TEST PAPER 4 Flashcards

Question

@# 25. An 8-year-old child with right upper-abdominal pain and a palpable mass was sent for US of the liver. The US showed a large heterogeneous mass occupying at least half of the right lobe of the liver. The rest of the liver was normal in appearance. Which one of the following is the most common benign primary liver tumour in children? A. Hepatocellular carcinoma B. Hepatoblastoma C. Angiosarcoma D. Infantile haemangioendothelioma E. Cholangiocarcinoma

Answer 1

25. D. Infantile haemangioendothelioma Although primary hepatic neoplasms represent only a small percentage of solid tumours that occur in children, the finding of focal hepatic lesions in a child is not an uncommon event in a busy radiology practice. The most common neoplasm involving the liver in children, as in adults, is metastatic disease. Most primary liver tumours in children are malignant, but one-third are benign; benign lesions may be of mesenchymal or epithelial origin. The most common benign tumours are, in decreasing order of frequency, infantile haemangioendothelioma, PNH, mesenchymal hamartoma, nodular regenerative hyperplasia (NRH) and hepatocellular adenoma.

Answer 2

26. C. Chronic destructive sinusitis with nasal perforation Wegener’s granulomatosis is a probable autoimmune disease characterised by systemic necrotising granulomatous destructive angitis, with a classic triad of respiratory tract inflammation, systemic small vessel vasculitis and necrotising glomerulonephritis. Sinus disease classically includes destructive sinusitis, nasal septal ulceration, septal perforation and saddle nose deformity.

Answer 3

27. D. Reverse rim sign The reverse rim sign refers to a hypoattenuating renal cortex visualised at CT, seen against a background of intact medullary perfusion after contrast material is given. This sign also implies severe derangement of cortical blood flow with development of cortical necrosis. Cortical necrosis may develop as a consequence of obstetric complications, shock from numerous causes, transfusion reaction or other causes of intravascular haemolysis, toxins and rejection in the transplanted kidney. The comet tail sign refers to pelvic phleboliths and the soft-tissue rim sign is related to distal ureteric calculus. The crescent sign refers to the appearance of concentrated contrast material in collecting tubules, arranged parallel to the margin of a dilated calix, which produces a thin line of contrast material at the edge of the calices, resembling a crescent.

Answer 4

28. E. Buttressing Periosteal reaction is a sign of new bone formation. Buttressing indicates a slow-growing process with a single, thick layer of periosteum (i.e., a solid periosteal reaction). It is found in conditions such as hypertrophic pulmonary osteoarthropathy, atherosclerosis and benign tumours. More aggressive, faster-growing lesions can cause an interrupted periosteal reaction; lamination (layering) of the periosteum, Codman’s triangles where new bone formation only occurs at the margins of the tumour, sunburst pattern and hair-on-end (this is seen in lesions that invade bone marrow). Periosteal reaction is, however, only one of a list of many characteristics of a bone lesion that help determine whether the lesion is biologically active or not.

Answer 5

29. C. Pheochromocytoma Tuberous sclerosis is a neuroectodermal disorder, characterised by the classic triad of adenoma sebaceum, seizures and mental retardation. CNS findings include subependymal hamartomas, giant cell astrocytoma (at the foramen of Monro), cortical tubers and heterotopic islands of grey in white matter. Pulmonary involvement include interstitial fibrosis at lung bases, LAM, multiple lung cysts and chylothorax. Cardiac involvement includes rhabdomyoma, aortic aneurysm and congenital cardiomyopathy. Renal involvement includes AML, cysts and RCCs. Ocular lesions include optic nerve glioma and hamartoma. Other visceral abnormalities include splenic tumour, pancreatic and hepatic adenomas.

Answer 6

30. D. A plain abdominal radiograph should be obtained prior to air enema reduction to rule out signs of perforation. The traditional role of plain radiography in the evaluation of children suspected to have intussusception is threefold: 1. When the clinical suspicion is low, the role of plain radiography is to allow exclusion of intussusception and diagnosis of other pathologic processes that are responsible for the patient’s symptoms. 2. When the clinical suspicion is high, the role of plain radiography is to allow confirmation of intussusception. 3. If intussusception is present, the role of plain radiography is to allow exclusion of intestinal obstruction or perforation.

Answer 7

31. D. Avid arterial-phase enhancement HEH is a low-grade primary malignancy of the hepatic vasculature with an incidence of less than 0.1 per 100,000 in the general population per year. Because its occurrence is so rare, the patient demographics cannot be accurately assessed. However, demographic data from case review studies indicate an age range of 25-58 years (average 43.5 years) and a slight female predominance (male to female ratio 2:3). Typical manifestations of HEH include non focal abdominal pain, jaundice and hepatosplenomegaly, but HEH has also been discovered incidentally in asymptomatic patients. Budd-Chiari syndrome can develop if the tumour invades the hepatic veins. Alternating high- and low-signal-intensity rings on T2-weighted and contrast-enhanced T1 weighted images have been characterised as a ‘target’ sign. The tumours typically exhibit central signal hypointensity on unenhanced T1-weighted images and a multilayered target-like appearance with prominent rim like enhancement on contrast-enhanced T1-weighted images. The presence of capsular retraction in subcapsular hepatic tumours, along with a target-like appearance of the tumours on contrast enhanced CT and MR images, is suggestive but not necessarily indicative of HEH. This constellation of findings can be found in peripheral cholangiocarcinoma, confluent foci of hepatic fibrosis (usually in the setting of advanced cirrhosis), previously treated primary or metastatic HCCs and large atypical cavernous haemangiomas. However, the absence of cirrhosis in a patient with multiple liver masses that coalesce over time to form larger masses, in combination with other characteristic imaging findings of HEH, increases the likelihood of this diagnosis.

Answer 8

32. A. Peripheral predominant lobular consolidation with centrilobular nodules. On thin-section CT, the parenchymal abnormal findings of CSS could be classified into three patterns. The first pattern is subpleural consolidation with lobular distribution. The second pattern is centrilobular perivascular densities, diffusely scattered centrilobular nodules <5 mm in diameter, especially within the ground glass opacity lesion. The third pattern is multiple larger nodules. Bronchial wall thickening, with or without bronchial dilatation, and hyperinflation are likely to be related to asthma. Interlobular septal thickening may reflect the interstitial pulmonary oedema attributed to the cardiac and pericardial involvement. Peripheral predominant homogenous consolidation is a feature of chronic pulmonary eosinophilia. Nodules arc not a feature of chronic pulmonary eosinophilia. Central bronchiectasis and mucous plugs are a feature of ABPA.

Answer 9

33. C. Pie-in-the-sky bladder sign Bilateral psoas hypertrophy The spoked wheel description was applied to the angiographic appearance of the vascular pattern seen in some oncocytomas. Centripetal ‘spoke’ vessels arising from a peripheral ‘rim' vessel were initially thought to be characteristic of this tumour. However, the pattern is now known to be non-specific, and a similar vascular arrangement has been described with renal cell carcinoma. The normal round shape of the opacified bladder may assume a pear or tear drop shape when it is symmetrically compressed in the pelvis by an extrinsic process. The differential diagnosis includes pelvic fluid (haematoma, lymphocele, urinoma or abscess), pelvic lipomatosis, vascular dilatation (aneurysm or collateral vessel development), symmetric lymph node enlargement and psoas muscle hypertrophy. A pie-in-the-sky bladder may be seen with pelvic trauma. The sign refers to the high position of the opacified bladder within the pelvis at imaging and implies the presence of a large pelvic haematoma; it should raise concern for an associated urethral injury. A linear filling defect within the bladder may result from extrusion of a blood clot from the ureter, which has acted as a mould, in gross haematuria. This spaghetti sign implies that the bleeding source is above the bladder. Balloon-on-a-string sign refers to the appearance of a high and somewhat eccentric exit point of the ureter from a dilated renal pelvis and is a typical finding of ureteropelvic junction obstruction.

Answer 10

34. B. Perilunate dislocation Lunate and perilunate dislocations and fracture dislocations may be easily overlooked on plain films and should be actively sought and excluded given an appropriate clinical history. On the AP view, the lines along the proximal poles of both the proximal and distal carpal rows should be smooth and uninterrupted. The lunate should appear trapezoid and not triangular in shape (AP radiograph), which may indicate dislocation and rotation. On the lateral view, the distal radius, lunate and capitate should be in alignment. Volar loss of lunate alignment is seen in lunate dislocation, and dorsal loss of capitate alignment is seen in perilunate dislocation. In addition, the scapholunate (normal 30-60 degrees) and the capitolunate (normal 0-30 degrees) should be assessed for evidence of intercalated segmental instability.

Answer 11

35. B. It contains small arterial channels Developmental venous anomalies (DVAs), also called venous angiomas, are variations of the normal veins that are necessary for the drainage of white and grey matter. They are associated with other vascular malformations like cavernoma. On contrast-enhanced CT, the venous collector of the DVA is readily detectable as a linear or curvilinear focus of enhancement, typically coursing from the deep white matter to a cortical or a deep vein or to the dural sinus. On MRI, DVAs typically have a trans-hemispheric flow void, on both T1-weighted and T2-weighted images. The collector vein is detected as a linear or small, round, signal-void structure on all sequences and is shown most clearly on T2 weighted imaging. On contrast-enhanced MRI, the cluster of veins in DVAs has a spoked wheel appearance; the veins are small at the periphery and gradually enlarge as they approach a central draining vein. This appearance has been referred to as caput medusae (or the ‘head of Medusa’).

Answer 12

36. A. Lymphoid interstitial pneumonitis Early complications complications that occur at any point from the time of transplantation to the end of the early post-engraftment period - include interstitial pneumonitis (infective and non- infective types), infection, oedema, haemorrhage, thromboembolism and calcification. Bronchiolitis obliterans with organising pneumonia (BOOP) is a rare complication that may occur during the early or late post-engraftment period. Late pulmonary complications - complications that occur more than 100 days after engraftment - include chronic GVH disease, infections, bronchiolitis obliterans, fibrosis and lymphoid interstitial pneumonitis.

Answer 13

37. E. Background cirrhotic change to the liver parenchyma Fibrolamellar HCC is a rare hepatic neoplasm that accounts for less than 1% of HCC in the United States. This tumour has unique clinicopathological features that are significantly different compared with conventional HCC. Fibrolamellar HCC predominantly occurs in young individuals. On MRI, fibrolamellar HCC is usually hypointense on T1-weighted images and hyperintense on T2 weighted images. The fibrous central scar is typically hypointense on both Tl weighted and T2-weighted images. This feature can help to distinguish fibrolamellar HCC from FNH because the central scar in the latter is predominantly T2 hyperintense. The presence of intralesional fat has not been reported in fibrolamellar HCC. Calcification may be difficult to identify on MRI. Gadolinium contrast enhancement characteristics of fibrolamellar HCC mimic the patterns seen on CT showing marked heterogeneous contrast enhancement on the arterial phase and becoming isointense or hypointense on the portal venous and delayed phase. Some authors have reported that fibrolamellar HCC does not retain hepatobiliary-specific contrast agents, such as gadoxetate disodium and gadobenate dimeglumine, on the hepatobiliary phase, which potentially may be useful in differentiating fibrolamellar HCC from FNH.

