Quai 2005; 1848
Suzuki et al. 2006). Fluoroscopy equipment intended for these procedures should, at a 1849
minimum, be compliant with the version of International Electrotechnical Commission Standard 1850
60601-2-43 (IEC 2010) applicable to the equipment at the time of purchase. New fluoroscopic 1851
imaging systems should incorporate high heat-loading tubes, adjustable-rate pulsed fluoroscopy 1852
capability, spectral shaping filters, and automatic exposure control logic to optimize radiation 1853
dose and ensure adequate image quality throughout the procedure. As future systems incorporate 1854
improved methods for both tracking and optimization of patient dose during fluoroscopically-1855
guided procedures, purchasers and operators should take advantage of them when appropriate. 1856
The additional cost of dose-reduction technology is justified because the reduction in patient 1857
radiation dose can be considerable. 1858
1859
Proper patient management during fluoroscopically-guided interventions requires appropriate use 1860
of the various features of the fluoroscopic equipment. This will permit patient dose to be 1861
optimized and staff dose to be minimized. There is an extensive literature on this subject which 1862
can be used for guidance (Chambers et al. 2011; Miller et al. 2010a; NCRP 2010; Stecker et al. 1863
2009; Steele et al. 2012). 1864
1865
Measurement or estimation of skin dose is desirable for all procedures which are high dose or 1866
have the potential to result in high patient dose. The quantity of interest is the peak skin dose 1867
(PSD), the highest dose at any point on the patient’s skin. This determines the severity of a 1868
radiation-induced skin injury. Ideally, equipment should also provide the operator with a near 1869
real-time indication of skin dose, including PSD in the current radiation field. The operator 1870
would then be able to modify his/her technique during the procedure to minimize skin dose 1871
(FDA 1994; Miller et al. 2002). Skin dose can be measured with special films, an array of 1872
thermoluminescent dosimeters (TLDs), optically stimulated luminescence (OSL) dosimeters or 1873
real-time point-measurement devices (Balter et al. 2002). Currently, these methods are 1874
expensive, cumbersome and inconvenient, and are not commonly used in routine clinical 1875
practice. In the future, software-based systems should be able to estimate and map skin dose in 1876
real time. 1877
1878
Cumulative air kerma (cumulative air kerma at the reference point; also called reference point 1879
39
dose, reference air kerma, reference point air kerma, or cumulative dose) is measured in Gy and 1880
displayed automatically on all fluoroscopic equipment in the United States sold after mid-2006 1881
per 21CFR1020.32(k) (FDA 2012d). It is the dose at a pre-defined reference point. This point is 1882
separately defined for different types of fluoroscopic equipment (FDA 2012d; FDA 2012f). For 1883
C-arm units, this point is located along the central ray of the x-ray beam, 15 cm from the 1884
isocenter towards the x-ray source (IEC 2010). Cumulative air kerma is not the same as skin 1885
dose. Cumulative air kerma is measured at a point in space that is fixed with respect to the 1886
gantry and can move with respect to the patient when the table is moved or the gantry is angled. 1887
Cumulative air kerma does not take table height or these motions into account. As a result, 1888
reference dose is usually greater than PSD (IEC 2010; Miller et al. 2003a; Miller et al. 2012). 1889
1890
Kerma-area product (KAP, also called dose-area product or DAP) is the product of the air kerma 1891
and the area of the irradiated field and is measured in Gy·cm2. It does not change with distance 1892
from the x-ray tube. It is a good measure of the total energy delivered to the patient, and 1893
therefore a good measure of stochastic risk. It is not a good indicator of deterministic risk 1894
(Kwon et al. 2011; Miller et al. 2012). 1895
1896
Fluoroscopy time has been the standard dose metric. It is easy to measure and the capability to 1897
measure it is widely available. However, fluoroscopy time does not reflect the effects of 1898
fluoroscopic dose rate or the radiation dose from fluorography (e.g., digital subtraction 1899
angiography or cinefluorography) and is a poor indicator of patient dose. As recommended in a 1900
joint Society of Interventional Radiology/Cardiovascular and Interventional Radiological Society 1901
of Europe (SIR/CIRSE) guideline, use of fluoroscopy time as the sole dose metric is not 1902
advisable, and should not be done unless no other dose metric is available (Stecker et al. 2009). 1903
Even then, the number of images and cine frames should also be recorded. Procedures with a 1904
potential for high patient doses should not be performed using fluoroscopy equipment that is not 1905
compliant with IEC 60601-2-43 or its successors (IEC 2010). 1906
1907
For patient care and for quality assurance purposes, it is highly desirable for all radiation data to 1908
be transferred automatically to the PACS (picture archiving and communication system), RIS 1909
(radiology information system), and Electronic Health Record (EHR) as part of the study data 1910
(along with images and demographic information) if the fluoroscopy unit is connected to a 1911
PACS. These data should include the peak skin dose, if available; the cumulative air kerma from 1912
both fluoroscopy and from image acquisition, if available; the kerma-area product, if available; 1913
and the cumulative fluoroscopy time and number of images or cine frames recorded (Miller et al. 1914
2012; NCRP 2010). The IHE REM integration profile provides a standard for the transfer of 1915
such information to the PACS ((IHE 2008) or current version). 1916
1917
There are several relatively new technologies as of 2012 (e.g., cone-beam CT, surgical O-arms,) 1918
(ACR 2008c; Orth et al. 2008; Wallace et al. 2008). Others will certainly appear in future 1919
interventional fluoroscopy equipment. Some of these technologies are intended to provide 1920
greater technical capability for complex surgical or interventional procedures. Currently, most of 1921
these technologies are designed to enhance the fluoroscopy unit’s surgical capability for 1922
procedures performed outside the Radiology Department. Mobile equipment with these 1923
technologies is smaller in size than its conventional fixed counterpart, but it can be just as 1924
dangerous to the operator and patient. Facilities should establish procedures for the testing and 1925
40
use of these types of equipment, and for the training and credentialing of its operators. 1926
1927
Testing and Quality Assurance 1928 1929
Equipment testing for quality assurance should be performed by or under the direction of a 1930
Qualified Physicist after installation but before first clinical use, annually thereafter, and after 1931
each repair or modification that may affect patient dose or image quality. Testing should be 1932
performed as specified in the section of this document entitled Technical Quality Assurance in 1933
Medical Imaging with X-Rays. 1934
1935
Personnel 1936 1937
Fluoroscopy can deliver a significant radiation dose to the patient, even when used properly. 1938
Also, fluoroscopy presents the potential for greater radiation dose to the operator as compared 1939
with other imaging modalities. Therefore, all fluoroscopic examinations should be performed by 1940
or under the direct supervision of a physician with demonstrated competence, who has received 1941
training in fluoroscopy and has been privileged by the facility to perform fluoroscopy. 1942
1943
In fluoroscopy, the operator effectively determines, prescribes and delivers the required x-ray 1944
dose to the patient in real-time. These systems are often used to guide imaging or interventions 1945
and the exposure is directly related to the complexity of the procedure and inversely related to 1946
the skill of the individual performing the procedure. Individuals who are privileged for the use 1947
of these systems, and particularly the high dose capable systems as are used in interventional 1948
procedures should have a thorough understanding of the biological effects of radiation exposure, 1949
the dose from this radiation exposure and its likely deterministic and stochastic risks, and of the 1950
available technique and technology based methods for minimizing the radiation dose to any 1951
portion of the patient’s tissue during the examination. 1952
1953
Every person who operates or directs the operation of fluoroscopic equipment should be trained 1954
in the safe use of fluoroscopic equipment, in order to optimize patient dose. Initial training 1955
should include didactic training, hands-on training, and clinical operation under a preceptor. 1956
1957
Didactic training is a formal course of instruction in radiation safety which meets guidelines 1958
established by the responsible authority. It should include the following topics: (a) physics of x-1959
ray production and interaction; (b) the technology of fluoroscopy machines, including modes of 1960
operation; (c) characteristics of image quality and technical factors affecting image quality in 1961
fluoroscopy; (d) dosimetric quantities, units, and their use in radiation management; (e) the 1962
biological effects of radiation; (f) principles of radiation protection in fluoroscopy, (g) applicable 1963
federal regulations and agency requirements; and (h) techniques for minimizing dose to the 1964
patient and staff. Completion of this phase of training should include successfully completing a 1965
written examination. Radiologists may fulfill the didactic portion of the initial training through 1966
the extensive training in radiation physics, radiation biology and radiation safety they receive 1967
during their residency. 1968
1969
Hands-on training is conducted by a qualified individual who is familiar with the equipment. 1970
Hands-on training means operation of the actual fluoroscope that is to be used clinically (or an 1971
41
essentially similar fluoroscope), including the use of controls, activation of various modes of 1972
operation, and displays. This phase of training could include demonstrations of the effect of 1973
different modes of operation on the dose rate to a simulated patient and could include 1974
demonstration of the dose-rates at various locations in the vicinity of the fluoroscope. 1975
1976
Clinical operation under a preceptor means operation of the fluoroscope for clinical purposes 1977
under the direct supervision of a preceptor experienced in the operation of the device. 1978
Completion of this phase of training should include written attestation, signed by the preceptor, 1979
that the individual has achieved a level of competency sufficient to function independently as a 1980
fluoroscopy operator. 1981
1982
Training should be conducted initially and then at periodic intervals. Records should be kept of 1983
the training. The records should include the date(s) of training, the name(s) of the person(s) 1984
providing the training, the topics included in the training, the duration of the training, the test 1985
questions, the names of the persons successfully completing the training, and the test scores of 1986
these persons. The training records should also include the signed preceptor statements 1987
described above. Training need not be performed at or by the medical facility, provided that the 1988
facility determines that it meets these requirements and was sufficiently recent, and the facility 1989
obtains written certification of successful completion of the training. Periodic refresher training 1990
should include the didactic training. At the facility’s discretion, it may also include hands-on-1991
operation and clinical operation under a preceptor physician. 1992
1993
Each person who operates or directs the operation of fluoroscopic equipment should be 1994
privileged by the medical facility. Privileging should be contingent upon successful completion 1995
of training as described above. Maintenance of privileges should be contingent upon successful 1996
completion of periodic refresher training and on complying with agency and facility 1997
requirements for the safe use of fluoroscopic equipment. In particular, it is not permissible for a 1998
physician or other medical professional who has not completed this training, and who is not 1999
privileged, to direct the operation of a fluoroscopy unit even if it is operated by a radiologic 2000
technologist. 2001
2002
Operators who perform fluoroscopically-guided procedures with the potential for high patient 2003
doses require additional knowledge and training beyond that necessary for operators whose 2004
practice is limited to low-dose fluoroscopy procedures (ICRP 2000a; Vano 2003). Operator 2005
knowledge includes all the information described in the current American College of Cardiology 2006
Foundation/ American Heart Association/ Heart Rhythm Society/ Society for Cardiac 2007
Angiography and Intervention fluoroscopy clinical competence statement and its successors . In 2008
general, radiologists and interventional cardiologists receive most or all of this information as 2009
part of their training, and are tested on this knowledge as part of the board certification processes 2010
by their respective Boards. Physicians in other medical specialties may or may not have received 2011
training or been examined on this subject matter during their residency or fellowship, and may 2012
require additional training. 2013
2014
2015
2016
42
Procedures 2017 2018
Fluoroscopic procedures should be performed so that procedure dose is optimized and skin dose 2019
is minimized. This requires the appropriate use of various features of the fluoroscopic 2020
equipment. Further details are available in the published literature (Miller et al. 2010b; NCRP 2021
2010; Sidhu et al. 2009; Stecker et al. 2009; Wagner et al. 2000). 2022
2023
Dose measurement 2024
2025 Methods for estimating PSD can be ranked from most reliable to least reliable. As of 2012, peak 2026
skin dose measuring software is the most reliable, followed by measurement of cumulative air 2027
kerma, KAP, and finally fluoroscopy time combined with a count of the number of fluorography 2028
frames or images. Dosimeters placed on the skin are useful but can provide underestimates for 2029
PSD if placed outside the area of highest skin dose. This area may be quite small (Miller et al. 2030
2003a). PSD and KAP are now the most useful predictors for deterministic and stochastic 2031
injury, respectively. Cumulative air kerma is readily available on fluoroscopy units purchased 2032
after mid-2006 and is an acceptable substitute for PSD. It does not correlate well with PSD in 2033
individual cases (Miller et al. 2003a; Miller et al. 2003b). Fluoroscopy time alone does not 2034
correlate with PSD (Fletcher et al. 2002). Monitoring fluoroscopy time alone also 2035
underestimates the risk of radiation-induced skin effects (O'Dea et al. 1999). 2036
2037
All statements of patient dose contain some degree of uncertainty. As of 2012, dose 2038
measurement accuracy in clinical units has an allowed calibration accuracy of ±35% (FDA 2039
2012d). Even the most sophisticated dose-measurement instrumentation has unavoidable 2040
uncertainties related to variations in instrument response with changes in beam energy, dose rate, 2041
and collimator size. Converting these measurements into skin dose introduces yet further 2042
uncertainties related to beam orientation and inconsistencies in the relationship between the 2043
patient’s skin and the interventional reference point. Finally, clinically available dose and KAP 2044
measurements ignore the effect of backscatter from the patient. Backscatter causes the skin dose 2045
to exceed air kerma at the same location by 10 to 40%, depending on the beam area and energy 2046
(ICRU 2005, or most current version). Skin doses estimated from reference dose, KAP, or 2047
fluoroscopy time may differ from actual skin dose by a factor of two or more. Users of dose data 2048
should be aware of these uncertainties. Federal facilities should strongly encourage the purchase 2049
of equipment with features that enhance the accuracy and clinical value of dosimetry systems. 2050
2051
Recordkeeping 2052 2053
A record should be kept of each fluoroscopic procedure. Whenever possible, this should be 2054
performed electronically, with automatic transfer of the necessary data, as appropriate, from the 2055
fluoroscopy unit to a PACS, RIS, and EMR (see above, under Equipment). The record should 2056
list the individual fluoroscopy unit, the date of the procedure, the procedure (e.g., barium enema, 2057
iliac artery angioplasty and stent placement), information identifying the patient, and the name of 2058
the physician operating or directing the operation of the device. The record should also list the 2059
cumulative air kerma from both fluoroscopy and from image acquisition, if available; the kerma-2060
area product, if available; the cumulative fluoroscopy time and number of images recorded; and 2061
other dose metrics as they are developed. This record should be maintained according to the 2062
43
Federal facility’s requirements. 2063
2064
It is strongly recommended that patient radiation dose data be recorded in the patient’s medical 2065
record, including patient skin dose data whenever possible. Where and how these data are 2066
recorded is subject to the policies and procedures of the individual institution. However, the 2067
choice of dose metrics to be recorded should be guided by published recommendations, such as 2068
the guidelines on recording dose in the medical record published by SIR (Miller et al. 2012; 2069
Miller et al. 2004; Stecker et al. 2009). 2070
2071
When the dose to one or more areas of a patient’s skin may have exceeded a threshold dose for 2072
deterministic effects, the physician performing the procedure should be advised of this event and 2073
should place an appropriate notation in the patient’s medical record (Stecker et al. 2009). The 2074
information should include information on the beam entry sites and the estimated skin dose for 2075
each, if available. Provisions should be made for clinical follow-up of those areas for monitoring 2076
radiation effects. The possibility of overlap of two separate adjacent fluoroscopic fields, where 2077
skin dose of the overlapping area may have exceeded the threshold dose, should be taken into 2078
account. Ideally, skin dose from radiation therapy and imaging modalities other than 2079
fluoroscopy should also be considered. It is recognized that at the time this report was prepared, 2080
no simple method for measuring or estimating skin dose is available. As a substitute, cumulative 2081
air kerma may be used. Threshold values recommended by professional societies or advisory 2082
bodies, such as the ACR, SIR, ICRP and NCRP, should be consulted (ACR 2008c; ICRP 2000a; 2083
Stecker et al. 2009). As of 2012, these threshold values are typically a PSD of 3 Gy or 2084
cumulative air kerma of 3 – 5 Gy (ACR 2008c; NCRP 2010). 2085
2086
Patient management 2087 2088
Management of patients who have received radiation doses high enough to cause deterministic 2089
effects should be guided by recommendations from appropriate advisory bodies, medical 2090
specialty societies, and other organizations, and by current practice (ACR 2008c; Balter and 2091
Moses 2007; Stecker et al. 2009). For these patients, this includes justifying and documenting 2092
the high radiation dose in their medical record, notifying the patient or their health care proxy 2093
(legally authorized representative) of the radiation dose that has been administered and the likely 2094
consequences, and follow-up by the physician who performed the procedure to determine 2095
whether a skin injury has occurred (Balter et al. 2010). 2096
2097
Device related deaths, including those related to radiation dose, must be reported by the device 2098
