23205019

29 th
Annual

In-Training Examination
for Diagnostic Radiology Residents
Rationales

February 2, 2006

Sponsored by:
Commission on Education
Committee on Residency Training in Diagnostic Radiology

Section I – Pediatric Radiology

Figure 1A

5. You are shown two single shot fast spin-echo images (Figures 1A and 1B) from an MR on a
22-week fetus. What is the MOST LIKELY diagnosis?

A. Posterior urethral valves
B. Multicystic dysplastic kidneys
C. Autosomal recessive polycystic kidney disease
D. Bilateral ureteropelvic junction (UPJ) obstruction

1
Diagnostic In-Training Exam 2006


Figure 1B

2 American College of Radiology

Question #5
Rationales:
A. Incorrect. While patients with severe obstruction from posterior urethral valves may also show
absence of amniotic fluid, posterior urethral valves lead to hydronephrosis, dilated ureters, and a
markedly distended bladder. Therefore, this choice is incorrect.
B. Incorrect. Although bilateral multicystic dysplastic kidneys would lead to absence of urine in the
bladder, and to lack of amniotic fluid, this abnormality is rarely bilateral. Further, the kidneys show
multiple, large macroscopic cysts of different size, which do not communicate. In this case, the kid-
neys appear solid, since the “cysts” consist of collecting tubules, are microscopic, and the kidneys
therefore appear solid. Therefore, this choice is incorrect.
C. Correct. The images show symmetrical, markedly enlarged, high signal kidneys, filling the
abdomen, displacing the diaphragms upwardly, small lungs, and no amniotic fluid. There is no urine
in the bladder. These findings of enlarged, solid, fluid-intensity kidneys without urine production
are typical of Autosomal Recessive Polycystic Kidney Disease.
D. Incorrect. Although UPJ obstruction can be bilateral, and can be severe; it is rare that it would be
severe enough to lead to complete lack of urine production. Furthermore, in those cases,
hydronephrosis, with dilatation of the calyces, would be evident. In this case, there is no
hydronephrosis. Therefore, Option D is incorrect.

3


Figure 2
6. You are shown an axial T1-weighted image of a newborn term infant (Figure 2). What is the
MOST LIKELY diagnosis?

A. Heterotopia
B. Lissencephaly
C. Schizencephaly
D. Hemimegalencephaly


Question #6
Rationales:
A. Incorrect. Heterotopia Consists Of Gray Matter In Abnormal Locations, Thought To Be An Arrest
Of Neuronal Migration Before It Reached The Brain Surface. The Most Common Locations Are
Subependymal. Single Or Multiple Masses Of Gray Matter May Be Seen In The Subependymal
Layer Of The Lateral Ventricles Or Subcortical White Matter. This Is Not Present In This Case, And
This Choice Is Incorrect.
B. Correct. The Image Shows An Abnormally Thickened, Agyric Cortex. Lissencephaly, Or “Smooth
Brain” Is A Condition In Which There Is A Lack Of Gyri. MRI Features Include Abnormally
Smooth Cerebral Surface, Cerebral Contour And Gray White Matter Distribution. The Cerebral
Contour Is Hourglass Shaped With Shallow Sylvian Grooves. There Is Increased Gray Matter.
C. Incorrect. Schizencephaly Is Believed To Result From Disordered Migration, Characterized By
Abnormal Transcerebral Columns Of Gray Matter. A Cleft Extends Across The Cerebral
Hemisphere From The Ventricular Surface To The Pial Surface, And Is Lined By The Abnormal
Gray Matter.
D. Incorrect. Hemimegalencephaly Is A Migrational Disorder Resulting In Hemihypertrophy Of The
Brain. Heterotopias, Pachygyric Or Agyric Cortex May Be Present.

5


Figure 3B
Figure 3A
7. You are shown T1 and post-contrast, fat-saturation coronal images from an MR examination in a
3-year-old boy with urinary retention (Figures 3A and 3B). What is the MOST LIKELY diagnosis?

