1 Answer A. A pulmonary artery sling causes an anterior impression on the esophagus (arrow) and a posterior impression on the trachea because of the left pulmonary artery passing between the trachea and esophagus (arrow in B). The left pulmonary artery arises from the posterior aspect of the right pulmonary artery. This condition occurs because of the obliteration of the primitive left sixth aortic arch.

A right arch with an aberrant left subclavian artery would produce a posterior impression on the esophagus, not an anterior impression.

Tracheomalacia is a condition where there is flaccidity of the airway wall and supporting cartilage. On imaging, there is collapse of the tracheal lumen most pronounced during expiration or coughing. This condition is associated with vascular rings such as pulmonary artery sling but is not demonstrated on this image.

Single-contrast barium upper gastrointestinal study demonstrates an anterior impression on the esophagus (arrow in A). There is no evidence of significant esophageal narrowing.

References: Lee EY, Dorkin H, Vargas SO. Congenital pulmonary malformations in pediatric patients: review and update on etiology, classification, and imaging findings. Radiol Clin N Am 2011;49(5):921-948.

Yedururi S, Guillerman P, Chung T, et al. Multimodality imaging of tracheobronchial disorders in children. Radiographics 2008;28(3):e29. doi:http://dx.doi.org/10.1148/rg.e29.

2 Answer B. When the magnification increases, the field of view becomes smaller. Unfortunately, when the field of view becomes smaller and the magnification increases, the dose also increases. Reducing the magnification or enlarging the field of view will therefore decrease the radiation dose.

The antiscatter grid attenuates scattered radiation. Given that detection of this scattered radiation decreases image quality, it is often necessary to use the grid in larger patients. With removal of the scattered radiation, the primary dose of radiation must be increased to replace the scattered dose at the image receptor. In pediatric patients, the smaller body produces less scatter, and therefore, use of a grid only minimally improves image quality. Children under the age of 3 to 5 years generally can be imaged without the grid with similar image quality.

Decreasing the source to skin distance (SSD) will decrease the dose to the child. The inverse square law states that the intensity of radiation of the beam is inversely proportional to the square of the SSD. Because of this, decreasing the SSD will decrease the dose to the child, and increasing the SSD will increase the dose to the child.

The pulse rate is the number of fluoroscopic images the fluoroscopy machine creates per second. Increasing the pulse rate would increase the number of images per second and therefore increase the dose. Decreasing the pulse rate would decrease the number of images per second and decrease the dose.

Reference: Hernanz-Schulman M, Strauss K, Bercha IH. Fluoroscopy and radiation safety content for radiologists. http://www.imagegently.org/Portals/6/Radiologists/Background4radiologists.pdf

3 Answer B. A type II pulmonary artery sling is characterized by a low position of the carina at the level of T6. A type II pulmonary artery sling is associated with long-segment tracheal stenosis, a T-shaped carina, and a bridging bronchus.

Reference: Lee EY, Dorkin H, Vargas SO. Congenital pulmonary malformations in pediatric patients: review and update on etiology, classification, and imaging findings. Radiol Clin N Am 2011;49(5):921-948.

4 Answer C. Right and left renal angiograms demonstrate a normal right main renal artery but an early upper pole branch with irregular narrowing and a small aneurysm (arrow in A). The left main renal artery also has irregular stenosis and two small aneurysms (arrows in B). These findings are most compatible with fibromuscular dysplasia, particularly in this age group. Fibromuscular dysplasia is a nonatherosclerotic disease involving medium-sized vessels, most commonly the renal and extracranial carotid and vertebral arteries. Percutaneous transluminal renal angioplasty is the treatment of choice for renal fibromuscular dysplasis.

References: Meuse MA, Turba UC, Sabri SS, et al. Treatment of renal artery fibromuscular dysplasia. Tech Vasc Interv Radiol 2010;13:126-133.

O’Connor SC, Gornik HL. Recent developments in the understanding and management of fibromuscular dysplasia. J Am Heart Assoc 2014;3(6):e001259. doi:10.1161/JAHA.114.001259.

