radiation protection chapter 6. copyright ©2012 by pearson education, inc. all rights reserved....

Radiation Protection

Chapter 6

Copyright ©2012 by Pearson Education, Inc.All rights reserved.

Essentials of Dental Radiography for Dental Assistants and Hygienists, Ninth EditionEvelyn M. Thomson • Orlen N. Johnson

Objectives

Define the key words. Adopt the ALARA concept. Use the selection criteria guidelines to

explain the need for prescribed radiographs.

Explain the roles communication, working knowledge of quality radiographs, and education play in preventing unnecessary radiation exposure.



Objectives Explain the roles technique and

exposure choices play in preventing unnecessary radiation exposure.

Explain the function of the filter. State the filtration requirements for an

intraoral dental x-ray unit that operates above and below 70 kVp.



Objectives Compare inherent, added, and total

filtration. State the federally mandated diameter

of the intraoral dental x-ray beam at the patient’s skin.

Explain the difference between round and rectangular collimation.

List the two functions of a collimator.



Objectives Explain how PID shape and length

contribute to reducing patient radiation exposure.

Identify film speeds currently available for dental radiography use.

Explain the role image receptor holders play in reducing patient radiation exposure.



Objectives Advocate the use of the lead/lead

equivalent thyroid collar and apron. Explain the role darkroom protocol and

film handling play in reducing patient radiation exposure.

Summarize the radiation protection methods for the patient.



Objectives Explain the roles time, shielding, and

distance play in protecting the radiographer from unnecessary radiation exposure.

Utilize distance and location to take a position the appropriate distance and angle from the x-ray source at the patient’s head during an exposure.



Objectives Describe monitoring devices used to

detect radiation. Summarize the radiation protection

methods for the radiographer.



Objectives List the organizations responsible for

recommending and setting exposure limits.

State the maximum permissible dose (MPD) for radiation workers and for the general public.



Introduction Although it is the consensus of

radiobiologists that the dose received from a dental x-ray exposure is not likely to be harmful, even the experts do not know what risk a small dose carries.



Introduction The patient has agreed to be subjected

to the risks of radiation exposure because he/she believes that the oral health care practitioner will follow safety protocols that protect the patient from excess exposure.



Introduction In this chapter, we discuss radiation

safety protocols, including selection criteria used in prescribing dental radiographs and methods to minimize x-ray exposure to both the dental patient and the radiographer.



ALARA

“As Low As Reasonably Achievable”



Protection Measures for the Patient Professional judgment Technical ability of the operator Technique standards Equipment standards Optimum film processing



Protection Measuresfor the Patient Professional Judgment

Use evidence-based selection criteria when determining which patients need radiographs.

Guidelines adopted by the American Dental Association that assist in deciding when, what type, and how many radiographs should be taken are shown in Table 6-1.



Table 6-1 Guidelines for Prescribing Dental Radiographs



Protection Measuresfor the Patient Technical Ability of the Operator

Communication — clear instructions; patient cooperation

Working knowledge of quality radiographs — understand what a quality dental radiograph should image

Education — continuing education is important



Protection Measuresfor the Patient Technique Standards

Intraoral technique choice — first choice; The paralleling technique yields more accurate and precisely sized radiographic images

Exposure factors — select the appropriate exposure factors — kilovoltage (kVp), milliamperage (mA), and time.



Protection Measuresfor the Patient Equipment Standards: The Federal

Performance Standard for Diagnostic X-ray Equipment, effective August 1974. Provisions require that all x-ray

equipment manufactured after this date meet certain radiation safety requirements including filtration, collimation, and PID



Figure 6-1 Collimator and filter. The collimator is a lead washer that restricts the size of the x-ray beam. The filter is an aluminum disc that filters (removes) the long wavelength x-rays.



Figure 6-2 Effect of filtration on skin exposure. Aluminum filters selectively absorb the long wavelength x-rays.



Figure 6-3 Effect of collimation on primary beam. Lead collimators control the shape and size of the primary beam. The beam is limited to the approximate size of the image receptor.



