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58. You are shown whole body images and selected spot images from a Tc-99m methylenediphosphonate bone scintigram obtained in an adult male patient presenting with joint pain(Figures 1A and 1B). What is the MOST LIKELY diagnosis?

A. Multiple cortical skeletal metastases

B. Osteomyelitis

C. Shin splints

D. Hypertrophic osteoarthropathy

Diagnostic In-Training Exam 2006 1

Section III – Nuclear Radiology

Figure 1A

Figure 1B

Question 58

Rationales:

A. Incorrect. Focal cortical metastases are uncommon, but do occur. However, the symmetrical metadi-aphyseal distribution of the lesions and involvement of both the proximal and distal appendicularskeleton are highly atypical for metastases. The clinical history of joint pain also points to othermore likely etiologies for the findings present.

B. Incorrect. Osteomyelitis may produce areas of increased cortical tracer uptake, secondary to perios-titis associated with the active infectious process. Abnormality is not usually limited to corticalareas alone, and is often more intense than the findings in this case. Furthermore, the bilaterallysymmetrical distribution of the findings is highly atypical for osteomyelitis.

C. Incorrect. Shin splints may also produce areas of increased uptake along the cortical surfaces oflong bones, as seen in this case. However, the findings in shin splints are usually confined to the tib-iae, and most often involve primarily the diaphyseal regions, often with only low-level increaseduptake. Furthermore, involvement of the upper extremities would not be expected with shin splints.

D. Correct. The findings in this case are characteristic in appearance and location for secondary hyper-trophic osteoarthropathy (formerly known as hypertrophic pulmonary osteoarthropathy or HPO).This disorder is most often associated with intrathoracic lesions, such as primary lung neoplasms ormesothelioma. It can also occur in association with other intrathoracic lesions, including bronchiec-tasis, emphysema, lung infections, metastatic disease, etc. It may be seen in patients with congenitalheart disease, inflammatory bowel disease and lymphoma. Patients may present with joint pain,clubbing and periosteal new bone formation on radiographs. The differential diagnosis also includespachydermoperiostosis and thyroid acropachy.

American College of Radiology2


59. You are shown serial 5-minute anterior images and final right anterior oblique and right lateralimages from a Tc-99m DISIDA hepatobiliary scan performed on a 55-year-old man withabdominal pain, fever and ascites, s/p paracentesis (Figures 2A and 2B). What is the MOSTLIKELY diagnosis?

A. Acute cholecystitis

B. Bile leak

C. Common bile duct obstruction

D. Normal study



Figure 2A



Figure 2B

Question 59

Findings: There is prompt hepatic uptake, with early visualization of activity in the region of the gall-bladder fossa. Faint, amorphous activity is noted inferior to the liver on the right, beginning at 10 min-utes and better seen thereafter. In addition, there is accumulation of activity throughout the peritonealcavity, beginning at 15 minutes post-injection, and progressively increasing throughout the study. Thereis also the appearance of abnormal linear activity along the inferior margin of the left lobe of the liver,beginning at 25-30 minutes into the study and progressively increasing in intensity. The right lateralimage demonstrates activity spreading anterior to the liver, also consistent with intraperitoneal biliaryleakage. Hepatic clearance is also moderately prolonged.

Rationales:

A. Incorrect. The findings are not consistent with acute cholecystitis. There is prompt visualization ofthe gallbladder as early as 5-10 minute post-injection, which essentially excludes acute cholecysti-tis. Furthermore, acute cholecystitis does not explain the presence of biliary leakage present in thiscase. Perforation of the gallbladder may occur in gangrenous cholecystitis, but that entity is virtual-ly always associated with cystic duct obstruction, which would result in non-visualization of thegallbladder as well.

B. Correct. The findings in this case described above are consistent with a relatively large bile leak,most likely arising in the region of the gallbladder fossa. In this case, the findings may be secondaryto trauma from paracentesis.

C. Incorrect. There is prolonged hepatic clearance and non-visualization of the small bowel, both find-ings that occur in the presence of common bile duct obstruction. However, in common duct obstruc-tion, there is often complete non-visualization of the biliary tree, including the gallbladder, even inthe absence of cholecystitis. In addition, common duct obstruction is not usually associated with bil-iary leakage, which is present in this case.

D. Incorrect. This study is not normal. A significant degree of biliary leakage is demonstrated, asdescribed above. Furthermore, the images also demonstrate prolonged hepatic clearance and non-visualization of the small bowel, both of which are also abnormal findings.



60. A 2-month-old male with marked hypertension is referred for captopril renography. You areshown serial 1-minute posterior pre- and post-captopril images (Figure 3). What is the MOSTLIKELY diagnosis?