5 Answer D. The most common presenting sign of fibromuscular dysplasia is hypertension followed by headache.

Reference: O’Connor SC, Gornik HL. Recent developments in the understanding and management of fibromuscular dysplasia. J Am Heart Assoc 2014;3(6):e001259. doi:10.1161/JAHA.114.001259.

6 Answer A. The most common histopathologic subtypes of fibromuscular dysplasia are medial (70%), perimedial (15% to 25%), and intimal fibrodysplasia (1% to 2%). Both medial and perimedial fibrodysplasia tend to develop stenosis and aneurysms, whereas intimal fibrodysplasia develops smooth focal or tubular narrowing.

Reference: Meuse MA, Turba UC, Sabri SS, et al. Treatment of renal artery fibromuscular dysplasia. Tech Vasc Interv Radiol 2010;13:126-133.

7 Answer F. Per the American College of Cardiology, the indications for percutaneous intervention in fibromuscular dysplasia include resistant hypertension, intolerance to antihypertensive medications, noncompliance with antihypertensive medications, and renal impairment. Other reasons for intervention are renal artery dissection and renal artery aneurysm.

References: Meuse MA, Turba UC, Sabri SS, et al. Treatment of renal artery fibromuscular dysplasia. Tech Vasc Interv Radiol 2010;13:126-133.

O’Connor SC, Gornik HL. Recent developments in the understanding and management of fibromuscular dysplasia. J Am Heart Assoc 2014;3(6):e001259. doi:10.1161/JAHA.114.001259.

8 Answer A. This patient has narrowing of the infrarenal aorta (arrows) consistent with middle aortic syndrome. The etiologies of this disorder include genetic causes such as Williams syndrome, Alagille syndrome, and neurofibromatosis. Additionally, vasculitis such as Takayasu arteritis and intrauterine infection such as rubella have been associated with this disorder.

References: Kim SM, Jung IM, Min SI, et al. Surgical treatment of middle aortic syndrome with takayasu arteritis or midaortic dysplastic syndrome. Eur J Endovasc Surg 2015;50:206-212.

Rumman RK, Nickel C, Matsuda-Abedini M, et al. Disease beyond the arch: a systemic review of middle aortic syndrome in childhood. Am J Hypertens 2015;28:833-846.

9 Answer A. Given the lack of ionizing radiation and the ability to perform without sedation, ultrasound with Doppler is the imaging modality of choice to initially evaluate a child with suspected middle aortic syndrome.

10 Answer C. The most commonly occurring collateral pathways in abdominal aortoiliac stenosis are

1. Superior mesenteric artery to inferior mesenteric artery to hemorrhoidal arteries to external iliac arteries

2. Intercostal, subcostal, and lumbar arteries to superior gluteal and iliolumbar arteries to internal iliac arteries to external iliac arteries

3. Intercostal, subcostal, and lumbar arteries to circumflex arteries to external iliac arteries

Reference: Sebastia C, Quiroga S, Boye R, et al. Aortic stenosis: spectrum of diseases depicted at multisection CT. Radiographics 2003;23:S79-S91.

11 Answer C. There is connection of the splenic and superior mesenteric vein (arrow) to the inferior vena cava consistent with a congenital extrahepatic portosystemic shunt. This is a condition in which the portomesenteric blood drains into a systemic vein therefore bypassing the liver.

References: Alonso-Gamarra E, Parrion M, Perez A, et al. Clinical and radiologic manifestations of congenital extrahepatic portosystemic shunts: a comprehensive review. Radiographics 2011;32:707-722.

Kobayashi N, Niwa T, Kirikoshi H, et al. Clinical classification of congenital extrahepatic portosystemic shunts. Hepatol Res 2010;40:585-593.

12 Answer B. Congenital portosystemic shunts are initially classified as intrahepatic or extrahepatic. In this case, the abnormal connection is extrahepatic. Extrahepatic shunts are classified into type 1 where there is absence of the intrahepatic portal venous supply or type 2 in which the intrahepatic portal venous supply is present. In this case, no portal vein is present, so it is a type 2 extrahepatic portosystemic shunt.