Showing posts from December, 2013

Vascular Imaging

Draped aorta sign Draped aorta sign: posterior wall of the aorta either is not identifiable or closely follows vertebral bodies Hyperattenuation crescent sign • Hyperattenuation crescent sign: welldefined peripheral crescent of increased attenuation within the thrombus of a large aneurysm indicates acute or impending rupture loss of “wink” sign Noncompressibility of vein (loss of “wink” sign) DVT popliteal “dog-leg” sign (aCute bend in the lumen of the popliteal artery) • Popliteal aneurysm: Most common peripheral arterial aneurysm. 50% of aneurysms are bilateral, and 80% are associated with aneurysm elsewhere. Commonly due to atherosclerotic disease or trauma. Angiography may show luminal dilatation or mural calcification. 25% of popliteal artery aneurysms may not be associated with visible arterial dilatation by angiography. In these cases, secondary signs such as the “dog-leg sign” (acute bend in lumen o


Adrenal hemorrhage Etiology: Underlying tumor; Coumadin; Trauma; Infection; Hypercoagability states; stress CT findings: high attenuation on NECT; may be unilateral or bilateral; in time may calcify; more common in females (3:1) If bilateral adrenal hemorrhage in trauma consider addison syndrome need hormonal replacement therapy as life treatening (Emergency Radiology 2012; Sacerdote) Variable appearnace of lesion: Round; Blunt abdominal trauma findings: Adrenal hematoma (oval or round); irregular hemorrhage obliterating the gland; uniform adrenal gland swelling with increased attenuation; preiadrenal hemorrhage or stranding; retroperitoneal hemorrhage; adrenal pseudocyst (chronic) (Emergency radiology 2012 To'o) Bright Adrenals in Trauma  Patient is hypotensive; hypovolemic shock syndrome  Hypovolemic shock CT findings Bright Adrenals; Diffuse fluid filled dilated small bowel; hyperenhancement

Radiation Risk

Biological Effects of radiation: Stocastic (delayed) effects and Non-stocastic (deterministic) effects Stocastic (delayed) effects - cancers in exposed individual: observed 3-20 years after exposure ; - Mutations in offspring of exposed individual - observed in future generations Probability of effect increases with dose, with no dose threshold, but the severity of the effect is not dose related. E.g. radiation induced cancer and genetic effects. Playing the Lottery game, more exposure, more chances of effect. Cancer risk: average risk for radiation induced cancer in general population is 5% per Sievert (Sv); Children are 2-3 times at higher risk then adults (as high as 15% per Sv); for persons aged >50 yars risk is 1/5 to 1/10 of the for younger adults Non-stocastic (deterministic) effects: - direct damage to tissue due to local cell death; - observable within days to weeks Threshold dose; >2 Grey of radiati

Pediatric Imaging

Adynamic ileus, Pneumatosis intestinalis,  Gas in portal vein may be seen transiently,  Pneumoperitoneum football sign NeCrotiziNg eNteroColitis (NeC) Radiographic Features (Fig. 11-30) • Small bowel dilatation: adynamic ileus (first finding), unchanging configuration over serial radiographs • Pneumatosis intestinalis, 80% (second most common sign) • Gas in portal vein may be seen transiently (US more sensitive than plain film); this finding does not imply as bad an outcome as it does in adults. • Pneumoperitoneum (20%) indicates bowel perforation: football sign (floating air and ascites give the appearance of a large elliptical lucency in supine position). • Barium is contraindicated; use water-soluble contrast if a bowel obstruction or Hirschsprung disease needs to be ruled out. Bilateral. C sign in subtalar bony coalition. tarsal CoalitioN (Fig. 11-69) Fusion of 2 or more tarsal bones. Union may be

Obstetric Imaging

Absent double decidual sign with MSD >10 mm prediCtors of poor outCome in first trimester  Anterior uterine wall displaced away from fetal body normal amniotiC fluid Volume Several methods are used for assessment of fluid; there is no evidence that any method is better than the other: • Subjective assessment (recommended by most sonographers) Anterior uterine wall displaced away from fetal body (good sign) Banana sign (spina bifida) Banana sign (spina bifida), Posterior fossa Cerebellar view • Banana sign (Fig. 10-28): represents the cerebellum wrapped around the posterior brainstem secondary to downward traction of the spinal cord as part of Arnold-Chiari malformation • Most cases of spina bifida are suspected because of head abnormalities (e.g., banana sign). Double decidual sac sign Pregnancy? • Visualize gestational sac • Double decidual sac sign Double Decidual