user facility to the device manufacturer and to the Food and Drug Administration in accordance 2099
with 21 CFR 803 (FDA 2012b). Device-related serious injuries, including those resulting from 2100
radiation, must be reported by the device user facility to the device manufacturer or, if the 2101
manufacturer is unknown, to the Food and Drug Administration. A serious injury is one that is 2102
life-threatening, results in permanent impairment of a body function or permanent damage to a 2103
body structure, or necessitates medical or surgical intervention to preclude permanent damage or 2104
impairment (FDA 2012a). If a patient’s skin receives an absorbed dose that meets the Joint 2105
Commission definition of a reviewable sentinel event from a fluoroscopically guided procedure, 2106
or a dose likely to result in a serious injury, the event also should be reported to the Radiation 2107
Safety Officer and the facility’s Patient Safety Manager, or designee (Balter and Miller 2007; 2108
44
The Joint Commission 2006). 2109
2110
Quality process 2111 2112
All QA/QI programs for interventional fluoroscopy should include patient radiation safety 2113
aspects. These include evaluation of operator performance in dose optimization and of 2114
procedures where patients received a radiation dose that caused a radiation injury. 2115
2116
A review of radiation doses delivered to patients during fluoroscopically guided interventional 2117
procedures is an essential aspect of any performance improvement program. The dose metrics 2118
for all procedures should be reviewed at intervals (quarterly, for example) for their magnitude 2119
and for the dose distribution of these cases. This will provide a picture of dose utilization; any 2120
abnormally high doses can be reviewed for appropriateness. For example, doses can be 2121
compared to available reference levels. Any recommendations and actions for improvement 2122
should then be implemented. 2123
2124
Analysis of overall dosimetric performance for interventional fluoroscopy procedures, 2125
incorporating the effects of equipment function, procedure protocols, and operator performance, 2126
requires a different process than the reference levels (RLs) used for radiography (NCRP 2010). 2127
It also requires a more detailed presentation of the reference data set. Guidance data for an 2128
interventional fluoroscopy procedure are generated by obtaining data for all instances of that 2129
procedure from a number of different facilities. These data are used to generate Guidance Levels 2130
(GLs), which are similar to the RLs used for radiography. The guidance data set includes the 2131
data for all instances of the procedure at each facility. This differs from the data set used to 2132
generate RLs, which typically includes only a single datum from each facility. 2133
2134
Guidance data sets for interventional fluoroscopy procedures usually demonstrate a lognormal 2135
distribution. The high dose tail is of particular interest, because this tail represents the cases 2136
where doses may be high enough to cause deterministic effects. Because differences between 2137
the shapes of the collected guidance data and the local facility data are potentially useful, the 2138
FGI-procedure guidance data set should characterize the entire distribution, rather than just the 2139
10th
and 75th
percentile values typically used for radiography RLs. Also, in order to provide a 2140
basis for comparison for facilities that use locally derived substantial radiation dose levels 2141
(NCRP 2010; Stecker et al. 2009), these data sets should indicate the percentage of instances of 2142
each procedure that exceed specific radiation dose levels. Ideally, these percentages should be 2143
presented at 0.5 Gy intervals from 2 Gy to the maximum value observed in the data set. 2144
2145
Guidance data and GLs can be used, to some extent, in a fashion similar to RLs, but the 2146
lognormal shape of dose distributions for interventional fluoroscopy procedures mandates that 2147
the local median (50th
percentile) be used for comparison with the guidance data, rather than the 2148
local mean dose. Also, high-dose interventional fluoroscopy cases require further evaluation. It 2149
is possible for the facility’s median dose for a procedure to be within an acceptable range (below 2150
the 75th
percentile of the guidance data) at the same time that there are an excessive number of 2151
cases with a radiation dose greater than the 95th
percentile of the guidance data. It is necessary to 2152
compare the percentage of cases at the facility that exceed the local substantial radiation dose 2153
level (the radiation dose level that triggers radiation follow-up) with the percentage of cases in 2154
45
the guidance data that exceed the same level. Local percentages that are markedly above or 2155
below the value obtained from the guidance data should be investigated (NCRP 2010). 2156
2157
The following method, using cumulative air kerma as the radiation dose metric, is suggested as 2158
one method of evaluating dose utilization for interventional fluoroscopy procedures (NCRP 2159
2010). It is not the only possible method. Kerma-area product could also be used to evaluate 2160
general dose performance. Kerma-area product can be used to evaluate operator performance 2161
with respect to collimation. However, it does not provide an unambiguous identification of the 2162
cases where a very high skin dose may result in deterministic effects. 2163
2164
An appropriate published guidance data set for the selected procedure (the guidance data) is used 2165
as the starting point, although published guidance data for FGI procedures are sparse as of 2012 2166
(Balter et al. 2008; Bleeser et al. 2008; Brambilla et al. 2004; IAEA 2009; Miller et al. 2009; 2167
Vano et al. 2008a; Vano et al. 2009). 2168
2169
A facility should judge its dose performance for interventional fluoroscopy procedures in several 2170
steps. The first step is to compare the local substantial dose radiation level to the guidance data. 2171
The facility’s local substantial radiation dose level is either a value taken from the literature 2172
(ACR 2008c; Mahesh 2008; Stecker et al. 2009) or a locally determined value. The percentage 2173
of procedures in the guidance data set that exceed this value can now be determined. 2174
2175
The next step is to characterize the dose distribution for all instances of a specific procedure 2176
performed at the facility. Evaluation of subsets of these data sorted by procedure room and 2177
operator can be useful as well, as discussed below. The percentage of instances exceeding the 2178
local substantial radiation dose level, and the median value of the entire local data set (and 2179
appropriate subsets) is calculated. 2180
2181
The local median can be compared with the 10th
, 50th
(median) and 75th
percentiles of the 2182
guidance data. A median value below the 10th
percentile of the guidance data may indicate 2183
incomplete procedures. A median value between the 50th
and 75th
percentile of the guidance data 2184
could be due to clinical differences between the guidance data population and the local facility 2185
population or other factors. Understanding the relevant reasons may be useful. An investigation 2186
is warranted if the local median exceeds the 75th
percentile of the guidance data (IAEA 2009; 2187
NCRP 2010). This step is analogous to the analysis performed using RLs for radiographic 2188
examinations. 2189
2190
The percentage of instances exceeding the local substantial radiation dose level can be compared 2191
to the percentage of instances exceeding the substantial radiation dose level in the guidance data. 2192
Local percentages significantly above or below the value obtained from the guidance data should 2193
be investigated. 2194
2195
It can be useful to perform the same analysis using a reference dose value of 3 Gy as well as the 2196
local substantial radiation dose level. An interventional fluoroscopy procedure is in the 2197
potentially-high radiation dose category if more than 5% of instances of that procedure exceed a 2198
reference dose of 3 Gy (NCRP 2010). If fewer than 5% of the instances of the procedure at the 2199
local facility exceed this value, then the procedure, as performed at the local facility, is not in 2200
46
that category. At that local facility, the procedure may be performed safely in a fluoroscopy 2201
suite that does not meet the requirements of IEC 60601-2-43 (IEC 2010). Also, those procedures 2202
at the local facility that are not in the potentially-high radiation dose category may be audited 2203
less frequently than those that are in that category. 2204
2205
Lastly, the overall distribution of the local data may be compared to the distribution of the 2206
guidance data. Displacement or distortion of the local distribution histogram relative to the 2207
guidance data may be due to differences in equipment, clinical complexity, or other factors. 2208
2209
The analysis may be extended to individual operators or interventional fluoroscopy procedure 2210
rooms by comparing operator- or room-specific data to either a facility’s local distributions or to 2211
pooled distributions of data for multiple facilities (e.g., (Miller et al. 2009)). Care should be 2212
taken in such an analysis to account for statistical interactions (e.g., statistical confounding 2213
between the operator and the interventional fluoroscopy procedure room). 2214
2215
Procedures resulting in a substantial patient radiation dose should be reviewed on a regular basis. 2216
Reported potential radiation injuries should be reviewed at the regular QA meeting, with any 2217
available diagnoses, planned patient follow-up, and outcomes. If a radiation injury occurred, the 2218
procedure should be reviewed for appropriate use of radiation in the clinical context. It may be 2219
appropriate to periodically re-report on the status of known radiation injuries. Additionally, 2220
reporting of these cases to the institution’s Radiation Safety Officer is desirable. 2221
2222
Staff safety 2223 2224
Other than the patient who is being examined, only staff and ancillary personnel required for the 2225
procedure, or those in training, should be in the room during the fluoroscopic examination. No 2226
body part of any staff or ancillary personnel involved in a fluoroscopic examination should be in 2227
the primary beam (Miller et al. 2010b). If primary beam exposure is unavoidable, it should be 2228
minimized. As required by various states, all personnel in the room during fluoroscopic 2229
procedures should be protected from scatter radiation by either protective aprons or whole-body 2230
shields of not less than 0.25 mm of lead-equivalent material. An apron with lead equivalence of 2231
at least 0.35 mm is recommended. Thyroid and eyes should be protected if the potential 2232
exposure to the worker will exceed 25% of the annual regulatory dose limits for those organs. It 2233
is strongly recommended that protective aprons and gloves be evaluated at least annually for lead 2234
protection integrity (Miller et al. 2010b; NCRP 2010). 2235
2236
Pregnant individuals involved in fluoroscopically guided procedures generally do not need to 2237
limit their time in the procedure room to remain below the dose limit for the embryo and fetus, as 2238
long as they use appropriate protective garments and radiation protection methods, and their 2239
occupational exposure is adequately monitored (NCRP 2010). 2240
2241
2242
2243
47
COMPUTED TOMOGRAPHY 2244
2245 Computed tomography (CT) is an imaging modality that utilizes one or more x-ray beams to 2246
acquire projection images from many angles around the patient. The projection images are 2247
mathematically manipulated to obtain tomographic images that depict x-ray attenuation in a two 2248
dimensional cross sectional, projectional or three dimensional representation of the subject’s 2249
anatomy. 2250
2251
There have been important technological advances that have greatly increased the clinical 2252
usefulness of CT imaging. However, these improvements have also led to increased use of CT, 2253
imaging of larger volumes of the body, and acquiring an increased number of image sequences 2254
either during the various phases of tissue enhancement following contrast injection or to 2255
dynamically evaluate areas affected by motion. These are incredibly powerful diagnostic tools 2256
that are invaluable to patient management and allow the elimination of more dangerous invasive 2257
procedures, such as exploratory surgery. But with this great benefit has come a price: there has 2258
been an increase in radiation dose to the population, as well as to the individual patient. 2259
2260
In the U.S., the number of CT procedures performed annually increased by 10% to 11% per year 2261
from 1993 to 2006 (NCRP 2009). Although CT procedures comprise only about 17 % of all 2262
medical x-ray imaging procedures, they now impart about 49 % of the cumulative effective dose 2263
from medical procedures received by the population of the U.S. (Mettler et al. 2008). As of 2264
2012, a typical single CT imaging procedure of the chest, abdomen, or pelvis of an adult imparts 2265
an effective dose on the order of 3-7 mSv (McCollough 2008; Mettler et al. 2008). These values 2266
are for single phase exams and the effective doses for multiple phase exams are correspondingly 2267
larger. Thus, CT imparts some of the largest doses per procedure in diagnostic medical imaging. 2268
These doses are significantly exceeded only by the doses from some complex fluoroscopically-2269
guided interventional procedures. 2270
2271
Except in the extreme circumstance of multiple irradiations of the same anatomic region, the 2272
doses from CT examinations are unlikely to cause deterministic effects such as erythema or 2273
epilation (hair loss). Instead, the main concern is stochastic effects, particularly cancer. The risk 2274
to the patient is determined mainly by the doses to organs in or near the scanned portion of the 2275
patient, the age and gender of the patient, and the likely remaining lifespan of the patient. 2276
2277
In 2001, it was reported that standard adult technique factors were commonly used for CT 2278
imaging of patients in the U.S. regardless of body habitus, including children and even infants 2279
(Brenner et al. 2001; Paterson et al. 2001). If adult technique factors are used for imaging the 2280
abdomen or thorax of a small child or infant, the larger doses together with the larger risk of 2281
cancer per unit dose is estimated to pose a risk of fatal cancer on the order of one per thousand 2282
examinations (Brenner et al. 2001). Therefore, it is essential to optimize dose when imaging 2283
children (FDA 2001). Of the many methods for adjusting CT techniques for children, perhaps 2284
the simplest and most widely used techniques utilizes the Breslow method familiar to clinical 2285
providers as a way to estimate the weight, drug dosing, and equipment sizing for children. Many 2286
sites have developed specific CT protocols that adjust the kVp and mAs based on the 2287
approximate size of a child matching each Breslow color scheme category. Professional 2288
48
societies provide excellent guidance on imaging, such as the “Image Gently” campaign (Goske 2289
MJ et al. 2008; Strauss et al. 2010). 2290
2291
Many advances in CT technique and technology have been specifically targeted at reduction of 2292
the radiation dose delivered to the patient during CT examinations. To be effective, these 2293
techniques must be used, and used properly. It is imperative that Radiological Medical 2294
Practitioners, physicists, and technologists involved in CT imaging keep abreast of current 2295
developments and utilize all techniques available to them to reduce the patient’s radiation 2296
exposure as much as possible while obtaining the clinically needed information. 2297
2298
Equipment 2299 2300
CT was introduced in the mid-1970s. For several decades, a constant x-ray tube current was the 2301
only available technology for performing a CT examination. Tube current did not change, 2302
regardless of the angle of the x-ray beam as the x-ray tube rotated around the patient, and 2303
regardless of the attenuation along the path of the beam through the patient. However, this 2304
attenuation varies greatly with the angle of the beam and the location on the patient’s body. As 2305
of 2012, developments in technology allow automated tube current modulation, providing 2306
similar image quality with lower radiation dose. Facilities should use equipment that provides 2307
relevant patient dose information. This equipment should allow the facility to program in dose 2308
alerts to inform operators if selected operating parameters might produce a radiation dose 2309
exceeding that recommended by the facility. Equipment manufacturers should incorporate these 2310
features into the equipment. 2311
2312
The dose of radiation to a patient, in conjunction with the attenuation provided by the part of the 2313
patient that is scanned and the presence or absence of IV contrast, determines the signal-to-noise 2314
ratio in the resultant images. The signal-to-noise ratio needed for diagnostic confidence depends 2315
upon the diagnostic task. Smaller and thinner patients require smaller doses than larger and 2316
thicker patients to produce similar signal to noise ratios in the images. Imaging procedures to 2317
detect or assess larger structures and structures with more inherent or enhanced contrast 2318
(difference in density) require a smaller dose than imaging procedures to detect or assess smaller 2319
structures and those with less inherent contrast. 2320
2321
Stand-alone CT scanners have been complemented by the development of hybrid modalities such 2322
as Positron Emission Tomography/CT [PET/CT] and Single Photon Emission Computed 2323
Tomography/CT [SPECT/CT]. These hybrid modalities use two equipment components to 2324
acquire two types of images of a patient in the same setting, without changing the patient’s 2325
position on the imaging system table. This allows co-registration of image data so that the 2326
anatomic detail provided by one imaging modality can be matched to the physiologic marker 2327
capability of the second modality to provide more specific information about the location and 2328
extent of disease. These CT devices may be operated at lower doses if the CT portions of the 2329
exams are not intended to be used for diagnosis independent of the SPECT or PET exam. 2330
2331
Technological development in image reconstruction, increases in computer processor power, 2332
equipment innovation, and optimization techniques in general have led to a marked increase in 2333
the ability to obtain adequate quality images at lower patient doses. These improvements should 2334
49
be implemented to the fullest extent practicable. Facilities should use equipment that provides 2335
relevant patient dose information. This equipment should allow the facility to program in dose 2336
alerts to inform operators if selected operating parameters might produce a radiation dose 2337
exceeding that recommended by the facility. Equipment manufacturers should incorporate these 2338
features into the equipment. 2339
2340
Testing and Quality Assurance 2341 2342
Equipment testing for quality assurance should be performed after installation but before first 2343
clinical use, annually thereafter, and after each repair or modification that may affect patient dose 2344
or image quality. Testing should be performed as specified in the section of this document 2345
entitled Technical Quality Assurance in Medical Imaging with X-Rays. In addition, the 2346
recommendations found in the current version of ICRP Publication 102 (NCRP 1989b) should be 2347
followed when applicable. 2348
2349
A quality control program should be established. The program should conform to the ACR 2350
Technical Standard for the Diagnostic Medical Physics Performance Monitoring of Computed 2351
Tomography (CT) Equipment or equivalent guidance. 2352
