This document contains 3 figures and associated questions from a diagnostic radiology in-training examination. Figure 1 shows images from an F-18 FDG PET study in a man with abdominal pain. Figure 2 shows a posterior Tc-99m bone scintigram in a man with back pain. Figure 3 shows an anterior whole body Tc-99m bone scan in a woman with head and neck pain and a history of thyroid cancer. The questions assess the examinee's ability to interpret the images and select the most likely diagnosis.

1. 28th Annual
In-Training Examination
for Diagnostic
Radiology Residents
Rationales
Sponsored by:
Commission on Education
Committee on Residency Training in Diagnostic Radiology
February 3, 2005
The American College of Radiology www.acr.org

2. Section XII – Nuclear
Figure 1
320. You are shown coronal images from an F-18 FDG PET study (Figure 1) performed in a 62-year-old
man with a history of alcohol abuse, presenting with abdominal pain. What is the MOST likely
diagnosis?
A. Hodgkin’s disease
B. Metastatic colon carcinoma
C. Hepatocellular carcinoma
D. Pancreatic carcinoma
American College of Radiology

3. Section XII – Nuclear
Question #320
Findings:
Coronal FDG-PET images demonstrate a focal area of markedly increased tracer uptake in the right lower
quadrant, in the region of the cecum. There are multiple focal right iliac and paraaortic lymph node metastases
and numerous focal hypermetabolic lesions in the liver, consistent with hepatic metastases.
Rationales:
A. Incorrect. Hodgkin’s disease is usually highly FDG-avid, and commonly involves abdominal and pelvic
lymph nodes and the liver.
However, the more discrete focal lesion in the right lower quadrant is more typical for a primary lesion
within the right colon.
In addition, there is no splenomegaly or other sites of lymphadenopathy, which would commonly be seen
in association with involvement of the liver and abdominal and pelvic nodes. Extensive involvement of the
liver is also more common in non-Hodgkin’s lymphoma.
Therefore, while Hodgkin’s disease is a plausible diagnosis, metastatic colon carcinoma is more likely in
this case.
B. Correct. The findings in this case are typical for advanced carcinoma of the cecum, with increased FDG
uptake noted in the primary lesion, regional lymph nodes, and extensive hepatic metastases visualized.
FDG-PET imaging is highly sensitive for the staging and re-staging of colon carcinoma, and is
substantially more sensitive and specific than CT for this purpose.
C. Incorrect. Hepatocellular carcinoma demonstrates variable FDG uptake on PET scans.
It can be solitary or multifocal.
However, it would be unusual to see lymph node metastases remote from the liver, and the larger focal
lesion in the right lower quadrant would not constitute a typical site of metastatic involvement.
D. Incorrect. FDG uptake of pancreatic carcinoma is also variable. Multiple hypermetabolic hepatic metastases
may occur, and can have the appearance seen in this case.
However, adenopathy in the pelvis would be uncommon, and there is also no evidence of increased FDG
uptake within a primary lesion in the pancreas.
The small foci of increased uptake in the lower epigastric region could conceivably be located within the
body of the pancreas, but are not striking, and are relatively inferiorly located.
These foci are more consistent with small paraaortic lymph node metastases.
Citations:
Lowe VJ, Delbeke D, Coleman RE. Applications of PET in oncologic imaging. In: Sandler MP, et al, eds.
Diagnostic Nuclear Medicine. 4th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2003:987-1014.
Bar-Shalom R, Valdivia AY, Blaufox MD. PET imaging in oncology. Semin Nucl Med. 2000; 30:150-185.
Hustinx R, Benard F, Alavi A: Whole-body FDG-PET imaging in the management of patients with cancer.
Semin Nucl Med. 2002;32:35-46.
Diagnostic In-Training Exam 2005

4. Section XII – Nuclear
Figure 2
321. You are shown a posterior Tc-99m MDP bone scintigram (Figure 2) obtained in a 58-year-old man
with back pain. What is the MOST likely diagnosis?
A. Metastatic prostate carcinoma
B. Acute osteomyelitis
C. Metastatic renal carcinoma
D. Prior radiation therapy
American College of Radiology

