23205016

Section III – Nuclear Radiology

Figure 1A

Figure 1B
58. You are shown whole body images and selected spot images from a Tc-99m methylene
diphosphonate 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

1
Diagnostic In-Training Exam 2006

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 appendicular
skeleton are highly atypical for metastases. The clinical history of joint pain also points to other
more 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 cortical
areas alone, and is often more intense than the findings in this case. Furthermore, the bilaterally
symmetrical distribution of the findings is highly atypical for osteomyelitis.
C. Incorrect. Shin splints may also produce areas of increased uptake along the cortical surfaces of
long 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 increased
uptake. 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 or
mesothelioma. 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 congenital
heart disease, inflammatory bowel disease and lymphoma. Patients may present with joint pain,
clubbing and periosteal new bone formation on radiographs. The differential diagnosis also includes
pachydermoperiostosis and thyroid acropachy.

2 American College of Radiology


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

A. Acute cholecystitis
B. Bile leak
C. Common bile duct obstruction
D. Normal study



Figure 2B

4

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 peritoneal
cavity, beginning at 15 minutes post-injection, and progressively increasing throughout the study. There
is 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 lateral
image demonstrates activity spreading anterior to the liver, also consistent with intraperitoneal biliary
leakage. Hepatic clearance is also moderately prolonged.
Rationales:
A. Incorrect. The findings are not consistent with acute cholecystitis. There is prompt visualization of
the 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 this
case. 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 the
gallbladder 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 secondary
to 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 in
the 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, as
described above. Furthermore, the images also demonstrate prolonged hepatic clearance and non-
visualization of the small bowel, both of which are also abnormal findings.



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

A. Normal study
B. Right renal artery stenosis
C. Left renal artery stenosis
D. Bilateral renal artery stenosis


Question 60
Findings: The baseline pre-captopril study demonstrates mildly decreased tracer uptake bilaterally, with
normal 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 bilateral
delay in cortical clearance and excretion on the post-captopril study.
B. Incorrect. In unilateral right renal artery stenosis, ACE-inhibitor should create an asymmetric delay
in 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 in
left 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 and
bladder activity seen at midpoint of the baseline pre-captopril study. Administration of the ACE
inhibitor has produced a symmetric delay in renal cortical clearance, manifested by marked bilateral
cortical retention and non-visualization of the renal pelves and bladder. These findings are typical
for bilateral ACE-inhibition of compensatory post-glomerular vascular constriction, with resultant
delay in transcortical clearance, in this child with bilateral congenital renal artery stenosis.

7


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 characteristic
of 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 of
mediastinal 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 expected
location of the esophagus, is characteristic in appearance for an esophageal neoplasm, most likely
representing 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 in
esophagitis. 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 with
a normal variant.

9


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

A. Lymphoma
B. Cytomegalovirus infection
C. Toxoplasmosis infection
D. Normal study


Question 62
Findings: Transaxial Tl-201 chloride SPECT images of the brain demonstrate a focal area of increased
tracer 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. These
findings 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 a
striking abnormality, which is not attributable to any normal finding. This is not a normal study.

11


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

A. Tc-99m methylene diphosphonate
B. Tc-99m sulfur colloid
C. F-18 fluorodeoxyglucose
D. F-18 sodium fluoride


Question 63
Rationales:
A. Incorrect. The normal biodistribution of Tc-99m methylene diphosphonate (MDP) includes the axial
and appendicular skeleton, kidneys and bladder. The liver, spleen, mediastinum, and brain, which
are 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 spleen
activity. Less intense activity is identified in the central bone marrow (skull, ribs, sternum, vertebral
bodies, 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 and
brain. This biodistribution is not typical for sulfur colloid.
C. Correct. The normal biodistribution of F-18 fluorodeoxyglucose (FDG) is accumulation in the
brain, myocardium, blood vessels, pharynx, liver, spleen, bone marrow, kidneys, ureters, urinary
bladder, 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 this
distribution 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 on
regional blood flow and osteoblastic activity by chemisorption. Hydroxyl groups are exchanged to
form fluoroapatite in the hydroxyapatite crystals. Because of the superior spatial resolution and
three-dimensional localization afforded by PET imaging, there is a high sensitivity for the detection
of metabolically active skeletal lesions using F-18 sodium fluoride.

13

64. Concerning subacute thyroiditis, serum thyroid hormone levels are elevated as the result of
which 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 thyroid
function 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 hormone
into the circulation results in a feedback inhibition of TSH secretion by the pituitary, resulting in
decreased 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 release
of pre-formed thyroid hormone into the circulation from the colloid. The increased serum thyroid
hormone 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 iodine
metabolism per se. The acute inflammatory response in this disorder is associated with decreased
iodide uptake and organification during the early stage of the disease.