A. Metastatic Wilms’ tumor
B. Rhabdomyosarcoma
C. Germ cell tumor
D. Hemorrhagic cystitis


Question #7
Rationales:
A. Incorrect. Wilms' Tumor Arises Peripherally In The Kidney Rather Than In Central Location And
Does Not Tend To Spread Via The Ureter. Wilms' Tumor Metastases Most Commonly Occur To
Local Nodes, Liver And Lung. Tumor Invasion Of The Renal Vein With Spread To The IVC And
Right Atrium Also Occurs Relatively Frequently.
Hemorrhage And Necrosis Within Wilms' Tumor Is Common, And Both Subcapsular And
Perinephric Hematoma Can Result. However, Hemorrhage Into The Collecting System And
Hematuria Is Quite Uncommon. In This Case No Renal Mass Is Evident. There Is A Large Irregular
Enhancing Bladder Mass Excluding Bladder Thrombus As A Diagnosis.
B. Correct. The Images Show An Enhancing Polypoid Mass In The Bladder Base And Posterior
Urethra, With Secondary Bilateral Hydroureteronephrosis, And A Right Perirenal Fluid Collection
Likely Representing Urinoma. Rhabdomyosarcomas In General Are More Common In Boys Than
Girls With A Mean Age Of Occurrence Of 7 Years. Genitourinary Rhabdomyosarcoma Most
Commonly Originates In The Prostate Or Bladder Base In Boys And The Vagina Or Bladder Base
In Girls. Urinary Retention, Dysuria, Hematuria, Fecal Retention And Vaginal Mass Are The Most
Common Presenting Features. This Tumor Is Also Known As Sarcoma Botryoides Because Of The
Irregular Grape-Like Appearance Of The Margins Of The Tumor Extending Into The Bladder. .
C. Incorrect. With The Exception Of Ovarian And Testicular Tumors, Germ Cell Tumors Tend To
Occur In Very Young Children (Less Than 2 Years). Sacrococcygeal And Head And Neck Tumors
Are Usually Present In The Newborn. An Occasional Site For Germ Cell Tumor Is In The Vagina In
Girls, With A Mass That May Mimic Sarcoma Botryoides; However Rhabdomyosarcoma Is The
Most Common Vaginal Tumor In Young Girls. Sacrococcygeal Teratomas Have Variable Internal
And External Pelvic Mass Components And Typically Cause Anterior Displacement Of The Rectum
And Bladder. The Images Depict A Botryoid Tumor Arising From The Bladder Base, And Therefore
This Choice Is Incorrect.
D. Incorrect. Hemorrhagic Cystitis Can Occur In Association With Viral Or Bacterial Infection As Well
As Related To Various Drugs (Ether And Hydrogen Peroxide) And Chemotherapeutic Agents
(Cyclophosphamide). There Is Usually Diffuse, Relatively Smooth Bladder Wall Thickening,
Although There May Be A More Focal Mass Mimicking A Tumor, And Extensive Clot May Be
Present In The Bladder. However, One Would Not Expect The Large Heterogeneous, Polypoid,
Enhancing And Obstructing Mass Seen Here, Therefore This Choice Is Incorrect.

7


Figure 4B
Figure 4A
8. You are shown the frontal and lateral chest radiographs of a previously healthy 6- year-old child
with cough and fever (Figures 4A and 4B). Which of the options below is the MOST appropriate
imaging recommendation to the referring physician?

A. Follow up chest radiograph
B. CT scan
C. Ultrasound
D. No further imaging is needed


Question #8
Rationales: ALL CHOICES ARE CORRECT
The finding consists of a round mass in the left paraspinal, retrocardiac region.
A. The radiographs demonstrate a round opacity in the retrocardiac area, most consistent with a round
pneumonia in a young child, particularly with the given history. Round pneumonias are common in
children and are thought to occur because of relatively poor development of collateral air pathways
for intra-alveolar spread of consolidation. When two views of the chest are obtained, frequently the
lesion only appears round or mass-like in one plane and not the other. The rounded appearance of
the mass is also often transient. Round pneumonias are usually associated with pneumococcal infec-
tion and are most commonly located posteriorly in the perihilar or lower lobe region. In the appro-
priate clinical situation the mass-like appearance of a round pneumonia should not prompt a pan-
icked work up for a neoplasm. However, since other lesions can be mistaken for round pneumonia,
it is considered appropriate to obtain a follow up chest x-ray to document resolution.
B. The images shown demonstrate posterior left retrocardiac opacity. This may be in the middle to pos-
terior mediastinum or left lower lobe. Differential considerations include round pneumonia, pul-
monary sequestration, foregut duplication or neurogenic tumor. The clinical history along with the
location tends to favor a round pneumonia, although no air bronchograms are seen. However air
bronchograms are only present in about 30% of round pneumonias. No mass effect is seen on ribs,
mediastinum or airway and the child has mild clinical symptoms. Therefore no urgent additional
imaging appears necessary. Use of CT scans in children should be carefully considered both in
order to obtain high quality studies that properly answer clinical questions because of the relatively
high attendant radiation dose, as well as the frequent need for intravenous contrast and sedation.
Clinical management and radiographic follow-up with CT obtained electively, if necessary, is a
more appropriate recommendation.
C. Ultrasound has been utilized in the pediatric chest especially in evaluating mediastinal or juxtamedi-
astinal lesions. Studies have the advantage of being able to be performed portably in ill patients and
there is no radiation exposure. However ultrasound is not usually the first choice examination to
assess an abnormal chest radiographic finding, any interposing aerated lung attenuates the ultra-
sound beam. The major use of chest ultrasound has been in evaluating pleural fluid collections and
assessing the cystic or solid nature of accessible lesions.
D. Fever is a common reason for obtaining a chest x-ray, and other lesions may be mistakenly diag-
nosed as round pneumonia in a child with an acute febrile illness. Therefore it is considered appro-
priate to obtain a follow up chest x-ray after resolution of the clinical illness. In this case a follow
up chest x-ray demonstrated that the lesion was unchanged one month later. Further workup
revealed an esophageal duplication cyst.

9


Figure 5A

Figure 5B

9. You are shown two images from a contrast CT image of an 8-year-old boy with leukemia who
complains of pain after upper endoscopy (Figures 5A and 5B). What is the MOST LIKELY
diagnosis?