A. Normal study

B. Right renal artery stenosis

C. Left renal artery stenosis

D. Bilateral renal artery stenosis



Figure 3

Question 60

Findings: The baseline pre-captopril study demonstrates mildly decreased tracer uptake bilaterally, withnormal excretion. The post-captopril images demonstrate significant bilateral deterioration in excretion,with marked cortical retention noted bilaterally.

Rationales:

A. Incorrect. Although initial (left) study appears symmetrically normal, there is clearly a bilateraldelay in cortical clearance and excretion on the post-captopril study.

B. Incorrect. In unilateral right renal artery stenosis, ACE-inhibitor should create an asymmetric delayin right renal washout, not the bilaterally delayed washout present in this case.

C. Incorrect. In unilateral left renal artery stenosis, ACE-inhibitor should create an asymmetric delay inleft renal washout, not the bilaterally delayed washout present in this case.

D. Correct. The post-captopril study fails to demonstrate sequential right and left renal pelvis andbladder activity seen at midpoint of the baseline pre-captopril study. Administration of the ACEinhibitor has produced a symmetric delay in renal cortical clearance, manifested by marked bilateralcortical retention and non-visualization of the renal pelves and bladder. These findings are typicalfor bilateral ACE-inhibition of compensatory post-glomerular vascular constriction, with resultantdelay in transcortical clearance, in this child with bilateral congenital renal artery stenosis.





Figure 4

61. You are shown representative coronal, transaxial and sagittal images from an F-18 FDG(fluorodeoxyglucose) PET scan (Figure 4). What is the MOST LIKELY diagnosis?

A. Lymphoma

B. Bronchogenic carcinoma

C. Esophageal carcinoma

D. Normal variant

Question 61

Rationales:

A. Incorrect. The abnormal uptake in this case is located in the posterior mediastinum, where adenopa-thy due to lymphoma may occur. However, the linear configuration of the activity is characteristicof esophageal activity, rather than the typical focal rounded appearance of adenopathy. Furthermore,no other sites of adenopathy are present. The findings are characteristic of an esophageal neoplasm,making squamous cell carcinoma or adenocarcinoma far more likely than lymphoma.

B. Incorrect. As discussed above, the linear uptake located in the posterior mediastinum is characteris-tic in appearance for an esophageal neoplasm. There are no focal pulmonary nodules or foci ofmediastinal or hilar adenopathy, as would be anticipated in the presence of bronchogenic carcinoma.

C. Correct. The linear pattern of increased FDG uptake in the posterior mediastinum, in the expectedlocation of the esophagus, is characteristic in appearance for an esophageal neoplasm, most likelyrepresenting squamous cell carcinoma of the esophagus.

D. Incorrect. Mildly increased uptake near the gastroesophageal junction may be seen as a normal vari-ant, or in patients with gastroesophageal reflux. Mild diffuse esophageal uptake may also occur inesophagitis. The uptake in this case is far more intense than would be anticipated as a normal vari-ant, and the location of the activity remote from the gastroesophageal junction is not consistent witha normal variant.



62. A 28 year-old HIV positive woman presents with headache, papilledema, and a ring-enhancingright thalamic mass on CT (not shown). You are shown a transaxial Tl-201 chloride image of thebrain (Figure 5). What is the MOST LIKELY diagnosis?

A. Lymphoma

B. Cytomegalovirus infection

C. Toxoplasmosis infection

D. Normal study



Figure 5

Question 62

Findings: Transaxial Tl-201 chloride SPECT images of the brain demonstrate a focal area of increasedtracer uptake near the midline, in the region of the CT lesion in the basal ganglia.

Rationales:

A. Correct. CNS lymphoma may produce a ring-enhancing lesion on CT and is thallium-avid. Thesefindings are most consistent with CNS lymphoma arising in an immunocompromised host.

B. Incorrect. CMV is not thallium-avid, as is the lesion in this case.

C. Incorrect. Toxoplasmosis can produce cerebral ring-enhancing CT lesion, but it is not thallium-avid,as is the lesion in this case.

D. Incorrect. The focal area of increased tracer uptake in the midline basal ganglia region represents astriking abnormality, which is not attributable to any normal finding. This is not a normal study.





63. You are shown representative coronal, transaxial and sagittal tomographic radionuclide images(Figure 6). Which one of the following radiotracers was MOST LIKELY utilized forthis study?

A. Tc-99m methylene diphosphonate

B. Tc-99m sulfur colloid

C. F-18 fluorodeoxyglucose

D. F-18 sodium fluoride

Figure 6

Question 63

Rationales:

A. Incorrect. The normal biodistribution of Tc-99m methylene diphosphonate (MDP) includes the axialand appendicular skeleton, kidneys and bladder. The liver, spleen, mediastinum, and brain, whichare visualized in this case, are not seen on a normal bone scintigram.