5. Section XII – Nuclear
Question #321
Findings:
Whole-body and spot images of the skeleton demonstrate a focal area of decreased tracer uptake within the
vertebral body of T12. The remainder of the study demonstrates only mild arthritic changes. The focal “hot
spot” in the region of the left elbow is related to a small amount of extravasation of the dose at the site of
injection.
Rationales:
A. Incorrect. Prostate carcinoma has a high predilection for metastasis to the skeleton, and bone scintigraphy
is a highly sensitive examination for detection of prostate carcinoma metastatic to bone. Prostate carcinoma
often metastasizes early to the thoracolumbar spine via the vertebral venous plexus of Batson. However,
in the vast majority of cases, prostate carcinoma bone metastases demonstrate increased tracer uptake on
Tc-99m MDP or Tc-99m HDP bone scans. Radiographically, prostatic carcinoma bone metastases are
often associated with sclerotic lesions on plain films or CT. In this case, the lesion demonstrates decreased
tracer uptake, a relatively uncommon finding that is more often associated with aggressive, lytic destructive
lesions or metastases from primary lesions less likely to result in blastic or bone-forming lesions, such as
renal and thyroid carcinoma. Statistically, “cold” bone metastases are most often due to metastatic lung or
breast carcinoma. Therefore, while plausible, metastatic prostate carcinoma is not the most likely etiology
for the findings in this case.
B. Incorrect. Acute osteomyelitis is most often associated with focal skeletal hyperemia on the flow portion
of 3-phase bone scans and with focal increased bone uptake on the blood pool and delayed static images.
In children, acute osteomyelitis is occasionally associated with decreased tracer uptake on bone scintigraphy
secondary to decreased perfusion to involved sites due to the presence of pus under pressure within the
involved bone. However, this appearance is much less commonly encountered in adult patients, and when
it occurs, it is primarily encountered in the long bones. Therefore, osteomyelitis would be an unlikely
explanation for the finding in this case. In addition, no history suggesting the presence of an infectious
process was given.
C. Correct. Renal carcinoma is one of the primary neoplasms that may be associated with well-circumscribed,
expansile lytic metastases on radiographs and “photopenic” skeletal metastases on bone scintigrams, along
with thyroid carcinoma. As noted above, statistically the most common primary neoplasms associated with
“cold” metastases are lung and breast carcinoma. “Cold” lesions or absence of abnormal tracer uptake may
also be seen in multiple myeloma, a lesion arising within the bone marrow, for which plain radiographs are
overall more sensitive than skeletal scintigraphy for detection. Only a small percentage of metastases
detected on bone scintigraphy are “cold” lesions, like the lesion in this case.
D. Incorrect. Radiation therapy can produce decreased tracer uptake on bone scintigrams secondary to
reduction in regional blood flow and microvascular injury and injury to osteoblasts, with resultant decreased
new bone formation. However, it would be unusual for a radiation therapy port to involve only a single
vertebral level. In addition, in the current case the entire vertebra is not involved, with activity remaining
in portions of the posterior elements, which would not be anticipated in the case of postradiation changes.
Therefore, radiation therapy is not the most likely etiology for the finding in this case.
Citations:
Alazraki NP: Case 1: “Cold” Bone Metastasis. In: Siegel BA, ed. Nuclear Radiology II. Chicago, Ill: American
College of Radiology; 1978:2-17.
Diagnostic In-Training Exam 2005

6. Section XII – Nuclear
Figure 3
322. You are shown anterior whole body Tc-99m MDP bone scan (Figure 3) in a 84-year-old woman
with head and neck pain and a history of papillary thyroid carcinoma. What is the MOST likely
explanation for the scintigraphic findings?
A. Poor bone uptake due to osteoporosis
B. Metastatic calcification due to hyperparathyroidism
C. Poor labeling of the MDP
D. Metastatic papillary thyroid cancer
American College of Radiology