2353
Personnel 2354 2355
A CT system should only be operated by a Radiologic Technologist registered by the American 2356
Registry of Radiological Technologists (ARRT) or equivalent, preferably with advanced 2357
certification in CT, operating under the supervision of a Radiological Medical Practitioner with 2358
appropriate training in CT physics, radiation safety and CT image interpretation. 2359
2360
Ideally, a PET/CT or SPECT/CT should be operated by a technologist certified in both nuclear 2361
medicine and CT. However, a PET/CT or SPECT/CT may also be operated by a nuclear 2362
medicine technologist with Certified Nuclear Medicine Technologist (CNMT) or Radiological 2363
Technologist Nuclear qualified (RT(N)) certification and additional training in CT imaging 2364
sufficient to safely operate a CT system. Alternatively, a PET/CT may be operated by a 2365
technologist who is qualified to operate a CT system and who also has additional training in PET 2366
imaging sufficient to safely operate a PET system. If a technologist who meets these 2367
requirements is not available, the PET/CT or SPECT/CT system should be operated by two 2368
technologists, one a nuclear medicine technologist qualified to operate the PET or SPECT 2369
system and the other a Diagnostic Radiological Technologist (DRT) or a therapist in radiation 2370
oncology who is qualified to operate the CT system. Utilization and training requirements for 2371
the operation of other hybrid modalities should be evaluated as new combinations of modalities 2372
emerge. 2373
2374
Procedures 2375 2376
One of the most effective ways to optimize the dose of radiation delivered to the patient in a CT 2377
study is to tailor the study to the patient’s specific needs. 2378
2379
50
A CT protocol specifies the parameters for the image acquisition and largely determines the dose 2380
to the patient. It defines the portion of the patient’s anatomy to be imaged, whether and how 2381
contrast agents will be administered, the number and timing of imaging sequences, and 2382
acquisition technical parameters. Imaging sequences in a multiphase study may include several 2383
phases, such as a pre-contrast phase, an arterial phase, a venous phase and/or a delayed phase. 2384
Acquisition technical parameters may include pitch, collimation (beam width), kV, mA (constant 2385
or modulated), rotation time, physiologic gating, image quality factors, and reconstruction 2386
method. In addition: 2387
1. In some cases, the kV may be adjusted for the type of examination (e.g., contrast enhanced 2388
angiography) to accommodate patient size. 2389
2. If constant mA is selected, the protocol should utilize a chart for adjusting the mA for the 2390
patient’s size (girth or thickness). If mA modulation is selected, the protocol should specify 2391
the parameters determining the balance between image noise and patient dose. 2392
3. Organ-specific tube current modulation, where available, technically feasible, and clinically 2393
appropriate, should be considered to protect organs such as the breast in younger female 2394
patients and the lens of the eye. 2395
4. Where applicable, the prescription of image acquisition technique factors should take into 2396
account the availability of advanced image reconstruction techniques to decrease the 2397
required patient dose. 2398
5. Once the image sequence is acquired, the user can select alternative reconstruction 2399
parameters (e.g., reconstructed slice thickness) to view the images differently without 2400
having to rescan the patient. 2401
2402
Each CT protocol should be documented in two ways. The first way is a document detailing all 2403
relevant information. The second way provides a more limited subset of programmable 2404
information, primarily acquisition parameters, stored on the imaging device. 2405
2406
It is important to image only the area of anatomy in question and acquire only the necessary 2407
sequences. This is accomplished by determining the imaging protocol for the examination. 2408
Where appropriate, the radiological medical practitioner should select and adjust the protocol to 2409
ensure that the patient is examined using the appropriate techniques and dose. 2410
2411
The technologist performing the study is responsible for limiting the length of the patient being 2412
scanned to the minimum clinically necessary. The technologist is also responsible for setting up 2413
the CT system so that the correct protocol is used and the imaging parameters are appropriate for 2414
the patient’s size, age, and intended examination. Before performing the study, the technologist 2415
should confirm that the technical parameters and the radiation dose metric are appropriate for the 2416
patient and planned study. If existing equipment does not provide a dose metric, efforts should 2417
be made to upgrade or replace it. To prevent accidental overexposure, the projected dose should 2418
correspond to the doses normally associated with the protocol, within reasonable variability. 2419
This should be confirmed again after the patient has been scanned. 2420
2421
Optimization of CT protocols is important for minimizing patient dose. The facility’s standard 2422
protocols for CT imaging should be reviewed by a team, including a physician expert in CT 2423
image interpretation, a technologist expert in performing CT examinations, and a qualified 2424
physicist: 2425
51
1. when the protocol is developed, 2426
2. when the protocol is significantly modified, 2427
3. on a regular basis (preferably annually), and 2428
4. after an equipment upgrade or replacement. 2429
2430
It is strongly recommended that procedures be established to avoid inadvertent or unapproved 2431
modification of CT protocols. Methods, such as limiting access through the use of passwords, 2432
should be adopted to implement these procedures. Superseded protocols should be archived for 2433
future reference. 2434
2435
Reviews and revisions should align protocols with current clinical practice, evaluate the 2436
magnitude of delivered radiation doses, and optimize the radiation dose. Modifications of the 2437
protocol to suit the needs of an individual patient generally do not require a specific review, but 2438
the impact on radiation dose should be understood and considered. 2439
2440
Operator selectable parameters on CT scanners that affect the dose to the patient include the 2441
voltage applied to the x-ray tube (kV), the x-ray tube current (mA) or current-time product per 2442
x-ray tube rotation (mAs), and the pitch (incremental table movement per x-ray tube rotation 2443
divided by the nominal x-ray beam width at isocenter). The radiation dose to the patient within 2444
the scanned volume is approximately proportional to the square of the kV and is proportional to 2445
the effective mAs (the mAs divided by the pitch). Technique factors should be appropriate for 2446
the size (and not just the age) of the patient and the body part being imaged. In particular, adult 2447
technique factors should not be used for children and infants. Technique factors should be 2448
chosen that produce a diagnostically adequate image rather than a “perfect image,” thus 2449
matching the radiation exposure to the diagnostic requirement. If available on the CT scanner, 2450
automated modulation of the tube current should be used for those procedures for which it 2451
produces substantial dose savings, e.g., scans of the thorax. Using this feature appropriately can 2452
reduce dose significantly, whereas errors in its use have produced substantial increases in dose. 2453
For gated cardiac CT imaging, utilize (when available) the feature that reduces or terminates the 2454
beam current during portions of the cardiac cycle that will not be used for image reconstruction 2455
(ICRP 2012). 2456
2457
Several phantom-derived dose indices specific to CT have been defined. These can be useful to 2458
compare one study protocol to another in the assessment of benefit and risk; these are described 2459
in the literature (McNitt-Gray 2002). Two indices in common use are the volumetric computed 2460
tomography dose index (CTDIVOL), which is approximately the average dose in the scanned 2461
volume, and the dose-length product (DLP), defined as the CTDIVOL multiplied by the scanned 2462
length. These indices indicate the radiation exposure delivered by the CT scanner to a phantom, 2463
not the specific radiation energy (i.e., dose) received by any patient. Both of these measures may 2464
be available from current CT scanners, and future devices may incorporate more accurate and 2465
useful dose metrics. The DLP and the portion of the patient that is scanned (e.g., head, thorax, or 2466
abdomen) may be used to estimate the effective dose to the patient. Effective dose is an 2467
indicator of stochastic risk. CT dose indices should be recorded as part of the patient record in 2468
the imaging study or medical record. 2469
2470
52
BONE DENSITOMETRY 2471 2472
Bone densitometry noninvasively measures certain physical characteristics of bone that reflect 2473
bone strength, typically reported as bone mineral content or bone mineral density. It is used for 2474
diagnosing osteoporosis and estimating fracture risk. It is also used to monitor changes in bone 2475
mineral content, whether from age, conditions causing bone mineral loss, or treatment. Devices 2476
that measure bone mineral content are called bone densitometers. Non-invasive methods for 2477
measuring bone mineral content are based on the transmission of x-rays or gamma rays through 2478
the bone. The radiation beams can be produced as pencil or fan beams. The advantage of the 2479
latter is that it is faster, but the radiation dose is increased by a factor of about 4. 2480
2481
There are also devices that use the transmission of sound waves through bone to assess bone 2482
structure. These are ultrasound devices that do not directly measure bone mineral content, but 2483
are also commonly called densitometers. 2484
2485
Equipment 2486 2487
The principal methods in routine clinical use in 2012 for the non-invasive measurement of bone 2488
mineral content using ionizing radiation include: x-ray absorptiometry and quantitative x-ray 2489
computed tomography (QCT). X-ray absorptiometers measure attenuation of two x-ray beams 2490
of well-separated average photon energies to discriminate between bone mineral and soft tissue. 2491
This method is called dual-energy x-ray absorptiometry (DXA or DEXA). The other principal 2492
method for assessment of bone structure regarding osteoporosis is quantitative ultrasound (QUS) 2493
(ACR 2008a; Bonnick and L. 2006). 2494
2495
Of all the methodologies available in 2012, DXA is the only one that can be used to make a 2496
diagnosis of osteoporosis. The World Health Organization has developed criteria for diagnosing 2497
normal bone density, osteopenia, and osteoporosis (Kanis et al. 1994). This classification is 2498
specific for DXA (total hip or femur and neck, PA lumbar vertebrae, or distal 1/3 radius) and 2499
cannot be applied to any other technology (ISCD 2007a; ISCD 2007b). As of 2012, DXA is also 2500
the most commonly used technology for monitoring changes in bone mineral density (BMD). 2501
QCT is sometimes used to monitor changes in the trabecular portion of the vertebrae when there 2502
is a need to measure changes more frequently than with DXA. QCT, nevertheless, involves a 2503
much higher exposure to radiation, especially if done sequentially, and is more expensive and 2504
requires more specialized equipment and staff expertise than DXA. 2505
2506
Bone mineral can be assessed non-invasively by these methods at several sites in the axial and 2507
appendicular skeleton. DXA is most commonly used to assess the lumbar spine, proximal 2508
femurs, and distal radii. DXA measurements of the thoracic spine cannot be performed because 2509
the ribs overlap the thoracic vertebrae. Measurements of the proximal femurs are commonly 2510
referred to as “hip” measurements, but the bone mineral content measurements themselves are 2511
limited to the proximal femurs. DXA and SXA devices are available for measurements of 2512
peripheral sites such as the radius and the calcaneus. The standard evaluation of bone mineral 2513
density includes evaluation of at least one proximal femur and the lumbar spine in the frontal 2514
plane. 2515
2516
53
Some DXA devices are also capable of imaging the spine to detect vertebral fractures. This is 2517
called vertebral fracture assessment (VFA). Detection of vertebral compression fractures is an 2518
independent method for diagnosing osteoporosis. This is performed with imaging of the thoracic 2519
and lumbar spine in the lateral plane. Exposure to radiation is higher with VFA than with DXA 2520
but still considerably lower than for conventional radiography of the same area (Genant et al. 2521
1996). 2522
2523
Some DXA devices allow the C-arm holding the x-ray tube and detector to rotate to a position 2524
permitting lateral bone mineral density measurements of the lumbar spine in the supine patient, 2525
in addition to the usual PA or AP measurements. Some DXA devices permit the acquisition of 2526
projection images of the entire lateral spine for vertebral morphometry. Furthermore, some 2527
DXA devices permit PA or AP scans of the entire body for body composition analysis, providing 2528
an estimation of total bone mineral mass, lean body mass, and fat mass. 2529
2530
QCT measurements are usually performed of the lumbar spine, but there are options to perform 2531
measurements at other anatomical sites as well. Unlike DXA, QCT is able to differentiate 2532
mineral content in the bone as opposed to mineral content outside bones, such as in osteophytes 2533
or aortic calcifications. The presence of these extra-osseous calcifications makes the use of 2534
DXA of the vertebrae less reliable in older people. QCT, on the other hand, is able to focus on 2535
the trabecular or cortical component of bone. QCT may be performed with a standard CT 2536
system; however, a special phantom and software are needed. QUS is used to measure sites in 2537
the appendicular skeleton, most commonly the calcaneus. 2538
2539
Testing and Quality Assurance 2540 2541
Each facility performing bone densitometry should have a quality assurance program. The 2542
procedures for this program should be documented in writing. The program should conform to 2543
manufacturer’s recommendations and recommendations of professional societies such as the 2544
International Society for Clinical Densitometry (ISCD) and the American College of Radiology. 2545
2546
The quality assurance program should include daily assessments of accuracy and periodic 2547
assessments of precision. Cross calibration should be performed whenever the densitometer is 2548
repaired, modified, or replaced. This helps ensure proper measurement of bone mineral content, 2549
detection of osteoporosis, estimation of fracture risk, and changes over short and long periods of 2550
time (i.e., minutes and years) even as equipment is repaired, modified, or replaced. 2551
2552
Accuracy check 2553 2554
Accuracy is the degree to which a measurement value estimates the actual value of the quantity 2555
being measured. The test for accuracy primarily measures equipment characteristics. Most 2556
densitometers will not allow a DXA scan to be performed unless the accuracy test is passed. 2557
Phantoms are available and an accuracy assessment should be obtained daily. 2558
2559
2560
2561
2562
54
Precision 2563 2564
Precision is the degree to which the same value is obtained when a measurement is repeated 2565
(Bonnick and L. 2006; ISCD 2012). The better the precision, the smaller the Least Significant 2566
Change (LSC), and the more likely is the detection of small changes in BMD. Precision studies 2567
assess the technologist’s skills at positioning the patient reproducibly. Several patient factors 2568
affect positioning, including obesity, arthropathies, pain, deformities, fractures, and other 2569
conditions limiting patient mobility. Phantoms are not available for assessing precision; this is 2570
due to the complexity of relating phantom data to patient results. Given these clinical variables 2571
and lack of appropriate phantom, precision studies should be conducted on subjects who are 2572
representative of the bulk of the population scanned at the particular facility. For instance, if 2573
most patients scanned in a facility are over the age of 65 years, precision studies should not be 2574
done in that facility on young athletes. Each facility should establish a range of acceptable 2575
precision performance and ensure that each technologist meets this standard. If a facility has 2576
more than one technologist, an average precision error combining data from all technologists 2577
should be used to establish precision error and LSC for the facility. 2578
2579
For DXA, precision is affected by the positioning of patients. Therefore, precision assessments 2580
should be performed using repeated measurements of patients, with repositioning of the patients 2581
between measurements. Precision studies can be done on either 30 patients scanned twice (after 2582
the patient is repositioned in between scans) or 15 patients scanned 3 times, also after 2583
repositioning in between each scan (ISCD 2012). The technician’s or facility’s precision is then 2584
used to calculate the Least Significant Change (LSC) to determine whether an observed change 2585
in BMD over a period of time is significant (higher than LSC) or not (less than the LSC). The 2586
patients imaged for precision studies should be representative of the facility’s patient population. 2587
Retraining should occur if a technologist's precision is worse than values recommended by 2588
professional societies, e.g., ACR and ISCD. 2589
2590
Cross calibration 2591 2592
Cross-calibration is a method to derive equivalent BMD values when measured on the original 2593
densitometer and a modified or new densitometer. Cross-calibration should be performed when 2594
repairing, modifying, or replacing the entire system or any portion of the system that might alter 2595
the absolute BMD value. The old and new densitometers should be cross-calibrated to establish 2596
a new baseline. As with precision assessments, phantoms are not available for cross calibration. 2597
Cross-calibration is conducted in-vivo by scanning 60 to 100 patients with a wide range of bone 2598
densities (normal to osteoporosis) on both the old and new densitometer. A cross-calibration 2599
equation is then developed (by using linear regression methods), and can be used to predict the 2600
BMD value on the different densitometer. 2601
2602
Justification for quality assurance studies 2603 2604
Patients enrolled in precision studies benefit indirectly and may benefit directly because these 2605
studies improve the reliability of the results. Patients enrolled in cross calibration studies benefit 2606
directly in that these processes allow a better comparison with future scans done on the same or 2607
different equipment. It is in a patient’s best interest to be scanned in a facility where precision is 2608
55
high and LSC small, as the results are more reliable and comparisons with other scans more 2609
meaningful. 2610
2611
Precision and cross-calibration studies conducted by scanning patients are not research. Thus, 2612
these studies do not need approval of an institutional review board. However, the facility should 2613
obtain informed consent from each patient participating in a precision or cross-calibration study. 2614
Although each scan results in a low effective dose to the individual patient, radiation doses to the 2615
individual patient can be reduced by scanning a larger number of patients a fewer number of 2616
times and by not including a patient in both precision and cross-calibration studies. Patients or 2617
staff should not be scanned solely for the purpose of training. 2618
2619
Cross-calibration should be performed when changing the entire system or any portion of the 2620