Answer 14

38. A. Cardiac concussion results in abnormal cardiac enzymes. Blunt cardiac injury (BCI) is the most common type of cardiac injury after blunt thoracic trauma. In cardiac concussion, the mildest form of cardiac injury, there is no myocardial cell damage or elevated enzyme levels. Cardiac contusion can present as bilateral cardiogenic pulmonary oedema and elevated cardiac enzymes. Echocardiography shows increased myocardial echogenicity and focal systolic hypokinesia, and it is useful in diagnosing other traumatic cardiac injuries that are commonly associated with myocardial contusion, such as pericardial effusion, tamponade, traumatic ventricular septal defect and valvular injury. Typically, traumatic ventricular septal defects occur in the muscular portion of the interventricular septum, near the cardiac apex. Haemopericardium is commonly associated with cardiac rupture. Tamponade resulting from ventricular rupture is often fatal; however, bleeding from lower pressure atria may be survivable. Besides cardiac chamber rupture, traumatic haemopericardium may also result from aortic root injury, myocardial contusion and coronary artery laceration. Traumatic pericardial rupture resulting from blunt chest trauma is rare. Tearing may involve either the pleuropericardium or the diaphragmatic pericardium. Cardiac herniation is a serious complication of pericardial rupture.

Answer 15

39. C. Low citrate peak, high choline/creatine peak MRS is a modality that provides information about the cellular metabolites within the prostate gland; it displays the relative concentrations of key chemical constituents, such as citrate, choline and creatine. The normal prostate gland contains low levels of choline and high levels of citrate, whereas prostate cancers have increased levels of choline and decreased levels of citrate. The high choline levels in prostate tumours are related to increased cell turnover. In prostate cancers, the levels of zinc in secretary epithelial cells are lower, which eventually leads to diminished amounts of citrate. Thus, the ratio of choline to citrate is an index of malignancy. The ratio of choline (Cho) plus creatine (Cr) to citrate (Cit) ([Cho + Cr]/Cit) has been widely studied and cut-off values have been suggested for detection of cancer. Besides analysis of choline, citrate and creatine content, newer image acquisition and analysis software may enable evaluation of other metabolites, such as polyamine peaks, which have also been associated with prostate cancers. MR spectroscopy of tissue samples revealed that levels of polyamines (putrescine and spermine) were reduced in prostate cancer compared with the levels in benign tissue.

Answer 16

40. A. Pigmented villonodular synovitis. Radiographs may be normal or may reveal periarticular soft-tissue swelling. Visible calcifications are extremely unusual. The joint space is normal in width until late in the course of the disease, and juxta-articular osteoporosis is absent or mild. Bone erosions with sclerotic margins may be present on both sides of the affected joints, particularly in joints with a tight capsule, such as the hip. On MRI, the synovial lesions have low to intermediate signal intensity relative to that of muscle on T1 weighted images and low signal intensity on T2-weighted images, caused by the magnetic susceptibility effect produced by haemosiderin at the periphery of the lesions. The ‘black synovium’ appearance can also be seen with amyloid deposition or recurrent intra- articular bleeding (e.g., in haemophiliac arthropathy). Synovial sarcoma presents as a solitary calcified mass outside the joint.

Answer 17

41. B. Syringomyelia Syringomyelia refers to any cavity within the substance of the spinal cord that may communicate with the central canal, usually extending over several vertebral segments. MRI shows a cystic area with low signal on T1-weighted and increased signal intensity on T2-weighted images. CSF flow void (low signal on T2-weighted images) is often seen in the cavity from pulsation. The cord may show' enlargement. Post-traumatic, post-inflammatory or idiopathic syringomyelia show no abnormal contrast enhancement post-administration of gadolinium. Tumour-associated syrinx may show abnormal enhancement.

Answer 18

42. C. Juvenile dermatomyositis All other options would cause bronchiectasis, apart from juvenile dermatomyositis (JDM). JDM is a multisystem autoimmune disease of unknown aetiology that results from inflammation of the small vessels of the muscles, skin, gastrointestinal tract and other organs. It accounts for 85% of cases of paediatric inflammatory myopathy. JDM affects children with an incidence of two or three cases per million children per year. Clinical characteristics of JDM include symmetric proximal muscle weakness, inflammatory cutaneous lesions and Gottron papules (erythematous scaly lesions over the metacarpophalangeal and/or interphalangeal joints), heliotrope (violaceous hue over the eyelids), periorbital oedema, malar erythema, periungual telangiectasia and erythematous scaly rashes over the neck, upper back and extensor surfaces of the extremities.

Answer 19

43. C. Simple bone cyst Simple bone cysts constitute 5% of primary bone lesions with unknown aetiology and consist of cysts filled with yellowish fluid lined by fibrous tissue (rather than epithelial cells; hence some dispute the term true cyst). They arc most commonly seen at the proximal humerus and femur; other sites include the fibula, calcaneus, talus and rarer sites like the ribs, hands and feet. They are metaphyseal, intramedullary and central in location (rather than eccentric like ABC). They are close to the epiphysis in the growth phase and migrate to the diaphysis with growth. They do not cross the epiphyseal plate, have a thin sclerotic rim, can cause endosteal scalloping and demonstrate the ‘fallen fragment sign' when complicated by pathological fracture.

Answer 20

44. E. Usually shows late arterial enhancement on the post-contrast sequence. Angiomyolipoma (AML) is a benign, unencapsulated mesenchymal tumour that is composed of varying proportions of three elements: smooth muscle cells, thick-walled blood vessels and mature adipose tissue. AML occurs more commonly in the kidneys; hepatic involvement is rare. In contrast to renal AML, which is associated with tuberous sclerosis in 20% of patients, hepatic AML is associated with tuberous sclerosis in only 6%. AML can be histologically classified on the basis of fat content into mixed, lipomatous (70% fat), myomatous (10% fat) and angiomatous types. US, CT and MR imaging typically demonstrate the fat component and prominent central vessels. At US, AML may be highly echogenic and is then indistinguishable from haemangiomas. Frequently, AML has a high fat content, with high signal intensity on T1-weighted images and a significant drop in signal intensity on fat-suppressed images. AML demonstrates early intense contrast enhancement that peaks later than that of a HCC. Dynamic contrast-enhanced CT or MR images obtained during the early phase of enhancement may be useful in discriminating between AML and fat-containing HCC. The fatty areas of AMLs are well vascularised and enhance early, whereas steatotic foci in HCC are relatively avascular and have less contrast enhancement. However, unlike renal AML, 50% of hepatic AMLs lack considerable fat content. Because of this variable fat content, it is difficult to accurately distinguish AML from other hepatic tumours.

Answer 21

45. D. Fat embolism appears in 6 hours and clears in 7-10 days. Lung contusion turns out to be the most common manifestation of blunt trauma to the chest. Contusions become visible on chest radiographs within 6 hours post-trauma and resolve within 3-7 days. Massive contusion can lead to pulmonary oedema and diffuse alveolar damage (DAD). Aspiration appears within minutes and clears in 24-48 hours unless it triggers an infection with subsequent pneumonia. Pneumonia appears after 5-7 days and clears in 2-4 weeks. Lung infarction due to pulmonary embolism manifests after 3-5 days and clears in approximately 3 weeks. Fat embolism appears after 24-48 hours and clears in 7-10 days. ARDS with diffuse alveolar damage appears after 24-48 hours and dears in 4-6 weeks.

Answer 22

46. A. High on DWI, low on ADC and corresponding low signal intensity on T2W MRI T2-weighted images are the ‘workhorse’ images for prostate cancer. The glandular peripheral zone appears high in signal, whereas the central stroma has lower signal intensity on T2-weighted images. Tumours are lower in signal intensity than normal peripheral zone glandular tissue on T2-weighted images. Peripheral zone cancers are usually round or ill-defined. Various conditions, such as prostatitis, haemorrhage, atrophy, benign prostatic hyperplasia (BPH) and post-treatment changes can mimic cancer. Cancers in the central gland are even more challenging to detect than peripheral zone cancers, because the signal characteristics of the normal and hypertrophic central gland arc usually similar to those of the tumour on T2-weighted images. Prostate cancers often include tightly packed glandular elements with increased cellular density and diminished extracellular spaces, which can be detected as high-signal-intensity foci on raw DW MRI (restricted diffusion) but are low in signal on apparent diffusion coefficient (ADC) maps. ADC maps reflect the amount of diffusion present - the lower the diffusion, the darker the lesion.

Answer 23

47. D. Soft tissue calcifications Acute arthritis may be the first manifestation of sarcoidosis. It is mainly oligoarticular but occasionally polyarticular, and rarely monoarticular. Ankles are the most commonly involved joints. Enthesitis, tendinosis and tenosynovitis are well recognised, especially around the ankle. The triad of acute arthritis, bilateral hilar adenopathy and erythema nodosum is known as Lofgren syndrome. Chronic arthritis tends to involve the shoulders, hands, wrists, ankles and knees. Dactylitis can be seen; it is very similar to that seen in patients with psoriatic arthritis. Osseous involvement causes cystic, reticular or destructive lesions involving mainly the hands and feet (lace-like pattern) but can affect the skull, ribs, sternum, vertebrae, nasal bones, pelvis, tibia and femur as well. MRI shows multiple bony lesions with high T2-weighted and intermediate T1-weighted signal, although diffuse involvement is also recognised. Sarcoid myopathy can also he acute and mimic polymyositis.

Answer 24

48. C. Sturge-Weber syndrome Sturge-Weber syndrome is a rare neurocutaneous disorder characterised by abnormal vascular malformation involving the skin (ophthalmic branch of the trigeminal nerve) and leptomeninges of the brain. The facial capillary port-wine stain is usually ipsilateral to the leptomeningeal venous angiomatosis. Tram-track cortical calcification (T2 hypointensity) and cortical atrophy is probably secondary to underlying ischaemia. Associated calvarial thickening, enlarging diploic space and increased pneumatisation of mastoid air cells (Dyke Davidoff-Mason Syndrome) and ipsilateral enlargement of choroid plexus may also be seen. Angioma of the choroid of the eye is also a characteristic finding.