B. Incorrect. The normal biodistribution of Tc-99m sulfur colloid includes intense liver and spleenactivity. Less intense activity is identified in the central bone marrow (skull, ribs, sternum, vertebralbodies, pelvis, proximal humeri and femora). The most intense activity in this study is osseous.Moderate activity is seen within the spleen and low level activity in the liver, mediastinum andbrain. This biodistribution is not typical for sulfur colloid.

C. Correct. The normal biodistribution of F-18 fluorodeoxyglucose (FDG) is accumulation in thebrain, myocardium, blood vessels, pharynx, liver, spleen, bone marrow, kidneys, ureters, urinarybladder, and GI tract. Intense marrow uptake is seen in this patient with lymphoma after administra-tion of granulocyte colony stimulating factor (G-CSF), which is given to support bone marrow func-tion following therapy. Normal marrow uptake is usually less intense than hepatic uptake. While thisdistribution is not normal, it is more characteristic of FDG than any of the other tracers listed.

D. Incorrect. The normal biodistribution of F-18 sodium fluoride is osseous, with uptake dependent onregional blood flow and osteoblastic activity by chemisorption. Hydroxyl groups are exchanged toform fluoroapatite in the hydroxyapatite crystals. Because of the superior spatial resolution andthree-dimensional localization afforded by PET imaging, there is a high sensitivity for the detectionof metabolically active skeletal lesions using F-18 sodium fluoride.



64. Concerning subacute thyroiditis, serum thyroid hormone levels are elevated as the result ofwhich one of the following?

A. Increased thyroid hormone production

B. Increased TSH secretion by the pituitary gland

C. Release of pre-formed thyroid hormone into the circulation

D. Iodine excess in the thyroid gland

Question 64

Rationales:

A. Incorrect. Thyroid hormone production is reduced in subacute thyroiditis. The elevated thyroidfunction tests and signs and symptoms of hyperthyroidism that occur early in the disorder are relat-ed to release of pre-formed thyroid hormone into the circulation from the inflamed thyroid gland.

B. Incorrect. The increased thyroid hormone levels produced by the release of pre-formed hormoneinto the circulation results in a feedback inhibition of TSH secretion by the pituitary, resulting indecreased serum TSH levels.

C. Correct. Subacute thyroiditis is a viral disorder, often following a recent upper respiratory infec-tion. The inflammatory response in the gland results in increased permeability and increased releaseof pre-formed thyroid hormone into the circulation from the colloid. The increased serum thyroidhormone levels, in turn, result in clinical evidence of hyperthyroidism, despite a low thyroid uptake.

D. Incorrect. The pathophysiology of subacute thyroiditis does not involve abnormalties in iodinemetabolism per se. The acute inflammatory response in this disorder is associated with decreasediodide uptake and organification during the early stage of the disease.



65. Gallium-67 citrate scintigraphy is preferred over In-111 leukocyte scintigraphy in which one ofthe following entities?

A. Abdominal abscess

B. Infected joint prosthesis

C. Disk space infection

D. Inflammatory bowel disease

Question 65

Rationales:

A. Incorrect. While both radiopharmaceuticals are efficacious for the detection of abdominal abscesses,Indium-111 leukocyte imaging is often preferred, as the result of the absence of potentially confus-ing normal bowel activity, as occurs in Gallium-67 scintigraphy. This normal bowel uptake maylead to false positive gallium studies.

B. Incorrect. Indium-111 leukocyte imaging is superior to gallium-67 scintigraphy in the evaluation ofsuspected infected joint prostheses, in part related to the bone seeking properties of gallium, leadingto potential false positive gallium studies due to increased tracer localization secondary to increasedbone turnover in the absence of infection.

C. Correct. While sensitive for osteomyelitis, Indium-111 leukocyte scintigraphy has been found to beless sensitive than gallium-67 scintigraphy for the detection of disc space infection.

D. Incorrect. Again, the absence of normal bowel localization makes In-111 leukocyte scintigraphybetter suited to the assessment of active inflammatory bowel disease. In gallium-67 scintigraphy,normal bowel uptake, especially in the colon, can be incorrectly attributed to inflammatory boweldisease.



66. Concerning the presence of multiple focal “hot spots” on a Tc-99m macroaggregated albumin(MAA) scan, which one of the following is CORRECT?

A. The study may need to be repeated on another day.

B. The patient is at risk for the development of acute hypoxemia.

C. A false positive study will result.

D. The patient has multiple arteriovenous malformations (AVMs).

Question 66

Rationales:

A. Correct. The finding of focal “hot spots” on a Tc-99m MAA scan indicates the aggregation of theradiopharmaceutical into larger particles, which lodge in the pulmonary vascular bed. This artifactmay be produced by drawing blood back into the syringe during injection or by failing to resuspendthe particles prior to injection, in the event the dose is left sitting for a prolonged time after beingdrawn up. While it is not associated with any adverse effects in the patient, these foci of increasedactivity may obscure portions of the underlying lungs, resulting in the need to repeat the study aftersignificant radioactive decay has occurred.