Figure 6-4 External collimator attaches to the PID to reduce the area of radiation exposure.



Figure 6-5 The collimator restricts the size of the primary beam to 2.75 in. (7 cm) at the end of the PID.



Figure 6-6 Although circular collimation provides a large enough area of exposure to adequately cover a size #2 image receptor, the patient also receives excess radiation not needed for the exposure of this receptor.



Figure 6-7 Rectangular PIDs restrict the x-ray beam to the approximate size of a #2 intraoral image receptor. Rectangular PIDs are available in 8, 12, and 16 inches (20.5, 30, and 41 cm). (Courtesy of Margraf Dental Manufacturing Inc.)



Figure 6-8 Plastic closed-ended, pointed “cones” are no longer used.



Figure 6-9 Round PIDs are available in 16, 12, and 8 inches (41, 30, and 20.5 cm).



Figure 6-10 Target-surface distance. The longer the target-surface distance, the more parallel the x-rays and the less tissue exposed. Note that the beam size at the patient’s skin entrance is 2.75 in. (7 cm) for both target-surface distances. It is the exit beam size that increases to expose a larger area when using the shorter target-surface distance.



Figure 6-11 Many image receptor holding devices are available to fit most situations. The use of a holder prevents asking patients to put their fingers in the path of the primary beam.



Figure 6-12 Lead aprons and thyroid collars are available in a wide range of sizes. Aprons are available with an attached thyroid collar, or the thyroid collar may be a separate part.



Figure 6-13 Patient protected with lead apron with thyroid collar in place.



Protection Measuresfor the Patient Optimum Film Processing

Processing errors increase patient radiation exposure by resulting in retake radiographs.

Patient protection techniques should be used at all times to keep radiation exposures as low as possible



Box 6-1 Summary of Protection Methods for the Patient



Protection Methods for the Radiographer

All measures taken to protect the patient from radiation also benefit the radiographer.

Radiation protection methods include time, shielding, and distance.

The radiographer should spend a minimal amount of time, protected by shielding, at the greatest distance from the source of radiation to avoid unnecessary exposure.



Box 6-2 Summary of Methods to Protect the Radiographer



Figure 6-14 Distance is an effective means of reducing exposure from scatter radiation.



Figure 6-15 When structural shielding is not available, the radiographer should stand in a position at least 6 ft (1.83 m) from the head of the patient at an angle of 45º to the exiting primary beam.



Radiation Monitoring Area monitoring Personnel monitoring: Types

Film badge Thermoluminescent dosimeter (TLD) OSL (optimally stimulated luminescence)

monitor DIS (direct ion stimulation) monitor



Table 6-2 Types of Personnel Monitoring Devices



Figure 6-16 OSL radiation monitor worn by the radiographer to monitor radiation exposure. (Courtesy of Landauer, Inc.)



Figure 6-17 DIS radiation monitor. Sized and shaped similar to a thumb drive, this device has a clip to allow the radiographer to wear the monitor while working with ionizing radiation. The device uses a USB connector to plug into a computer with Internet access. When logged on to the manufacturer’s Web site, real-time radiation exposure readings may be downloaded from the device. (Courtesy of Quantum Products.)



Organizations Responsible for Recommending/Setting Exposure Limits

Maximum permissible dose (MPD) Radiation workers General public



Table 6-3 Radiation Protection Organizations



Guides for Maintaining Safe Radiation Levels

Radiation safety legislation



Review: Chapter Summary Oral healthcare professionals have an

ethical responsibility to adopt the ALARA concept.

The most important step in keeping the patient’s exposure to a minimum is the use of evidenced-based selection criteria to assess patients for radiographic need.



Review: Chapter Summary The technical ability of the radiographer

will aid in preventing unnecessary radiation exposure to the patient. Technical ability includes: communication, working knowledge of quality radiographs, and education.



Review: Chapter Summary Technique standards, including the

choice of paralleling or bisecting technique, and the selection of exposure factors also aid in preventing unnecessary radiation exposure.