Answer 25

49. B. Hepatocellular adenoma Hepatic adenomas were virtually unknown prior to 1960, the year in which oral contraceptives were introduced. Although the precise pathogenic mechanism of hepatic adenomas is still unknown, the use of oestrogen-containing or androgen-containing steroid medications clearly increases their prevalence, number and size within the affected population and often within individual patients. Moreover, this causal relationship is related to dose and duration, with the greatest risk encountered in patients taking large doses of oestrogen or androgen for prolonged periods of time. In women who have never used oral contraceptives, the annual incidence of hepatic adenoma is about 1 per million. This increases to 30-40 per million in long-term users of oral contraceptives. Another risk group for hepatocellular adenoma are patients with Type 1 glycogen storage disease. In these patients, the adenomas are also more likely to be multiple and to undergo malignant transformation, although the latter is still quite rare. Adenomas rarely undergo malignant transformation to HCC, even after years of maintaining a stable appearance.

Answer 26

50. C. Metastatic angiosarcoma Squamous cell carcinomas are regarded as the most common type of cavitating metastases, although adenocarcinomas are also implicated. Metastatic sarcomas can also cavitate, and a pneumothorax can be complicated. Angiosarcoma represents the most common non-lymphoid malignant tumour of the spleen. Imaging reveals splenomegaly and an ill-defined heterogeneous mass.

Answer 27

51. E. The higher the tumour grade, the greater the grade of enhancement DCE-MRI evaluates the vascularity of tumours by providing quantitative kinetic parameters that reflect the flow of blood and the permeability of the vessels. DCE-MRI increases the specificity of prostate tumour detection. Tumours show early enhancement and early washout of the contrast agent - the higher the tumour grade, the higher would be the permeability parameters (Ktrans - wash-in, Kcp washout). A disadvantage of DCE-MRI is that small, low-grade tumours may not demonstrate abnormal enhancement. Furthermore, abnormal enhancement patterns can also be seen in patients with BPH, which can make assessment of the central gland difficult. However, in the glandular peripheral zone and anterior gland, DCE-MRI can be helpful in identifying lesions that are not suspected on T2-weighted images. The degree of enhancement on DCE-MRI correlates positively with tumour grade.

Answer 28

52. A. Melorheostosis Melorheostosis is a very rare non-hereditary disease of unknown aetiology. Patients can present with pain and restricted movements of the joint, but the disease is usually asymptomatic and is discovered incidentally. Some patients may have thickening and fibrosis of overlying skin, resembling scleroderma or joint contractures. Radiographic features include dense irregular bone running down the cortex of a tubular long bone, which can cross the joint. This has the appearance of flowing/molten wax and is usually limited to one side of cortex, although the internal or external cortex may be affected. The lower limbs are the most commonly affected. Other notable features are discrepant leg length on the affected side and the presence of adjacent ossified soft-tissue masses (27%).

Answer 29

53. B. Multiple sclerosis The spinal cord is known to be frequently involved in MS or in combination with lesions in the brain; as many as 25% of cases have been found to involve only the spinal cord. Most spinal cord lesions occur in the cervical cord. Cervical spinal MRI is particularly useful when the patient is suspected to have MS and brain lesions are absent. On T2-weighted spinal imaging, most plaques are peripherally located (commonly dorsolateral) and less than two vertebral body segments in length. The lesions tend to be multifocal and present as well-circumscribed foci with an increased T2 signal intensity. With acute spinal cord lesions, enhancement is frequently seen. Spinal cord atrophy, which may reflect axonal loss, may also be observed and is believed to be an important element in disability. Though rarely seen in other diseases, asymptomatic lesions of the spinal cord can be present in MS and may help lead to the correct diagnosis. Unlike its applicability to the brain, FLAIR imaging appears unreliable in the detection of MS lesions in the spinal cord. The short inversion time inversion-recovery (STIR) sequence has been found to be sensitive for lesion detection, particularly diffuse lesions.

Answer 30

54. D. Autoimmune haemolytic anaemia Mature cystic teratoma can be associated with complications from rupture, malignant degeneration or (most commonly) torsion. Mature cystic teratomas affected by torsion are larger than average (mean diameter 11 cm vs. 6 cm); this enlargement could be the result of the torsion rather than the cause of it Most mature cystic teratomas can be diagnosed at US. However, the US diagnosis is complicated by the fact that these tumours may have a variety of appearances. Three manifestations occur most commonly. The most common manifestation is a cystic lesion with a densely echogenic tubercle (Rokitansky nodule) projecting into the cyst lumen. The second manifestation is a diffusely or partially echogenic mass with the echogenic area usually demonstrating sound attenuation owing to sebaceous material and hair within the cyst cavity.

Answer 31

55. E. Elevated CA-125 levels are commonly seen in children with germ cell tumours. Mature cystic teratoma, often called dermoid cyst when the ectodermal elements predominate, is the most common ovarian tumour in children and adolescents, accounting for approximately 50% of all paediatric ovarian neoplasms. CA-125 levels are more frequently elevated in patients with epithelial ovarian cancers than in those with germ cell tumours (GCTs). CA 125 levels should not be routinely obtained in children, particularly in premenarcheal girls, as epithelial ovarian tumours are extremely rare before menarche. The serum AFP level is elevated in patients with GCTs such as yolk sac tumours, immature teratomas, embryonal carcinomas and mixed GCTs with yolk sac elements.

Answer 32

56. E. Haemangioma The classic haemangioma is an asymptomatic lesion that is discovered at routine examination or autopsy. At US, the typical appearance is a homogeneous, hyperechoic mass with well-defined margins and posterior acoustic enhancement. The CT findings consist of a hypoattenuating lesion on non enhanced images. After intravenous administration of contrast material, arterial-phase CT shows early, peripheral, globular enhancement of the lesion. The attenuation of the peripheral nodules is equal to that of the adjacent aorta. Venous-phase CT shows centripetal enhancement that progresses to uniform filling .This enhancement persists on delayed-phase images. At MR imaging, haemangiomas are characterised by well-defined margins and high signal intensity on T2-weighted images, which is identical to that of cerebrospinal fluid. Specificity is improved by using serial gadolinium-enhanced gradient-echo imaging. The gadolinium intake is similar to the intake of iodinated contrast material during enhanced CT. With T2-weighted spin- echo and dynamic gadolinium-enhanced T1 -weighted gradient-echo sequences, the sensitivity and specificity of MR imaging are 98% and the accuracy is 99%. The imaging features of a haemangioma depend on its size; typical haemangiomas are mostly less than 3 cm in diameter.

Answer 33

57. A. Surgery is preferred over embolisation Treatment of pulmonary AVMs is with either surgery or embolotherapy, with the latter being the preferred option. Indications for treatment include intolerance to exercise, aneurysms greater than 2 cm in diameter or feeding arteries of 3 mm or larger, which are associated with increased risk of stroke and brain abscess. Coils and Amplatzer plugs are used for large vessel permanent occlusion, like embolisation of pulmonary AVM.

Answer 34

58. A. Hyperintense on T1W imaging and hypointense on T2W imaging T1-weighted images are important in prostate cancer staging, because they show the presence of haemorrhage secondary to a recent biopsy; haemorrhage is almost always hyperintense compared with normal parenchyma on T1-weighted MRI. Haemorrhage typically appears low in signal on T2-weighted MRI and mimics cancer.

Answer 35

59. D. Paget disease (acute phase) Paget disease is a multifocal skeletal condition whereby bone remodelling becomes abnormal and eventually exaggerated. It typically affects middle-aged to elderly people and has acute and chronic phases with differing radiographic appearances. The acute phase, also known as the active or osteolytic phase, is characterised by aggressive bone resorption secondary to disordered osteoclastic activity. This manifests as lucency within the medulla of the long bones, typically in a flame shape or ‘blade of grass’ configuration. Over time, osteoblastic activity overtakes the osteoclastic resorption, resulting in osteosclerosis, cortical thickening and increased trabeculation. Giant cell tumour is a benign neoplasm of the mature skeleton, seen almost exclusively in those under 30 years of age. Although osteomyelitis can result in bony lucency, it is typically patchy with a moth-eaten texture.

Answer 36

60. D. Superior sagittal sinus thrombosis In neonates, shock and dehydration is a common cause of venous sinus thrombosis. In older children it is often local infection; in adults, coagulopathies are more common than infection. In women, OCP use and pregnancy arc strong risk factors. Imaging findings of cerebral venous thrombosis can be categorised as direct, as when there is visualisation of cortical or dural sinus thrombus (delta sign on unenhanced CT and empty delta sign on post-contrast CT venogram), or indirect, as when there are ischaemic or vascular changes related to the venous outflow disturbance. Venous infarction manifests as a low-attenuation lesion with or without subcortical haemorrhage. Brain lesions are related to a venous distribution. Bilateral parasagittal hemispheric lesions are suggestive of superior sagittal sinus thrombosis. Ipsilateral temporo-occipital and cerebellar lobe lesions can be found in transverse sinus thrombosis. In bilateral thalamic lesions, deep cerebral venous thrombosis should be suspected.

Answer 37

61. D. Hypointense to surrounding liver on the enhanced portal venous phase Typically, FNH is iso- or hypointense on T1-weighted images, is slightly hyper- or isointense on T2-weighted images and has a hyperintense central scar on T2-weighted images. FNH shows intense homogeneous enhancement in the arterial phase and enhancement of the central scar in the later phases of gadolinium-enhanced imaging. FNH does not have a tumour capsule, although the pseudocapsule surrounding some FNH lesions may be quite prominent. The pseudocapsule of FNH results from compression of the surrounding liver parenchyma by the FNH, peri-lesion vessels and inflammatory reaction. The pseudocapsule is usually a few millimetres thick and typically shows high signal intensity on T2-weighted images. The pseudocapsule may show enhancement on delayed contrast-enhanced images. A central scar is present at imaging in most patients with FNH. The amount of scar tissue within FNH and the size of the central scar may vary. The central scar is typically high in signal intensity on T2-weighted images and low in signal intensity on T1-weighted images. It shows visible enhancement on delayed contrast enhanced images. High signal intensity of the central scar may be caused by the inflammatory reaction around the ductular proliferation as well as the vessels within the septa and central scar. The central scar is not a specific finding of FNH and can be seen in a variety of other focal liver lesions, such as giant haemangiomas.

Answer 38

62. C. Osler-Rendu-Weber syndrome Osler-Rendu-Weber syndrome is an uncommon genetic disorder characterised by arteriovenous malformations in the skin, mucous membranes and visceral organs. The brain, gastrointestinal tract, skin, lung and nose are the primary sites affected. Pulmonary AVM typically appears as a round or oval mass of uniform density, which can be tabulated but with well-circumscribed and sharply defined margins. The feeding arteries are seen radiating from the hilum of the lung, and the draining veins are seen coursing towards the left atrium. Multiple ischaemic strokes in different arterial territories at different ages characterise the embolic mechanism in HHT. Brain abscess is the most serious neurologic complication in PAVM. Typically in HHT these abscesses are multiple and recurrent, affecting the superficial layers of the cerebral lobes (mostly the parietal lobe).