B. Incorrect. While technically these foci do represent small, iatrogenic pulmonary emboli, they arevirtually never associated with any clinically demonstrable adverse effects. In general, pulmonaryperfusion imaging with Tc-99m MAA is associated with transient occlusion of less the 0.1% of thepulmonary capillary bed. Thus, this occurrence is unlikely to produce acute hypoxemia.

C. Incorrect. While these “hot spots” may obscure underlying detail in evaluating pulmonary perfu-sion, they are not associated with artifactual perfusion defects that would produce a false positivestudy.

D. Incorrect. Pulmonary AVMs are associated with right to left shunting, permitting Tc-99m MAA par-ticles to bypass the pulmonary capillary bed. Thus, AVMs would tend to produce focal perfusiondefects, rather than focal areas of increased tracer localization.



67. Concerning the analysis of radionuclide gated blood pool (MUGA) studies, which one of thefollowing will result in an UNDERESTIMATION of the left ventricular ejection fraction?

A. Placement of the background region of interest over the splenic blood pool activity

B. Assignment of too small a systolic region of interest

C. Use of a single region of interest for both the systolic and diastolic frames

D. Inclusion of a portion of the left atrium in the diastolic region of interest

Question 67

Distractors: SCORE ALL CHOICES AS CORRECT

A. Placement of the background region of interest over the splenic blood pool activity

B. Assignment of too small a systolic region of interest

C. Use of a single region of interest for both the systolic and diastolic frames

D. Inclusion of a portion of the left atrium in the diastolic region of interest

Rationales:

A. Placement of the background ROI over the spleen will result in excessive background subtraction.The relative effect of the extra background subtraction will be greater on the systolic ROI, whichhas fewer counts, and therefore will not “cancel out”. Thus, the denominator of the ejection fractionequation will be relatively reduced, resulting in an artifactually elevated, rather than reduced.

B. Too small of a systolic region will result in exclusion of value counts from the systolic region, mak-ing the percentage change between systolic and diastolic counts appear to be larger than it actuallyis. Again, this error would result in an artifactually elevated calculated ejection fraction.

C. This technique was initially used when the procedure was originally introduced. However, by usingthe same region for both measurements, the systolic region extends beyond the actual margins ofthe ventricle in end-systole, thus including background counts from adjacent structures, making theapparent ejection fraction artifactually too low. For this reason, the standard method of analysis atpresent requires assignment of separate diastolic and systolic regions of interest, in order to improvethe accuracy of the measurement.

D. Inclusion of a portion of the left atrium in the diastolic region of interest will have the effect ofintroducing additional counts into the region that are not valid ventricular counts. Thus, the apparenttotal end-diastolic counts will be inappropriately high, resulting in an apparent higher percentage ofventricular emptying and a falsely elevated ejection fraction calculation.



68. Concerning radionuclide myocardial perfusion imaging, which one of the following is NOTassociated with an inferior wall perfusion defect on a stress Tc-99m sestamibi SPECT study?

A. Inferior wall exercise-induced ischemia

B. Prior inferior wall myocardial infarction

C. Left bundle branch block

D. Diaphragmatic attenuation artifact

Question 68

Rationales:

A. Incorrect. Inferior wall ischemia characteristically produces a perfusion defect in this region onstress myocardial perfusion images. In the case of reversible ischemia, the defect would be expectedto resolve on a resting study.

B. Incorrect. An area of prior myocardial infarction typically produces a “fixed” perfusion defect,which would be visible both on stress and resting images. Thus, from evaluation of stress imagesalone, it cannot be differentiated from a defect due to exercise-induced ischemia, as in item A.

C. Correct. Left bundle branch block may be the result of myocardial ischemia or infarction, or maybe an incidental finding. It may produce perfusion abnormalities on myocardial perfusion scintigra-phy in the absence of coronary artery disease. When it produces abnormalities, the most commonfinding is a reversible perfusion defect in the interventricular septum, not in the inferior wall. Inpatients with known left bundle branch block, it is preferable to perform a pharmacologic stress test,using dipyridamole or adenosine, rather than treadmill exercise in conjunction with the imaging,since this artifact is more commonly associated with the latter procedure.

D. Incorrect. Diaphragmatic attenuation artifact commonly produces apparent defects in the inferiorwall. These defects may or may not be present both on stress and resting images, and may be sus-pected by inspection of planar rotating images from the raw data set. This artifact most often occursin male patients, and is more common in obese patients as well.



69. Which is an appropriate use of F-18 fluorodeoxyglucose (FDG) PET imaging in breastcarcinoma?

A. Screening

B. Initial staging

C. Differentiating between a pulmonary metastasis and a primary lung carcinoma

D. Treatment monitoring

Question 69

Rationales:

A. Incorrect. FDG PET imaging is not an appropriate or approved study for breast cancer screening.Screening is best done by self-examination and periodic mammography, which are more sensitiveand cost-effective approaches to breast cancer screening.