system that might alter the absolute BMD value. 2621
2622
Patient radiation dose should be determined by a qualified physicist or a qualified medical health 2623
physicist after installation, after service that may affect the radiation dose, and at least annually 2624
thereafter. 2625
2626
In most cases, structural shielding will not be required for DXA or SXA devices or for QCT 2627
devices designed for use only on the appendicular skeleton. Nonetheless, the radiation safety 2628
officer or a qualified physicist should make a determination whether shielding is needed. After 2629
device installation, whether or not additional shielding is installed, dose measurements should be 2630
made in adjacent areas and at the operator’s station (which may be inside the room) and should 2631
be documented in a written report. This will help determine the need for occupational dosimetry 2632
and provide a historical record to ensure proper equipment functioning. 2633
2634
Personnel 2635 2636
Technologists performing absorptiometry should have documented formal training in the use of 2637
the absorptiometry equipment they are operating, including performance of all manufacturer-2638
specified and facility quality assurance (QA) procedures. Each person performing bone 2639
densitometry should meet the State licensing requirements in addition to at least one of the 2640
following qualifications: 2641
1. be a Diagnostic Radiologic Technologist (DRT), 2642
2. be certified by the American Registry of Radiologic Technologists (ARRT) in Nuclear 2643
Medicine Technology, 2644
3. be certified by the Nuclear Medicine Technology Certification Board, 2645
4. be certified by the International Society of Clinical Densitometry as a Certified 2646
Densitometry Technologist, 2647
5. have ARRT post-primary certification in Bone Densitometry, or 2648
6. have state licensure or limited licensure in Bone Mineral Densitometry, when the licensure 2649
requires successful completion of the ARRT Limited Scope Bone Densitometry 2650
Examination. 2651
2652
56
Interpretation of the results is important and the interpreting Radiological Medical Practitioner 2653
should be knowledgable in bone densitometry. Reliance on the report generated by the 2654
equipment alone is inadequate. Clinicians should also examine the plates and raw data. 2655
2656
Procedures 2657 2658
Organizations that use bone densitometry should refer to current versions of procedures or 2659
position statements issued by professional organizations (ISCD 2007a; ISCD 2007b). The 2660
following guidance applies to DXA scans. 2661
2662
Before the DXA scan, the technologist should: 2663
1. Ensure that the various quality assurance parameters have been fulfilled. 2664
2. Verify that there are no contraindications to the DXA scans. Pregnant patients or patients 2665
likely to be pregnant should not have a DXA scan. It is also not recommended to scan 2666
patients whose weight exceeds the weight limit of the densitometer as the results may not 2667
be accurate and the densitometer table may be damaged. 2668
3. Verify that there are no artifacts. Patients who have a prosthetic hip or orthopedic device in 2669
the lumbar vertebrae should not have this part of the body scanned. It is also recommended 2670
not to scan patients who have taken calcium supplements the day of the scan as the calcium 2671
tablet may be in the path of the X-rays and artificially elevate the mineral content of the 2672
area scanned. Similarly patients who have undergone radiological contrast studies on the 2673
abdomen should not be scanned until the contrast material is no longer in the patient’s 2674
body. Patients should not have metallic objects on the parts scanned, including navel rings 2675
which interfere with the absorption of radiation. Other common artifacts include zippers, 2676
buttons and wallets. 2677
4. Enter and verify the accuracy of all the relevant patient demographic information, such as 2678
the age, race, gender, weight and height. Any erroneous information will invalidate the 2679
subsequent calculation of the T- and Z-scores and hence the validity of the scan. 2680
5. Position the patient according to the criteria set by the manufacturer. If it is not possible to 2681
position the patient as per the recommendations because the patient is unable to be placed 2682
in that position because of pain or limitation of movement, the technologist should make a 2683
note to that effect. 2684
6. Note the scan mode (e.g., fan beam or pencil beam) and the type of leg block used. 2685
2686
During the DXA scan: 2687
1. The patient must refrain from moving. 2688
2. The technologist should: 2689
a. Ascertain that the patient’s positioning is good. If the patient positioning is not as per 2690
the accepted recommendations, the subsequent analysis of the scan will not be valid. 2691
b. Ascertain that there are no artifacts. 2692
c. Ascertain that all the regions of interest are clearly visualized. 2693
d. Stop the DXA scan and restart it if positioning is not adequate, if there are artifacts, or if 2694
the regions of interest are not clearly visualized. 2695
2696
Analysis of the DXA scan: 2697
1. Before the analysis, the technologist needs to ascertain that: 2698
57
a. The patient’s demographics are correctly noted. 2699
b. The patient’s positioning is good. 2700
c. There are no artifacts. 2701
d. The various regions of interest are clearly visualized. 2702
2. During the analysis, the technologist will follow the manufacturer’s recommended 2703
procedure to identify the various regions of interest. 2704
2705
After the analysis the technologist will print out the results of the exam that would have been 2706
configured according to parameters set by the facility where the scans are done. 2707
2708
Reporting the DXA scan results: 2709
1. Reports are automatically generated by the equipment, and should be modified to meet the 2710
needs of the facility where the scans are done. Other information also may be added such 2711
as risk factors for osteoporosis and fracture risk assessment FRAX scores for hips and other 2712
major fracture sites. FRAX is the World Health Organization’s (WHO’s) Fracture 2713
Assessment Tool, a computer program used to estimate the probability of the patient 2714
sustaining a hip or other major osteoporotic fracture in the following ten years (WHO 2004; 2715
WHO 2012). Various models of reporting are also available from the International Society 2716
of Clinical Densitometry. These may include information about recommended diagnostic 2717
tests and treatment options. It is important however, to tailor the reports to the needs of the 2718
referring physicians. 2719
2. Various report styles exist. The ones preferred by the facility and which satisfy the needs 2720
of the referring physician should be used. Structured reports should be used if electronic 2721
records are maintained by the facility. 2722
2723
58
DENTAL 2724 2725
Diagnostic imaging is an integral part of dentistry. Dental radiographs are estimated to 2726
contribute approximately one percent (0.006 mSv) of the total population’s effective dose. The 2727
daily background effective dose to a member of the U.S. general population is estimated to be 2728
3.0 mSv/365 = 0.008 mSv/day (NCRP 2009). As of 2012, there is no scientific or epidemiologic 2729
evidence to suggest that the effective dose to the U.S. population from dental diagnostic 2730
radiographic procedures estimated to be in the range of 0.006 mSv carries significant potential 2731
biological risk either at the population level, or individual level. 2732
2733
The dental health-care worker’s goal is to keep radiation exposures to the minimum necessary to 2734
meet diagnostic requirements. In 2003, the NCRP updated its recommendations on radiation 2735
protection in dentistry (NCRP 2003). The Centers for Disease Control and Prevention published 2736
its Guidelines for Infection Control in Dental Health-Care Settings in 2003, and the U.S. Food 2737
and Drug Administration along with the American Dental Association updated selection criteria 2738
for dental radiographs in 2004 (ADA FDA 2004; CDC 2003). In 2006, the American Dental 2739
Association published its practice recommendation for the use of dental radiographs . All of 2740
these recommendations were considered when developing the following guidelines. 2741
2742
Equipment 2743 2744
It is strongly recommended that dental x-ray machine be capable of being operated in at least the 2745
60-90 kVp range, with the x-ray beam filtration consistent with the FDA requirements ((FDA 2746
2012f) Table 1). It is also strongly recommended that the equipment be collimated with a lead-2747
lined 40 cm (16 in) beam indicating device (BID) (NCRP 2003), which results in less beam 2748
divergence and less volume of patient’s tissue irradiated per exposure. Utilization of rectangular 2749
collimation is recommended for intra-oral techniques. This further restricts the beam to 2750
approximately the size of the film/imaging receptor being used (Gibbs 2000; NCRP 2003). Use 2751
of rectangular collimation reduces the exposed area to approximately 48% compared with round 2752
collimation. This improves image quality by reducing scatter, resulting in a radiograph with 2753
better resolution and better contrast. 2754
2755
The dental health professional (dentist or dental hygienist) has a variety of image receptors to 2756
select from that include conventional film, along with evolving digital technology which include 2757
photostimulable imaging plates and digital imaging sensors. Although digital radiography offers 2758
a potential for significant dose reduction, the number of retakes (commonly due to poor 2759
positioning of the bulky sensors with encumbering wire) may result in actual increased dose for 2760
the patient unless care is given to providing proper training and the use of image receptor 2761
positioning devices. Furthermore, due to the smaller active area of some sensors, more than one 2762
exposure may be required to cover the anatomical area imaged using a single conventional film. 2763
Therefore, it is recommended that an image receptor positioning device be used with sensors, 2764
that specific and ongoing training be given to orient operators on ways to eliminate the need for 2765
retakes, and that technique charts provided by manufacturers be reviewed for proper sensor 2766
placement. 2767
2768
59
In clinics or field use environments where film is still used, the fastest appropriate film should be 2769
used. For periapical and bite-wing radiographs, only films of American National Standard 2770
Institute Speed Group “F” or faster are recommended (NCRP 2003). Since there are minimal 2771
diagnostic differences between the various intraoral films available in 2012, the use of faster 2772
films (E- or F-speed) is preferred because they reduce the radiation dose by more than 50% when 2773
compared with D-speed film. 2774
2775 When panoramic and other extraoral projections are taken, it is recommended that high speed 2776
films be matched to their rare earth intensifying screens. The higher speed of the rare earth 2777
screen-film combinations (400 or higher system speed) are twice as fast as conventional calcium 2778
tungstate screen-film combinations with equivalent diagnostic value at 1/2 to 1/4 the dose to the 2779
patient (Miles et al. 1989). 2780
2781 It is imperative that the operator’s manual for all imaging acquisition hardware is readily 2782
available to the user, and that the equipment is operated and maintained following the 2783
manufacturer’s instructions, including any appropriate adjustments for optimizing dose and 2784
image quality. 2785
2786
Leaded aprons were recommended for dentistry when dental x-ray equipment was poorly 2787
collimated, unfiltered, and films were much slower than those available in 2012. Given the 2788
advent of good collimation, filtration, direct current x-ray machines, faster film speeds, and 2789
digital sensors, gonadal and effective doses resulting from scatter radiation are extremely low 2790
and are not significantly reduced by the use of the leaded aprons. According to NCRP Report 2791
No. 145 , technological advancements have eliminated the requirement for lead aprons on 2792
patients when all of the following recommendations are followed: a 60-80 kVp intraoral 2793
exposure unit is used, the source-to-image receptor distance for intraoral radiography is between 2794
20-40 cm, a rectangular collimator is used for intraoral radiographs, and a minimum of E-speed 2795
equivalent exposure film/sensors is used. It is not unreasonable to have aprons available for 2796
patients who request their use (NCRP 2003). 2797
2798
The thyroid gland is among the most sensitive organs to radiation-induced tumors, especially in 2799
children. NCRP Report No. 145 states that, “thyroid shielding shall be provided for children, and 2800
should be provided for adults, when it will not interfere with the examination” (NCRP 2003). 2801
These recommendations may be relaxed in the cases where anatomy or the inability of the 2802
patient to cooperate makes beam-receptor alignment awkward. The positive projection-angle of 2803
the panoramic x-ray beam of +4o to +7
o essentially eliminates thyroid dose. 2804
2805
Protective aprons and thyroid shields should be hung or laid flat and never folded, and 2806
manufacturer’s instructions should be followed. All protective shields should be evaluated for 2807
damage (e.g., tears, folds, and cracks) at least annually using visual and manual inspection 2808
(Miller et al. 2010b). If a defect in the attenuating material is suspected, radiographic or 2809
fluoroscopic inspection may be performed as an alternative to immediately removing the item 2810
from service. Consideration should be given to minimizing the radiation exposure of inspectors 2811
by minimizing unnecessary fluoroscopy. 2812
2813
60
As of 2012, hand-held, battery-powered x-ray systems are available for intra-oral radiographic 2814
imaging. The hand-held exposure device is activated by a trigger on the handle of the device. 2815
Device operation, at first glance, poses several concerns, which appear inconsistent with 2816
previously established dental radiological protection guidelines. These concerns include: (1) the 2817
x-ray tube assembly is hand-held by the operator rather than wall mounted, (2) the trigger for x-2818
ray exposure is on the hand-held device and not remotely located away from the source of 2819
radiation, and (3) the operator does not stand behind a barrier. However, dosimetry studies 2820
indicate that these hand-held devices present no greater radiation risk than standard dental 2821
radiographic units to the patient or the operator (Goren et al. 2008; Masih et al. 2006; Witzel 2822
2008). No additional radiation protection precautions are needed when the device is used 2823
according to the manufacturer’s instructions. These include: (1) holding the device at mid-torso 2824
height, (2) orienting the shielding ring properly with respect to the operator, and (3) keeping the 2825
cone as close to the patient’s face as practical. If the hand-held device is operated without the 2826
ring shield in place, it is recommended that the operator wear a lead apron. 2827
2828
All operators of hand-held units should be instructed on their proper storage. Due to the portable 2829
nature of these devices, they should be secured properly when not in use to prevent accidental 2830
damage, theft or operation by an unauthorized user. Hand held units should be stored in locked 2831
cabinets, locked storage rooms or locked work areas when not under the direct supervision of an 2832
individual authorized to use them. Units with user-removable batteries should be stored with the 2833
batteries removed. Records listing the names of approved individuals who are granted access 2834
and use privileges should be prepared and kept current. 2835
2836
Testing and Quality Assurance 2837 2838
Quality assurance refers to those steps that are taken to make sure that a dental facility or 2839
imaging facility consistently produces images that are adequate for the purpose with optimal 2840
patient and minimal operator exposure. Quality assurance may be divided into two major 2841
categories: quality administration and quality control. Quality administration refers to the 2842
management aspect of a quality assurance program. It includes those organizational steps taken 2843
to make sure that testing techniques are properly performed and that the results of tests are used 2844
to effectively maintain a consistently high level of image quality. An effective program includes 2845
assigning personnel to determine optimum testing frequency of the imaging devices, evaluate 2846
test results, schedule corrective action, provide training, and perform ongoing evaluation and 2847
revision of the quality assurance program. 2848
2849
Quality control comprises the procedures used for the routine physical testing of the primary 2850
components of the dental imaging chain from the x-ray machine, through processing, to the 2851
viewing of dental images. Quality control measures are listed in Table 2. Each facility, through 2852
its radiation quality control team (e.g. health physicist, medical physicist, biomedical 2853
maintenance personnel), needs to track maintenance and monitoring procedures. Dental clinics 2854
that use film should evaluate film processing darkrooms and daylight loaders for light leaks and 2855
safelight performance. 2856
2857
2858
61
Personnel 2859 2860
As in general medical radiology, it is important to eliminate unproductive radiation exposure in 2861
dentistry; thus, privileges to order dental x-ray examinations should be limited to Doctors of 2862
Dental Surgery or Dental Medicine who are eligible for licensure in the United States or one of 2863
its territories or commonwealths. Exception may be granted for persons in post graduate training 2864
status under the supervision of a person meeting such requirements. Variances to the above 2865
qualification requirements should occur only for emergency or life-threatening situations, such as 2866
natural disasters. Also, non-peacetime operations in the field or aboard ship could require such 2867
variances. Dental equipment operators should receive appropriate education and training in the 2868
areas of anatomy, physics, technique and principles of radiographic exposure, radiation 2869
protection, radiographic positioning, and image processing that are relevant to dental imaging. 2870
Proficiency can be demonstrated by satisfying existing state certification programs for dental 2871
auxiliaries. Also, proficiency can be improved by reviewing dental radiology practice 2872
recommendations from the American Dental Association. 2873
2874
Operators of dental x-ray equipment may be exposed to primary radiation in the useful beam, 2875
leakage radiation from the tube housing, and scattered radiation. Operator protection measures 2876
are required to minimize their occupational exposure. There are three basic methods to reduce 2877
the occupational dose from x-rays: position, distance, and shielding. The most effective way of 2878
reducing operator exposure to primary radiation is to enforce strict application of the position 2879
and distance rule (i.e., the operator should stand at least 2 m (6 ft) away from the tube head of 2880
the dental x-ray generator). If the operator cannot stand at least this far from the patient during 2881
the exposure, he or she should stand behind an appropriate barrier or outside the operatory 2882
behind a wall. In clinics or field situations, where the operator is required to be in the immediate 2883
exposure area, the operator should be positioned at the location of minimum exposure. This 2884
location, also known as the safe quadrant, is at an angle between 90 and 135o to the primary 2885
beam. Dental personnel should not hold image receptors in patients’ mouths. If a patient has to 2886
be restrained during exposure, a relative or friend of the patient should do so. The relative or 2887