A. Chloroma
B. Traumatic perforation of the duodenum
C. Intramural duodenal hematoma
D. Pancreatitis


Question #9
Rationales:
A. Incorrect. Chloroma, Also Known As Granulocytic Sarcoma, Is A Localized Tumor Of Leukemic
Cells. In General, Chloromas Are Uncommon, But Are A Diagnostic Consideration With Any Solid
Mass In A Patient With Leukemia. Chloromas Most Commonly Involve Bone, But May Involve
Other Organ Systems. A Focal Chloroma Involving Duodenum; However, Would Be Distinctly
Unusual, Particularly In This Clinical Setting Of Pain After Upper Endoscopy In A Potentially
Thrombocytopenic Patient. This Option Is Therefore Incorrect.
B. Incorrect. The Mass Is Confined To The Wall Of The Duodenum. No Extraluminal Fluid And No
Extraluminal Gas Are Seen To Suggest A Perforation Of The Duodenum. This Option Is Therefore
Incorrect.
C. Correct. Intramural Duodenal Hematoma May Arise From Trauma As Might Occur As A
Complication Of Upper Endoscopy. Duodenal Hematomas May Also Occur From Blunt Trauma
(Motor Vehicle Accidents, Bicycle Handle Bar Injuries, Child Abuse) And In Children With
Bleeding Disorders. Patients With Leukemia May Be Thrombocytopenic Due To The Primary
Disease Or As Consequence Of Therapy, Further Predisposing To The Development Of Duodenal
Hematoma. As In This Case, The Mass Is Confined To The Duodenal Wall. The Duodenal Lumen Is
Compressed By The Hematoma. This Option Is Therefore Correct.
D. Incorrect. Pancreatitis May Be A Complication Of Upper Endoscopy. However, More Commonly,
Pancreatitis May Be A Complication Of Endoscopic Retrograde Pancreatography (ERCP). In This
Image, A Mass Is Seen Which Appears To Involve The Duodenum Rather Than The Pancreas. Only
A Small Portion Of Pancreas Is Displayed On The Higher Of The Two Images, And It Appears
Normal. There Is No Evidence Of Peripancreatic Edema, Or Significant Inflammatory Changes.
The Diagnosis Of Pancreatitis Therefore Cannot Be Made From These Images. This Option Is
Incorrect.

11


Figure 6A Figure 6B
10. You are shown plain films and MR (T1 coronal and T1, fat-saturation, post-gadolinium sagittal)
images of the proximal right tibia in a 12-year-old boy with a swollen and painful right leg
(Figures 6A through 6C). What is the MOST LIKELY diagnosis?

A. Healing stress fracture
B. Brodie’s abscess
C. Osteoid osteoma
D. Osteosarcoma



Figure 6C

13

Question #10
Rationales:
A. Incorrect. A Healing Stress Fracture Demonstrates Sclerosis And Periosteal Reaction On Plain Film
And Some Marrow Edema On MRI. There Is Not Extensive Mass With Enhancement, Extending
Into The Surrounding Soft Tissues, As Is Seen In This Case. This Option Is Therefore Incorrect.
B. Incorrect. A Brodie’s Abscess Usually Appears As A Well Defined Lytic Lesion With A Sclerotic
Rim. Marrow Edema Is Seen On MRI. There Is No Soft Tissue Mass. This Option Is Therefore
Incorrect.
C. Incorrect. An Osteoid Osteoma Has A Central Lucent Nidus And Surrounding Sclerosis. There Is
No Extension Into The Epiphysis Or Soft Tissue Mass.
D. Correct. The Images Demonstrate An Aggressive, Bone-Producing Mass Involving The Proximal
Right Tibia With Abnormal Periosteal Reaction. The MRI Demonstrates A Solid, Enhancing Lesion
Replacing The Marrow Cavity, Crossing The Medial Physis, And An Enhancing Soft Tissue
Extension Beyond The Bone. The Most Likely Diagnosis Is Osteosarcoma.


11. A newborn infant presents on the second day of life with a distended abdomen and bilious eme-
sis. A radiograph of the abdomen demonstrates markedly distended intestinal loops throughout
the abdomen. What is the BEST next diagnostic examination?

A. Upper GI study
B. Contrast enema
C. CT of the abdomen with IV contrast
D. Ultrasound examination of the abdomen

Question #11
Rationales:
A. Incorrect. The Case Describes A Distal Bowel Obstruction In A Newborn. An Upper GI Study
Would Not Be Warranted In Cases Of A Newborn With A Distal Bowel Obstruction. The Correct
Test Of Choice Would Be A Contrast Enema, Preferably Performed With Water Soluble, Isotonic
Contrast In Case Of A Perforation.
B. Correct. The Case Describes A Distal Bowel Obstruction In A Newborn. The Correct Test Of
Choice Would Be A Contrast Enema, Preferably Performed With Water Soluble, Isotonic Contrast
In Case Of A Perforation.
C. Incorrect. The Case Describes A Distal Bowel Obstruction In A Newborn. Abdominal CT Plays No
Role In The Workup. The Correct Test Of Choice Would Be A Contrast Enema, Preferably
Performed With Water Soluble, Isotonic Contrast In Case Of A Perforation.
D. Incorrect. The Case Describes A Distal Bowel Obstruction In A Newborn. Abdominal Sonography
Plays No Role In The Workup, And The Gas-Filled Bowel Would Render The Examination Difficult
At Best. The Correct Test Of Choice Would Be A Contrast Enema, Preferably Performed With
Water Soluble, Isotonic Contrast In Case Of A Perforation.

15

Concerning holoprosencephaly, which one is TRUE?
12.

A. The fornix and septum pellucidum are absent in all forms of holoprosencephaly.
B. The posterior portion of the corpus callosum is absent in lobar holoprosencephaly.
C. 10% of cases with holoprosencephaly are associated with cytogenetic abnormalities.
D. Cebocephaly is most common in patients with lobar holoprosencephaly.