B. Incorrect. FDG PET imaging is less sensitive for the initial staging of breast cancer than lym-phoscintigraphy with sentinel lymph node biopsy. Very high sensitivity is provided by the latterapproach, particularly when immunohistochemistry techniques are utilized. This approach to stagingis rapidly becoming the standard of care for these patients.

C. Incorrect. FDG PET imaging is not capable of differentiating between a solitary pulmonary metas-tasis and a primary lung tumor. In most cases, both lesions are associated with increased glucosemetabolism and thus, increased FDG uptake.

D. Correct. As is true for a number of neoplasms, FDG PET imaging is very sensitive and specific forassessing the response to therapy in breast carcinoma, whether performed after the completion oftherapy (re-staging) or during the course of therapy (treatment monitoring).



70. A post-menopausal woman with osteoporosis undergoes dual-energy x-ray absorptiometry(DEXA) scanning, demonstrating marked osteopenia of the lumbar spine and hip, but normalbone density of the distal forearm. What is the BEST explanation for these findings?

A. Inappropriate scanning of the dominant forearm rather than the non-dominant

B. Insensitivity of forearm bone density measurement secondary to preponderance of cortical bone

C. Underestimation of the bone density in the spine and hip secondary to arthritic changes

D. Scan performed too distally in the forearm

Question 70

Rationales:

A. Incorrect. While it is true that it is preferable to scan the non-dominant forearm or hip in DEXAscanning, and scanning the dominant side could produce a higher bone density value, the differ-ences between the dominant and non-dominant sides are often minimal, and this is therefore not thebest explanation for the findings.

B. Correct. The bones of the extremities, such as the radius and ulna, are composed primarily of corti-cal bone, and contain relatively less trabecular bone than either the spine or hip. Quantitatively, theextremities account for the majority of the whole body bone mineral content. Thus, bone densitymeasurements of the forearm are most valuable in patients with metabolic bone disease, or otherconditions associated with decreases in total skeletal calcium content. Post-menapausal osteoporosispreferentially involves the trabecular bone initially, which is present in higher percentages in thevertebral bodies and femoral neck regions. Therefore, forearm measurements tend to be relativelyinsensitive for the early detection of post-menopausal osteoporosis.

C. Incorrect. In fact, the opposite is true. The presence of arthritic changes is most often associatedwith falsely elevated bone density measurements, especially in the spine, secondary to increasedbone density at sites of spurring or sclerosis associated with arthritic involvement.

D. Incorrect. Again, the opposite is true. Moving from proximal to distal in the forearm, there is a pro-gressive increase in the relative trabecular bone content. Typically, bone density measurements ofthe forearm are performed in the distal third of the radius and ulna, in order to maximize the contri-bution of trabecular bone in the measurement. Scanning more distally may also be performed, tofurther increase the percentage of trabecular bone being evaluated. Thus, scanning more distallywould tend to decrease the measured bone mineral density of the forearm.



71. What is the most commonly cited threshold for the diagnosis of malignancy using standardizeduptake value (SUV) on PET imaging for a solitary pulmonary nodule?

A. 1.0

B. 1.5

C. 2.5

D. 3.0

Question 71

Rationales:

A. Incorrect. The correct value is 2.5.

B. Incorrect. The correct value is 2.5.

C. Correct. Many malignant lesions will greatly exceed this value, and some lesions with SUV values< 2.5 are malignant, but 2.5 is the most commonly cited threshold for the diagnosis of malignancyusing SUV analysis.

D. Incorrect. The correct value is 2.5.



72. Concerning infection imaging with In-111 labeled leukocytes, which one is CORRECT?

A. Uptake is dependent on regional blood flow.

B. It is insensitive for the detection of inflammatory bowel disease.

C. Transient pulmonary uptake clears within 15 minutes post-injection.

D. It is more sensitive than Ga-67 citrate imaging for detection of Pneumocystis carinii pneumonia(PCP).

Question 72

Rationales:

A. Correct. While not the sole determinant of uptake, the uptake of In-111 labeled leukocytes isdependent upon regional blood flow. For example, a walled-off abscess without a direct blood sup-ply will not accumulate In-111 labeled leukocytes, and may appear as a photopenic defect.

B. Incorrect. In-111 WBC imaging is very sensitive for active inflammatory bowel disease. It hasadvantages over Ga-67 citrate imaging in this clinical setting, as a result of the absence of normalbowel uptake of the tracer.

C. Incorrect. Transient lung uptake can be seen 4 hours after injection or even longer, sometimes mak-ing the diagnosis of pulmonary infection difficult.