friend may be provided a lead apron and latex gloves if the image receptor is to be held in the 2888
mouth so they have protection during exposure. 2889
2890
In panoramic imaging, scattered radiation is typically low due to the narrow beam of radiation 2891
and the shielding incorporated into the cassette carrier. With a typical workload, operators can 2892
produce panoramic images without the use of shielding as long as they are at least 2 meters (6 2893
feet) from the unit. An appropriate shield should be used if this distance cannot be maintained. 2894
2895
Structural shielding criteria are provided by NCRP (NCRP 2003). Only a qualified individual 2896
(preferably a qualified physicist) can determine how much shielding is needed for a given 2897
situation. The walls of the dental x-ray operatory must provide sufficient attenuation to limit the 2898
exposure of other individuals to permissible levels. Usually, it is not necessary to line the walls 2899
with lead to meet this requirement when intraoral or panoramic equipment is used. A wall 2900
constructed of gypsum wall board (drywall) has been determined to be sufficient for use of this 2901
equipment in the average dental office (MacDonald et al. 1983). 2902
2903
62
Any individual who is likely to exceed a designated fraction of the regulatory dose limit shall be 2904
enrolled in a radiation monitoring program (OSHA 2012; USNRC 2012c). Historically, dental 2905
radiation workers have not approached these limits and have not required dosimetry when good 2906
radiation practices have been used. To determine if dosimeters are required, evaluations of 2907
occupational dose should be conducted by a qualified physicist when a program is initiated, 2908
facilities are significantly modified, or equipment or processes change. The evaluation may 2909
consist, for example, of monitoring personnel for a period of time or assessing the radiation field 2910
around the equipment. With regard to workers who have declared their pregnancy, NCRP 2911
Report No. 145 states that “Personal dosimeters shall be provided for known pregnant 2912
occupationally-exposed personnel” (NCRP 2003). 2913
2914
Procedures 2915 2916
Justification applies to imaging in dentistry. The number of images obtained should be the 2917
minimum necessary to obtain essential diagnostic information. Dental radiographs should be 2918
prescribed only following an evaluation of the patient’s needs that includes a health history 2919
review, a clinical dental history assessment, a clinical examination and an evaluation of 2920
susceptibility to dental diseases. A full mouth survey or panoramic radiograph of the teeth and 2921
jaw structure may be justified for forensic purposes for military personnel. Postoperative 2922
radiographs should be taken only when there is clinical indication and not as verification for 2923
third-party payment plans. This is consistent with the recommendations of the Food and Drug 2924
Administration and the American Dental Association (ADA FDA 2004; NCRP 1990). In cases 2925
where emerging new dental imaging technologies are used by physicians for non-dental 2926
evaluations, these physicians should request these studies through their medical imaging ordering 2927
procedures as determined by their local facility. 2928
2929
Optimization also applies to imaging in dentistry. In order to achieve lower exposures, the 2930
operator’s manual should be readily available to the user, and the equipment should be operated 2931
following the manufacturer’s instructions, including any appropriate adjustments for optimizing 2932
dose and ensuring adequate image quality. The x-ray machine should be operated at the highest 2933
kilovoltage (kVp) adequate for diagnosis. An image receptor holding device should be used for 2934
proper film, photostimulable phosphor (PSP) plates, or sensor positioning whenever possible. 2935
Technique charts provided by manufacturers should be reviewed for proper image receptor 2936
placement. Protocols may be relaxed in the cases where anatomy or the inability of the patient to 2937
cooperate makes beam-receptor alignment awkward. 2938
2939
Cone beam computed tomography (CBCT) is used for dental implant planning, orthodontics, 2940
surgical assessment of pathology, pre- and postoperative assessment of craniofacial fractures, 2941
and temporomandibular joint assessment. CBCT provides high-resolution computed 2942
tomographic images with short scanning times (approximately 20 seconds) and high geometric 2943
accuracy (actual size of item imaged without distortion) (Scarfe et al. 2006). The major 2944
advantage of CBCT over multi-row detector computed tomography systems (MDCT) is the 2945
lower radiation dose . CBCT scanners utilize a narrow, collimated cone beam of radiation that 2946
scans both the maxilla and mandible at one time. The effective dose of a CBCT examination is 2947
approximately 7 times greater than a panoramic image but only 2-5% of a conventional CT of 2948
the same region (Scarfe et al. 2006). Given these low radiation doses, the same radiation 2949
63
protection guidelines recommended for conventional dental imaging should be implemented for 2950
CBCT. 2951
2952
64
VETERINARY 2953 2954
Diagnostic radiology is an essential part of present-day veterinary practice. The typical imaging 2955
workload in a veterinary practice is low on the average; however, certain practices unique to 2956
veterinary radiology can expose the staff at a greater rate than typical operators. In veterinary 2957
medicine, the possibility that anyone may be exposed to enough radiation to create deterministic 2958
effect is extremely remote. 2959
2960
There are two main aspects of the problem to be considered. First, personnel working with x-ray 2961
imaging equipment should be protected from excessive exposure to radiation during their work. 2962
Secondly, personnel in the vicinity of veterinary radiology facilities and the general public 2963
require adequate protection (NCRP 2004b; OSHA 2012; USNRC 2012c). 2964
2965
Equipment 2966
2967 The recommendations pertaining to the use of medical radiographic equipment and shielding 2968
requirements for humans apply to the use of similar equipment in veterinary medicine. The 2969
following points are highlighted for veterinary applications: 2970
2971
1. In a fixed facility, the floors, walls, ceilings and doors should be built with materials 2972
providing adequate radiation protection to workers. 2973
2. The shielding should be constructed to form an unbroken barrier. 2974
3. In a fixed facility, a control booth should be provided for the protection of the operator. 2975
Mobile protective barriers are not considered adequate as a control booth except for 2976
facilities requiring no shielding at 1 meter from source, or where 1/20 of permissible dose 2977
equivalent limits are not likely to be exceeded at 1 meter. 2978
4. The control booth should be located, whenever possible, such that the radiation has to be 2979
scattered at least twice before entering the booth. In facilities where the radiation beam 2980
may be directed toward the booth, the booth becomes a primary barrier and should be 2981
shielded accordingly. 2982
5. The control booth should be positioned so that during an irradiation no one can enter the 2983
radiographic room without the knowledge of the operator. 2984
6. Required warning signs should be posted on all entrance doors of each x-ray imaging room. 2985
7. Mobile x-ray equipment used routinely in one location is considered to be a fixed 2986
installation, and the facility should be shielded accordingly. 2987
8. Protective aprons, gloves and thyroid shields used for veterinary x-ray examinations should 2988
provide attenuation equivalent to at least 0.5 mm of lead-equivalence at x-ray tube voltages 2989
of up to 150 kVp. Protection should be provided throughout the glove, including fingers 2990
and wrist. Further discussion is provided in the section on RADIATION SAFETY 2991
PROCEDURES FOR FLUOROSCOPY. 2992
2993
2994 An addition to the diagnostic veterinary imaging inventory as of 2012 is hand-held, battery-2995
powered x-ray systems which have been developed for radiographic imaging. The hand-held 2996
exposure device is activated by a trigger in the handle of the device by the operator. This 2997
technology, at first glance, poses several concerns, which appear inconsistent with previously 2998
65
established radiological protection guidelines. The first concern is that the x-ray tube assembly 2999
is hand-held by the operator rather than wall mounted. The second concern is that the trigger for 3000
x-ray exposure is within the hand-held device and not remotely located away from the source of 3001
radiation. The final concern is that the operator does not stand behind a barrier. These concerns 3002
arise from previous guidelines that were established to: 1) protect the operator from possible 3003
radiation leakage from the housing of the device; 2) protect the operator from backscatter from 3004
the patient; and 3) protect the patient from excessive radiation or repeat exposures when 3005
inadequate image quality results from movement of the hand-held x-ray generator. 3006
3007
For additional information, see the veterinary section below on SPECIAL PROCEDURES FOR 3008
PORTABLE HAND-HELD SYSTEMS. 3009
3010
Testing and Quality Assurance 3011
3012 Since veterinary equipment is generally identical to medical equipment all the quality assurance 3013
tasks associated with medical equipment can be applied to veterinary equipment; however, based 3014
on the typical workload a reduced quality assurance program is probably warranted in most 3015
cases. A typical testing and QA program would consist of at least the following: 3016
1. It is essential that a radiation safety survey be completed on all new veterinary x-ray 3017
equipment by or under the direction of a qualified expert. As stated in NCRP Report No. 3018
148, “Resurveys shall be made following replacement of irradiation equipment, or 3019
modifications that could change the radiation source, whenever the workload increases 3020
significantly, or if other operating conditions are modified that could affect the radiation 3021
dose in occupied areas. Resurveys are required after the installation of supplementary 3022
shielding to determine the adequacy of the modification” (NCRP 2004b). 3023
2. Prior to the first use of a mobile fluoroscope, a radiation exposure survey should be done 3024
with the x-ray beam and maximum operating potential and with an appropriate test 3025
phantom in place to determine the perimeter of the area within which individuals without 3026
radiation protection apparel should not be present (NCRP 2004b). 3027
3. Reduce radiation exposure to the animal patient, operator, and members of the public by 3028
minimizing the need for repeat exposures because of inadequate image quality (NCRP 3029
2004b). 3030
4. For film-based systems, a sensitometry and densitometry test should be done each day the 3031
system is used in order to ensure consistent operation. A step wedge test may be used as a 3032
substitute for the standard sensitometry and densitometry test. 3033
5. Darkroom fog or darkroom integrity should be evaluated biannually. This may be 3034
especially relevant if the darkroom is not a single use room. 3035
6. It is strongly recommended that lead personnel protective equipment (e.g., aprons, gloves, 3036
thyroid collars) be evaluated at least annually for lead protection integrity using visual and 3037
manual inspection (Miller et al. 2010b; NCRP 2010). If a defect in the attenuating material 3038
is suspected, radiographic or fluoroscopic inspection may be performed as an alternative to 3039
immediately removing the item from service. Consideration should be given to minimizing 3040
the radiation exposure of inspectors by minimizing unnecessary fluoroscopy. 3041
3042
3043
66
Personnel 3044
3045 Veterinary x-ray equipment operators, similar to medical x-ray equipment operators, should 3046
receive appropriate education and training in the areas of anatomy, physics, technique and 3047
principles of radiographic exposure, radiation safety, radiographic positioning, and image 3048
processing that are relevant to veterinary imaging. Only personnel with specific, appropriate 3049
training should be permitted to operate x-ray equipment. It is strongly recommended that the 3050
veterinary medical application of x-ray equipment be performed only by or under the general 3051
supervision of a veterinarian properly trained and credentialed to operate such equipment. 3052
Individuals who routinely use veterinary radiologic equipment need a basic understanding of the 3053
following: 3054
3055 1. animal positioning techniques to allow for minimal radiation exposure for employees; 3056
2. basic principles and concepts of radiation in general and x-radiation in particular; 3057
3. component parts/workings of the x-ray machine and the production of x-rays; 3058
4. factors affecting the quality of the x-ray beam and the radiographic image; 3059
5. effects of ionizing radiation on living tissues; 3060
6. radiation bioeffects, health, and safety; 3061
7. radiation protection procedures for the operator and the patient; 3062
8. selection of appropriate imaging surveys, image receptor types, duplicating, and record 3063
keeping; 3064
9. technique of proper image processing, handling, and record keeping; 3065
10. viewing techniques and principles of interpretation; 3066
11. digital imaging and alternate imaging modalities; 3067
12. appearances of normal radiographic landmarks, artifacts, and shadows; and 3068
13. requirements for monitoring and documenting staff occupational radiation exposure. 3069
3070
Procedures 3071
3072 The procedures pertaining to the use of veterinary radiography are generally equivalent to 3073
procedures for medical (human) radiography. The following recommendations will minimize 3074
the dose to veterinary facility staff and clients from veterinary diagnostic radiographic 3075
procedures. All suggestions will secondarily minimize the dose to the radiation operator and 3076
consequently, the results may be considered as a double benefit to the patient and the worker. 3077
The guidelines and procedures outlined in this section are primarily directed toward occupational 3078
health protection. Adherence to these guidelines will also provide protection to visitors and 3079
other individuals in the vicinity of an x-ray facility. However, the safe work practices and 3080
procedures for using various types of x-ray equipment should be regarded as a minimum to be 3081
augmented with additional requirements, when warranted, to cover special circumstances in 3082
particular facilities. To achieve optimum safety, operators should make every reasonable effort 3083
to keep exposures to themselves and to other personnel as low as reasonably achievable. 3084
3085
Veterinary clinic setup 3086
3087
1. An x-ray room should be used for only one x-ray procedure at a time. 3088
67
2. All entrance doors to an x-ray room should be kept closed while a radiographic procedure is 3089
being performed. 3090
3. Where a control booth or protective barrier is available, it is strongly recommended that 3091
operators remain inside or behind when making an irradiation. If a control booth or 3092
protective screen is not available, the operator should always wear protective clothing. 3093
4. When film screen imaging is used, the fastest combination of films and intensifying screens 3094
consistent with diagnostically acceptable results and within the capability of the equipment 3095
should be used. 3096
5. When digital x-ray imaging is used, procedures should be established to prevent 3097
excessively high doses, also known as dose creep, as addressed in the radiography section 3098
of this document. 3099
3100
Personal protective equipment 3101 3102
1. Personnel should use protective devices, as appropriate. 3103
2. Protective aprons, gloves and thyroid shields should be hung or laid flat and never folded, 3104
and manufacturer’s instructions should be followed. 3105
3. Armored gloves (welding gloves) should be used to restrain fractious animals. Since lead-3106
lined gloves will not protect against bites that could puncture the lead, the radiation 3107
protection provided by the garment may be compromised (NCRP 2004b). 3108
3109
Animal restraint 3110 3111
1. If necessary, the animal should be sedated or holding devices used during radiography. 3112
However, if this is not possible and a person must restrain the animal, that person should 3113
wear appropriate radiation protective equipment (aprons, gloves, etc.) and avoid direct 3114
irradiation by the primary x-ray beam. No person should routinely hold animal patients 3115
during x-ray examinations (NCRP 2004b). 3116
2. Individuals under the age of 18 and pregnant or potentially pregnant women should not be 3117
permitted to hold animals during radiography. 3118
3119
Use of x-ray equipment 3120 3121
1. X-ray equipment should be operated only by or under the direct supervision of qualified 3122
individuals. 3123
2. X-ray machines that are energized and ready to produce radiation should be supervised. 3124
3. The x-ray room should contain only those persons whose presence is essential when a 3125
radiological procedure is carried out. 3126
4. The radiation beam should always be directed toward adequately shielded or unoccupied 3127
areas. 3128
5. The radiation beam and scattered radiation should be attenuated as closely as possible to the 3129
source. 3130
6. Personnel should keep as far away from the x-ray beam as is practicable at all times (2 m). 3131
Exposure of personnel to the x-ray beam should never be allowed unless the beam is 3132
adequately attenuated by the animal and by protective clothing or barriers. 3133
7. A hand-held radiographic cassette or image receptor should not be used. 3134
68
8. For table-top radiography when the sides of the table are not shielded, a sheet of lead at 3135
least 1 mm in thickness and slightly larger than the maximum beam size should be placed 3136
immediately beneath the cassette or film. 3137
9. Veterinarians should not allow veterinary diagnostic radiation devices under their control to 3138
be used on human beings (NCRP 2004b). 3139
10. Technique charts should be developed for all animal types that are routinely radiographed. 3140
3141
Personal dosimetry 3142 3143
1. The workload in a typical veterinary clinic may not be sufficient to require the issuance of 3144
personal dosimetry; however, a qualified expert should be consulted for a clinic’s particular 3145
situation. 3146
2. Personal dosimetry should be worn in a manner that complies with regulatory requirements 3147
and ensures that radiation doses can be determined accurately. See the section on 3148
PERSONNEL AND AREA MONITORING. 3149
3. Occupational radiation dose limits in veterinary and human medical practice should be the 3150
same. See the section on PERSONNEL AND AREA MONITORING. 3151
3152
Special procedures for portable hand-held systems 3153 3154
1. Portable hand-held x-ray systems should be used as outlined in the instructions that come 3155
with the unit. Exposures using this unit should be made only when the area adjacent to the 3156
clinical area is free of all individuals not directly involved in the imaging procedure. When 3157
standard radiology protocols are utilized according to manufacturer instructions, with the 3158
ring shield in place, there is no indication for additional radiation protection 3159
recommendations. 3160
3161
2. Portable hand-held x-ray systems use essentially the same amount of radiation as 3162
traditional wall mounted x-ray units since the amount of radiation needed to generate an 3163
adequate image is determined by the image receptor, not by the x-ray device. Radiation 3164
safety criteria for operators of the hand-held device should be the same as mentioned 3165
earlier for conventional exposure systems. 3166
3167
3. All operators of these units should be instructed on its proper storage. Due to the portable 3168