Answer 39

63. C. Low serum estradiol levels Ovarian hyperstimulation syndrome is usually iatrogenic secondary to ovarian stimulant drug therapy for infertility but may occur as a spontaneous event in pregnancy and is associated with raised serum estradiol levels. The syndrome consists of ovarian enlargement with extra vascular accumulation of exudates leading to weight gain, ascites, pleural effusions, intravascular volume depletion with hemoconcentration and oliguria in varying degrees, with increased risk of thrombosis and stroke. Pain, abdominal distention, nausea and vomiting are frequently seen. The imaging findings are similar at US, CT and MR imaging and reflect ovarian enlargement by distended corpora luteal cysts of varying sizes. Because the enlarged follicles are often peripheral in location, a spoked wheel appearance has been described. Ascites, pleural effusion and pericardial effusion are also described. Familiarity with ovarian hyperstimulation syndrome and the appropriate clinical setting should help avoid the incorrect diagnosis of an ovarian cystic neoplasm.

Answer 40

64. A. A comparison radiograph of the contralateral knee The appearance is likely to represent post-traumatic cortical desmoid. It is also known as avulsive cortical irregularity or Bufkin lesion. It results from chronic avulsive stress at the femoral region of the medial head of the gastrocnemius. It is usually an incidental finding. One-third of cases are bilateral and a comparison photograph of the contralateral knee is helpful to assess the other side. If plain films are not helpful, an MRI can be useful to assess soft tissues. Post-traumatic cortical desmoid does not involve soft tissues.

Answer 41

65. B. Tuberous sclerosis Tuberous sclerosis is a neuroectodermal disorder, characterised by the classic triad of adenoma sebaceum, seizures and mental retardation. CNS findings include subependymal hamartomas, which can calcify (classic calcified subependymal nodules), giant cell astrocytoma (at the foramen of Monro, often replacing the third ventricle), cortical tubers and heterotopic islands of grey in white matter. Pulmonary involvement includes interstitial fibrosis at lung bases, LAM, multiple lung cysts and chylothorax. Cardiac involvement includes rhabdomyoma, aortic aneurysm and congenital cardiomyopathy. Renal involvement includes AML, cysts and RCCs. Ocular lesions include optic nerve glioma and hamartoma. Other visceral abnormalities include splenic tumour and pancreatic and hepatic adenomas.

Answer 42

66. C. Bronchial atresia This is the classic description of a mucocoele. Congenital bronchial atresia is a congenital abnormality caused by focal interruption of a lobar, segmental or subsegmental bronchus with associated peripheral mucous impaction (bronchocoele/mucocoele) and associated hyperinflation of the obstructed lung segment. The apicoposterior segmental bronchus of the left upper lobe is most commonly affected. The condition is usually benign and asymptomatic and is often an incidental chest X-ray finding. Mean age at diagnosis is 17 years and symptoms, if present, include recurrent pulmonary infection, mild wheeze and dyspnoea. The typical appearance of Swyer-James syndrome is that of a small, hyperlucent lung, with overexpansion of the contralateral lung. A diffuse pattern of scarring or irregular vessels may also be present. Cystic fibrosis is unlikely in a previously well individual. Kartagener syndrome appears as bilateral bronchiectasis. Allergic bronchopulmonary aspergillosis is a possibility, but the minor symptoms fit best with bronchial atresia.

Answer 43

67. D. The most common malignant germ cell tumour is a dysgerminoma. Germ cell tumours are the most common type of ovarian neoplasm, with one third of these being malignant in children and adolescents. A dysgerminoma is the most common malignant germ cell tumour and is associated with gonadal dysgenesis. The majority of germ cell tumours are mature cystic teratomas (also known as dermoid cysts), which account for 50% of all paediatric ovarian neoplasms. These are bilateral in 10% of cases.

Answer 44

68. E. CT imaging best demonstrates the pericyst, matrix and daughter cysts. Hydatid disease is a severe and common parasitic disease that is endemic to the Mediterranean basin and other sheep raising areas. Humans become infected by ingesting the eggs of the tapeworm Echinococcus granulosus, either by eating contaminated food or from contact with dogs. The ingested embryos invade the intestinal mucosal wall and proceed to the liver via the portal venous system. Although the liver filters out most of these embryos, those that are not destroyed become hepatic hydatid cysts. US findings are variable and range from purely cystic to solid-appearing pseudotumours. Wavy bands of delaminated endocyst (water lily sign) may be noted internally. Daughter cysts, sometimes surrounded by echogenic debris (matrix), are frequently seen. Calcifications, varying from tiny to massive, are often present peripherally. At CT, a hydatid cyst usually appears as a well-defined, hypoattenuating lesion with a distinguishable wall. Coarse wall calcifications are present in 50% of cases, and daughter cysts are identified in approximately 75%. Because of its superb contrast resolution, MR imaging best demonstrates the pericyst, the matrix or hydatid sand (debris consisting of freed scolices) and the daughter cysts. The pericyst is seen as a hypointense rim on both T1-weighted and T2-weighted images because of its fibrous composition and the presence of calcifications. The hydatid matrix appears hypointense on T1-weighted images and markedly hyperintense on T2-weighted images; when present, daughter cysts are hypointense relative to the matrix on both Tl - weighted and T2-weighted images.

Answer 45

69. E. Bronchial dehiscence Immediate complications (<24 hours) * Malpositioned monitoring tubes and lines * Donor-recipient size mismatch * Hyperacute rejection Early complications (24 hours to 1 week) * Ischaemia-reperfusion injury (reperfusion oedema) * Acute pleural complications Intermediate complications (8 days to 2 months) * Acute rejection * Bronchial anastomotic complications like dehiscence * Infections Primary late complications (2-4 months) * Bronchial stenosis and bronchomalacia * Viral infection * Pulmonary embolism and infarction * Complications that affect the native lung Secondary late complications (>4 months) * Mycobacterial infection * Chronic rejection * Cryptogenic organising pneumonia * Post-transplantation lymphoproliferative disorder * Upper-lobe fibrosis * Recurrence of primary disease * Bronchogenic carcinoma

Answer 46

70. C. MRI Uterine dehiscence is characterised by incomplete rupture of the uterine wall, usually involving the endometrium and myometrium but with an intact overlying serosal layer. MR imaging may be better than CT in evaluating for uterine dehiscence because of its multiplanar capability and greater soft tissue contrast and its ability to help identify an intact serosal layer.

Answer 47

71. D. Posterior translation of tibia An ACL injury results in anterior translation of the tibia. The ‘kissing contusions’ from a pivot shift mechanism of injury results in marrow oedema in the posterolateral region of the tibial plateau and the mid portion of the lateral femoral condyle. A deep lateral femoral sulcus, more than 1.5 mm, may be appreciated on plain film. Uncovering of the posterior horn of the lateral meniscus is associated with the anterior translation of the tibia. The PCL tends to buckle after an ACL injury resulting in a reduced PCL angle less than 105 degrees.

Answer 48

72. C. Basal meningitis suggests neurosyphilis. The finding of diffuse cerebral atrophy in HIV can be accompanied by diffuse, confluent, ill-defined areas of abnormally increased signal intensity on T2-weighted MR images of the periventricular white matter. No enhancement is noted. These findings were initially attributed to CMV infection, as autopsy studies have shown that a high percentage of AIDS patients had concomitant CMV infection of the CNS. It was subsequently recognised that HIV is neurotrophic and directly infects the CNS; these global abnormalities were then attributed to a subacute encephalitis caused by HIV. It now seems likely that both HIV and CMV can cause subacute encephalitis and encephalopathy; these conditions have an identical non-specific imaging appearance. CMV encephalopathy appears to manifest itself late in the illness, whereas HIV rather than HIV dementia (although usually presenting late) can occasionally be the AIDS-defining illness. In addition to subacute encephalitis, CMV infection can manifest as a more virulent ventriculoencephalitis. This is most often seen in concert with CMV infection elsewhere in the body (such as CMV retinitis) and is usually a late manifestation of AIDS. The infection appears to begin in the ependymal or subependymal region and spread into the adjacent brain. The ventricles are enlarged, and hypoattenuation on CT or increased signal intensity on T2-weighted MRI is noted in the periventricular white matter. Ill-defined periventricular enhancement can also be seen following injection of contrast medium. Meningitis - particularly basilar meningitis - and hydrocephalus occur often in the setting of neurotuberculosis. Meningitis manifests on CT scans and MR images as prominent enhancement and thickening of the meninges and it can be associated with infarcts secondary to vascular stenosis or occlusion. Neurosyphilis, which is being diagnosed with increased frequency among patients with AIDS, can cause infarcts secondary to arteritis.

Answer 49

73. D. Hilar lymph nodes are more common in MRSA Radiological findings of MRSA pneumonia reported in the current literature are limited to descriptions of necrotising pneumonia. The frequencies of bronchial wall thickening and centrilobular nodules were significantly higher in patients with MSSA than MRSA pneumonia. Moreover, the frequency of centrilobular nodules with a tree-in-bud pattern was significantly higher in patients with MSSA than MRSA pneumonia. There were no significant differences in other CT findings including ground-glass opacity and consolidation between the two groups. Ground-glass change and bronchial wall thickening were the two most common CT findings in both groups. There were no significant differences in zonal distributions between the two groups. Both groups showed unilateral or bilateral opacities and predominantly upper zone changes. The frequency of pleural effusion was significantly higher in patients with MRSA than in those with MSSA pneumonia. There was no difference in hilar or mediastinal lymphadenopathy.

Answer 50

74. A. Klippel-Trenaunay syndrome Klippel-Trenaunay syndrome is a sporadic rare mesodermal abnormality that usually affects a single lower limb. It is characterised by a triad of a port wine naevus (unilateral cutaneous capillary haemangioma, often in a dermatomal distribution on the affected limb), overgrowth of distal digits/entire extremity (involving soft tissue and bone) and varicose veins on the lateral aspect of the affected limb. Although the other options can produce limb hypertrophy, they would not be expected to show all the features of the triad described.