D. Incorrect. In-111 WBC’s are less sensitive than Ga-67 citrate for detecting chest infections, such asPCP. As a result, Ga-67 citrate imaging is preferred in the clinical settings of suspected chest infec-tion or in immunocompromised patients presenting with fever of unknown origin.



73. The Nuclear Regulatory Commission (NRC) mandates daily performance testing of the ioniza-tion chamber radioisotope dose calibrator for which one of the following?

A. Geometry

B. Constancy

C. Linearity

D. Accuracy

Question 73

Rationales:

A. Incorrect. Assessment of the effects of geometry is required at time of initial setup or after alter-ation/repair of well calibrator only. This insures that variations in radioactive dose volume or posi-tion in counting chamber will not produce aberrant dose determination.

B. Correct. This daily mandated test measures instrument precision and is designed to show repro-ducible readings day after day on all clinical energy settings. This is essentially a mini-accuracy testthat does not account for half-life of long-lived low, medium, and high energy sealed standards.More or less rigor is applied, depending on whether a single 137Cs source is counted in all standardenergy settings (Tc99m, 201TI, 123I, 131I, etc.) and the same reading is compared day to day or a moreelaborate daily count of multiple sealed sources (57Co, 133Ba, 137Cs) is obtained. No more than a 5%daily count rate variation is allowable.

C. Incorrect. Sequential assay of count rates of the same radioisotope from low to high activity, usuallyby counting an initially high activity Tc-99m source as it decays over 48 hours. This multi-daystudy can’t be performed daily, and is usually performed at installation, quarterly thereafter andwhenever the device undergoes repair.

D. Incorrect. Designed to insure correct readings throughout the entire energy spectrum clinicallyencountered, this rigorous test requires reproduction of count rates with low, medium, and highenergy sealed standard sources 57Ba, 137Cs. This elaborate test is performed at installation of thedevice, annually thereafter and whenever the device undergoes repair.



74. For the man-made radiation contributions to the background radiation in the United States, whichof the following represents the MOST significant source of exposure to the U.S. population?

A. Medical x-rays

B. Radon

C. High-altitude air travel

D. Nuclear medicine

Question 74

Rationales:

A. Correct. Medical x-rays are the most significant source of man-made radiation sources. They con-tribute an annual effective dose of 0.39 mSv or 39 mrem to the U.S. population.

B. Incorrect. Radon is a naturally occurring source of radiation.

C. Incorrect. High-altitude air travel adds to an individual’s cosmic ray exposure, and is of very smallquantity.

D. Incorrect. Nuclear does not contribute as much as medical x-rays as a source of exposure to the U.S.population. They contribute an annual effective dose of 0.14 mSv or 14 mrem to the U.S. popula-tion.



75. Which one of the following sets of I-123 thyroid scintigraphy findings and history of radiationexposure is associated with the LOWEST relative risk for thyroid carcinoma?

A. Multiple cold nodules with previous head and neck irradiation

B. Multiple cold nodules without prior head and neck irradiation

C. Solitary cold nodule without prior head and neck irradiation

D. Solitary cold nodule with previous head and neck irradiation

Question 75

Rationales:

A. Incorrect. This combination of scan findings and history is associated with the highest relative like-lihood of malignancy of all those listed, in the range of 40%.

B. Correct. The finding of multiple cold nodules without prior radiation exposure is consistent with anon-specific multinodular goiter, and carries a risk of underlying malignancy of only ~ 5%.

C. Incorrect. While the absence of prior head and neck irradiation reduces the likelihood of malignan-cy, the prevalence of malignancy in patients presenting with solitary cold thyroid nodules is still inthe range of about 15-20% overall.

D. Incorrect. The history of prior head and neck irradiation significantly increases the likelihood ofmalignancy in a patient with a solitary cold nodule, with the likelihood being somewhere in therange of 30-40%, slightly lower than for option A.



76. Which one of the following is NOT a normal site of F-18 fluorodeoxyglucose (FDG) localization?

A. Salivary glands

B. Gallbladder

C. Colon

D. Kidneys

Question 76

Rationales:

A. Incorrect. Symmetrical salivary gland uptake is a normal finding on FDG PET imaging.

B. Correct. The gallbladder is not a normal site of FDG localization. Increased uptake in the gallblad-der suggests the presence of cholecystitis or a neoplastic process within the gallbladder.

C. Incorrect. While variable in intensity and extent, colonic uptake of FDG is normal.

D. Incorrect. Renal uptake is almost always visualized on FDG PET studies. Renal excretion into thecollecting systems and bladder is also seen in the majority of cases.



77. What is the basic principle underlying the C-14 urea breath test for Helicobacter pyloriinfection in patients with peptic ulcer disease?