nature of the hand-held device, it should be secured properly when not in use to prevent 3169
accidental damage, theft or operation by an unauthorized user. Hand held units should be 3170
stored in locked cabinets, locked storage rooms or locked work areas when not under the 3171
direct supervision of an individual authorized to use them. Units with user-removable 3172
batteries should be stored with the batteries removed. Records listing the names of 3173
approved individuals that are granted access and use privileges should be prepared and kept 3174
current (quarterly review). 3175
3176
69
MEDICAL IMAGING INFORMATICS 3177 3178
Digital information systems are used for the ordering, scheduling, tracking, processing, storage, 3179
transmission, and viewing of imaging studies and providing the reports of study interpretations. 3180
These systems should be used to the greatest extent possible. They include picture archiving and 3181
communication systems (PACSs), teleradiology systems, radiology information systems, 3182
hospital information systems, and the Electronic Health Record (Congress 2007). For efficiency 3183
of workflow, these systems do not operate independently, but instead are connected to the 3184
imaging devices and each other by computer networks and exchange information in accordance 3185
with standards such as TCP/IP (Transmission Control Protocol/Internet Protocol, or the Internet 3186
protocol suite), DICOM, HL7, and IHE. These information systems are complex and will not be 3187
discussed in detail in this report. However, there are certain aspects of these systems that 3188
indirectly can affect the radiation doses to patients from imaging studies. Proper planning, 3189
design, management, and use of these systems can help avoid performing unnecessary or 3190
inappropriate studies and repeat studies. These systems can also help in monitoring doses to 3191
patients and image receptors and monitoring retakes; the information from this monitoring can 3192
help in optimizing doses from imaging procedures. 3193
3194
These information systems can help avoid the ordering of unnecessary or inappropriate imaging 3195
studies. At the time that a Referring Medical Practitioner places the order for an imaging study, 3196
the system can provide decision support regarding the appropriateness of the study for the 3197
particular patient and notification of alternatives that may impart less or no radiation. These 3198
information systems can also notify the Referring Medical Practitioner of previously acquired 3199
studies that may render an additional imaging study unnecessary. 3200
3201
The inability to retrieve an imaging study can create the need for a repeat study. These digital 3202
information systems and procedures for their use should be designed to protect against data loss. 3203
Such measures should include administrative, physical, and technical safeguards, including 3204
storing information on stable media, ensuring the storage location is secure from natural and 3205
human threats, ensuring the stored information is secure from deliberate or accidental erasure or 3206
modification, storing duplicate backup copies of the information on media in a remote location 3207
or locations, and precautions against loss of information from media wear and aging and media 3208
obsolescence. Additionally, the facility should have a disaster plan in place to guide operations 3209
when the network is inoperable or power outage affects operation of the PACS system. It is the 3210
responsibility of the institution to meet the records retention, security, privacy, and retrieval 3211
requirements of its agency and other Federal requirements (e.g., HIPAA and associated Federal 3212
regulations) (ACR 2007c; ACR 2009a; DHHS 2012b), and to address the aforementioned issues. 3213
3214
These systems also provide an important quality assurance function. They should facilitate 3215
monitoring of patient dose indices, the doses to radiographic image receptors, and the 3216
number of retakes and inadequate images. This requires both capture and storage of this 3217
information and appropriate software tools for data analysis and display. Equipment 3218
manufacturers should be encouraged to work with professional societies and standards 3219
organizations to develop and implement standardized dose reporting systems. These 3220
systems should provide an estimate of patient radiation dose that is accurate for the 3221
individual, available in real time to the operator, and documented for the individual 3222
70
patient. These systems should also be capable of transmitting de-identified patient 3223
radiation dose data to a central dose registry. To this end, Federal facilities should give 3224
preference to equipment with these standardized dose reporting systems when making 3225
purchasing decisions. 3226
3227
71
SUMMARY AND RECOMMENDATIONS FOR FACILITY ACTION 3228 3229
GENERAL 3230 3231
1. Each facility should establish a formal mechanism whereby Referring Medical Practitioners 3232
have sources of information available at the time of ordering regarding appropriate 3233
diagnostic imaging methods to answer the clinical question and to optimize ionizing 3234
radiation dose to the patient. These may include decision support software or 3235
appropriateness criteria. A mechanism for consultation with Radiological Medical 3236
Practitioners should also be made available. 3237
2. The Universal Protocol should always be followed to ensure the right patient gets the right 3238
procedure. 3239
3. Physicians and staff should always strive to limit patient irradiation to that necessary to 3240
perform the procedure. 3241
4. Facilities involved in health care delivery should ensure that operators of medical imaging 3242
equipment that use x-rays: 1) are adequately trained to produce acceptable quality images, 3243
2) know how to produce these images with appropriate patient doses, and 3) periodically 3244
demonstrate continuing competence. 3245
5. Facilities should ensure that the operator’s manual is readily available to the user, and the 3246
equipment is operated following the manufacturer’s instructions, including any appropriate 3247
adjustments for optimizing dose and ensuring adequate image quality. 3248
6. Facilities should establish a formal mechanism whereby Radiological Medical Practitioners 3249
are available to consult with Referring Medical Practitioners regarding the optimal 3250
diagnostic imaging method to answer the clinical question while minimizing ionizing 3251
radiation dose to the patient. 3252
7. Facilities should use equipment that provides relevant patient dose information. This 3253
equipment should allow the facility to program in dose alerts to inform operators if selected 3254
operating parameters might produce a radiation dose exceeding that recommended by the 3255
facility. 3256
8. Facilities should use the dose information from individual patient imaging procedures that 3257
is provided by imaging equipment as part of the quality assurance program for identifying 3258
opportunities to reduce dose. . 3259
9. Facilities should use reference levels as a quality improvement tool by collecting and 3260
assessing radiation dose data. Each facility should also submit its radiation dose data to a 3261
national registry, if and when such a registry is available. 3262
10. Facilities should be aware of upgrades to software and hardware of x-ray imaging systems 3263
that enhance safety. These should be evaluated and considered for implementation. 3264
11. Facilities should assess the radiation exposure of workers and provide periodic feedback to 3265
them. In addition, each worker who is expected to receive more than 10% of the applicable 3266
dose limit should be required to wear one or more dosimeters. 3267
3268
BONE DENSITOMETRY 3269 3270
1. Facilities should establish a range of acceptable precision performance and ensure each 3271
technologist is trained and meets this standard. 3272
72
2. The facility should ensure that patients imaged for precision and cross-calibration studies 3273
should be representative of the facility’s patient population 3274
3. Facilities should ensure that practitioners who interpret bone densitometry results are 3275
knowldegable in this field and not rely solely on a report produced by the equipment.. 3276
3277
CHILDREN AND PREGNANT WOMEN 3278 3279
1. Facilities should ensure that when a monitored radiation worker declares her pregnancy she 3280
wears a dosimeter on the lower abdomen, underneath the apron at the level of the fetus. 3281
The dosimeter should be exchanged monthly. She should be issued this dosimeter unless 3282
such a dosimeter is already being worn. 3283
2. Children are more radiosensitive than adults. Facilities should ensure that technique and 3284
imaging protocols are appropriate for the child’s size or weight to ensure adequate image 3285
quality and optimize radiation dose. 3286
3. In general, facilities should ensure that neither screening nor elective x-ray examinations 3287
are performed on pregnant women. 3288
3289
DENTISTRY 3290 1. Facilities should ensure that beam indicating devices are used with sensors, specific and 3291
ongoing training is given to orient operators on ways to eliminate the need for retakes, and 3292
technique charts provided by manufacturers are reviewed periodically for proper sensor 3293
placement. 3294
2. In clinics or field use environments where film may still need to be used, the fastest and 3295
most appropriate film should be used. 3296
3. In facilities where panoramic and other extraoral projections are obtained using film, it is 3297
recommended that high speed film be used and spectrally matched to its appropriate rare 3298
earth intensifying screen. 3299
4. An image receptor holding device for proper film, PSP or sensor positioning should be used 3300
whenever possible. 3301
5. Thyroid shielding shall be provided for children, and should be provided for adults, when it 3302
will not interfere with the examination (NCRP 2003). 3303
6. Dental clinics that use film should evaluate film processing darkrooms and daylight loaders 3304
for light leaks and safelight performance. 3305
3306
FLUOROSCOPY 3307 1. The facility’s procedures should be written with the understanding that fluoroscopy can 3308
deliver a significant radiation dose to the patient, even when used properly. 3309
2. The facility should ensure that every person who operates or directs the operation of 3310
fluoroscopic equipment is trained in the safe use of the equipment. 3311
3. When a facility purchases fluoroscopic equipment, the additional cost of including dose-3312
reduction technology is justified because the reduction in patient radiation dose can be 3313
considerable. 3314
4. Some types of fluoroscopic procedures have a potential for patient skin doses exceeding 2 3315
Gy. The facility should ensure that there are additional training requirements for operators 3316
and additional equipment requirements for these procedures. 3317
73
5. The facility should ensure that patient radiation dose data, including patient skin dose data 3318
when available, are recorded in the patient’s medical record. 3319
3320
VETERINARY 3321 3322
1. Facilities should ensure that the veterinary medical application of x-ray equipment is 3323
performed only by or under the general supervision of a veterinarian properly trained and 3324
credentialed to operate such equipment. 3325
2. Facilities should ensure that individuals who routinely use veterinary radiographic 3326
equipment have a basic understanding of using medical x-rays and animal positioning 3327
techniques. 3328
3. Facilities should ensure that armored gloves (welding gloves) are used to restrain fractious 3329
animals since lead-lined gloves will not protect against bites that could puncture the lead. 3330
4. Facilities should have animal sedatives and holding devices available, and ensure they are 3331
used, if necessary. 3332
5. Facilities should not allow anyone to routinely hold animal patients during x-ray 3333
examinations. 3334
6. Facilities should not allow veterinary diagnostic radiation devices under their control to be 3335
used on human beings. 3336
3337
INFORMATICS 3338 3339
1. Patient safety requires that infrastructure exists for collecting, storing, and analyzing patient 3340
dosimetry data. Facilities should plan for longitudinal tracking of patient radiation doses. 3341
This planning should address the data acquisition, networking, storage, analysis, and 3342
security requirements of existing and planned future diagnostic devices. 3343
2. Digital information systems should be used in Federal facilities to the greatest extent 3344
possible. 3345
3. Facilities should give preference to equipment with standardized dose reporting systems 3346
when making purchasing decisions. 3347
4. Facilities should ensure that their health professionals use digital information systems, to 3348
help avoid the ordering of unnecessary or inappropriate imaging studies. 3349
3350
INFORMED CONSENT 3351 3352
Federal facilities should ensure that, except in emergency situations, informed consent is 3353
obtained from the patient or the patient’s legal representative and is appropriately 3354
documented prior to the initiation of any procedure that is likely to expose the patient, or 3355
fetus if the patient is pregnant, to significant risks and potential complications. 3356
3357
PRESCRIPTION 3358 3359
Facilities should ensure that appropriate information is obtained and reviewed at the time of 3360
ordering/prescribing to optimize the choice of study and protocol, and to optimize the dose. 3361
3362
74
REFERENCE LEVELS 3363 3364
1. Reference levels are dose values for a standard phantom or actual patient for specific 3365
procedures measured at a number of representative clinical facilities. Facilities should use 3366
reference levels as quality assurance and quality improvement tools. 3367
2. National reference levels that are specific for the U.S. population should continue to be 3368
developed. The on-going nationwide collection of these data from government and non-3369
government facilities, such as by NEXT and ACR, is essential to this effort. Facilities 3370
should submit radiation dose data to a national registry, if and when available. 3371
3. Facilities should ensure that a representative sampling and assessment of exposure 3372
indicators from each modality is performed at least annually, but preferably quarterly. It 3373
should be reviewed by the chief technologist. This effort should be performed under the 3374
guidance of a qualified physicist. 3375
4. If the mean radiation dose at the facility exceeds the reference level, the facility should 3376
investigate as appropriate to reduce radiation dose. If the mean radiation dose is 3377
significantly lower than the reference level, the facility should evaluate image quality. 3378
5. If local practice at a facility results in a mean radiation dose that is greater than the RL, the 3379
facility should investigate the equipment. If the equipment is functioning properly and 3380
within specification, operator technique and procedure protocols should be examined. 3381
3382
A-75
ACRONYMS AND ABBREVIATIONS 3383 3384
AAPM American Association of Physicists in Medicine 3385
ACC American College of Cardiology 3386
ACCF American College of Cardiology Foundation 3387
ACGME Accreditation Council for Graduate Medical Education 3388
ACR American College of Radiology 3389
ACS American Cancer Society 3390
ADA American Dental Association 3391
AEC automatic exposure control 3392
AHA American Heart Association 3393
ALARA as low as reasonably achievable 3394
AMA American Medical Association 3395
ANSI American National Standards Institute 3396
AOA American Osteopathic Association 3397
AOBR American Osteopathic Board of Radiology 3398
ARRT American Registry of Radiologic Technologists 3399
ATSDR Agency for Toxic Substances and Disease Registry 3400
BEIR Biological Effects of Ionizing Radiation 3401
BID beam indicating device 3402
BMD bone mineral density 3403
CBCT cone beam computed tomography (cone beam CT) 3404
CFR Code of Federal Regulations 3405
CIRSE Cardiovascular and Interventional Radiology Society of Europe 3406
cm centimeter 3407
CNMT Certified Nuclear Medicine Technologist 3408
CR computed radiography 3409
CRCPD Conference of Radiological Control Program Directors 3410
CT computed tomography 3411
CTDI computed tomography dose index 3412
CTDIvol volumetric CTDI 3413
DAP dose area product (units are Gy-cm2) 3414
DC direct current 3415
DDM Doctor of Dental Medicine 3416
DDR Direct digital radiography 3417
DDS Doctor of Dental Surgery 3418
DEXA see DXA 3419
DHHS Department of Health and Human Services 3420
DLP dose length product 3421
DoD Department of Defense 3422
DR digital radiography 3423
DRT Diagnostic Radiologic Technologist 3424
DXA dual-energy x-ray absorptiometry (formerly DEXA) 3425
EHR Electronic Health Record 3426
EPA Environmental Protection Agency 3427
ESE entrance skin exposure 3428
76
ESEG entrance skin exposure guide 3429
FDA Food and Drug Administration 3430
FGI Fluoroscopically-guided interventional 3431
FGR Federal Guidance Report 3432
FOV field of view 3433
GI gastrointestinal 3434
GSD genetically significant dose 3435
Gy gray (radiation dose, equal to 100 rem). Subunit is mGy (milligray) 3436
HRS Heart Rhythm Society 3437
ICRP International Commission on Radiological Protection 3438
IEC International Electrotechnical Commission 3439
IRB Institutional Review Board 3440
ISCD International Society for Clinical Densitometry 3441
ISCORS Interagency Steering Committee on Radiation Standards 3442
KAP kerma area product 3443
kerma kinetic energy released in matter (type of radiation measurement in air) 3444
kV kilovolts 3445
kVp kilovolts potential (or kilovolts peak) 3446
mA milliampere 3447
mammo mammography 3448
mAs milliampere-second 3449
MDCT multi-row detector computed tomography (multi-detector CT) 3450
MQSA Mammography Quality Standards Act 3451
mrem millirem 3452
mSv millisievert 3453
NCI National Cancer Institute 3454
NCRP National Council on Radiation Protection and Measurements 3455
NEXT Nationwide Evaluation of X-ray Trends 3456
NIH National Institutes of Health 3457
OSHA Occupational Safety and Health Administration 3458
OSL optically stimulated luminescence 3459
PACS picture archiving and communication system 3460
PET positron emission tomography 3461
PSD position-sensitive x-ray detection 3462
PSP photostimulable phosphor 3463
RCIS Registered Cardiovascular Invasive Specialists 3464
rem Traditional radiation unit for equivalent dose (product of absorbed dose [rad] and 3465
radiation weighting factor). Subunit is mrem (millirem) or µrem (microrem) 3466
RSO Radiation Safety Officer 3467
RT(N) Radiological Technologist Nuclear qualification 3468
SCAI Society for Cardiac Angiography and Intervention 3469
SPECT single particle emission computed tomography 3470
SIR Society of Interventional Radiology 3471
SSD source-to-skin distance 3472
Sv sievert (SI radiation unit for equivalent dose or effective dose). Subunit is mSv 3473
(millisievert) or µSv (microsievert) 3474
77
TLD thermoluminescent dosimeter 3475
USPSTF United States Preventive Services Task Force 3476
USN United States Navy 3477
VA US Department of Veterans Affairs 3478
3479
78
GLOSSARY 3480 3481
Acceptance test – a test carried out after new equipment has been installed or major 3482
modifications have been made to existing equipment, in order to verify compliance with the 3483
manufacturer’s specifications, contractual specifications, and applicable local regulations or 3484
equipment standards 3485
Adequate image – an image that provides the information needed to answer the clinical question 3486
at an optimized dose, i.e., the lowest dose possible to produce that image 3487
Adequate image quality – image quality sufficient for the clinical purpose. Whether the image 3488
quality is adequate depends on the modality being used and the clinical question being asked. 3489