Question #12
Rationales:
A. Correct. While The Severity Of Holoprosencephaly Varies From Severe Alobar To Lobar, By
Definition, All Forms Of Holoprosencephaly Do Not Have A Fornix Or Septum Pellucidum, And
May Have Hypoplasia Of The Pituitary And Optic Nerves.
B. Incorrect. The Cerebral Vesicles Cleave In A Dorsofrontal Direction. In Patients With Lobar And
Semilobar Holoprosencephaly, The Posterior Portion Of The Corpus Callosum Is Present While The
Anterior Portion Is Absent; The Entire Corpus Callosum May Be Present In Lobar
Holoprosencephaly.
C. Incorrect. Up To 40% Of Cases Are Linked To Chromosomal Anomalies, 20% With Syndromes,
With Only 40% Cases Isolated.
D. Incorrect. Severe Facial Anomalies, Such As Cyclopia, Cebocephaly And Ethmocephaly, Are Most
Likely In Patients With Alobar Holoprosencephaly. However, A Normal Face Does Not Exclude A
Severe Form Of Holoprosencephaly.


Which one of the following findings is seen in most patients with Dandy
13.
Walker malformation?

A. Intact vermis
B. Small cisterna magna
C. Elevated tentorium cerebelli
D. Agenesis of the corpus callosum

Question #13
Rationales:
A. Incorrect. By Definition, The Most Characteristic Finding Of Dandy Walker Malformation Is
Complete Or Partial Absence Of The Cerebellar Vermis.
B. Incorrect. Fourth Ventricle Communicates With An Enlarged Cisterna Magna Bordered By The
Cerebellar Hemispheres.
C. Correct. The Tentorium And Torcula Are Elevated With Dandy Walker Malformation, Best
Evaluated On Midline Sagittal Images Of The Brain. On Plain Films, The Anomaly Is Characterized
By Lambdoid-Torcular Inversion.
D. Incorrect. Dysgenesis Of The Corpus Callosum Occurs In Only 20-25% Of Patients. Gyral
Abnormalities Also Occur In A Small Number Of Patients With Dandy Walker Malformation.

17

Concerning periventricular leukomalacia, which one is CORRECT?
14.

A. Injury is secondary to venous infarction.
B. Areas of cystic necrosis develop 1-3 weeks after injury.
C. Infants are at greatest risk for PVL at 36-38 weeks gestation.
D. Ultrasound is sensitive in the identification of the acute lesions.

Question #14
Rationales:
A. Incorrect. Injury is thought to be arterial watershed infarction of the premature infant’s periventricu-
lar white matter. Venous infarction is believed to be the mechanism of the parenchymal hemorrhagic
component in Grade IV germinal matrix hemorrhage.
B. Correct. The multicystic periventricular components, characteristic at sonography, represent areas
of cystic necrosis in ischemic areas, and develop 1-3 weeks after the acute injury, after resolution of
the initially echodense lesions.
C. Incorrect. Injury typically occurs in preterm infants less than 32 weeks gestation.
D. Incorrect. Ultrasound is often insensitive in the acute stage, with as many as 50% of initial studies
in the first few days following injury reported as normal in appearance.


15. Which one of the following is characterized by the finding of a microcolon?

A. Duodenal atresia
B. Meconium plug syndrome
C. Meconium ileus
D. Short-segment Hirschsprung’s disease

Question #15
Rationales:
A. Incorrect. In patients with duodenal atresia, sufficient succus entericus is produced to allow normal
colonic caliber.
B. Incorrect. Mecomiun plug syndrome is associated with dysmotility of the colon; infants are typical-
ly full term, often with maternal history of preeclampsia. Colon is normal in caliber and filled with
meconium plugs. Once the meconium is extruded, the patient is relieved of symptoms.
C. Correct. Meconium ileus, associated with cystic fibrosis, is the result of inspissation of tenacious
meconium in the ileum, which prevents passage of meconium into the colon. The colon is not used
prenatally, resulting in a microcolon.
D. Incorrect. Hirschsprung’s disease is characterized by a distal aperistaltic segment, typically of nor-
mal caliber, with a more dilated proximal bowel as the transition zone develops. The abnormal seg-
ment may demonstrate a serrated appearance, believed to result from uncoordinated, aperistaltic
contractions. Suction biopsy can confirm the diagnosis.

19

Concerning the presence of a perirenal fluid collection in a newborn infant, which one is
16.
CORRECT?

A. This finding is associated with posterior urethral valves.
B. The finding represents sympathetic transudation of fluid due to obstruction.
C. Secondary infection is not a significant concern.
D. Early post-contrast CT or MR images are diagnostic.

Question #16
Rationales:
A. Correct. Long standing high grade obstruction in utero is associated with renal dysplasia and poor
renal function. The presence of loculated or free urine extravasation from the kidney of a newborn
infant is most commonly associated with posterior urethral valves, and is secondary to forniceal
rupture and decompression into the perirenal space, at times extending into the peritoneal cavity,
presenting as urinary ascites. This finding has been associated with relative preservation of function
in the kidney, probably due to decompression of the obstruction.
B. Incorrect. This fluid collection results from forniceal rupture of a calyx and extravasation of urine
forming a subcapsular urinoma. Subcapsular, perinephric and paranephric urinomas can occur in
association with urinary obstruction, including posterior urethral valves, ureteropelvic junction
obstruction, neurogenic bladder and bladder tumors or after trauma to the urinary tract. The collec-
tion may rupture into the peritoneal space producing urinary ascites.
C. Incorrect. Secondary infection of fluid collections in a newborn is always of concern, especially
when there is underlying obstruction and/or reflux.
D. Incorrect. If a contrasted examination (CT or MRI) were done, delayed images would be most use-
ful in demonstrating contrast accumulation within the urinoma, confirming the connection to the
urinary tract. In the setting of posterior urethral valves, however, upper tract contrast examinations
are unnecessary for diagnosis.