A. Absence of urease in mammalian cells

B. Chemical breakdown of C-14 urea by gastric acid

C. Formation of C-14 labeled glucose

D. Renal excretion of C-14 urea absorbed from the stomach

Question 77

Rationales:

A. Correct. The basis of this study is that the Helicobacter pylori bacteria present in the stomach inpatients with this infection contain the enzyme urease, necessary for the breakdown of urea. Thismetabolism of C-14 labeled urea results in the formation of C-14 labeled CO2 gas, which is thendetected using a liquid scintillation counter. In the absence of the bacterial infection, the cells of thegastric mucosa, which lack the enzyme urease (like all mammalian tissue), are unable to breakdown the urea, and thus no C-14 labeled CO2 gas is formed, resulting in a negative study.

B. Incorrect. The study has nothing to do with the presence or absence of gastric acid. Only the pres-ence of the enzyme urease, found in the Helicobacter pylori organisms, but not in the gastric cells,can break down the C-14 urea to form C-14 labeled CO2 gas.

C. Incorrect. The physiology of the study is as described above. In no way is the formation of glucoseor other aspects of carbohydrate metabolism involved.

D. Incorrect. Again, the metabolism of C-14 labeled urea by bacterial urease is the basis of the study.Renal excretion is not involved, and no urine collections are performed. The study is performed byhaving the patient ingest the radiopharmaceutical, followed by collection of two breath samples,which are analyzed in a liquid scintillation counter for the presence of C-14 labeled CO2 gas.



78. A patient with pernicious anemia had a normal Stage 1 Schilling Test. Which one of thefollowing could explain the result?

A. Prior radioisotope study

B. Incomplete urine collection

C. Prior resection of terminal ileum

D. Concurrent vitamin B-12 therapy

Question 78

Rationales:

A. Correct. The situation described is one where the test yields a false-negative result in a patient withpernicious anemia (as indicated in the history). Measurement of the excreted Cobalt-57 labeled vita-min B-12 is performed by counting the urine. Typical window settings used for counting are 50-200keV for the 122 and 136-keV photons of Cobalt-57. The presence of other radioactive material inthe urine that emits photons within the acceptance window will increase the measured counts, andcan result in an inaccurate determination of the excretion of the radiolabeled vitamin B-12.

B. Incorrect. The situation described is one where the test result is a false-negative. Incomplete urinecollection could result in a low measured excretion, and a false positive (not a false negative) result

C. Incorrect. The situation described is one where the test result is a false-negative. Prior resection ofterminal ileum could result in a reduced absorption of the orally administered vitamin B-12, andthereby a low excretion

D. Incorrect. The situation described is one where the test result is a false-negative. Prior vitamin B-12therapy may result in a low measured excretion, and a false positive study. The patient should notreceive parental vitamin B-12 for at least 3 days prior to the study. Biliary excretion of the previous-ly administered vitamin B-12 may decrease the fractional absorption of the test dose. If it does notget absorbed, it cannot get excreted into the urine, so measured excretion will be low.



79. In nuclear medicine, what is the main difference between an intrinsic uniformity and extrinsicuniformity quality control test?

A. The intrinsic test is performed without the collimator, and the extrinsic test is performed with thecollimator.

B. The intrinsic test uses Co-57, while the extrinsic test uses Tc-99m.

C. The intrinsic test utilizes an internal electronic test mode of the gamma camera, while the extrin-sic test utilizes an external flood source.

D. The intrinsic mode uses an internal calibration source within the gamma camera, while theextrinsic test utilizes an external flood source.

Question 79

Rationales:

A. Correct. The intrinsic uniformity or flood test is performed without the collimator and is an indica-tion of the uniformity of the camera itself. The extrinsic test is performed with the collimator onusing a large flood source.

B. Incorrect. Either source material may be used. Typically a syringe of Tc-99m at a distance severaltime larger than the camera crystal is used for the intrinsic test, and the extrinsic test is performedwith a large water and Tc-99m filled flood source, or a solid Co-57 flood source.

C. Incorrect. Internal electronic checks are different from the measured uniformity tests.

D. Incorrect. There are no internal radiation sources to a gamma camera used for uniformity testing.



80. Concerning the presence of hydrolyzed reduced Tc-99m in a dose of Tc-99m MDP (methylenediphosphonate) administered intravenously for a bone scan, which is CORRECT?

A. It results in thyroid visualization.

B. It can be identified using a dose calibrator.

C. It is more likely to occur in the presence of excess stannous ion.

D. It occurs more commonly when multidose vials are used.

Question 80

Rationales:

A. Incorrect. Hydrolyzed reduced technetium-99m is a colloidal impurity that results in hepatic andreticuloendothelial visualization, not thyroid visualization, which is typical of the presence of freepertechnetate as an impurity.

B. Incorrect. Only chromatography pre-imaging will detect this radiopharmaceutical impurity.

C. Incorrect. On the contrary, Sn(II)ion is a reducing agent protecting MDP from hydrolysis.

D. Correct. The introduction of air into a multidose MDP vial is the most frequent cause of thishydrolyzed technetium-99m contaminant. The more violations of the vial, the more likely air willbe introduced.