ALARA (as low as reasonably achievable) – a principle of radiation protection philosophy that 3490
requires that exposures to ionizing radiation be kept as low as reasonably achievable, 3491
economic and social factors being taken into account. The protection from radiation exposure 3492
is ALARA when the expenditure of further resources would be unwarranted by the reduction 3493
in exposure that would be achieved. 3494
Ancillary personnel – personnel beyond the operational medical staff who provide support 3495
services 3496
Angiography – radiography of vessels after the injection of a radiopaque contrast material; 3497
usually requires percutaneous insertion of a radiopaque catheter and positioning under 3498
fluoroscopic control (Stedman 2006) 3499
Attenuation – reduction in radiation intensity, such as via the use of shielding 3500
Backscatter (as opposed to scatter) – a Compton scattering event in which a photon strikes an 3501
object and deflects at an angle greater than 90°, i.e., in a direction back toward its source 3502
Beam indicating device (BID) – a lead lined tube attached to an x-ray tube head through which 3503
the primary x-ray beam will travel, used by the operator, especially in a dental setting, to align 3504
the beam with the image receptor 3505
Benefit – the probability or quantifiable likelihood that health will improve or deterioration will 3506
be prevented as a result of performing or not performing a medical procedure 3507
Benefit:risk ratio – a determination (possibly subjective) of the benefit to the patient from 3508
undergoing a procedure involving imaging using ionizing radiation compared with the risk to 3509
the patient from receiving a radiation dose associated with the consequent imaging. 3510
Maximizing the benefit:risk ratio involves balancing the benefit:risk ratio to the patient from 3511
an x-ray procedure against that from alternatives (e.g., ultrasound, MRI, or no action). 3512
Bone densitometry – the noninvasive measurement of certain physical characteristics of bone 3513
that reflect bone strength (typically reported as bone mineral content or bone mineral density) 3514
and used for diagnosing osteoporosis, estimating fracture risk, and monitoring changes in 3515
bone mineral content 3516
Collimator – a device used to reduce the cross-sectional area of the useful beam of photons or 3517
electrons with an absorbing material 3518
Computed radiography (CR; also see DR) – a projection x-ray imaging method in which a 3519
cassette houses a sensor plate rather than photographic film. This photo-stimulable phosphor-3520
coated plate captures a latent image when exposed to x-rays and, when processed, releases 3521
light that is converted to a digital image. 3522
Computed tomography (CT) – an imaging procedure that uses multiple x-ray transmission 3523
measurements and a computer program to generate tomographic images of the patient (NCRP 3524
2000) 3525
79
Cone – an open-ended device on a dental x-ray machine designed to indicate the direction of the 3526
central ray and to serve as a guide in establishing a desired source-to-image receptor distance 3527
(NCRP 2000) 3528
Cone Beam Computed Tomography system (CBCT) – A digital volume tomography method 3529
used in some imaging applications using two dimensional digital detector arrays, and a cone-3530
shape x-ray beam (instead of fan-shaped) that rotates around the patient to generate a high-3531
resolution, 3D image, with high geometric accuracy. Reconstruction algorithms can be used 3532
to generate images of any desired plane. 3533
Credential – diploma, certificate, or other evidence of adequate educational performance that 3534
gives one a title or credit 3535
CTDIvol – a radiation dose parameter derived from the CTDIw (weighted or average CTDI given 3536
across the field of view). The formula is: 3537
CTDIvol = N·T·CTDIw / I, where 3538
N = number of simultaneous axial scans per x-ray source rotation, 3539
T = thickness of one axial scan (mm), and 3540
I = table increment per axial scan (mm). 3541
Deterministic effects – effects that occur in all individuals who receive greater than the threshold 3542
dose and for which the severity of the effect varies with the dose (NCRP 2003) 3543
Diagnosis – the determination of the nature of a disease, injury, or congenital defect (Stedman 3544
2006) 3545
Digital radiography (DR) – an x-ray imaging method (or radiography) which produces a digital 3546
rather than film projection image. Includes both CR and DDR 3547
Direct digital radiography (DDR; also see CR and DR) – an x-ray imaging method in which a 3548
digital sensor, rather than photographic film, is used to capture an x-ray image. DDR is a 3549
cassette-less imaging method (providing faster acquisition time than cassette-based CR) using 3550
an electronic sensor that converts x-rays to electronic signals (charge or current) when 3551
exposed to x-rays. 3552
Dose – a measure of the energy deposited by radiation in a target. Used in this report as a 3553
generic term unless context refers to a specific quantity, such as absorbed dose, committed 3554
equivalent dose, committed effective dose, effective dose, equivalent dose or organ dose, as 3555
indicated by the context. 3556
Cumulative air kerma – sum of the kinetic energy released to a small volume of air at a 3557
specific point in space during a specified event or time frame when irradiation by an x-3558
ray beam 3559
Cumulative dose – total radiation dose from all delivered to any specific organ or tissue 3560
Dose area product (DAP), also called kerma-area product (KAP) – the product of the air 3561
kerma and the area of the irradiated field and is measured in Gy·cm2, so it does not 3562
change with distance from the x-ray tube. A good measure of total energy delivered to 3563
the patient, and of stochastic risk. Not a good indicator of deterministic risk 3564
Dose alert value - a value of CTDIvol (in units of mGy) or of DLP (in units of mGy·cm) 3565
that is set by the operating institution to trigger an alert to the operator prior to 3566
scanning within an ongoing examination if it would be exceeded by an accumulated 3567
dose index, on acquisition of the next confirmed protocol element group. An alert 3568
value represents a value above which the accumulated dose index value would be well 3569
above the institution’s established range for the examination that warrants more 3570
stringent review and consideration before proceeding. (see dose notification value) 3571
80
Dose equivalent – the product of the absorbed dose at a point in the tissue or organ and 3572
the appropriate quality factor for the type of radiation giving rise to the dose 3573
Dose length product (DLP) – an indicator of the integrated radiation dose from a 3574
complete CT examination. It addresses the total scan length by the formula DLP = 3575
CTDIvol x scan length, with the units mGy-cm. 3576
Dose notification value - A value of CTDIvol (in units of mGy) or of DLP (in units of 3577
mGy·cm) that is set by the operating institution to trigger a notification to the operator 3578
prior to scanning when exceeded by a corresponding dose index value expected for the 3579
selected protocol element. A notification value represents a value above which a dose 3580
index value would be above the institution’s established range for the protocol 3581
element. (see dose alert value) 3582
Dose registry – see registry 3583
Effective dose – (E) – the sum of the weighted equivalent doses for the radiosensitive 3584
tissues and organs of the body. It is given by the expression E = ΣT (wT HT), in which 3585
HT is the equivalent dose in tissue or organ T and wT is the tissue weighting factor for 3586
tissue or organ T. The unit of E and HT is joule per kilogram (J kg–1
), with the special 3587
name sievert (Sv) (see equivalent dose and tissue weighting factor). 3588
Equivalent dose (formerly dose equivalent) – (HT): the mean absorbed dose (DT) in a 3589
tissue or organ modified by the radiation weighting factor (wR) for the type and energy 3590
of the radiation. The quantity HT,R, defined as HT,R = wR ⋅DT,R, where DT,R is the 3591
absorbed dose delivered by radiation type R averaged over a tissue or organ T and wR 3592
is the radiation weighting factor for radiation type R (IAEA 2011a). The unit for HT is 3593
J kg–1
, with the special name sievert (Sv). 3594
Reference point dose – radiation dose at the reference point, selected for reporting 3595
purposes, which is located at the center or in the central part of the planning target 3596
volume (PTV) 3597
Skin dose – radiation dose to the dermis 3598
Dosimeter – dose measuring device (NCRP 2003) 3599
Electronic Health Record (EHR) – an electronic record of health-related information on an 3600
individual that is created, gathered, managed, and consulted by authorized health 3601
professionals and staff (Congress 2007) 3602
Exposure – in this report, exposure is used most often in its general sense, meaning to be 3603
irradiated. When used as the specifically defined radiation quantity, exposure is a measure of 3604
the ionization produced in air by x or gamma radiation. The unit of exposure is coulomb per 3605
kilogram (C kg–1
). The special unit for exposure is roentgen (R), where 1 R = 2.58 × 10–4
C 3606
kg–1
. 3607
Exposure categories – 3608
Medical exposure – exposure incurred by patients for the purpose of medical or dental 3609
diagnosis or treatment; by carers and comforters associated with medical, dental, and 3610
veterinary procedures; and by volunteers in a program of biomedical research involving their 3611
exposure 3612
Occupational exposure – exposure of workers incurred in the course of their work 3613
Public exposure – exposure incurred by members of the public from sources in planned 3614
exposure situations, emergency exposure situations, and existing exposure situations, 3615
including incidental medical exposure, but excluding any occupational or prescribed medical 3616
exposure 3617
81
Film/film radiograph – film is a thin, transparent sheet of polyester or similar material coated on 3618
one or both sides with an emulsion sensitive to radiation and light; a radiograph is a film or 3619
other record produced by the action of x-rays on a sensitized surface (NCRP 2003) 3620
Filtration – material in the useful beam that usually absorbs preferentially the less penetrating 3621
radiation (NCRP 2003) 3622
Fluoroscopy – the process of producing a real-time image using x-rays (NCRP 2003) 3623
Gamma ray – a photon emitted in the process of nuclear transition or radioactive decay 3624
Gray (Gy) – the special SI name for the unit of the quantities absorbed dose and air kerma. 1 Gy 3625
= 1 J kg–1
(see rad, rem, gray, and Sievert) 3626
Guidance level – optimal range of detector exposure index values that should be based on patient 3627
body habitus, anatomical view, clinical question, and other relevant factors 3628
Health physics – the field of science concerned with radiation physics and radiation biology and 3629
their application to radiation protection. Health physicists may specialize in nuclear power, 3630
environmental and waste management, laws and regulations, dosimetry, emergency response, 3631
medicine or a host of other sub-specialties where radiation is utilized. Of particular interest 3632
for this document is the medical health physics sub-specialty. 3633
Health physicist – a health professional, with education and specialist training in the concepts 3634
and techniques of applying physics in medical, environmental, or occupational settings, or 3635
competent to practice independently in one or more of the subfield specialties of medical 3636
physics or in health physics 3637
Health professional – an individual who has been formally recognized through appropriate 3638
national procedures to practice a profession related to health (e.g., medicine, dentistry, 3639
chiropractic, podiatry, nursing, veterinary medicine) (adapted from (IAEA 2011a)) 3640
Helical – spiral in form; a curve traced on a cylinder (or human body) by the rotation of a point 3641
crossing its right section at a constant oblique angle 3642
Image – representation of an object produced by machine-produced ionizing radiation 3643
Image receptor – a system for deriving a diagnostically usable image from the x-rays transmitted 3644
through the patient (NCRP 2003) 3645
Incidental exposure – exposure not associated with the primary purpose for which it was 3646
delivered 3647
Informed consent – voluntary agreement given by a person or a patients' responsible proxy (e.g., 3648
a parent) for participation in a study, immunization program, treatment regimen, invasive 3649
procedure, etc., after being informed of the purpose, methods, procedures, benefits, and risks. 3650
The essential criteria of informed consent are that the subject has both knowledge and 3651
comprehension, that consent is freely given without duress or undue influence, and that the 3652
right of withdrawal at any time is clearly communicated to the patient. Other aspects of 3653
informed consent in the context of epidemiologic and biomedical research, and criteria to be 3654
met in obtaining it, are specified in International Guidelines for Ethical Review of 3655
Epidemiologic Studies (Chanaud 2008; Stedman 2006)(Geneva: CIOMS/WHO 1991) and 3656
International Ethical Guidelines for Biomedical Research Involving Human Subjects (Geneva: 3657
CIOMS/WHO 1993). 3658
Intensifying screen – a device consisting of fluorescent material, which is placed in contact with 3659
the film in a radiographic cassette. Radiation interacts with the fluorescent material, releasing 3660
light photons. (adapted from (NCRP 2003) 3661
82
Interlock – device that automatically shuts off or reduces the radiation emission rate from an 3662
accelerator to acceptable levels (e.g., by the opening of a door into a radiation area). In 3663
certain applications, an interlock can be used to prevent entry into a treatment room. 3664
Intervention – any measure taken to alter the course of medical diagnosis whose purpose is to 3665
improve a health outcome 3666
Isocenter – the small point in space (or generally spherical or elliptical volume) where radiation 3667
beams emitted during the rotational swing of an x-ray tube gantry intersect 3668
Justification – the process of determining for a planned exposure situation whether a practice is, 3669
overall, beneficial, i.e. whether the expected benefits to individuals and to society from 3670
introducing or continuing the practice outweigh the harm (including radiation detriment) 3671
resulting from the practice (IAEA 2011a) 3672
Kerma (kinetic energy released per unit mass, or kinetic energy released in matter) – the sum of 3673
the initial kinetic energies of all the charged particles liberated by uncharged particles (e.g., x-3674
rays) in a material of mass δm (IAEA 2011a). The unit for kerma is J kg–1, with the special 3675
name gray (Gy). Kerma can be quoted for any specified material at a point in free space or in 3676
an absorbing medium (e.g., air kerma). 3677
Kerma-area product (KAP, also called dose-area product or DAP) – the product of the air kerma 3678
and the area of the irradiated field and is measured in Gy·cm2, so it does not change with 3679
distance from the x-ray tube. A good measure of total energy delivered to the patient, and of 3680
stochastic risk. Not a good indicator of deterministic risk. 3681
Licensed independent practitioner – any individual permitted by law and by the organization to 3682
provide care and services, without direction or supervision, within the scope of the 3683
individual's license and consistent with individually granted clinical privileges (see Referring 3684
Medical Practitioner and Radiological Medical Practitioner) 3685
Mammography – the use of x-rays to produce a diagnostic image of the breast 3686
Medical exposure – exposure incurred by patients for the purposes of medical or dental diagnosis 3687
or treatment; by careres and comforters; and by volunteers subject to exposure as part of a 3688
program of biomedical research (IAEA 2011a) 3689
Medical health physics – the profession dedicated to the protection of healthcare providers, 3690
members of the public, and patients from unwarranted radiation exposure. Medical health 3691
physicists are knowledgeable in the principles of health physics and in the applications of 3692
radiation in medicine. While medical physics and medical health physics have a number of 3693
similarities and overlapping fields of study and interest, the emphasis of practice or day-to-3694
day routines are different. 3695
Medical physics – a field of science concerned with applying physics to medical imaging and 3696
determining patient dose. The Medical Physicist's clinical practice focuses on methods to assure 3697
the safe and effective delivery of radiation to achieve a diagnostic or therapeutic result as 3698
prescribed in patient care. 3699
Medical physicist – a health professional, with education and specialist training in the concepts 3700
and techniques of applying physics in medicine, competent to practice independently in one or 3701
more of the subfield specialties of medical physics (IAEA 2011a) 3702
Medical technologist – a health professional, with specialist education and training in medical 3703
radiation technology, competent to carry out radiological procedures, on delegation from the 3704
radiological medical practitioner, in one or more of the specialties of medical radiation 3705
technology (IAEA 2011a) 3706
83
Members of the public – all persons who are not already considered occupationally exposed by a 3707
source or practice under consideration. When being irradiated as a result of medical care, 3708
patients are a separate category. 3709
Occupational exposure – exposure to an individual that is incurred in the workplace as a result of 3710
situations that can reasonably be regarded as being the responsibility of management 3711
(exposures associated with medical diagnosis or treatment for the individual are excluded). 3712
(NCRP 2003) 3713
Optically stimulated luminescent (OSL) dosimeter – a dosimeter containing a crystalline solid 3714
for measuring radiation dose, plus filters to help characterize the types of radiation 3715
encountered. When irradiated with intense light, OSL crystals that have been exposed to 3716
ionizing radiation give off light proportional to the energy they receive from the radiation 3717
(NCRP 2003). 3718
Optimal dose – the minimum radiation dose required to be delivered by an x-ray imaging system 3719
to produce an image that is of adequate quality for the intended purpose. This requires that 3720
the x-ray generator and imaging equipment to be working appropriately, (see adequate image). 3721
Optimization of protection – the process of determining what level of protection and safety 3722
would result in the magnitude of individual doses, the number of individuals (workers and 3723
members of the public) subject to exposure and the likelihood of exposure being “as low as 3724
reasonably achievable, economic and social factors being taken into account” (ALARA) (as 3725
required by the System of Radiological Protection). For medical exposures of patients, the 3726
optimization of protection and safety is the management of the radiation dose to the patient 3727
commensurate with the medical purpose. “Optimization of protection and safety” means that 3728
optimization of protection and safety has been applied and the result of that process has been 3729
implemented. (IAEA 2011a) 3730
Personal protective equipment – specialized clothing or equipment (e.g., leaded or tungsten 3731
apron, gloves, thyroid collar, eyeglasses) worn by an employee to protect against a hazard. 3732
General work clothes not intended to serve as a protection against a hazard are not considered 3733
to be personal protective equipment. 3734
Phantom – as used in this report, a volume of tissue- or water-equivalent material used to 3735
simulate the absorption and scattering characteristics of the patient’s body or portion thereof 3736