17. Concerning leakage radiation for a unit used for pediatric chest filming, what is the maximum
leakage radiation allowed at 1 meter from the x-ray tube source when the system is operated at the
maximum continuous allowable tube current and kilovoltage?

A. 2 mR/week
B. 10 mR/hour
C. 100 mR/hour
D. No specified limits

Question #17
Rationales:
A. Incorrect. This is maximum permissible dose limit outside an x-ray room.
B. Incorrect. See correct answer.
C. Correct. According to NCRP report no. 91, the allowed maximum limit for leakage radiation is 100
mR/hr at 1 meter when the system is operated at maximum continuous mA and kVp.
D. Incorrect. See correct answer.

21

18. Which of the following radiographic findings is MOST useful in excluding the diagnosis of
hyaline membrane disease in a newborn infant?

A. Pleural effusion
B. Hyperinflation
C. Unossified humeral epiphyses
D. Asymmetric pulmonary opacity

Question #18
Rationales:
A. Incorrect. While pleural effusion is an uncommon finding in hyaline membrane disease, its presence
or absence is not specific in excluding the diagnosis. Small pleural effusion may be seen in transient
tachypnea of the newborn which can co-exist with hyaline membrane disease, especially on early
radiographs. Although in the appropriate clinical setting, the presence of diffuse ground glass opaci-
ty with accompanying pleural effusion should raise the question of infection, particularly group B
streptococcal pneumonia, pleural effusion alone cannot exclude hyaline membrane disease.
B. Correct. The underlying cause of hyaline membrane disease is deficiency of surfactant; this
lipoprotein complex produced by Type II pneumocytes coats alveoli and prevents them from col-
lapsing in expiration. Diffuse alveolar atelectasis with pulmonary underaeration is the hallmark of
this disease. Increased lung volumes would strongly suggest excluding hyaline membrane disease as
a diagnostic possibility. With early intubation and administration of exogenous surfactant, character-
istic radiographic findings may be less marked and more transient.
C. Incorrect. Ossification of humeral epiphyses may be used as a sign of skeletal maturity on a chest
radiograph. Ossified humeral epiphyses are not seen in infants less than thirty-six weeks of gesta-
tion and are present in approximately 40% of term infants. Therefore the presence of humeral epi-
physes would diminish the likelihood of hyaline membrane disease, a disease of prematurity.
Unossified epiphyses would not be useful in excluding the disease.
D. Incorrect. While diffuse symmetric ground glass opacity is the characteristic feature of hyaline
membrane disease, some variation of this pattern is not uncommon. Lower lobe involvement tends
to be more marked than upper lobe; opacity may be more marked on the right than on the left side.
After surfactant administration there is often asymmetric clearing of the lungs. Therefore, the pres-
ence of asymmetry does not exclude the diagnosis of hyaline membrane disease.


Concerning the thymus in childhood, which one is CORRECT?
19.

A. Hodgkin’s disease rarely involves the thymus.
B. Normal thymus obscures the great vessels at sonography.
C. Thymic cysts may occur in the neck.
D. Normal thymus is bright on T1- and dark on T2-weighted MR images.

Question #19
Rationales:
A. Incorrect. Hodgkin’s disease often occurs in the anterior mediastinum and typically infiltrates the
thymus. Bulky adjacent mediastinal adenopathy usually occurs. On CT imaging, the thymus is
enlarged, nodular and heterogeneous with areas of necrosis frequently present, as opposed to the
smooth homogenous normal thymus. Compression of the airway is often a significant concern.
B. Incorrect. The normal thymus is of uniform, midi-level echogenicity, and offers an excellent win-
dow into the mediastinum, by displacing surrounding air-filled lung.
C. Correct. Thymic cysts are most commonly found in thymic rests in the neck, rather than in the
main gland. These may present acutely due to infection or hemorrhage. They may be associated
with bone marrow aplasia and have been reported in patients with HIV and treated lymphoma.
D. Incorrect. On MR images the normal thymus in childhood is relatively dark (slightly hyperintense
to muscle) on T1 weighted images and has uniform bright signal on T2 weighted sequences. In
younger infants the thymus has a quadrilateral shape with convex borders, becoming more triangu-
lar in children over five years of age. Fatty infiltration of the thymus is usually not seen until the
late teenage years or adulthood.

23

Concerning imaging of a child with a bronchial foreign body, which one is CORRECT?
20.

A. A decubitus radiograph with the affected side up will be helpful in demonstrating ipsilateral air
trapping.
B. A nuclear medicine ventilation perfusion scan will likely demonstrate symmetric lung perfusion
but asymmetric ventilation.
C. On fluoroscopy the mediastinum will shift away from the affected side in expiration.
D. The majority of foreign bodies are radiopaque and visible on chest radiographs.

Question #20
Rationales:
A. Incorrect. When placed in the decubitus position, the dependent (down) lung deaerates and the non-
dependent lung expands. Therefore to demonstrate air trapping i.e. lack of dependent deflation, the
useful decubitus view is with the affected side down.
B. Incorrect. When the lung is abnormally ventilated there is also decreased perfusion due to reflex
vasoconstriction. There may be very little perfusion of the affected side when significant air trap-
ping is present.
C. Correct. This is one of the cardinal observations in fluoroscopic evaluation of a foreign body. On
inspiration the mediastinum is in its normal location i.e. central. With expiration the mediastinum
shifts towards the normal lung which deflates, and away from the persistently hyperinflated abnor-
mal lung. Other fluoroscopic observations include lack of deflation and decreased diaphragmatic
excursion on the affected side
D. Incorrect. Only a small number of foreign bodies are radiopaque. The most common endobronchial
foreign bodies are ingested foods, such as peanuts and raw carrots. Therefore the radiographic fea-
tures rely on secondary findings, predominantly air trapping distal to the foreign body due to partial
obstruction of the affected airway. With a larger or more long standing foreign body, pulmonary
opacity due to atelectasis or post obstructive pneumonia may occur.


