Iran Specialty Board Radiology flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Half-value layer

Thickness of a material that reduces beam intensity to half; equals ln2 divided by the linear attenuation coefficient, and increases as the beam hardens with higher kVp or added filtration.

Effective dose formula

Sum over tissues of tissue weighting factor times equivalent dose; equivalent dose is the radiation weighting factor times absorbed dose, with X-rays and gamma rays weighted at 1.

Silhouette sign

Loss of the normal border between a thoracic opacity and an adjacent structure, indicating they are in physical contact; right heart border effacement localizes disease to the right middle lobe.

Honeycombing pattern

Clustered subpleural cystic spaces 3 to 10 millimeters with basal and peripheral predominance; it is the hallmark of usual interstitial pneumonia and indicates established fibrosis.

Stanford type A dissection

Aortic dissection involving the ascending aorta, regardless of the site of the intimal tear; it is a surgical emergency because of risk of rupture, tamponade, and coronary involvement.

Late gadolinium enhancement

Cardiac MRI technique showing myocardial scar or fibrosis; subendocardial distribution suggests ischemic disease, whereas mid-wall or epicardial patterns suggest non-ischemic cardiomyopathy.

LI-RADS LR-5

Definite hepatocellular carcinoma category in at-risk livers, requiring arterial phase hyperenhancement plus washout, capsule appearance, or threshold growth; it has a very high positive predictive value.

Double duct sign

Simultaneous dilatation of the common bile duct and pancreatic duct, suggesting obstruction at the pancreatic head or ampulla, most often by a pancreatic or ampullary carcinoma.

Bosniak category IIF

Indeterminate renal cyst with minimal features such as thin septa or fine calcification; it requires imaging follow-up rather than immediate surgery because malignancy risk is low.

T2 shading sign

Reduced signal intensity on T2-weighted MRI within a T1-hyperintense adnexal lesion, characteristic of an endometrioma containing concentrated blood products.

Codman triangle

Elevated periosteum at the margin of an aggressive bone lesion, producing a triangular spur on radiographs; it indicates rapid tumor growth, classically osteosarcoma.

Double-line sign

MRI finding in early avascular necrosis of the femoral head, consisting of an inner high-signal and outer low-signal band on T2-weighted images representing the reactive interface.

ASPECTS score

Ten-point scoring system on non-contrast CT quantifying early ischemic change in the middle cerebral artery territory; a score of 6 or more supports mechanical thrombectomy.

Dawson's fingers

Ovoid perivenular demyelinating plaques oriented perpendicular to the lateral ventricles, seen on sagittal FLAIR images; they are characteristic of multiple sclerosis.

BI-RADS category 3

Probably benign finding with a malignancy likelihood of 2 percent or less; short-interval follow-up is recommended rather than immediate biopsy, usually at 6 months.

Clustered pleomorphic microcalcifications

Multiple small calcifications of varying size and shape within a small area; this mammographic pattern is suspicious for ductal carcinoma in situ and warrants biopsy.

Pyloric stenosis ultrasound criteria

Pyloric muscle thickness greater than 3 millimeters and canal length greater than 15 millimeters in an infant with projectile non-bilious vomiting, typically at 3 to 6 weeks of age.

Intussusception target sign

Concentric rings of alternating echogenicity on ultrasound representing intussusceptum within intussuscipiens; it is most common in children aged 6 months to 2 years.

TIPS indication

Transjugular intrahepatic portosystemic shunt is used for refractory variceal bleeding and refractory ascites; main complications are hepatic encephalopathy and shunt stenosis.

Microwave versus radiofrequency ablation

Microwave ablation achieves larger and more uniform zones with less heat-sink effect near vessels, whereas radiofrequency ablation is effective for small hepatocellular carcinomas under 3 centimeters.

Bone scan superscan

Diffusely increased skeletal uptake with absent or faint renal visualization, indicating widespread osteoblastic metastases, often from prostate or breast cancer.

High-probability V/Q scan

Multiple segmental or larger mismatched perfusion defects with normal ventilation; this pattern has a high predictive value for pulmonary embolism.

Twinkling artifact

Rapid alternating color Doppler signal behind a strongly reflecting calcification or stone; it helps identify small calculi but is not specific for them.

Venous non-compressibility

Failure of a vein to collapse with graded transducer pressure; it is the primary ultrasound criterion for deep vein thrombosis in the lower extremity.

Aortic isthmus injury

Traumatic aortic tear at the ligamentum arteriosum, shown on CT as an intimal flap, pseudoaneurysm, or periaortic hematoma; a normal chest radiograph does not exclude it.

FAST exam windows

Focused assessment with sonography for trauma examines pericardial, perihepatic, perisplenic, and pelvic regions for free fluid in hemodynamically unstable patients.

Sarcoidosis staging

Scadding stages: I bilateral hilar lymphadenopathy, II adenopathy with parenchymal disease, III parenchymal disease alone, and IV pulmonary fibrosis.

Tuberous sclerosis renal lesions

Bilateral angiomyolipomas containing macroscopic fat, often multiple and enlarging, with hemorrhage risk increasing when lesions exceed 4 centimeters; cortical cysts also occur.

CT dose-length product

Product of volume CT dose index and scan length, expressed in milligray-centimeters; multiplying by a body-region conversion factor estimates effective dose.

Tree-in-bud pattern

Centrilobular branching nodular opacities reflecting impacted bronchioles, seen in infectious bronchiolitis, aspiration, and tumor spread through airways.

PI-RADS score 5

Very high likelihood of clinically significant prostate cancer on multiparametric MRI, based on marked diffusion restriction or definite extraprostatic extension; biopsy is indicated.

Gout erosion appearance

Juxta-articular erosion with an overhanging cortical edge and preserved joint space, often with soft tissue tophi; it contrasts with the marginal erosions of rheumatoid arthritis.