Picture archiving and communications system (PACS) – electronic system for the archival 3737
storage and transfer of information associated with x-ray images 3738
Pitch – in CT, table incrementation per x-ray tube rotation divided by the nominal x-ray beam 3739
width at isocenter 3740
Prescribe – the process of requesting or ordering an exam to be performed, or the process of 3741
determining how an exam should be done in order to optimize the choice of study and 3742
protocol, and optimize the radiation dose 3743
Protocol – selected parameters for image acquisition that defines the portion of the patient’s 3744
anatomy to be imaged, whether and how contrast agents will be administered, the number and 3745
timing of imaging sequences, and acquisition technical parameters (pitch, collimation or beam 3746
width, kV, mA (constant or modulated and specifying the parameters determining the balance 3747
between image noise and patient dose), rotation time, physiologic gating, image quality 3748
factors, and reconstruction method 3749
Pulsed (as in pulsed fluoroscopy) – x-rays not produced continuously, but in rapid succession as 3750
pulses. Reduces dose by using a lower pulse rate (e.g., 15 or 7.5 pulses/sec) and in 3751
conjunction with digital image memory to provide a continuous video display 3752
84
Qualified expert – an individual who, by virtue of certification by appropriate boards or societies, 3753
professional licenses or academic qualifications and experience, is duly recognized as having 3754
expertise in a relevant field of specialization, e.g. medical physics, radiation protection, 3755
occupational health, fire safety, quality assurance or any relevant engineering or safety 3756
specialty (IAEA 2011a) 3757
Qualified physicist – an individual who is competent to practice independently in the relevant 3758
medical subfield of medical physics or health physics. In general, a health physicist or 3759
medical physicist with appropriate training and experience regarding the medical use of x-rays 3760
is considered a qualified physicist. Ideally, persons should have certification from the 3761
American Board of Health Physics, the American Board of Medical Physics, the American 3762
Board of Radiology, or the American Board of Industrial Hygiene, to be considered a 3763
qualified expert in these respective fields. For the purposes of this document, the relevant 3764
subfield of medical physics is diagnostic radiological physics. Certification, continuing 3765
education, and experience are factors toward demonstrating that an individual is a qualified 3766
physicist. Individual federal agencies may develop their own criteria for determining when a 3767
physicist is a “Qualified Physicist” as defined in this document. 3768
Qualified medical physicist – an individual who is competent to practice independently in the 3769
relevant subfield of medical physics. For the purposes of this document, the relevant subfield 3770
is diagnostic radiological physics. Certification and continuing education and experience in 3771
the relevant subfield is one way to demonstrate that an individual is competent to practice in 3772
that subfield of medical physics and to be a qualified medical physicist. 3773
Quality assurance – the function of a management system that provides confidence that specified 3774
requirements will be fulfilled 3775
Rad – the special (traditional or historical) name for the unit of absorbed dose. 1 rad = 0.01 J kg-
3776 1. In the SI system of units, it is replaced by the special name gray (Gy). 1 Gy = 100 rad 3777
(NCRP 2000). (see rad, rem, gray, and Sievert) 3778
Radiation Safety Officer – the individual whose responsibility it is to ensure adequate protection 3779
of workers and the public from exposure to ionizing radiation 3780
Radiation weighting factor, wR – a number (as specified in the System for Radiological 3781
Protection) by which the absorbed dose in a tissue or organ is multiplied to reflect the relative 3782
biological effectiveness of the radiation in inducing stochastic effects at low doses, the result 3783
being the equivalent dose (IAEA 2011a) 3784
Radiography – the production of images on film or other record by the action of x-rays 3785
transmitted through the patient (NCRP 2003) 3786
Radiological Medical Practitioner – a health professional with specialist education and training 3787
in the medical uses of radiation, who is competent to perform independently or to oversee 3788
procedures involving medical exposure in a given specialty (IAEA 2011a) (see licensed 3789
independent practitioner) 3790
Reference dose, patient entrance reference dose (or reference air kerma, reference dose, 3791
cumulative dose, cumulative air kerma, KA,R) – the dose at the patient entrance reference 3792
point. For C-arm fluoroscopic equipment, this is also known as the interventional reference 3793
point, and is located along the central ray of the x-ray beam, 15 cm back from the isocenter 3794
toward the x-ray tube. The isocenter is the central point about which the C-arm rotates. 3795
Reference dose is measured in Gy and is not the same as skin dose (IEC 2008). 3796
85
Reference level – a level used in medical imaging to indicate whether, in routine conditions, the 3797
dose to the patient in a specified radiological procedure is unusually high or low for that 3798
procedure 3799
Referring Medical Practitioner – a health professional who, in accordance with national 3800
requirements, may refer individuals to a radiological medical practitioner for medical 3801
exposure (IAEA 2011a) (see licensed independent practitioner) 3802
Registry – central national repository for patient radiation dose and equipment parameter data 3803
Rem – the special (traditional or historical) name for the unit of dose equivalent numerically 3804
equal to the absorbed dose (D) in rad, modified by a quality factor (Q). 1 rem = 0.01 J kg-1
. In 3805
the SI system of units, it is replaced by the special name sievert (Sv), which is numerically 3806
equal to the absorbed dose (D) in gray modified by a radiation weighting factor (ωR). 1 Sv = 3807
100 rem (NCRP 2003). (see rad, rem, gray, and Sievert) 3808
Resolution – in the context of an imaging system, the output of which is finally viewed by the 3809
eye, it refers to the smallest size or highest spatial frequency of an object of given contrast that 3810
is just perceptible. The resolution actually achieved with imaging lower contrast objects is 3811
normally much less, and depends upon many variables such as subject contrast levels and 3812
noise of the overall imaging system (NCRP 2003). 3813
Risk – the probability or quantifiable likelihood that a detriment to health will occur as a result of 3814
performing or not performing a medical procedure 3815
Roentgen – the special name for exposure, which is a specific quantity of ionization (charge) 3816
produced by the absorption of x- or gamma-radiation energy in a specified mass of air under 3817
standard conditions. 1 R = 2.58 x 10-4
coulombs per kilogram (C kg-1
) (NCRP 2003). 3818
Screening – the evaluation of an asymptomatic person in a population to detect a disease process 3819
not known to exist at the time of evaluation 3820
Sievert (Sv) - the special SI name for the quantities equivalent dose or effective dose. 3821
Equivalent dose is the radiation protection quantity used for setting limits that help ensure that 3822
deterministic effects (e.g. damage to a particular tissue) are kept within acceptable levels. The 3823
SI unit of equivalent dose is the J kg-1
, and is abbreviated HT. It is numerically equal to a 3824
radiation weighting factor (ωR) [or quality factor (Q)] multiplied by the absorbed dose in 3825
tissue T (DT,R). 1 Sv = 100 rad (NCRP 2003). The formula is: 3826
HT = ∑R ωR DT,R or ∑R QR DT,R 3827
where 3828
ωR = radiation weighting factor, 3829
DT,R = absorbed dose to tissue T from radiation type R, and 3830
QR= quality factor. 3831
3832
Effective dose is the radiation protection quantity used for setting limits that help ensure that 3833
stochastic effects (i.e., cancer and genetic effects) are kept within acceptable levels. The SI 3834
unit of effective dose is the J kg-1
, and is abbreviated HE. It is numerically equal to a radiation 3835
weighting factor (ωR) multiplied by a tissue weighting factor (ωT) and the absorbed dose from 3836
that radiation in tissue T (DT,R) in gray. Identically, it is the equivalent dose multiplied by a 3837
tissue weighting factor. 1 Sv = 100 rem (NCRP 2003). The formula is: 3838
HE = ∑T ωT ∑R ωR DT,R = ∑T HT ωT 3839
where 3840
HE = the effective dose (or effective dose equivalent) to the entire individual, 3841
ωT = the tissue weighting factor in tissue T, 3842
86
HT = the equivalent dose (or dose equivalent), 3843
ωR = the radiation weighting factor, and 3844
DT,R = the absorbed dose to tissue T from radiation type R. 3845
(see rad, rem, gray, and Sievert) 3846
Signal to noise ratio – the ratio of input signal to background interference. The greater the ratio, 3847
the clearer the image (NCRP 2003). 3848
Skin dose – radiation dose to the dermis, measured for example as entrance skin dose or peak 3849
skin dose 3850
Slice – a 2-dimensional reconstructed cross-sectional image depicting a patient’s anatomy 3851
produced using x-rays, MRI, ultrasound, or other non-invasive means 3852
Step wedge – a device with various thicknesses of aluminum used to verify the consistency of 3853
the x-ray and film processing systems. Typically each step of the stepwedge is about 1 mm 3854
thick and about 3 to 4 mm wide with at least 6 steps. The device is placed on a film cassette 3855
and exposed under the exact same exposure parameters and geometry set up. The film is then 3856
developed and the steps are visually compared to the reference film identically exposed and 3857
processed in fresh solutions under ideal conditions. A reproducible change of one step or 3858
more in density should signal the need for corrective action. 3859
Stochastic effects – effects, the probability of which, rather than their severity, is a function of 3860
radiation dose, implying the absence of a threshold. More generally, stochastic means random 3861
in nature (NCRP 2003). 3862
Supervision, general – means the procedure is furnished under the supervising individual’s 3863
overall direction and control, but the supervising individual’s presence is not required during 3864
the performance of the procedure. Under general supervision, the training of the personnel 3865
who actually perform the task and the maintenance of the necessary equipment and supplies 3866
are the continuing responsibility of the supervising individual (adapted from (DHHS 2012a) 3867
Supervision, direct – means the supervising individual must be present in the local area (for 3868
physicians, in the office suite) and immediately available to furnish assistance and direction 3869
throughout the performance of the procedure. It does not mean that the supervising individual 3870
must be present in the room when the task is performed (adapted from (DHHS 2012a)). 3871
Supervision, personal – means a supervising individual must be in attendance in the room during 3872
the performance of the task (adapted from (DHHS 2012a)) 3873
Technique factor – operator selectable parameter affecting the x-ray beam (e.g., kV, mA, time) 3874
Tissue weighting factor, wT – multiplier of the equivalent dose to an organ or tissue, as given by 3875
the System for Radiological Protection, used for radiation protection purposes to account for 3876
the different sensitivities of different organs and tissues to the induction of stochastic effects 3877
of radiation (IAEA 2011a) 3878
Tomography – a special technique to show in detail images of structures lying in a 3879
predetermined plane of tissue, while blurring or eliminating detail in images of structures in 3880
other planes (NCRP 2003) 3881
Total effective dose equivalent (TEDE) – the sum of the deep-dose equivalent (for external 3882
exposures) and the committed effective dose equivalent (for internal exposures) 3883
Universal Protocol – A Joint Commission process developed to address wrong site, wrong 3884
procedure, and wrong person surgeries and other procedures. The three principal components 3885
of the Universal Protocol include a pre-procedure verification, site marking, and a timeout 3886
(The Joint Commission 2012a; The Joint Commission 2012b) 3887
87
Worker – any person who works, whether full time, part time or temporarily, for an employer 3888
and who has recognized rights and duties in relation to occupational radiation protection 3889
(IAEA 2011a) 3890
A-1
3891
APPENDIX A – NIH INFORMED CONSENT TEMPLATES 3892 3893
3894
The guidance in this appendix is suitable for research involving diagnostic and interventional x-3895
ray procedures. It applies to radiation use indicated for research involving human subjects. 3896
Examples might include evaluating new mammography protocol using lower kVp as 3897
recommended by ICRP, virtual colonoscopy, and national lung screening trials. It excludes 3898
radiation oncology research, in which radiation doses to subjects may be much higher. A 3899
discussion of human subjects research ethics, patient benefit:risk considerations, and the role of 3900
Institutional Review Boards is beyond the scope of this document, but is an essential process 3901
prior to the conduct of research involving human subjects. 3902
3903
The risk from research protocols involving radiation use indicated for research, as described 3904
above, can be categorized into groups. A useful approach is to group risk as minimal, minor to 3905
intermediate, or moderate. The templates on the following pages are adapted from those used by 3906
the NIH in 2012 (less than 1 mSv (100 mrem) “minimal” and 1-50 mSv (100 mrem – 5 rem) 3907
“minor to intermediate”). Doses above 50 mSv (5 rem) may be considered to range from 3908
moderate to substantial. The specific ranges and text may be adjusted as required by the specific 3909
IRB (NIH 2001; NIH 2008a; NIH 2008b; NIH 2010). Another approach to selecting the dose 3910
ranges and descriptors for these templates is shown below. 3911
3912
Classification schemes for use of E as a qualitative indicator of stochastic risk for diagnostic and
interventional x-ray procedures
Range of E
(mSv)
Radiation Risk Descriptor Expected Minimum
Individual or Societal Benefit ICRP Martin (2007) NCRP
<0.1 Trivial Negligible Negligible Describable
0.1-1 Minor Minimal Minimal Minor
1-10 Intermediate Very low Minor Moderate
10-100 Moderate Low Low Substantial
>100 - - Acceptable (in
context of the
expected benefit)
Justifiable expectation of very
substantial individual benefit
Adapted from: (ICRP 1991b; Martin 2007)
3913
3914
3915
A-2
MINIMAL RISK 3916 Adapted from NIH TEMPLATE A (Total effective dose less than or equal to 1 mSv (100 mrem)) 3917
3918
This research study involves exposure to radiation from (insert type of procedure or procedures). 3919
Please note that this radiation exposure is not necessary for your medical care and is for research 3920
purposes only. 3921
3922
The total amount of radiation you will receive in this study is from (insert maximum number) of 3923
(insert description of type of x-ray procedure). The Radiation Safety Committee has reviewed 3924
the use of radiation in this research study and has approved this use as involving minimal risk 3925
and necessary to obtain the research information desired. 3926
3927
You will receive a total of (XX) mSv or (YY) rem to your (insert highest-dosed organ, typically 3928
skin) from participating in this study. All other parts of your body will receive smaller amounts 3929
of radiation. Although each organ will receive a different dose, the amount of radiation exposure 3930
you will receive from this study is equal to a uniform whole-body exposure of less than (insert 3931
total effective dose value). This calculated value is known as the “effective dose” and is used to 3932
relate the dose received by each organ to a single value. 3933
3934
For comparison, the average person in the United States receives a radiation dose of 3 mSv (300 3935
mrem) per year from natural background sources, such as from the sun, outer space, and from 3936
radioactivity found naturally in the earth’s air and soil. The dose that you will receive from 3937
participation in this research study is about the same amount you would normally receive in 3938
(insert number) months from these natural sources. 3939
3940
While there is no direct evidence that the small radiation dose received from participating 3941
in this study is harmful, there is indirect evidence it may not be completely safe. There 3942
may be an extremely small increase in the risk of cancer. 3943
3944
A-3
MINOR TO INTERMEDIATE RISK 3945 Adapted from NIH TEMPLATE B (1 mSv < Total effective dose = < 50 mSv) or (100 mrem < 3946
Total effective dose = < 5 rem) 3947
3948
This research study involves exposure to radiation from (insert type of procedure or procedures). 3949
Please note that this radiation exposure is not necessary for your medical care and is for research 3950
purposes only. 3951
3952
The total amount of radiation you will receive in this study is from (insert maximum number) 3953
(scans or repetitions) of (insert description of type of x-ray procedure). The Radiation Safety 3954
Committee has reviewed the use of radiation in this research study and has approved this use as 3955
involving low risk (more than minimal but less than moderate) and necessary to obtain the 3956
research information desired. 3957
3958
Although each organ will receive a different dose, the amount of radiation exposure you will 3959
receive from this study is equal to a uniform whole-body exposure of less than (insert total 3960
effective dose value). This calculated value is known as the “effective dose” and is used to relate 3961
the dose received by each organ to a single value. The amount of radiation you will receive in 3962
this study is less than the annual radiation dose of 50 mSv per year (5 rem per year) permitted for 3963
someone who works with radiation on a daily basis. 3964
3965
For comparison, the average person in the United States receives a radiation dose of 3 mSv (300 3966
mrem) per year from natural background sources, such as from the sun, outer space, and from 3967
radioactivity found naturally in the earth’s air and soil. The dose that you will receive from 3968
participation in this research study is about the same amount you would normally receive in 3969
(insert number) months from these natural sources. 3970
3971
The effects of radiation exposure on humans have been studied for over 60 years. In fact, these 3972
studies are the most extensive ever done of any potentially harmful agent that could affect 3973
humans. In all these studies, no harmful effect to humans has been observed from the levels of 3974
radiation you will receive by taking part in this research study. However, scientists disagree on 3975
whether radiation doses at these levels are harmful. Even though no effects have been observed, 3976
some scientists believe that radiation can be harmful at any dose - even low doses such as those 3977
received during this research. 3978
3979
While there is no direct evidence that the radiation dose received from participating in this 3980
study is harmful, there is indirect evidence it may not be completely safe. There may be a 3981
small increase in the risk of cancer. 3982 3983
(INCLUSION OF THIS PARAGRAPH IS OPTIONAL) Some people may be concerned that 3984
radiation exposure may have an effect on fertility or cause harm to future children. The radiation 3985
dose you will receive in this research study is well below the level that affects fertility. In 3986
addition, radiation has never been shown to cause harm to the future children of individuals who 3987
have been exposed to radiation. Harm to future generations has been found only in experiments 3988
on animals that have received radiation doses much higher than the amount you will receive in 3989
this study.3990
REF-1
3991
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