OMSB Diagnostic Radiology (OEDR) flashcards

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

Hounsfield unit formula

HU equals 1000 times the difference between the tissue linear attenuation coefficient and water, divided by the water coefficient. Water is 0 HU and air is approximately -1000 HU.

CT dose-length product

DLP equals CTDIvol multiplied by the scanned length in centimeters. Multiplying DLP by a body-region conversion coefficient estimates effective dose in millisieverts.

Larmor frequency

The precession frequency of a nucleus in a magnetic field equals the gyromagnetic ratio times field strength. For hydrogen, it is about 42.58 MHz per tesla.

Silhouette sign

Loss of a normal mediastinal or diaphragmatic border on a radiograph occurs when an adjacent opacity has similar density. It localizes the abnormality to the contiguous lobe.

Tree-in-bud pattern

Small centrilobular nodules connected to branching linear opacities on CT reflect bronchiolar impaction with mucus or pus, typical of infectious bronchiolitis.

Honeycombing

Clustered cystic airspaces with thick walls, typically subpleural and basal, indicate established fibrosis and define a usual interstitial pneumonia pattern.

Stanford type A dissection

Aortic dissection involving the ascending aorta regardless of entry site. It is a surgical emergency because of risk of rupture, tamponade, and coronary involvement.

Agatston calcium score

A non-contrast CT measure of coronary calcification based on density and area. Higher scores indicate greater atherosclerotic burden and cardiovascular risk.

Late gadolinium enhancement

Cardiac MRI technique showing scar or fibrosis as bright myocardium. Subendocardial patterns suggest ischemic disease; mid-wall patterns suggest non-ischemic cardiomyopathy.

LI-RADS LR-5

A definite hepatocellular carcinoma category in at-risk livers, requiring arterial phase hyperenhancement with washout and either capsule appearance or threshold growth.

Bosniak category IIF

An indeterminate cystic renal mass requiring follow-up imaging. It has minimal complexity such as thin septa or small calcification without measurable enhancement.

PI-RADS score

A standardized multiparametric prostate MRI assessment from 1 to 5. Scores of 3 or higher in the peripheral zone warrant targeted biopsy.

Salter-Harris type II

A pediatric physeal fracture extending through the growth plate and out through the metaphysis, producing a metaphyseal fragment known as a Thurston-Holland fragment.

Codman triangle

A periosteal reaction in which the elevated periosteum forms an angle with the cortex, suggesting an aggressive bone lesion such as osteosarcoma.

ASPECTS score

A ten-point scoring system on non-contrast CT quantifying early ischemic change in the middle cerebral artery territory. Lower scores indicate larger infarct core.

Restricted diffusion

High signal on diffusion-weighted imaging with low apparent diffusion coefficient, indicating reduced water motion, seen in acute infarction, abscess, and highly cellular tumors.

BI-RADS category 3

A probably benign finding with less than 2 percent likelihood of malignancy. Short-interval follow-up imaging is recommended rather than immediate biopsy.

Target sign intussusception

An ultrasound appearance of concentric rings representing bowel within bowel. It supports the diagnosis and guides enema reduction in children.

Deauville score

A five-point scale comparing FDG uptake in lymphoma to mediastinal blood pool and liver. Scores of 1 to 3 generally indicate complete metabolic response.

TIPS

A transjugular intrahepatic portosystemic shunt decompresses portal hypertension in refractory variceal bleeding or ascites. Hepatic encephalopathy is a major complication.

Nephrogenic systemic fibrosis

A fibrosing disorder associated with gadolinium exposure in severe renal impairment. Macrocyclic agents carry lower risk than linear agents.

Contrast extravasation management

Elevate the limb, apply cold or warm compresses, and monitor for compartment syndrome. Severe swelling or pain warrants surgical consultation.

Time-out

A pre-procedure pause with the full team to confirm patient identity, site, procedure, and consent. It is a core patient safety practice.

Failure mode and effects analysis

A proactive quality tool that identifies ways a process can fail and prioritizes interventions by severity and likelihood before harm occurs.

Dual-energy CT

Acquisition at two photon energy levels allows material decomposition, useful for detecting bone marrow edema, gout crystals, and differentiating iodine from hemorrhage.

Fleischner nodule guidance

Follow-up CT recommendations for incidentally detected pulmonary nodules depend on size, morphology (solid versus subsolid), and patient risk factors.

CT pulmonary angiography

Contrast-enhanced CT of the pulmonary arteries detects emboli as intraluminal filling defects. Right ventricular enlargement suggests right heart strain.

Revised Atlanta classification

A system grading acute pancreatitis by interstitial versus necrotizing morphology and by presence of organ failure, with severity categories mild, moderate, and severe.

Ovarian torsion imaging

An enlarged edematous ovary with peripherally displaced follicles and a twisted vascular pedicle. Doppler flow may be preserved, so absence of flow is not required.

Anterior cruciate ligament tear

Sagittal MRI shows tendon discontinuity and abnormal signal. Bone contusions of the lateral femoral condyle and posterior tibial plateau are secondary signs.

Extranodal extension

Tumor spread beyond the lymph node capsule in head and neck cancer. It upstages nodes to N3b and worsens prognosis, often requiring adjuvant chemoradiation.

Stereotactic breast biopsy

A biopsy method using mammographic guidance for calcifications or lesions seen only on mammography, not visible on ultrasound.