Concerning Tetralogy of Fallot, which one is CORRECT?
21.

A. A right-sided aortic arch is present in approximately 60% of cases.
B. The four features consist of ASD, VSD, overriding aorta and right ventricular outflow tract
obstruction.
C. Radiographs typically demonstrate marked cardiomegaly with a “boot shaped” heart.
D. Right-sided obstruction may include infundibular, valvular and peripheral pulmonic stenoses.

Question #21
Rationales:
A. Incorrect. Tetralogy of Fallot is one of the most frequent lesions to be associated with a right-sided
aortic arch. This occurs however in approximately 20 - 30% of cases. Other cardiac lesions associat-
ed with a right-sided aortic arch include truncus arteriosus (30%), tricuspid atresia (10 - 15%) and
double outlet right ventricle (12%).
B. Incorrect. ASD is not one of the four cardinal features in Tetralogy of Fallot. Right ventricular
hypertrophy is the fourth feature in addition to VSD, overriding aorta and right ventricular outflow
obstruction. ASD occurs in approximately 15% of cases; when present the entity is termed
Pentalogy of Fallot.
C. Incorrect. Although the quot;boot shapedquot; heart is the classically described configuration in Tetralogy of
Fallot, preoperatively the heart is usually normal in size, or only mildly enlarged. The “boot-shaped
heart” is produced by the combination of a concave main pulmonary artery segment and an elevated
cardiac apex, indicative of right ventricular hypertrophy without dilatation and cardiac enlargement.
D. Correct. Right-sided obstruction is often at multiple levels. Typically there is infundibular obstruc-
tion without or with valvular stenosis, or even atresia. Peripheral pulmonary artery coarctation, uni-
lateral hypoplasia or absence of a pulmonary artery also occurs, most often on the left side.
Conversely there may be complete absence of the pulmonary valve leaflets with marked pulmonic
regurgitation and very large central pulmonary arteries.

25

Concerning slipped capital femoral epiphysis, which one is CORRECT?
22.

A. The frog lateral radiograph is contraindicated
B. Produces knee pain in one quarter of patients
C. Is bilateral in 75 – 80% of cases
D. Is most common in athletes

Question #22
Rationales:
A. Incorrect. The femoral head slips posteriorly and medially. The frog lateral view is essential to
detect the posterior component of the slip, which may be the major component in some patients.
B. Correct. Patients with slipped capital femoral epiphysis usually present with hip or groin pain;
however, in approximately 25% of patients pain is referred to the ipsilateral knee. These patients
may present with knee pain alone or knee pain in combination with hip/groin pain. In a patient in
the typical age range for slipped capital femoral epiphysis, unexplained knee pain should prompt
consideration for slipped capital femoral epiphysis.
C. Incorrect. Slipped capital femoral epiphysis is bilateral in approximately one quarter to one third of
patients, much less than 75-80%.
D. Incorrect. Slipped capital femoral epiphysis is most common in obese adolescents.


Concerning Ewing sarcoma of bone, which one is CORRECT?
23.

A. It is most common in children under 5 years of age.
B. It is the most common primary bone malignancy in childhood.
C. The more aggressive tumors produce more osteoid.
D. Histologically it is identical to primitive neuroectodermal tumor (PNET).

Question #23
Rationales:
A. Incorrect. Although Ewing sarcoma can occur in a child under 5 years of age, it is relatively rare in
this age group. Ewing sarcoma is most common in the second decade of life.
B. Incorrect. Ewing sarcoma is the second most common primary bone malignancy in childhood.
Osteosarcoma is considerably more common.
C. Incorrect. Ewing sarcoma does not produce osteoid. Osteoid is produced by osteosarcoma. A scle-
rotic response may be seen within the host bone and up to 15% of Ewing sarcomas will thus appear
sclerotic at presentation; however, the tumor itself does not produce osteoid.
D. Correct. Ewing sarcoma and PNET are histologically identical. Moreover, they are cytogenetically
identical and now considered by pathologists to be the same tumor.

27

24. Concerning the conversion of hematopoietic bone marrow to fatty bone marrow in the femur of a
child, which portion of the femur is the LAST to convert?

A. Proximal femoral epiphysis
B. Proximal femoral metaphysis
C. Diaphysis
D. Distal femoral metaphysis

Question #24
Rationales:
A. Incorrect. The epiphyses almost immediately convert from hematopoietic marrow to fatty marrow
as soon as they are ossified.
B. Correct. The epiphyses convert to fatty marrow soon after they ossify. Diaphysis precedes metaph-
ysis and distal precedes proximal. Therefore, within the femurs, the proximal metaphyses are the
last portion of the bone to convert from hematopoietic marrow to fatty marrow. Commonly in
teenagers, residual patchy hematopoietic marrow is still present within the proximal femoral meta-
physis on MR imaging.
C. Incorrect. The diaphysis converts from hematopoietic marrow to fatty marrow before the metaphy-
ses.
D. Incorrect. Conversion proceeds from distal to proximal. The distal femoral metaphyses therefore
convert from hematopoietic marrow to fatty marrow prior the proximal femoral metaphyses.