7. Section XII – Nuclear
Question #322
Findings:
There is marked increased activity in the stomach, thyroid, and salivary glands, with some activity seen in bowel
and bladder.
Rationales:
A. Incorrect. Patients with severe osteoporosis may demonstrate relatively decreased activity in the skeletal
system, with increased soft tissue activity.
Diffusely increased skeletal uptake may also occur.
However, osteoporosis would not show localization in the sites mentioned above.
B. Incorrect. Metastatic calcifications can result in increased activity in the stomach, lungs, kidneys, and other
soft tissue locations.
However, it would not demonstrate increased activity in salivary glands or thyroid.
C. Correct. Free Technetium-99m pertechnetate, which occurs when there is poor labeling of the MDP, will
localize in the locations mentioned above, the stomach, thyroid, and salivary glands. This condition can
be confirmed by performing thin-layer paper chromatography on the radiopharmaceutical.
D. Incorrect. Metastatic papillary thyroid cancer may show areas of increased or decreased activity in the skeleton
on a bone scan. Soft tissue metastases in the thyroid bed, cervical lymph nodes, lungs or mediastinum may
be seen on a whole body I-131 or I-123 scan, but are not normally visualized on a bone scan. Thus,
metastatic papillary thyroid carcinoma would not demonstrate the distribution of radiotracer seen above.
Diagnostic In-Training Exam 2005

8. Section XII – Nuclear
Figure 4
323. A 54-year-old diabetic man presents 5 days following renal transplantation with pain at the graft
site. You are shown anterior Tc-99m MAG-3 scintigraphic images of the pelvis (Figure 4). What is
the MOST likely diagnosis?
A. Urinoma
B. Acute tubular necrosis
C. Lymphocele
D. Acute rejection
American College of Radiology

9. Section XII – Nuclear
Question #323
Findings:
There is prompt perfusion to the transplanted kidney in the right iliac fossa, with normal tubular transit time
and prompt excretion into the collecting system and bladder. In addition, there is progressive accumulation of
activity in the right lower quadrant appearing during the excretory phase of the study.
Rationales:
A. Correct. An often-painful surgical complication, urinary extravasation (urinoma) is demonstrated by
progressive accumulation of tracer, which persists postvoiding. The current case findings are diagnostic
of a urinoma.
B. Incorrect. Acute tubular necrosis (ATN), though common, is typically painless. ATN is associated with
relatively preserved perfusion to the transplant with poor tubular function, without extrarenal tracer
accumulation. The findings in this case are not consistent with ATN.
C. Incorrect. A common postsurgical complication, lymphoceles typically produce photopenic fluid collections
adjacent to the transplant, since they are not in communication with the renal collecting system. In
addition, lymphoceles are a later complication, not usually occurring during the first postoperative week.
D. Incorrect. Acute rejection is occasionally painful, and is associated with poor flow and function of the graft,
manifested by delayed and reduced uptake and excretion by the transplanted kidney.
Neither finding is present in this case. In addition, the progressive accumulation of activity in the right
lower quadrant, surrounding the transplant, cannot be explained by acute rejection.
Citations:
Dubovsky E. Evaluation of renal transplants. In: Henkin R, et al, ed. Nuclear Medicine. St Louis, Mo: Mosby;
1996.
Diagnostic In-Training Exam 2005

10. Section XII – Nuclear
Figure 5
324. You are shown stress and rest vertical long-axis images (Figure 5) from a SPECT myocardial
perfusion scan in a 50-year-old woman with chest discomfort. During treadmill exercise, the patient
achieved 70% of the maximum predicted heart rate. What is the MOST likely explanation of the
findings?
A. Normal study
B. Diaphragmatic attenuation artifact
C. Inferior wall ischemia
D. Non-diagnostic study due to inadequate heart rate response
American College of Radiology