Answer 51

75. C. They are high signal intensity on T1W MR images. Biliary hamartomas, also known as biliary microhamartomas or von Meyenburg complex, are composed of one or more dilated duct-like structures lined by biliary epithelium and accompanied by a variable amount of fibrous stroma. Biliary hamartomas arc typically multiple round or irregular focal lesions of nearly uniform size (up to 15 mm) scattered throughout the liver. 'These lesions are often discovered incidentally, and if the patient has a primary neoplasm they can be mistaken for metastatic disease. The lesions are hypoattenuating at CT, hypointense at T1-weighted MR imaging and hyperintense at T2-weighted imaging. If the echo time is increased at T2-weighted imaging, the signal intensity of these lesions increases further and approaches that of cerebrospinal fluid. The lesions do not usually show contrast enhancement, although a peripheral enhancing rim has been described. The differential diagnoses for biliary hamartomas include metastatic disease and simple hepatic cysts. Biliary hamartomas are relatively uniform in size, whereas metastatic lesions are usually more heterogeneous in size and in attenuation or signal intensity. Compared with biliary hamartomas, hepatic cysts are rarely as uniformly small or numerous, whereas the cysts in autosomal dominant polycystic disease are usually larger and more numerous.

Answer 52

76. B. HELLP syndrome HELLP (haemolysis, elevated liver enzymes, low platelets) syndrome is one of the hypertensive disorders of pregnancy, occurring in 4%-12% of pre-eclamptic patients, from vascular endothelial injury, which results in intravascular deposition of fibrin with end organ damage and can occur prior to or after delivery. Disseminated intravascular coagulation (DIG) is seen in 20%-40% of patients. Other major complications include placental abruption, acute renal failure, pulmonary oedema, pleural and pericardial effusions, hepatic infarction, haematoma and rupture. Pelvic pain may occur in the setting of haemoperitoneum. Spontaneous intrahepatic haemorrhage and rupture likely result from toxaemia-related vasculopathy with endothelial damage, leading to haemorrhage. Supportive therapy is usually offered initially, with capsular rupture necessitating surgery. Embolisation of the hepatic artery may be attempted. CT is important in initial diagnosis and for serial follow up. Findings may include subcapsular or intrahepatic haemorrhage, capsular rupture and areas of confluent necrosis secondary to infarction. Intravenous contrast-enhanced CT allows identification of active arterial extravasation, which cannot be seen on US.

Answer 53

77. C. SAPHO syndrome The acronym SAPHO (synovitis, acne, palmoplantar pustulosis, hyperostosis and osteitis), which was coined in 1987, is applied to occurrences of a wide spectrum of aseptic neutrophilic dermatoses in association with aseptic osteoarticular lesions. The sternoclavicular joint (most frequently affected) is involved in 65%-90% of cases. Hyperostosis and osteosclerosis are characteristic findings at conventional radiography and CT. Other findings include joint erosion and ankylosis. In the presence of active lesions, MR imaging with T2-weighted or STIR sequence may depict bone marrow oedema, a feature that helps differentiate active lesions from chronic ones. The ‘bull’s head’ sign (i.e., increased radiotracer uptake in the sternal manubrium and both sternoclavicular joints at delayed scintigraphy) is highly specific for the diagnosis of SAPHO and may obviate biopsy. Acute septic arthritis of the sternoclavicular joint is an uncommon infectious condition that is usually monoarticular and insidious in onset. Changes that are visible at CT include destruction of the articular surface, widening of the joint space, gas and fluid collections in the chest wall and mediastinum, and mediastinal soft-tissue stranding. MR images in addition may depict bone marrow oedema. The sternoclavicular joint can be affected by osteoarthrosis, RA, and seronegative and crystalline arthropathy, which depict their respective specific features on imaging; however, imaging is often non-specific.

Answer 54

78. D. HSV encephalitis Herpes simplex virus (HSV) is notable for its typical imaging appearance and because it is readily treatable when diagnosed early but potentially devastating in cases of delayed diagnosis. The typical appearance of HSV encephalitis includes parenchymal oedema (hypoattenuating on CT; hyperintense on FLAIR) with variable patchy or gyriform enhancement and variable degrees of restricted diffusion; parenchymal haemorrhage and necrosis may occur in severe or untreated cases. MRI findings are seen earlier in the course of infection than CT findings, with DWT changes most sensitive among routine sequences. The classic distribution includes bilateral (though asymmetric) involvement of the limbic system (most notably the mesial temporal lobes, i.e., the hippocampus, amygdala and parahippocampal gyrus). Other cortical regions may also be involved, while the basal ganglia are typically spared.

Answer 55

79. A. Long or short segments of marked stricture in the main pancreatic duct IPMNs are a group of neoplasms in the biliary duct or pancreatic duct that cause cystic dilatation from excessive mucin production and accumulation. There are three main types of pancreatic IPMNs: main duct, branch duct and combined. A main duct IPMN commonly causes dilatation of the papilla, with bulging of the papilla into the duodenal lumen. Filling defects caused by mural nodules or mucin may be seen at MRCP or ERCP. At CT and MR imaging, filling defects caused by mural nodules enhance, while filling defects caused by mucin do not enhance.

Answer 56

80. B. Gas locules in the fluid is most specific Thoracic empyema is defined as purulent content in the pleural cavity. Empyemas usually form an obtuse angle with the chest wall and are lenticular in shape (bi-convex) in comparison to the crescentic shape of pleural effusion. Empyema also shows enhancing thickened pleura, the split pleura sign (which differentiates it from peripheral lung abscesses), septations, associated consolidation or infected foci like subdiaphragmatic abscess, and so on. Gas can be present in both an empyema and pulmonary abscess.

Answer 57

81. A. Uterine dehiscence Uterine dehiscence is characterised by incomplete rupture of the uterine wall, usually involving the endometrium and myometrium but with an intact overlying serosal layer. Uterine dehiscence is a very difficult imaging diagnosis. The presence of a bladder flap haematoma greater than 5 cm and larger pelvic haematomas should be considered abnormal and highly suspicious for uterine dehiscence in the proper clinical setting. MR imaging may be better than CT in checking for uterine dehiscence because of its multiplanar capability and greater soft-tissue contrast, with its ability to help identity an intact serosal layer. Uterine rupture is the most severe potential complication of caesarean delivery and is defined as separation of all layers of the uterine wall, including the serosal layer, with abnormal communication between the uterine cavity and the peritoneal cavity. The presence of gas/blood within the uterine defect extending from the endometrial cavity to the extrauterine parametrium in association with haemoperitoneum increases the likelihood of rupture in the appropriate clinical setting.

Answer 58

82. B. Primary osteomyelitis is more common than secondary osteomyelitis. Primary osteomyelitis of the sternum is uncommon, with only a small number of cases reported in the literature. It may occur in patients with a history of intravenous drug abuse, AIDS, haemoglobinopathy or other immune deficiency states. Staphylococcus aureus infection is the most common cause of sternal osteomyelitis. Secondary osteomyelitis of the sternum is more common than the primary form, particularly after sternotomy. This is a potentially severe complication because of the risk of mediastinitis. Risk factors for secondary osteomyelitis include obesity, insulin-dependent diabetes and internal mammary artery grafts. The presence of one or more sternal fractures implies high-energy trauma. The importance of sternal fractures lies in the high frequency of associated injuries. Spontaneous fractures of the sternum have occurred in the presence of a neoplasm (e.g., multiple myeloma, metastasis), strain from heavy lifting, labour and bone insufficiency (e.g., in osteoporosis). Sternoclavicular dislocation is a rare occurrence; anterior (or presternal) displacement is more common, but posterior (or retrosternal) displacement is more frequently associated with life threatening complications caused by the compression of vital structures such as the trachea, great vessels and nerves. CT provides a detailed depiction of the sternoclavicular joint and helps characterise dislocation.

Answer 59

83. D. Ultrasound neck with FNA The National Institute for Health and Clinical Excellence (NICE) guidance on cancer services published in 2004, entitled Improving Outcomes in Head and Neck Cancers, recommended that specialist clinics should be set up for the assessment of patients with head and neck lumps, structured in a similar way to one stop breast lump clinics with radiologist and cytopathologist present, and availability of US and fine-needle aspiration (FNA) for initial assessment US is well established as a primary investigation for patients presenting with a lump in the neck, and FNA cytology is also established as initial investigation for lesions in the head and neck. The cost effectiveness and diagnostic accuracy of FNA can be increased by using US guidance and the presence of an on-site cytopathologist

Answer 60

84. A. Acute appendicitis The plain film findings and clinical history are suggestive of acute appendicitis, which is the most common reason for abdominal surgery in children. It is one of the most common causes of intestinal obstruction in children. Other causes include adhesions, intussusception, incarcerated inguinal hernia, malrotation with volvulus and Meckel’s diverticulum. The primary' imaging modality in suspected acute appendicitis remains controversial. Several authors advocate plain films, US and CT as primary diagnostic sets, with various arguments. On plain films, a faecolith or appendicolith with small bowel obstruction (seen in 10% of cases) and displacement of bowel gas from the right iliac fossa are all typical signs of acute appendicitis. However, an abdominal US examination is the preferred imaging modality of choice for investigation of acute appendicitis in children rather than abdominal radiograph. Acute cholecystitis and renal colic are not common diagnoses in children. Intussusception most often occurs between 3 months and 1 year of age.

Answer 61

85. D. VHL syndrome - renal and pancreatic cysts The description of the posterior fossa tumour is typical of either a pilocytic astrocytoma or haemangioblastoma. The multiple flow voids suggest a haemangioblastoma. VHL syndrome is an autosomal dominant condition with haemangioblastomas, renal cysts, clear cell renal carcinoma, phaeochromocytoma, pancreatic cysts and islet cell tumours. Neurofibromatosis Type 1 presents with cutaneous lesions, multiple T2 hyperintensities and plexiform neurofibromas. Neurofibromatosis Type 2 presents with bilateral acoustic schwannomas. Sturge- Weber syndrome is a combination of a facial port-wine stain and cortical calcification. It usually presents with seizures. Li-Fraumeni syndrome is a hereditary cancer syndrome with a susceptibility to breast cancer, sarcomas and brain tumours (astrocytoma and choroid plexus carcinoma). Renal and pancreatic cysts are not typical features of any of the others.

Answer 62

86. D. Serous cystadenoma In 70% of cases, Serous cystadenomas demonstrate a polycystic or microcystic pattern consisting of a collection of cysts (usually more than six) that range from a few millimetres up to 2 cm in size. Fine, external lobulations are a common feature, and enhancement of septa and the cyst wall may be seen. **A fibrous central scar with or without a characteristic stellate pattern of calcification is seen in 30% of cases and, when demonstrated with CT or MR imaging, is highly specific and is considered to be virtually pathognomonic for serous cystadenoma.** Pancreatic ductal dilatation is an uncommon finding in these patients. The macrocystic or oligocystic variant of these tumours is very uncommon and is seen in less than 10% of cases. Either of these variants can take the form of a single dominant macrocavity, in which case it will appear as a unilocular cyst or may contain fewer large (2 cm) cysts. The latter variant is classified as a macrocystic lesion and may be difficult to differentiate from a mucinous cystic tumour. Mucinous cystic neoplasms (mucinous cystadenomas) mainly involve the body and tail of the pancreas and do not communicate with the pancreatic duct At CT/MR, they are multilocular macrocystic lesions occasionally containing debris or hemorrhage. The complex internal architecture of the cyst, including septa and an internal wall, is best appreciated at MR imaging and endoscopic US, allowing differentiation from serous cystadenomas. Although peripheral eggshell calcification is not frequently seen at CT, it is specific for a mucinous cystic neoplasm and is highly predictive of malignancy. Pseudopapillary tumour is a solid tumour with a cystic component. Others in this group are islet cell tumour, pancreatic adenocarcinoma, and metastasis.