Nuclear Imaging

Cystic duct sign • Morphine is often given before 4 hours to make the diagnosis of acute cholecystitis. Dose is 0.04 mg/kg given slowly. Causes spasm of sphincter of Oddi Can convert true-positive result in case of cystic duct sign to false-negative result DIFFUSE PERIOSTEAL UPTAKE (TRAMTRACK SIGN) Criteria: bilateral, diffuse periosteal uptake • Hypertrophic osteoarthropathy (lower extremity > upper extremity) • Child abuse • Thyroid acropachy dilated cavity on initial but not delayed images Heart size and wall thickness • Subjective assessment • Transient cavitary dilatation (dilated cavity on initial but not delayed images) is a sign of LV dysfunction. Hot nose sign Imaging Findings • No flow Absent ICA Absent sinuses • Absent cerebral uptake of HMPAO • Slight perfusion of scalp veins may be present. • Hot nose sign: increased intracranial pressure

Neurologic Imaging

atherosCLerotiC disease Slim sign: collapse of ICA above stenosis atherosCLerotiC disease atherosCLerotiC disease Color Doppler flow imaging of carotid arteries • High-grade stenosis with minimal flow (string sign in angiography) is detected more reliably than with conventional Doppler US. CT • To determine complete occlusion versus a string sign (near but not complete occlusion), delayed images must be obtained immediately after the initial contrast images. Bifid post-CS sign (85%) Bifid post-CS sign (85%) cap sign • T2W: hyperintense. 20%-33% of ependymomas demonstrate the “cap sign,” a rim of extreme hypointensity (hemosiderin) seen at the poles of the tumor on T2W images. Most cases (60%) also show evidence of cord edema around the masses. Classification of Plain Radiographic Abnormalities of the Infant Skull Variations in skull density Decreased density: generalized or local

Musculoskeletal Imaging

achondroplasia Achondroplasia is an autosomal dominent anomaly that affects the cartilage growth and development. The individual is a short limbed dwarf with a relatively normal sized trunk, large head, frontal bossing, and a depressed nasal bridge. ULTRASOUND The diagnosis can be made by fetal ultrasound by progressive discordance between the femur length and biparietal diameter by age. The trident hand configuration can be seen if the fingers are fully extended. A skeletal survey is useful to confirm the diagnosis of achondroplasia. SKULL The skull is large, with a small narrow foramen magnum, and relatively small skull base. LIMBS Short wide tubular bones with metaphyseal cupping and flaring and irregular growth plates. Fibular overgrowth is present. The hand is broad with short metacarpals and phalanges, and a trident configuration. ‘Trident hand’: the fingers are all the same length and diverge into 2 pa


Blood–brain barrier damage A pathological increase of permeability of the blood–brain barrier occurs in several conditions, e.g. many cerebral and meningeal tumours, cerebral infarcts and in some infections. This is the basis of the very useful diagnostic sign of tumour staining, which is particularly well seen on CT, even after IV injection of contrast medium.

Head and Neck Imaging

multiplicity is not a sign of a benign condition US guidelines for thyroid nodules: • 80% of nodular disease is due to hyperplasia (pathologically they are referred to as hyperplastic, adenomatous, or colloid nodules). • Malignant and benign nodules present simultaneously in 10%-20% of cases; thus multiplicity is not a sign of a benign condition. • Nodules with large cystic components are usually benign; however, 20% of papillary cancers are cystic. • Comet-tail artifacts are seen in colloid cysts.

Genitourinary Imaging

Beak sign on IVP • “Beak sign” can be seen with large cysts seen on IVP Bergman's coiled catheter sign Bergman's coiled catheter sign: on retrograde pyelogram the catheter is typically coiled in dilated portion of ureter just distal to the lesion. Doughnut sign on IVP or angiography Lobar dysmorphism: doughnut sign on IVP or angiography Goblet sign Goblet sign: retrograde pyelogram demonstrates dilated ureteral segment distal to obstruction with filling defect and meniscus Ureteral tumors Pseudokidney sign (US) Elliptical structure in pelvis or abdomen with an echogenic center (blood, prominent mucosa, infiltrated bowel wall) resembling the US appearance of a kidney. • Inflammatory bowel disease Crohn disease Infectious colitis • Tumor • Intussusception • Always exclude pelvic kidney Ring sign Sequestered, sloughed papillae cause filling d

Gastrointestinal Imaging

Accordion sign • Contrast between thickened folds (accordion sign) Pseudomembranous colitis (PMC) Bull's eye pattern (hypoechoic halo around lesion) LIVER US FOR METASTASIS Echogenic metastases • GI malignancy • HCC • Vascular metastases Hypoechoic metastases • Most metastases are hypovascular. • Lymphoma • Bull's eye pattern (hypoechoic halo around lesion) Nonspecific sign but frequently seen in bronchogenic carcinoma Hypoechoic rim represents compressed liver tissue and tumor fibrosis. Calcified metastases: hyperechoic with distal shadowing • All mucinous metastases: colon > thyroid, ovary, kidney, stomach Cystic metastases: necrotic leiomyosarcoma; mucinous metastases Carman's (meniscus) sign* *Results from the fluoroscopically induced apposition of rolled halves of the tumor margin forming the periphery of the ulcerated carcinoma; meniscus refers to menisco