25. To keep patient dose as low as reasonably achievable for digital radiography examinations using
a CR or DR detector, the mAs is selected to provide acceptable:

A. image contrast.
B. optical density.
C. luminance on the image monitor.
D. signal to noise ratio.

Question #25
Rationales:
A. Incorrect. Digital detectors are inherently limited by signal to noise ratio, and contrast is variable
according to digital grayscale translation tables (windowing and leveling the image).
B. Incorrect. There is no optical density measure with digital images. For analog screen-film images
this, of course, is what is required.
C. Incorrect. The luminance of the monitor is independent of the characteristics of the image. Also, for
digital images, the overall signal intensity of the output image is scaled so that the proper range of
signals is displayed (or at least they can be adjusted to the appropriate luminance range)
D. Correct. Digital detectors are inherently signal to noise ratio (SNR) limited, because of the ability
to vary the image display characteristics by post-processing (contrast enhancement, spatial resolu-
tion enhancement, etc.) The mAs is linearly related to the number of x-ray photons on the patient
and also to the number of x-ray photons absorbed by the x-ray detector. Therefore, the SNR (N/√N
= √N) is determined by the number of x-rays detected and converted to an output signal. Even
though digital systems have the ability to enhance contrast, noise will also be enhanced and the SNR
will remain constant. So, the ability to detect a subtle finding in a noisy background for a digital
image depends on the required SNR for a given examination. The mAs should be chosen at a level
that gives just enough (not too much) radiation such that the SNR will be high enough to make the
diagnosis.

29

Which one of the following is a characteristic feature of renal duplication in girls?
26.

A. Reflux into the upper system
B. Ectopic lower pole ureter
C. Incontinence
D. Duplication of the uterus

Question #26
Rationales:
A. Incorrect. Although reflux may occur into either the upper or lower moieties of an uncomplicated
duplication, the typical consequence of duplication is obstruction of the ectopic upper pole ureter,
and reflux into the lower moiety, likely secondary to interference of the abnormal upper pole ureter
with the normal antireflux tunnel mechanism of the orthotopic lower pole.
B. Incorrect. The lower pole ureter inserts normally at the trigone. The upper pole ureter arises above
the normal ureteric bud, and therefore inserts ectopically, medially and inferiorly within the bladder,
or along the course of the mesonephric duct. Therefore, option B is false.
C. Correct. The ureters are derivatives of the mesonephric duct, and therefore ectopic ureters insert
along its derivatives or remnants. In boys, the ectopic ureter will always insert above the sphincter,
medially into the bladder, or into the seminal vesicles. However, in girls with duplex kidney, the
ectopic ureter may insert below the sphincter, into the urethra, or into the vagina, resulting in uri-
nary incontinence. This is characterized by constant dampness. Therefore, option C is correct.
D. Incorrect. Duplication of the uterus, with obstruction of one of the two systems, is typically associ-
ated with ipsilateral renal agenesis or dysgenesis. However, renal duplications are not typically
associated with duplication of the uterus.


Regarding duodenal obstruction, which one is CORRECT?
27.

A. Plain films may be normal in patients with volvulus.
B. Nonbilious vomiting excludes the diagnosis.
C. Atresia is secondary to intrauterine ischemia.
D. Windsock duodenum is typically found in neonates.

Question #27
Rationales:
A. Correct. Volvulus obstructs at the third portion of the duodenum, and presents with bilious vomit-
ing. Volvulus occurs about the axis of the superior mesenteric artery, and leads to ischemia of its
territory, from the duodenojejunal junction to the splenic flexure. Therefore, insufficient time elaps-
es for marked duodenal dilatation to occur, and the plain films may be normal, or demonstrate rela-
tive paucity of distal gas with longer or more severe obstruction. Absence of bowel distension may
lead to a false sense of security and diminished concern for obstruction.
B. Incorrect. Although most cases of duodenal atresia or stenosis occur distal to the ampulla of Vater,
the obstruction may lie proximal to the ampulla in a minority of patients, in whom the emesis may
be nonbilious. Therefore, nonbilious vomiting does not exclude the diagnosis, and this option is
incorrect.
C. Incorrect. Although small bowel and colonic atresias are considered to be secondary to an intrauter-
ine ischemic event, duodenal atresia is believed to be the result of failure of recanalization.
Therefore this option is incorrect.
D. Incorrect. Windsock duodenum is the result of stretching of duodenal membrane in patients with
membranous duodenal stenosis. Therefore, it is typically seen in older patients.

31

Regarding pyloric stenosis, which one is TRUE?
28.

A. It is present at birth.
B. Affected infants present with paradoxical aciduria.
C. Paternal history is a greater risk factor than maternal history.
D. Affected infants have no appetite.

Question #28
Rationales:
A. Incorrect. Pyloric stenosis develops after birth, and typically presents in infants at 4-12 weeks of
age.
B. Correct. Vomiting leads to dehydration and waste of sodium, potassium and hydrochloric acid.
Renal mechanisms supervene, with conservation of sodium at the expense of hydrogen ion, leading
to a paradoxical aciduria in a patient with hypochloremic alkalosis.
C. Incorrect. Male and female children of affected mothers carry a 20% and 7% respective risk of
developing the condition, whereas male and female children of affected fathers carry a respective
risk of 5% and 2.5%.
D. Incorrect. Despite the distended stomach, the infants are malnourished, and exhibit a voracious
appetite, typically gnawing at their hands in an effort to obtain nourishment.