11. Section XII – Nuclear
Question #324
Findings:
There is a moderate area of mildly decreased perfusion in the inferior wall, with reversibility noted on the
resting study.
Rationales:
A. Incorrect. There is a moderate reversible defect of mild severity noted in the inferior wall. This is not a
normal study.
B. Incorrect. Diaphragmatic attenuation can produce artifactual defects in the inferior wall region. Typically,
diaphragmatic attenuation affects both the stress and resting studies, producing fixed defects, unless there
is significant patient motion between the two sets of images.
Diaphragmatic attenuation is more commonly seen in male patients.
Therefore, while plausible, diaphragmatic attenuation artifact is not the most likely diagnosis in this case.
C. Correct. The best explanation for the findings in this case is exercise-induced ischemia involving the
inferior wall, corresponding to the right coronary artery territory.
D. Incorrect. The patient achieved only 70% of maximum predicted heart rate during treadmill exercise. The
usual target for exercise studies is 85% of maximum predicted heart rate (based on maximum predicted
heart rate = 220 – age). A submaximal exercise test reduces the sensitivity of the study. However, if the
patient demonstrates ischemia despite failure to achieve the target heart rate, then the findings are still valid,
although it should be noted that the degree or extent of exercise-induced ischemia may be underestimated.
Diagnostic In-Training Exam 2005

12. Section XII – Nuclear
325. What factor is MOST important in identifying sentinel lymph nodes on breast lymphoscintigraphy
studies?
A. Nodal size
B. Proximity to the injection site
C. Intensity of uptake
D. Timing of visualization
Question #325
Rationales:
A. Incorrect. Nodal size is not a factor considered in identifying sentinel lymph nodes.
The sentinel node(s) may or may not be the largest ones visualized, but are correctly identified as being the
first node(s) visualized.
B. Incorrect. The sentinel node(s) are often located close to the site of injection, and are usually closer to the
injection site than other visualized nodes. However, as a result of the variability of lymphatic pathways, it is
possible for the sentinel node to be located farther from the site of injection than other nodes that visualize
later.
C. Incorrect. The sentinel node may or may not be the “hottest” node seen on imaging.
This factor is irrelevant in the identification of the sentinel node(s).
D. Correct. The essential element in the identification of the sentinel node(s), whether single or multiple, is
the fact that they are visualized prior to any other nodes seen.
Citations:
Glass EC, Essner R, Giuliano AE. Sentinel node localization in breast cancer. Semin Nucl Med. 1999; 29:57-68.
American College of Radiology

13. Section XII – Nuclear
326. The likelihood of malignancy in a hypofunctioning (“cold”) thyroid nodule identified on I-123
thyroid scintigraphy is increased by ALL of the following EXCEPT:
A. Female gender
B. Age < 30 years old
C. Prior head and neck irradiation
D. Absence of other thyroid nodules
Question #326
Rationales:
A. Correct. The overall incidence of thyroid carcinoma is greater in females than males. However, the
incidence of benign thyroid nodular disease is substantially greater in females than in males. As a result,
in a given patient with a solitary thyroid nodule, the risk of malignancy is relatively greater in males, and
female gender is therefore not a relative risk factor.
B. Incorrect. The incidence of thyroid carcinoma increases overall with increasing age, with a bimodal
distribution. However, the incidence of benign thyroid nodules increases more rapidly with increasing age,
therefore the relative risk of malignancy is greater in younger patients.
C. Incorrect. The incidence of thyroid carcinoma is increased 3- to 4-fold in patients exposed to radiation
than the general public. In particular, more than 1 million patients were given hundreds of rads of
radiation to the head and neck region for the treatment of benign pediatric conditions such as acne,
tonsillitis, and thymic enlargement, before the risks of this exposure were widely known. This practice was
commonplace during the period from 1940-1960, and some of these patients are still being monitored for
the development of thyroid cancer. The distribution of lesions in these patients is not significantly different
than that encountered in spontaneously occurring thyroid carcinoma. The incidence of benign thyroid
nodules is also significantly increased in this patient population. By contrast, the much higher radiation
exposure to the thyroid gland that occurs with radioiodine treatment for Graves’ disease, in the order of
tens of thousands of rads, is not associated with an increased risk of thyroid carcinoma.
D. Incorrect. The likelihood of malignancy in a cold nodule is substantially greater if the lesion is either
solitary or a dominant lesion, ie, one that is substantially larger than any other focal thyroid nodule
present. On the other hand, the incidence of thyroid carcinoma in patients with multinodular goiters is
only in the range of 5%, provided that they were not previously exposed to head and neck irradiation.
Citations:
Martin WH, Sandler MP. Thyroid imaging. In: Sandler MP, et al, eds. Diagnostic Nuclear Medicine. 4th
Philadelphia, Pa: Lippincott Williams & Wilkins; 2003:616-625.
Diagnostic In-Training Exam 2005