Review: Chapter Summary Equipment standards that play an

important role in reducing patient radiation dose include collimation, filtration, and PID length.

Filtration is the absorption of long wavelength, less penetrating x-rays from the x-ray beam by passage through a sheet of material called a filter.



Review: Chapter Summary Present safety standards require an

equivalent of 1.5 mm aluminum filtration for dental x-ray machines operating in ranges below 70 kVp and a minimum of 2.5 mm aluminum for machines operating at or above 70 kVp. Total filtration is the sum of inherent and added filtration.



Review: Chapter Summary

Collimation — control of the size and shape of the

useful beam. Federal regulations require round

opening collimators restrict the x-ray beam to 2.75

in. (7 cm) at the patient end of the PID.

Rectangular collimation reduces patient radiation

dose by 70 percent over round collimation.

Collimation reduces scattered radiation that

contributes to poor contrast of radiographic

images.



Review: Chapter Summary (PID) is an extension of the tube

housing; used to direct the primary x-ray beam. The length of the PID helps establish the desired target–surface distance. PIDs have either a round or rectangular shape and are available in lengths of 8 in. (20.5 cm), 12 in. (30 cm), and 16 in. (41 cm)



Review: Chapter Summary Fast film requires less radiation for

exposure. Film speed groups D, E, or F are currently available for use in dental radiography.

The use of digital image receptors can further reduce the radiation dose to the patient.



Review: Chapter Summary Image receptor holders eliminate using

the patient’s fingers to stabilize the receptor intraorally, avoiding unnecessary radiation exposure to the patient’s fingers.

A lead or lead-equivalent thyroid collar with apron should be placed on all patients during intraoral x-ray exposures.



Review: Chapter Summary Optimum film processing using time —

temperature techniques in an adequately equipped darkroom will help avoid retakes.

Reduce operator exposure — reduce time spent near the source of radiation; use structural shielding; or stand 6 feet away from the source of radiation at a 45-degree angle to the exiting primary beam.



Review: Chapter Summary Area and personnel radiation monitoring

can be used to measure radiation exposures. The ICRP and the NCRP recommend dose limits. Federal, state, and local agencies set regulations governing exposure.



Review: Chapter Summary The American Dental Association and

the American Academy of Oral and Maxillofacial Radiology work closely with all agencies responsible for radiation safety.



Review: Chapter Summary The maximum permissible dose (MPD) is

50 mSv (5 rem) per year for radiation workers and 5 mSv (0.5 rem) for the general public, radiation workers who are pregnant, and children under 18 years of age.



Recall: Study Questions General Chapter Review



Reflect: Case Study Use the selection criteria guidelines to

make a preliminary recommendation and/or to explain to the patient why the dentist has prescribed or has not prescribed radiographs. Consider the following three cases:



Reflect: Case Study1. A 17-year-old patient presents with a

healthy oral assessment. No active caries were clinically detected. No periodontal pockets were noted. His record indicates that his last radiographs were bitewings taken 6 months ago. Based on the evidence-based selection criteria guidelines, what would be the most likely recommendation for radiographs for this patient?



Reflect: Case Study2. A 25-year-old female recall patient

presents for her 6-month check-up. Although her homecare is good, Class II (multisurface) restorations are present on several molars and premolars. Her last radiographs were bitewings taken 3 years ago. Based on the evidence-based selection criteria guidelines, what would be the most likely recommendation for radiographs for this patient?



Reflect: Case Study3. A 45-year-old male patient, new to

your practice, presents with a moderate periodontal condition and evidence of generalized dental disease. He reveals that he has not been “to the dentist” in several years, but is here today to begin to “take care of his teeth.” Based on the evidence-based selection criteria guidelines, what would be the most likely recommendation for radiographs for this patient?



Relate: Laboratory Application Proceed to Chapter 6, Laboratory

Application, to complete this activity.

radiation protection chapter 6. copyright ©2012 by pearson education, inc. all rights reserved....

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