29. Which of the following conditions is associated with pulmonary hypoplasia?

A. Bochdalek hernia
B. Potter syndrome
C. Vascular ring
D. Tracheal bronchus

Question #29
Rationales: A & B ARE BOTH CORRECT
A. Correct. The posterolateral Bochdalek diaphragmatic hernia is usually large and associated with
considerable mass effect on the developing lung. The anteromedial Morgagni hernia is typically
small and most often asymptomatic. Bochdalek hernia is strongly associated with pulmonary
hypoplasia whereas hypoplasia is usually not a feature of the Morgagni defect. Occasionally
Morgagni hernia may be large or bilateral often with herniation into the pericardial sac with car-
diorespiratory compromise.
B. Correct. Potter syndrome was originally described as renal agenesis in association with fetal anuria
and oligohydramnios. Bilateral pulmonary hypoplasia is thought to be caused by extrinsic compres-
sion of the fetal thorax by the uterus in association with decreased amniotic fluid. Other causes of
olgohydramnios including bilateral urinary obstruction, bilateral cystic or dysplastic kidneys and
prolonged amniotic fluid leak have also been found to be associated with pulmonary hypoplasia.
Thoracic cage compression, most commonly due to bone dysplasia and intrathoracic lung compres-
sion, notably associated with congenital diaphragmatic hernia, pleural fluid or a large thoracic or
abdominal mass are also causes of bilateral pulmonary hypoplasia. Additional etiologic factors in
bilateral pulmonary hypoplasia are conditions associated with decreased fetal breathing (e.g.
myotonic dystrophy, myasthenia gravis, hypotonia) and decreased pulmonary blood flow, such as in
Tetralogy of Fallot and pulmonary atresia.
C. Incorrect. Vascular ring is a result of abnormal vascular and ligamentous mediastinal structures,
with encirclement of the trachea and esophagus. The symptomatic vascular ring typically causes
compression of the trachea and presents with respiratory distress and repeated episodes of pneumo-
nia. However, this abnormality is not associated with pulmonary hypoplasia.
D. Incorrect. A tracheal bronchus describes the situation where the right upper lobe, or one of its seg-
ments, is supplied directly from the trachea, rather than as a branch of the right mainstem bronchus.
When the bronchus supplies the entire lobe, it is termed a “bronchus sui” or pig bronchus, as this is
the normal porcine anatomical arrangement. The tracheal bronchus may be asymptomatic and dis-
covered incidentally, or may be associated with repeated right upper lobe infections. Its incidence is
reported as 0.1 – 2% of the population, and is associated with rib anomalies and Down syndrome.
However, it is not associated with pulmonary hypoplasia.

33

30. Regarding pulmonary sling, which of the following is TRUE?

A. The right pulmonary artery arises aberrantly from the left.
B. The abnormal artery crosses posterior to the esophagus.
C. Pulmonary expansion on the chest radiograph is usually normal.
D. It can be complicated by tracheal stenosis.

Question #30
Rationales:
A. Incorrect. The pulmonary artery sling consists of abnormal origin of the left pulmonary artery from
the right. The aberrant left artery does not arise from the main pulmonary artery at the bifurcation,
but from the right branch; it then courses posteriorly, and turns to the left between the trachea and
the esophagus to the left hilum. Therefore, this choice is incorrect.
B. Incorrect. As stated above, the course of the aberrant pulmonary artery lies between the trachea and
the esophagus, therefore it courses anterior to the esophagus. This is in contradistinction to vascular
rings, where the abnormal vessel courses posterior to the esophagus, encircling both the trachea and
esophagus within the vascular ring.
C. Incorrect. Plain chest radiographs on patients with pulmonary artery sling typically show abnormal
inflation, with hyperinflation or asymmetrical inflation of the lungs. There may be a low position of
the left hilum, as the normal epibronchial left pulmonary artery is absent. Anterior bowing of the
trachea is often seen on the lateral view, as the aberrant vessel courses between the trachea and the
esophagus.
D. Correct. Tracheal stenosis may occur at the site of the crossing vessel, or may be part of a more
generalized anomaly with complete cartilage rings. The anomaly is typically symptomatic early in
life, with infants presenting with respiratory stridor, feeding difficulties, and repeated respiratory
infections.


31. Which of the following is a Salter IV fracture?

A. Lateral condylar fracture of the distal humerus
B. Avulsion of the medial epicondyle of the distal humerus
C. Juvenile Tillaux fracture
D. Bucket handle fracture of non-accidental trauma

Question #31
Rationales: A & C ARE BOTH CORRECT
A. Correct. The lateral condylar fracture extends through distal humeral metaphysis, distal humeral
growth plate and distal humeral epiphysis. This is a Salter IV fracture. When the epiphyseal portion
of the fracture passes through cartilage and is not seen on radiographs, it can be delineated by MR
or ultrasound. If the fracture is complete there may be displacement of the lateral condylar frag-
ment. If the fracture through the epiphyseal cartilage is incomplete, there may be minimal or no dis-
placement of the lateral condylar fragment.
B. Incorrect. An avulsion fracture of the medial epicondyle goes through the growth plate of the medi-
al epicondylar apophysis. This is a Salter I fracture.
C. Correct. Juvenile Tillaux fracture is a Salter III fracture. The fracture line course through epiphysis,
usually in a sagittal or oblique sagittal plane, and through the lateral portion of growth plate. This
fracture occurs near puberty when the distal tibial growth plate is beginning to fuse. Fusion begins
medially. The Tillaux fracture involves the lateral aspect of the growth plate which is not yet fused.
D. Incorrect. The “bucket handle” fracture of non-accidental trauma does not involve the growth plate
and is not classified by the Salter-Harris system. Histologically, Kleinman et al have shown that
this fracture is a transverse fracture through the metaphysis close to the growth plate.

35

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