14. Section XII – Nuclear
327. ALL of the following are associated ventilation-perfusion mismatch EXCEPT:
A. Hypoplastic pulmonary artery
B. Chronic pulmonary embolism
C. Mucus plugging
D. Radiation therapy
Question #327
Rationales:
A. Incorrect. Hypoplastic pulmonary arteries are often associated with a degree of ventilation-perfusion
mismatch.
B. Incorrect. Chronic pulmonary embolism will demonstrate ventilation-perfusion mismatches.
C. Correct. Mucus plugging is a primary ventilatory disorder, and most commonly demonstrates matching
ventilation and perfusion abnormalities, secondary to reflex vasoconstriction.
D. Incorrect. Radiation therapy to the lungs may produce ventilation-perfusion mismatches in the areas
irradiated, corresponding to the geometry of the radiation port.
American College of Radiology

15. Section XII – Nuclear
328. Aluminum ion (Al3+) breakthrough following elution of a Molybdenum-99/Tc-99m generator is:
A. Physically harmful to the patient
B. Detectable colorimetrically
C. Detectable with a dose calibrator
D. A radiochemical impurity
Question #328
Rationales:
A. Incorrect. Although a heavy metal, the chemical quantity is inadequate to cause direct physical harm to
a patient. Aluminum impurities are only indirectly harmful by their unexpected chemical interaction
with various radiopharmaceutical preparations, with resultant colloid formation and subsequent altered
biodistribution of the radiopharmaceutical, including increased hepatic or pulmonary localization.
B. Correct. Qualitative colorimetric analysis of generator eluate placed upon a special test paper
chemically sensitive to Al3+ ion is mandated. Excessive amounts of aluminum ion capable of disturbing
radiopharmaceutical purity and scan quality will produce an obvious pink color change on the test paper.
For a fission-produced generator, the maximum allowable limit for alumina breakthrough is 10 ug/ml of
eluate.
C. Incorrect. Generator parent Molybdenum-99 breakthrough, a radionuclide impurity, increases the patient
radiation dose and also degrades image quality by its high-energy gamma rays (primarily 740 keV) as a
result of beta decay, detectable in the dose calibrator.
Aluminum 3+ ion is not radioactive, and thus not detectable with a radiation detector device.
D. Incorrect. Aluminum ion is a nonradioactive (stable) ionic contamination of a generator eluate, ie, a
chemical impurity. Hydrolyzed reduced technetium and free pertechnetate are examples of radiochemical
impurities.
Citations:
Henkin et al. ED. Nuclear Medicine. Vol. I, Chapter 33. Quality control in the hot lab. S. Karesh, Mosby, 1996.
Diagnostic In-Training Exam 2005

16. Section XII – Nuclear
329. Concerning Tc-99m sestamibi uptake, ALL of the following are true EXCEPT:
A. The mechanism of uptake is identical to that of Tl-201 chloride.
B. Uptake does not directly involve the sodium-potassium ATPase pump.
C. It distributes preferentially into tissues with high mitochondrial content.
D. Its retention is related to membrane potential.
Question #329
Rationales:
A. Correct. The mechanism of Tc-99m sestamibi uptake is different than Tl-201. Sestamibi uptake relates to
negative plasma membrane potential and cellular mitochondrial content. Therefore, this statement is false,
and is the correct answer to this question.
B. Incorrect. Tc-99m sestamibi uptake does not directly involve the sodium potassium ATPase pump. By
contrast, the uptake of T1-201, a potassium analog, does directly involve the sodium-potassium ATPase
pump.
C. Incorrect. Tc-99m sestamibi distributes into tissues with relatively high mitochondrial content. The
presence of a negative plasma membrane potential and high mitochondrial content are thought to explain
the normal uptake in such organs as the heart, liver, kidney, and skeletal muscle.
D. Incorrect. Tc-99m sestamibi retention is related to membrane potential.
American College of Radiology