81. Concerning treatment of intractable pain from widespread metastatic bone lesions withMetastron® (Sr-89) and Quadramet® (Sm-153), which one is CORRECT?

A. Both can be imaged using a gamma camera to assess the biodistribution of the therapeutic dose.

B. The longer half-life of Metastron (50 days) versus Quadramet (1.9 days) provides a superiortherapeutic effect.

C. Because of the highly energetic beta particles produced by both agents, a lead syringe shield isemployed during dose administration.

D. Recovery from bone marrow toxicity is faster following Quadramet administration.

Question 81

Rationales:

A. Incorrect. Metastron is a pure beta emitter. The absence of an imagable gamma photon precludesverification of bone lesion uptake. By contrast, Sm-153 has an imagable gamma photon energy of103 keV, permitting bone scintigraphy to be performed in conjunction with the therapeutic proce-dure.

B. Incorrect. While it is true that the half-life of Metastron is significantly longer, resulting in moreprolonged lesion irradiation, the clinical efficacy of both treatments are quite similar.

C. Incorrect. Due to bremsstrahlung production of high energy photons when high atomic numbermaterial (eg. lead) is used for shielding, acrylics are the preferred material for handling of thesematerials. Materials with lower atomic numbers, such as plastic or acrylics make ideal shields. Inaddition, bremsstrahlung production is proportional to the atomic number, which is lower for thesematerials.

D. Correct. The major limitation of both therapies is myelosuppression. Metastron causes 15-30%drops in the platelet and WBC counts from pre-injection values, and Quadramet, 40-50%. However,8-12 weeks are required for full bone marrow recovery from Metastron, versus only 6-8 weeks forQuadramet.



82. Reduced occipital lobe glucose metabolism on F-18 FDG (fluorodeoxyglucose) cerebral PETimaging is MOST common in which one of the following progressive dementias?

A. Alzheimer’s

B. Pick’s

C. Parkinson’s

D. Lewy body

Question 82

Rationales:

A. Incorrect. Alzheimer’s dementia at the earliest stages is associated with temporoparietal and laterfrontal lobe FDG hypometabolism, with typical sparing of sensorimotor and visual cortex (occipitallobe).

B. Incorrect. Pick’s disease is a degenerative dementia predominately involving frontal and temporallobes. Frontal hypometabolism precedes development of temporal hypometabolism. The visual cor-tex is generally uninvolved.

C. Incorrect. Parkinson’s dementia is a late manifestation of a neurodegenerative disease, primarilyaffecting the basal ganglia. There is occasional involvement of the occipital cortex, although tem-poroparietal hypometabolism pattern similar to that of Alzheimer’s, but with additional striatalhypometabolism, is a more common FDG pattern.

D. Correct. Decreasing cognitive function accompanied by visual disturbance including hallucinationsis common presentation in diffuse Lewy body disease (DLBD) which is becoming more widely rec-ognized and accounts for up to 20% of all autopsy confirmed dementias. Medical and lateral occipi-tal lobe FDG metabolism is more severely reduced in DLBD than other dementias. When identifiedon FDG PET images, cholinergic therapy has been useful in controlling the disease.



83. Concerning the biodistribution of Indium-111 ibritumomab tiuxetan (Zevalin®) 48 hoursfollowing intravenous administration, which one is CORRECT?

A. Persistent blood pool activity indicates the presence of a human anti-mouse antibody (HAMA)response.

B. Absence of bone marrow activity indicates > 25% marrow infiltration by lymphoma.

C. Renal activity less intense than hepatic is indicative of altered biodistribution.

D. Hepatic activity more intense than bowel uptake is normal.

Question 83

Rationales:

A. Incorrect. The cardiac blood pool activity gradually decreases with time as Zevalin is distributed tothe other organs and a small component is excreted. Persistent but decreased blood pool activity isnormal at 48 hours. The development of a HAMA response occurs in < 2% of patients. More rapidclearance of the Zevalin antibody can occur with the development of a HAMA response, and hence,a shorter circulation time.

B. Incorrect. The Zevalin therapeutic regime should not be given to patient’s with greater than or equalto 25% lymphoma marrow involvement. Altered biodistribution is suggested with rapid blood poolclearance and increased marrow uptake.

C. Incorrect. Normal renal activity with Indium-111 Zevalin is generally manifested as faint activity(moderately low to very low activity), which is much less intense than hepatic uptake. Altered renalbiodistribution is present if renal activity greater than liver is demonstrated on the posterior images.

D. Correct. Bowel activity is common and normal. However, normal gastrointestinal biodistribution isactivity that is less intense than liver and decreases over time (moderately low to very low intensi-ty). Bowel activity more intense than hepatic uptake is indicative of altered biodistribution.



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