Gallium-67 citrate scintigraphy is preferred over In-111 leukocyte scintigraphy in which one of
65.
the 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 may
lead to false positive gallium studies.
B. Incorrect. Indium-111 leukocyte imaging is superior to gallium-67 scintigraphy in the evaluation of
suspected infected joint prostheses, in part related to the bone seeking properties of gallium, leading
to potential false positive gallium studies due to increased tracer localization secondary to increased
bone turnover in the absence of infection.
C. Correct. While sensitive for osteomyelitis, Indium-111 leukocyte scintigraphy has been found to be
less 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 scintigraphy
better 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 bowel
disease.

15

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 the
radiopharmaceutical into larger particles, which lodge in the pulmonary vascular bed. This artifact
may be produced by drawing blood back into the syringe during injection or by failing to resuspend
the particles prior to injection, in the event the dose is left sitting for a prolonged time after being
drawn up. While it is not associated with any adverse effects in the patient, these foci of increased
activity may obscure portions of the underlying lungs, resulting in the need to repeat the study after
significant radioactive decay has occurred.
B. Incorrect. While technically these foci do represent small, iatrogenic pulmonary emboli, they are
virtually never associated with any clinically demonstrable adverse effects. In general, pulmonary
perfusion imaging with Tc-99m MAA is associated with transient occlusion of less the 0.1% of the
pulmonary 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 positive
study.
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 perfusion
defects, rather than focal areas of increased tracer localization.


Concerning the analysis of radionuclide gated blood pool (MUGA) studies, which one of the
67.
following 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, which
has fewer counts, and therefore will not “cancel out”. Thus, the denominator of the ejection fraction
equation 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 actually
is. 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 using
the same region for both measurements, the systolic region extends beyond the actual margins of
the ventricle in end-systole, thus including background counts from adjacent structures, making the
apparent ejection fraction artifactually too low. For this reason, the standard method of analysis at
present requires assignment of separate diastolic and systolic regions of interest, in order to improve
the accuracy of the measurement.
D. Inclusion of a portion of the left atrium in the diastolic region of interest will have the effect of
introducing additional counts into the region that are not valid ventricular counts. Thus, the apparent
total end-diastolic counts will be inappropriately high, resulting in an apparent higher percentage of
ventricular emptying and a falsely elevated ejection fraction calculation.

17

Concerning radionuclide myocardial perfusion imaging, which one of the following is NOT
68.
associated 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 on
stress myocardial perfusion images. In the case of reversible ischemia, the defect would be expected
to 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 images
alone, 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 may
be 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 common
finding is a reversible perfusion defect in the interventricular septum, not in the inferior wall. In
patients 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 inferior
wall. 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 occurs
in 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 breast
carcinoma?

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 sensitive
and 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 latter
approach, particularly when immunohistochemistry techniques are utilized. This approach to staging
is 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 glucose
metabolism and thus, increased FDG uptake.
D. Correct. As is true for a number of neoplasms, FDG PET imaging is very sensitive and specific for
assessing the response to therapy in breast carcinoma, whether performed after the completion of
therapy (re-staging) or during the course of therapy (treatment monitoring).

19

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 normal
bone 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 DEXA
scanning, 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 the
best 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, the
extremities account for the majority of the whole body bone mineral content. Thus, bone density
measurements of the forearm are most valuable in patients with metabolic bone disease, or other
conditions associated with decreases in total skeletal calcium content. Post-menapausal osteoporosis
preferentially involves the trabecular bone initially, which is present in higher percentages in the
vertebral bodies and femoral neck regions. Therefore, forearm measurements tend to be relatively
insensitive for the early detection of post-menopausal osteoporosis.
C. Incorrect. In fact, the opposite is true. The presence of arthritic changes is most often associated
with falsely elevated bone density measurements, especially in the spine, secondary to increased
bone 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 of
the 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, to
further increase the percentage of trabecular bone being evaluated. Thus, scanning more distally
would 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 standardized
uptake 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 malignancy
using SUV analysis.
D. Incorrect. The correct value is 2.5.