Answer 63

87. C. Fissural and septal nodules Frequently, the CT findings are far more extensive than expected from a review of the plain chest radiograph. The lung abnormalities show a characteristic peripheral or peribronchial distribution, and the lower lung lobes are more frequently involved. In some cases, the outermost subpleural area is spared. The lung opacities vary from ground glass to consolidation; in the latter, air bronchograms and mild cylindrical bronchial dilatation are a common finding. These opacities have a tendency to migrate, changing location and size, even without treatment. They are of variable size, ranging from a few centimetres to an entire lobe. Some patients present with nodular opacities on the chest radiograph. Lung volumes are preserved in most patients.

Answer 64

88. C. Leiomyosarcoma The presence of fat in a retroperitoneal tumour limits the differential diagnosis. A mass that is homogeneous and well defined and consists almost entirely of fat represents lipoma. When the mass is somewhat irregular and ill-defined but contains fat, a diagnosis of liposarcoma should be considered. Liposarcomas are the most common sarcomas of the retroperitoneum. Extremely hypervascular tumours such as paragangliomas sometimes contain haemorrhagic necrosis and manifest with fluid-fluid levels. Necrotic portions within tumours have low attenuation without contrast enhancement at CT and are hyperintense at T2-weighted MR imaging. Necrosis is usually seen in tumours of high grade malignancy such as leiomyosarcomas, which have central necrosis more commonly than other sarcomas. Lymphomas grow and extend into spaces between pre-existing structures and surrounding vessels without compressing their lumina, manifesting with the ‘CT angiogram sign’ or ‘floating aorta sign’. Some tumours, like lymphangioma, are completely cystic in appearance. Solid tumours with a partially cystic portion include neurogenic tumou

Answer 65

89. A. McCune-Albright syndrome Fibrous dysplasia is a relatively common benign skeletal disorder typically seen in adolescents and young adults. It can be monostotic (affecting one bone) or polyostotic (affecting multiple bones). Polyostotic fibrous dysplasia is commonly associated with cafe au lait spots, with irregular edges (‘coast of Maine’), in contrast to regular edges (‘coast of California’) observed in neurofibromatosis. Multiple endocrine disorders are described in association with fibrous dysplasia. McCune- Albright syndrome refers to the triad of polyostotic fibrous dysplasia (usually unilateral), cafe au lait spots and precocious puberty. Fibrous dysplasia is also associated with hyperthyroidism, hyperparathyroidism, acromegaly, diabetes mellitus and Cushing syndrome. Mazabraud syndrome refers to the association of polyostotic fibrous dysplasia with multiple soft-tissue myxomas, which are typically intramuscular. Cherubism is a special form of fibrous dysplasia with symmetric involvement of both the maxilla and mandible. It typically affects men and tends to regress after adolescence.

Answer 66

90. A. Pleomorphic adenoma Nearly 80% of benign parotid neoplasms are pleomorphic adenomas. The most common malignancy of the parotid gland is mucoepidermoid carcinoma and that of the submandibular gland is adenoid cystic carcinoma. On non-enhanced and enhanced IT weighted series, no histologic discrimination is possible because almost all masses are low in intensity and enhance. Benign cysts (mucous retention cyst, lympho-epithelial cyst, first branchial cleft cyst, ranula, etc.) appear hyperintense on T2 weighted images, and, depending on the presence of haemorrhage, infection or hyper-proteinaceous fluid, the T1-weighted image may show intermediate (solid-appearing) intensity. For this reason, administration of contrast material is helpful because cysts usually enhance on their periphery, whereas pleomorphic adenomas enhance solidly. Adenoid cystic carcinoma has a very high rate of perineural spread (50%-60%). Cystic degeneration of a benign-appearing neoplasm suggests a Warthin tumour or pleomorphic adenoma. Multiple parotid masses are usually due to lymphadenopathy or Warthin tumours, the latter appearing almost exclusively in the parotid gland, usually in the tail of the gland in older men. Specific signs predictive of malignancy were T2 hypointensity of the parotid tumour, ill-defined margins, diffuse growth, infiltration of subcutaneous tissue and lymphadenopathy. The predilection of deep lobe involvement was only indicative but not significant for malignancy. However, involvement of both lobes was significant for malignant lesions. Clinically, involvement of the facial nerve is highly suspicious of a malignant mass. For determination of benign disease, a strong signal intensity on T2-weighted images, well defined borders and a location in the superficial lobe were significant MR imaging findings for benignity. The degree of tumour enhancement after contrast administration did not help to distinguish benign from malignant tumours, though there was a tendency towards strong enhancement of benign tumours

Answer 67

91. C. Communication with the pancreatic duct In 70% of cases, these benign tumours Serous cystadenomas demonstrate a polycystic or microcystic pattern consisting of a collection of cysts (usually more than six) that range from a few millimetres up to 2 cm in size. Fine, external lobulations are a common feature, and enhancement of septa and the cyst wall may be seen. A fibrous central scar with or without a characteristic stellate pattern of calcification is seen in 30% of cases and, when demonstrated at CT or MR imaging, is highly specific and is considered to be virtually pathognomonic for serous cystadenoma. Pancreatic ductal dilatation is an uncommon finding in these patients. In 20% of cases, these tumours are composed of microcysts in a honeycomb pattern and appear as well marginated, ‘spongy’ lesions with soft-tissue or mixed attenuation and a sharp interface with the vascular structures at CT. In patients with indeterminate CT findings, further characterisation with MR imaging or endoscopic US may be possible. At MR imaging, the microcysts may be seen as numerous discrete foci with bright signal intensity on T2-weighted images. Likewise, endoscopic US can help accurately depict these small microcysts as discrete small anechoic areas. Because of the benign nature of serous cystadenomas, some surgeons recommend imaging surveillance of microcystic tumours as being sufficient in asymptomatic patients. Unlike IPMN, serous or mucinous cystadenomas do not communicate with the pancreatic duct.

Answer 68

92. D. Right middle lobe and lingular bronchiectasis HRCT scanning is more sensitive than chest radiographs for detecting the abnormalities of Mycobacterium avium complex (MAC) lung disease. The presence of bronchiectasis and multiple small nodules are predictive of MAC lung disease with pleural thickening or adhesions, usually adjacent to the pulmonary parenchymal abnormalities in about 50% of cases. Other reported abnormalities include atelectasis, consolidation, tree in bud and ground-glass opacities. Bronchiectasis is more common in MAC lung disease than MTB. Some nodules will disappear with successful treatment. It has been suggested that MAC-related cavities tend to be thinner with less surrounding parenchymal opacification. In the absence of underlying lung disease, they primarily involve the right middle lobe or lingual. Pleural effusions are not common in MAC.

Answer 69

93. B. Pial angioma demonstrated by leptomeningeal enhancement The clinical picture is very suggestive of Sturge-Weber syndrome. The major pathological abnormality in Sturge-Weber syndrome is a meningeal tangle of vessels, commonly referred to as an angioma, which is ordinarily confined to the pia mater. This pathological process consists of multiple capillaries and small venous channels that are matted together on the surface of the brain. Non-contrast CT shows cortical calcification and atrophy. MRI will show diffuse leptomeningeal enhancement and ipsilateral choroid plexus enlargement. Cortical calcification can be demonstrated on T2 gradient echo. The other options suggest different diagnoses respectively: posterior fossa haemangioblastoma - VHL; bilateral acoustic schwannomas - neurofibromatosis Type 2; multiple white matter T2 hyperintensities - unidentified bright spots in neurofibromatosis Type 1; multiple T1-weighted hyperintensities and cerebellar hypoplasia - neurocutaneous melanosis.

Answer 70

94. E. Soft-tissue rim sign Before a tumour can be described as primarily retroperitoneal, the possibility that the tumour originates from a retroperitoneal organ must be excluded. When a mass deforms the edge of an adjacent organ into a ‘beak' shape, it is likely that the mass arises from that organ (beak sign). When a large mass arises from a small organ, the organ sometimes becomes undetectable. This is known as the phantom organ sign. When a tumour compresses an adjacent plastic organ (e.g., gastrointestinal tract, inferior vena cava) that is not the organ of origin, the organ is deformed into a crescent shape (negative embedded organ sign). In contrast, when part of an organ appears to be embedded in the tumour (positive embedded organ sign), it is likely that the tumour originates from the involved organ. Hypervascular masses are often supplied by feeding arteries that are prominent enough to be visualised at CT or MR imaging, a finding that provides an important key to understanding the origin of the mass. Some tumours grow and extend into spaces between preexisting structures and surrounding vessels without compressing their lumina. Lymphangiomas, ganglioneuromas and lymphomas are examples of such tumours manifesting with the CT angiogram sign' or ‘floating aorta sign’. The soft-tissue rim sign is described with distal ureteric calculus.

Answer 71

95. D. Osteophytes Synovial hyperplasia and formation into pannus is the fundamental pathogenesis of RA. Hyperaemia is the first step in the inflammatory cascade that can be identified with imaging. Power Doppler, contrast-enhanced sonography and MR imaging (especially T1-weighted contrast-enhanced sequences with spectral fat saturation and water-weighted inversion recovery images) are very helpful in identifying the pathologic condition. X-rays are often normal at this stage. MR imaging is an excellent tool for assessing .synovial swelling and volume. The use of a T1-weighted spin-echo sequence early after intravenous contrast material administration is highly recommended, as it helps differentiate effusion and synovium. Plain radiograph shows soft-tissue swelling, joint effusion and joint widening. Para-articular osteoporosis is cited as an early sign of joint involvement in RA. Up to 47% of patients may develop erosions within 1 year after onset of RA. MR imaging demonstrates erosions first. Sometimes, contrast enhancement helps distinguish erosions and pre-erosions from simple and degenerative bone cysts, which are less likely to enhance. Joint subluxation, loose bodies (rice bodies) and ankylosis are other destructive/late features. Rotator cuff tear is often associated at the shoulder, and superior subluxation of the humeral head is often evident. Osteophytosis are a feature of osteoarthrosis.

