ABPS Diagnostic Radiology key terms

A calibrated scale expressing CT attenuation relative to water, where water is 0 and air is about -1000; dense structures such as bone and metal have high positive values.

Display settings that map a chosen range of CT attenuation values to the visible gray scale, controlling contrast (width) and brightness (level) without changing the underlying data.

Dark streaks or bands on CT caused by preferential absorption of low-energy photons as the beam passes through dense material, producing a hardened, higher-energy beam.

Noise and streaking on CT that occurs when too few photons reach detectors, typically through very thick or dense body parts or during low-dose scanning.

The principle of keeping radiation dose as low as reasonably achievable while still obtaining the diagnostic information needed, balancing image quality against patient risk.

A benchmark dose value for a given examination, derived from surveys of local practice, used to flag protocols that deliver unusually high radiation for the same clinical task.

A standardized measure of radiation output per slice from a CT scanner, reflecting dose to a phantom and used with scan length to estimate patient dose.

The product of CTDIvol and the scanned length in centimeters; it estimates total radiation burden for a CT study and supports dose comparison across protocols.

Kinetic energy released per unit mass of air by ionizing radiation, expressed in gray; it is the basis for fluoroscopic dose display and for skin dose estimation.

Tracking cumulative fluoroscopic exposure and displayed dose indices during a procedure to keep skin and operator doses within safe limits, especially in long interventions.

Hazy increased lung attenuation that does not obscure underlying bronchial and vascular margins, reflecting partial alveolar filling or interstitial thickening.

Lung opacity that obscures underlying vessels and airway walls, usually from alveolar airspace filling by fluid, pus, blood, or cells.

Air-filled bronchi made visible as branching dark tubular structures within an opaque, airless region of lung, indicating airspace disease rather than airway obstruction.

Clustered, thick-walled cystic airspaces typically in subpleural lung, a hallmark of usual interstitial pneumonia and advanced pulmonary fibrosis.

Irregular widening of bronchi caused by surrounding fibrotic lung tissue pulling on the airway walls; it accompanies architectural distortion in pulmonary fibrosis.

Occlusion of pulmonary arteries by thrombus, diagnosed on CT pulmonary angiography as an intraluminal filling defect, sometimes with vessel enlargement or infarction.

A nuclear medicine study comparing inhaled tracer distribution with injected particle distribution in the lungs; mismatched defects suggest pulmonary embolism.

Blockage of small bowel transit producing dilated fluid- and gas-filled loops with a transition point, often with collapsed distal bowel and sometimes bowel-wall ischemia.

Bowel obstruction in which a segment is blocked at two points, trapping a loop that can rapidly strangulate; CT shows a U- or C-shaped dilated loop with converging vessels.

Free gas in the peritoneal cavity, seen on CT as gas outside the bowel lumen; on upright radiographs it may appear as a crescent under the diaphragm.

Abnormal increase in the thickness of the intestinal wall, which may reflect inflammation, ischemia, infection, or neoplasm and is assessed on contrast-enhanced CT.

Dilatation of the renal collecting system from obstructed urine flow, appearing as fluid-filled branching structures within the kidney on ultrasound or CT.

A stone lodged in the ureter causing upstream dilation and pain; CT shows a calcific density at the transition from dilated to normal ureter.

A malignant tumor arising from renal tubular epithelium, often appearing as an enhancing renal mass; clear cell subtype is most common and may invade the renal vein.

Twisting of the ovary and its vascular pedicle, causing venous and then arterial compromise; ultrasound may show an enlarged ovary with reduced or absent Doppler flow.

Implantation of a pregnancy outside the uterine cavity, most often in the fallopian tube; ultrasound may show an adnexal mass with positive pregnancy test and no intrauterine sac.

Inflammation of the fallopian tube, often from ascending infection; imaging may show a thickened, fluid-filled tube with pelvic inflammatory changes.

Disruption of collagen fibers connecting bones, evaluated on MRI as discontinuity, altered signal, and surrounding edema; grading depends on the extent of fiber failure.

Tear of the ligament stabilizing the knee against anterior tibial translation, seen on MRI as fiber discontinuity, abnormal signal, and secondary signs such as bone contusions.

A break in the fibrocartilage of the knee, seen on MRI as linear signal contacting an articular surface, often with a displaced fragment or parameniscal cyst.

Bone infection that on MRI shows marrow edema and enhancement, with possible cortical destruction and abscess; radiographs may remain normal early in the disease.

A fragment of dead bone separated from living bone by infection or ischemia, appearing as a dense or non-enhancing piece surrounded by inflammatory tissue.

Reduced water molecule motion on MRI, appearing bright on diffusion-weighted images and dark on the apparent diffusion coefficient map; typical of acute infarction and dense cellular tumors.

Sudden brain injury from arterial occlusion, with restricted diffusion in the affected territory and possible vessel occlusion on angiography; time-critical for reperfusion therapy.

Bleeding into the cerebrospinal fluid spaces, seen as hyperdense material in basal cisterns or sulci on noncontrast CT; may follow aneurysm rupture.

Enlargement of the ventricular system from impaired cerebrospinal fluid flow, absorption, or overproduction, often with transependymal edema and sulcal effacement.

A standardized breast imaging assessment scale from 0 to 6 that communicates likelihood of malignancy and recommended management, guiding biopsy and follow-up decisions.

Imaging of asymptomatic breasts to detect early cancer, typically with two views per breast; findings are reported using a standardized assessment category.

A tear in the aortic intima allowing blood into the media, creating a false lumen; CT angiography shows an intimal flap separating true and false channels.

Abnormal focal enlargement of the aorta, often from degenerative wall disease; size and growth rate determine rupture risk and need for repair.

Hypertrophy of the pyloric muscle in infants causing projectile vomiting; ultrasound shows a thickened, elongated pyloric muscle and narrowed canal.

Telescoping of one bowel segment into another, causing obstruction and ischemia; ultrasound shows a target or pseudokidney sign and may guide enema reduction.

Nuclear medicine study using a bone-seeking radiotracer; areas of increased uptake reflect bone turnover from fracture, infection, metastasis, or other active processes.

Combined imaging that fuses metabolic positron emission tomography with computed tomography anatomy, commonly using fluorodeoxyglucose to stage malignancy and assess treatment response.

A percutaneously created channel within the liver connecting hepatic and portal veins to relieve portal hypertension, placed through a transjugular approach.

Elevated pressure in the portal venous system, causing varices and ascites; imaging shows enlarged veins and may guide shunt or embolization therapy.

Image-guided destruction of tissue using heat generated by alternating current, commonly applied to small tumors in liver, kidney, lung, or bone.

A structured set of tests and reviews ensuring imaging equipment, protocols, and interpretations meet performance standards, including equipment testing and peer review.