21

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

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 is
dependent 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 has
advantages over Ga-67 citrate imaging in this clinical setting, as a result of the absence of normal
bowel 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 as
PCP. 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 test
that 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 standard
energy settings (Tc99m, 201TI, 123I, 131I, etc.) and the same reading is compared day to day or a more
elaborate 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, usually
by counting an initially high activity Tc-99m source as it decays over 48 hours. This multi-day
study can’t be performed daily, and is usually performed at installation, quarterly thereafter and
whenever the device undergoes repair.
D. Incorrect. Designed to insure correct readings throughout the entire energy spectrum clinically
encountered, this rigorous test requires reproduction of count rates with low, medium, and high
energy sealed standard sources 57Ba, 137Cs. This elaborate test is performed at installation of the
device, annually thereafter and whenever the device undergoes repair.

23

74. For the man-made radiation contributions to the background radiation in the United States, which
of 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 small
quantity.
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.


Which one of the following sets of I-123 thyroid scintigraphy findings and history of radiation
75.
exposure 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 a
non-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 in
the range of about 15-20% overall.
D. Incorrect. The history of prior head and neck irradiation significantly increases the likelihood of
malignancy in a patient with a solitary cold nodule, with the likelihood being somewhere in the
range of 30-40%, slightly lower than for option A.

25

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

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 the
collecting 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 pylori
infection 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 in
patients with this infection contain the enzyme urease, necessary for the breakdown of urea. This
metabolism of C-14 labeled urea results in the formation of C-14 labeled CO2 gas, which is then
detected using a liquid scintillation counter. In the absence of the bacterial infection, the cells of the
gastric mucosa, which lack the enzyme urease (like all mammalian tissue), are unable to break
down 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 glucose
or 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 by
having 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.

27

A patient with pernicious anemia had a normal Stage 1 Schilling Test. Which one of the
78.
following 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 with
pernicious 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 50-200
keV for the 122 and 136-keV photons of Cobalt-57. The presence of other radioactive material in
the urine that emits photons within the acceptance window will increase the measured counts, and
can 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 urine
collection 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 of
terminal ileum could result in a reduced absorption of the orally administered vitamin B-12, and
thereby a low excretion
D. Incorrect. The situation described is one where the test result is a false-negative. Prior vitamin B-12
therapy may result in a low measured excretion, and a false positive study. The patient should not
receive 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 not
get 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 extrinsic
uniformity quality control test?

A. The intrinsic test is performed without the collimator, and the extrinsic test is performed with the
collimator.
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 the
extrinsic 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 on
using a large flood source.
B. Incorrect. Either source material may be used. Typically a syringe of Tc-99m at a distance several
time larger than the camera crystal is used for the intrinsic test, and the extrinsic test is performed
with 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.

29

80. Concerning the presence of hydrolyzed reduced Tc-99m in a dose of Tc-99m MDP (methylene
diphosphonate) 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 and
reticuloendothelial visualization, not thyroid visualization, which is typical of the presence of free
pertechnetate 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 this
hydrolyzed technetium-99m contaminant. The more violations of the vial, the more likely air will
be introduced.


81. Concerning treatment of intractable pain from widespread metastatic bone lesions with
Metastron® (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 superior
therapeutic effect.
C. Because of the highly energetic beta particles produced by both agents, a lead syringe shield is
employed 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 precludes
verification of bone lesion uptake. By contrast, Sm-153 has an imagable gamma photon energy of
103 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 more
prolonged lesion irradiation, the clinical efficacy of both treatments are quite similar.
C. Incorrect. Due to bremsstrahlung production of high energy photons when high atomic number
material (eg. lead) is used for shielding, acrylics are the preferred material for handling of these
materials. Materials with lower atomic numbers, such as plastic or acrylics make ideal shields. In
addition, bremsstrahlung production is proportional to the atomic number, which is lower for these
materials.
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 for
Quadramet.

31

82. Reduced occipital lobe glucose metabolism on F-18 FDG (fluorodeoxyglucose) cerebral PET
imaging 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 later
frontal lobe FDG hypometabolism, with typical sparing of sensorimotor and visual cortex (occipital
lobe).
B. Incorrect. Pick’s disease is a degenerative dementia predominately involving frontal and temporal
lobes. 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, primarily
affecting 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 striatal
hypometabolism, is a more common FDG pattern.
D. Correct. Decreasing cognitive function accompanied by visual disturbance including hallucinations
is 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 identified
on FDG PET images, cholinergic therapy has been useful in controlling the disease.


83. Concerning the biodistribution of Indium-111 ibritumomab tiuxetan (Zevalin®) 48 hours
following 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 to
the other organs and a small component is excreted. Persistent but decreased blood pool activity is
normal at 48 hours. The development of a HAMA response occurs in < 2% of patients. More rapid
clearance 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 equal
to 25% lymphoma marrow involvement. Altered biodistribution is suggested with rapid blood pool
clearance 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 renal
biodistribution 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 is
activity 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.

33

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