Answer 72

96. D. Branchial cyst Second branchial cleft anomalies comprise 95% of all branchial cleft lesions, most commonly presenting as cystic masses. A second branchial cleft cyst (BCC) can occur anywhere in the lateral aspect of the neck but is classically seen as a well-marginated anechoic mass with a thin, well- defined wall at the anteromedial border of the sternocleidomastoid muscle at the junction of its upper and middle third. It may show thick walls or internal septations or echoes. On CT, it is seen as a well-circumscribed, non-enhancing mass of homogenous low attenuation. Wall thickening and enhancement may occur due to associated inflammation. Metastatic nodes from head-and-neck malignancy, especially papillary carcinoma of the thyroid, are the most common types of nodal metastases presenting as cystic masses in the neck. Eighty percent of the cystic masses in patients over 40 years of age are due to necrotic lymph nodes. On US, a central cystic area with thick irregular walls or an eccentric solid component may be seen. These solid areas usually demonstrate increased peripheral and intralesional vascularity on Doppler. The presence of punctate calcification within the solid component of the cystic node warrants careful search for primary papillary carcinoma in the thyroid gland. Occasionally necrosis within a metastatic lymph node may be veiy florid, mimicking a congenital cyst, such as a second BCC.

Answer 73

97. B. Mounier-Kuhn syndrome Mounier-Kuhn syndrome is characterised by distinct tracheobronchial dilation that is due to atrophy of the muscular and elastic tissues in the trachea and main bronchial wall. Diagnosis is often made by using CT, through which abnormally large air passages are detected. In adults, the diagnostic criteria are trachea >30 mm, right main bronchus >20 mm and the left main bronchus >18 mm. Upper zone emphysema, lower zone bronchiectasis and tracheal diverticulae are recognised. Connective-tissue diseases, ataxia-telangiectasia, ankylosing spondylitis, Ehlers-Danlos syndrome, Marfan syndrome, Kenny-Caffev syndrome, Brachmann-de Lange syndrome and cutis laxa are also associated with secondary tracheobronchial enlargement. All of these conditions should be considered in the differential diagnosis. Williams-Campbell syndrome is a rare form of congenital cystic bronchiectasis, in which distal bronchial cartilage is defective with preservation of central bronchi and trachea.

Answer 74

98. E. Side-branch intraductal papillary mucinous neoplasm IPMNs can be classified as main duct, branch duct (side-branch) or mixed IPMNs, depending on the site and extent of involvement. Main duct IPMN is a morphologically distinct entity and cannot be included in the discussion of pancreatic cysts. However, a side-branch IPMN or a mixed IPMN (in which a side-branch tumour extends to the main pancreatic duct) can have the morphologic features of a complex pancreatic cyst, making clear-cut distinction from a mucinous cystic neoplasm difficult. Identification of a septated cyst that communicates with the main pancreatic duct is highly suggestive of a side-branch or mixed IPMN. However, it is important to be aware that lack of communication with the main pancreatic duct at imaging does not exclude an IPMN. Currently, MR cholangiopancreatography is considered the modality of choice for demonstrating the morphologic features of the cyst (including septa and mural nodules), establishing the presence of communication between the cystic lesion and the pancreatic duct, and evaluating the extent of pancreatic ductal dilatation. Because these lesions are considered premalignant, surgical resection has typically been recommended. The occurrence of malignancy is significantly higher in main duct and mixed IPMNs than in side-branch IPMNs. Therefore, in cases of side-branch IPMN, the treatment decision should be based on the risk-benefit ratio. taking into account the patient’s clinical presentation, age and surgical risk and the size and imaging morphologic features of the cyst.

Answer 75

99. B. T1W TSE T1-weighted images are the most sensitive in children less than 1 year of age. T2 weighted images are the most sensitive in children between the ages of 1 and 2 years, demonstrating a gradual shift from hyperintense to hypointense relative to grey matter. The only area to remain hyperintense alter the age of 2 years, and often for quite some time, is the peritrigonal region. FLAIR unsurprisingly follows the same pattern as T2 but lags behind somewhat. Both T1 - weighted and T2-weighted images should be used to assess myelination. All children should achieve the adult appearance of white matter by 36-40 months.

Answer 76

100. C. Haemorrhagic cyst Haemorrhagic ovarian cysts are likely caused by bleeding into a corpus luteum. The majority have typical US features that allow a confident diagnosis to be made. A reticular pattern of internal echoes due to fibrin strands is a strong predictor of a haemorrhagic cyst This pattern has also been referred to as having a fishnet, lacy, cobweb or spiderweb appearance. Although a clot may occasionally simulate a solid nodule, it is usually recognisable by its concave outer margin and/or absence of detectable flow at colour or power Doppler US. Bloodclot can sometimes be recognised on a grey-scale US scan by its jellylike movement when pressure is applied with the transducer. A fluid level occasionally occurs in a haemorrhagic cyst.

Answer 77

101. C. 2 The MRI sequences typically used are STIR, T1W, and T2W. The grading of such fractures is based on the MR findings and are as follows: Grade 1 - Periosteal oedema on STIR, no marrow change Grade 2 - Periosteal oedema on STIR plus marrow change on T2-weighted only Grade 3 - Periosteal oedema on STIR plus marrow changes on T2-weighted and T1-weighted Grade 4 - Visible fracture line

Answer 78

102. A. Cystic hygroma A cystic hygroma is the most common form of lymphangioma and constitutes about 5% of all benign tumours of infancy and childhood. The overwhelming majority (about 80%-90%) are detected by the time the patient is 2 years old. These lesions are characteristically infiltrative in nature and do not respect fascial planes; hence recurrence post surgery is not uncommon. On US scans, most cystic hygromas manifest as a multilocular predominantly cystic mass with septa of variable thickness. The echogenic portions of the lesion correlate with clusters of small, abnormal lymphatic channels. Fluid-fluid levels can be observed with a characteristic echogenic, haemorrhagic component layering in the dependent portion of the lesion. The most common pattern is that of a mass with low or intermediate signal intensity on T1-weighted images and hyperintensity on T2-weighted images. Infrequently, this lesion may be hyperintense on T1-weighted images, a finding associated with clotted blood or high lipid (chyle) content. In the case of haemorrhage, fluid-fluid levels may be observed.

Answer 79

103. C. Lack of tapering of a bronchus Bronchiectasis is defined as an ‘irreversible localised or diffuse dilatation, usually resulting from chronic infection, proximal airway obstruction, or congenital bronchial abnormality. On chest radiographs, bronchiectasis manifests as tram tracks, parallel line opacities, ring opacities and tubular structures. CT is substantially more sensitive than chest radiography for showing bronchiectasis, which is characterised by lack of bronchial tapering, bronchi visible in the peripheral 1 cm of the lungs, and an increased broncho-arterial ratio producing the so-called signet-ring sign. Mucoid impaction, segmental atelectasis and secondary bronchial wall thickening are all associated secondary signs.

Answer 80

104. D. The submucosal gas in pneumatosis cystoides intestinalis can mimic colonic polyps on a barium enema when viewed en face. Pneumatosis is the presence of gas bubbles within the wall of the involved segment of bowel. The patterns of pneumatosis vary from circular to linear to bubble and curvilinear gas collections. Such patterns can differentiate benign and clinically worrisome pneumatosis intestinalis. The circular form is usually benign and most often seen with pneumatosis cystoides intestinalis and affect the whole colon. Pseudopneumatosis is more common in the right colon because of the presence of liquid fecal matter. Linear or bubble- like air can be due to both benign and life- threatening causes, and its radiographic appearance alone does not allow differentiation between them. In PI due to benign causes, the bowel wall is usually normal. Additional CT findings such as soft-tissue thickening of the bowel wall, free fluid and peri- intestinal soft-tissue stranding are more frequently associated with clinically worrisome than benign pneumatosis intestinalis. Portal venous gas is differentiated from biliary gas by its characteristic tubular branching lucencies that extend to the periphery of the liver, whereas biliary air is more central.

Answer 81

105. D. Visualisation of a heartbeat Ninety-five percent of ectopic pregnancies are tubal; they' occur mostly in the ampulla (70%). An adnexal mass that is separate from the ovary is the most common finding of a tubal pregnancy and is seen on US images. Although not common, an adnexal mass is more specific for an ectopic pregnancy when it contains a yolk sac or a living embryo. The tubal ring sign is the second most common sign of a tubal pregnancy. The tubal ring sign describes a hyperechoic ring surrounding an extrauterine gestational sac. A related finding is the ‘ring of fire’ sign, which is recognised by peripheral hypervascularity of the hyperechoic ring. The term previously described the high-velocity, low-impedance flow surrounding an ectopic adnexal pregnancy. Peripheral hypervascularity is a non-specific finding of the ring of fire sign and may also be seen surrounding a normal maturing follicle or a corpus luteal cyst. Location of the ring of fire in an ovary distinguishes a corpus luteal cyst from an ectopic pregnancy where the ring is extra-ovarian. Intrauterine findings of an ectopic pregnancy include a ‘normal endometrium’, a pseudo-gestational sac, a trilaminar endometrium and a thin-walled decidual cyst. Extrauterine findings of ectopic pregnancy include pelvic free fluid, hematosalpinx and haemoperitoneum.

Answer 82

106. D. Peritrigonal region Myelin development correlates with functional milestones. By 2 years, the infant brain should resemble the adult brain with the exception of the peritrigonal area, which is the last area to myelinate. This area can remain unmyelinated long after the age of 2 years. This can be seen on MRI as persistent T2-weighted and FLAIR hyperintensity and should not be confused with a pathological process. The process of myelination is predictable and follows a few simple rules: central to peripheral, caudal to rostral, dorsal to ventral. At birth, the cerebellum, brainstem and posterior limb of the internal capsule should normally be myelinated. The anterior limb should myelinate by 2 months.

Answer 83

107. E. Pleural plaque secondary to asbestos exposure There are many causes of HPOA, most of which are pulmonary in origin: intrathoracic malignant tumours, including metastasis, mesothelioma, bronchogenic carcinoma and lymphoma; benign tumours, including benign pleural fibroma, thymoma and pulmonary haemangiomas; chronic pulmonary infection (e.g., bronchiectasis and lung abscesses); and cyanotic congenital heart disease. Extrathoracic causes include ulcerative colitis, Crohn’s disease, Whipple disease, liver disease (e.g., cirrhosis, liver abscesses and primary biliary cirrhosis) and gastric and pancreatic carcinomas. Although asbestosis (i.e., asbestos-induced pulmonary fibrosis) is a known cause of HPOA, pleural plaques are not. Radiological abnormalities most commonly affect the lower limb or forearm bones with cortical thickening and lamellar periosteal proliferation. Hypertrophic pulmonary osteoarthropathy is commonly present in conjunction with finger clubbing. If the underlying condition is treated, then this often quickly leads to remission of their symptoms and about a month later to resolution of the radiological findings.

Answer 84

108. B. Dentigerous cyst Odontogenic keratocysts are believed to arise from the dental lamina and other sources of odontogenic epithelium. At radiography, an odontogenic keratocyst usually appears as a unilocular, lucent lesion with smooth, corticated borders that is often associated with an impacted tooth. Such lesions are indistinguishable from dentigerous cysts at radiography. They are more likely to show aggressive growth than other odontogenic cysts and may have undulating borders and a multilocular appearance; these characteristics make odontogenic keratocysts indistinguishable from ameloblastomas. The dentigerous (follicular) cyst is the most common type of non-inflammatory odontogenic cyst and the most common cause of a pericoronal area of lucency associated with an impacted tooth. At radiography, dentigerous cysts appear as well-defined, round or ovoid, corticated, lucent lesions around the crowns of unerupted teeth, usually third molars. The roots of the involved tooth are often outside the lesion and in mandibular bone.

Answer 85

109. A. High-density mucus plugging A 'finger-in-glove’ pattern can be seen at chest radiography in ABPA that corresponds to mucoid bronchial impaction at chest CT. CT findings in ABPA include cystic or varicoid bronchiectasis, a tree-in-bud pattern of nodules, bronchial wall thickening and air trapping with a central or proximal upper-lobe predominance. High-attenuating (>70-100 HU) bronchial contents at CT represent fungal debris containing iron and manganese. The classic diagnostic triad in patients with cystic fibrosis includes an abnormal sweat chloride test result and manifestations of pulmonary and pancreatic disease. Upper-lobe predominance is seen in many but not ail cases; a diffuse distribution is also a common sign. Normal to increased lung volumes are typical in CF and indicate air trapping and small airways disease. CT images show extensive cystic and cylindrical bronchiectasis and bronchial wall and peribronchial interstitial thickening. Findings arc typically more extensive in patients with bronchiectasis due to cystic fibrosis than in patients with bronchiectasis due to other causes. Nodular opacities throughout the lungs correlate with areas of mucoid bronchial or bronchiolar impaction. 'Tree-in-bud' nodules indicate the diffuse bronchiolitis that typically occurs in cystic fibrosis. In addition, a mosaic pattern of attenuation secondary to air trapping due to obstructed bronchi and bronchioles is commonly seen.

Answer 86

110. D. Surgical placement of a jejunostomy tube Pneumatosis is the presence of gas bubbles within the wall of the involved segment of bowel. It is seen in a wide variety of conditions. It is widely divided into two groups: primary (idiopathic) and secondary. Conditions associated with secondary pneumatosis include obstruction; pulmonary disease such as COP.D and asthma; vascular conditions such as ischaemia and infarction; inflammatory conditions such as Crohn’s and UC; necrotising enterocolitis; drugs such as steroids and chemotherapy; and collagen vascular diseases such as scleroderma, SLE and dermatomyositis.

Answer 87

111. E. Solid component with intense enhancement on Doppler Endometriomas typically appear as complex cysts, either unilocular or multilocular, that have a ground-glass appearance due to diffuse, homogeneous, low- to medium-level internal echoes. Similar internal echoes may occur in haemorrhagic cysts, dermoids and some ovarian carcinomas. Thus, it is important to carefully evaluate for other features like a solid component that would suggest a different diagnosis. An endometrioma is very likely when there are diffuse internal echoes in a cystic mass lacking other US features. Additional features reported include echogenic foci in the wall and small solid areas along the wall, most likely representing solid endometrial tissue, which can mimic malignant cysts. Endometrial solid deposits are less likely to be vascular on Doppler compared to tumour, but the role of Doppler imaging is unclear. A small percentage (probably <15%) of endometriomas have less-typical US features such as anechoic fluid, a fluid- fluid level, heterogeneity or calcification. Endometriomas may occasionally simulate a solid mass, especially when they are chronic. Rarely, endometroid or clear cell carcinoma may develop within an endometrioma; this is more likely in women over 45 years of age and in endometriomas larger than 9 cm.

Answer 88

112. B. Sclerotic bone lesions The patient has tuberous sclerosis, an inherited autosomal dominant multisystem disorder with multifocal systemic hamartomas. Osseous manifestations include cyst-like lesions, hyperostosis of the inner table of the calvaria, osteoblastic changes, periosteal new bone formation and scoliosis. These osseous lesions can occur anywhere in bone, commonly in the calvaria, short tubular bones of the hand or foot, spine and pelvis. The cyst-like lesions are usually irregularly circumscribed and have a sclerotic appearance peripherally

Answer 89

113. B. Retrosternal goitre Most thyroid masses in the mediastinum represent downward retrosternal extension of multinodular colloid goitre. They' usually have a well defined outline, which may be spherical and lobulated. Round or irregular well-defined areas of calcification may be seen in benign areas, whereas amorphous cloud-like calcification is occasionally seen within carcinomas. Almost all intrathoracic masses displace and narrow the trachea, which is well recognised in plain film. On US, the inability to see the inferior extent of a thyroid mass is suggestive of retrosternal extension. CT is the best modality for initial investigation because it confirms the finding, displays its anatomical location and provides information should the lesion not be a retrosternal goitre. Clinically within 30 seconds after raising both arms simultaneously (Pemberton’s manoeuvre), marked facial plethora (Pemberton’s sign) develops, indicating compression of the jugular veins by the enlarged multinodular goitre.

Answer 90

115. B. Sarcoidosis Bronchiectasis with Upper or Mid-Lung Predominance * Cystic fibrosis * ABPA * Sarcoidosis * TB Bronchiectasis with Anterior Predominance * Atypical mycobacterial infection * ARDS Bronchiectasis with Lower Lung Predominance * Pulmonary fibrosis * Chronic aspiration * Kartagener’s syndrome * Common variable immunodeficiency * -Antitrypsin deficiency Bronchiectasis with Central Predominance * Mounier-Kuhn syndrome * Williams-Campbell syndrome

Answer 91

114. E. Central to peripheral, caudal to rostral, dorsal to ventral Myelination begins at 16 weeks in utero and is far from complete at term birth. It continues during the first 2 years of life until it reaches the level of myelination seen in a normal adult brain. Learning development coincides with myelination. CT and MRI can be used to assess myelination. On CT, unmyelinated white matter will appear hypodense. Unmyelinated white matter will appear hypointense on T1-weighted and hyperintense on T2-weighted. This can be confusing as many other conditions of interest in the neonate can cause T2-weighted hyperintensity. Knowing the pattern of normal myelination is therefore essential when interpreting paediatric neuroimaging.

Answer 92

116. C. Heterogeneous content is detected within the mass on CT. This uncommon, typically benign tumour is found mainly in young, non-Caucasian women between the second and third decades of life. It seems to have a predilection for Asian and African American women, although rare cases have been reported in children and men. Although most solid pseudopapillary tumours (SPTs) exhibit benign behaviour, malignant degeneration does occur. Patients with SPT of the pancreas are often clinically asymptomatic. They may present with a gradually enlarging abdominal mass or complain of vague abdominal pain or discomfort The abdomen is usually non-tender on palpation, but obstructive symptoms may occur if the tumour grows large enough to compress adjacent viscera. There are usually no abnormalities in clinical laboratory tests (e.g., serum amylase levels) or in pancreatic cancer markers (e.g., CA19-9, carcinoembryonic antigen, fetoprotein). The diagnosis is not uncommonly made incidentally at abdominal examination, US or CT performed for other reasons. SPT of the pancreas has distinctive pathologic features. The mass may occur anywhere in the pancreas but is most frequently found in the head or tail. At gross examination, the mass is usually large (mean maximum dimension 9.3 cm) and well encapsulated and contains varying amounts of necrosis, haemorrhage and cystic change.

Answer 93

117. B. Hydrosalpinx Hydrosalpinx should be suspected based on location and configuration. Characteristically, it is a tubular shaped cystic structure that is separate from the ipsilateral ovary. Its configuration may reveal indentations on the opposite sides of the wall referred to as the ‘waist sign'. The waist sign in combination with a tubular shaped cystic mass has been found to be pathognomonic of a hydrosalpinx. Incomplete septa, due to the wall of the tube folding on itself, or small mural nodules, due to thickening of endosalpingeal folds (termed ‘beads on a string’), are also typical and are more predictive of hydrosalpinx when the mass is tubular in shape. The distinction from tumour nodule is easier when one recognises that the mass is separate from the ovary. Additionally, the solid component of the rare fallopian tube carcinoma is usually larger and less numerous than the multiple small nodules due to thickened endosalpingeal folds.

Answer 94

118. B. Mid-shaft of the second metatarsal Stress fractures of the metatarsals account for between 9% and 24.6% of stress fractures in athletes. Plain radiographic evaluation may reveal normal appearances. Two to three weeks after the injury, periosteal bone reaction may be visible on radiographs. MRI has high sensitivity in the diagnosis of these fractures, depicting oedema of the bone marrow and periosteum. A hypointense fracture line may also be visible on MRI. The most common site of metatarsal stress fractures are the distal shaft and neck of the second and third metatarsals, especially in long-distance runners. They are usually thinner than the first metatarsal and bear a large amount of weight during the ‘push off' phase of running. Stress fractures of the fifth metatarsal base occurring approximately 1.5 cm distal to the tubercle, at the junction of the metaphysis and diaphysis (Jones’ fracture), deserve special mention as high-performance athletes with this injury, because of their propensity to be delayed or non-union, and refracture, may benefit from early operative intervention.

Answer 95

119. D. US neck with FNA Thyroid scanning using pertechnetate (99mTc) is traditionally used to screen thyroid nodules for malignancy. The finding of a hyperfunctioning or ‘hot’ nodule (uptake of tracer within the nodule with suppression of uptake in the surrounding normal thyroid tissue) excludes malignancy in almost all patients. A non-functioning or ‘cold’ nodule was thought to indicate increased risk of malignancy, with 5%—15% of these being malignant FNA should be the first-line investigation for assessment of all solitary nodules or a dominant nodule in a multinodular goitre. US is well established as a primary investigation for patients presenting with a lump in the neck; moreover, the cost effectiveness and diagnostic accuracy of FNA can be increased by using US guidance and the presence of an on site cytopathologist.

Answer 96

120. B. Discharge with reassurance This is a description of the normal appearances of the thymus for a child of this age. The wavy margins result from interdigitation of soft thymic tissue in the intercostal spaces. Sometimes a definite notch (unilateral or bilateral) can be seen at the junction of the inferior aspect of the gland and the cardiac silhouette. The thymus gradually involutes with age and may acutely shrink during periods of bodily stress. During the recovery period, it grows back to its original size or even larger, a phenomenon known as thymic rebound hyperplasia. The thymus becomes less evident between 2 and 8 years of age, after which it cannot be visualised on the frontal chest X-ray.

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