OMSB Diagnostic Radiology (OEDR) key terms

A calibrated scale expressing CT attenuation relative to water, which is set at 0 HU and air at about -1000 HU. It allows comparison of tissue density across scanners and helps characterize lesions such as fat, fluid, calcification, and hemorrhage.

Display settings that map a chosen range of CT attenuation values onto the available gray shades. Level sets the center of the range and width sets its span, so adjusting them optimizes viewing of soft tissue, lung, or bone.

Dark streaks or bands produced because lower-energy photons are absorbed preferentially as the X-ray beam passes through dense material. It is common near bone, metal, or concentrated contrast and can mimic pathology or obscure anatomy.

The principle that radiation dose should be kept as low as reasonably achievable while still obtaining the diagnostic information needed. It underpins protocol optimization, shielding decisions, and justification of every examination in radiology practice.

Two core radiation protection duties: justification confirms that an examination has a net clinical benefit, and optimization ensures the dose is appropriate for that benefit. Together they guide referral decisions and technical protocol choices in daily practice.

A benchmark dose value for a standard examination, used to identify unusually high exposures at a facility. Values are typically set at a high percentile of a survey, and exceeding them prompts review rather than automatic limitation of clinical practice.

A measure of the radiation dose delivered per unit volume during a CT acquisition, expressed in milligray. It reflects scanner output and protocol settings but does not account for the scanned length, so it is paired with dose-length product.

The product of volume CT dose index and the scanned length in centimeters, giving an indicator of total radiation output for a CT study. Multiplying DLP by a body-region conversion factor estimates effective dose.

Airspace opacification that obscures underlying vessels and bronchial walls on chest imaging. It may be lobar or patchy and is typical of pneumonia, pulmonary edema, or hemorrhage; air bronchograms are often visible within it.

Hazy increased lung attenuation that does not obscure the underlying vessels or bronchial margins. It reflects partial airspace filling or interstitial thickening and is a key pattern in diffuse lung disease and early infection.

Clustered, thick-walled cystic spaces of similar size, usually subpleural and basal, representing end-stage lung remodeling. It is a hallmark of usual interstitial pneumonia and implies irreversible fibrosis rather than active inflammation.

Dilated, irregular airways caused by surrounding fibrotic lung tissue pulling them open. Seen in fibrosing interstitial lung disease, it helps distinguish true fibrosis from reversible airway dilation and often accompanies honeycombing.

A tubular lucency representing an air-filled bronchus outlined by surrounding opacified lung. Its presence indicates that the opacity is parenchymal rather than pleural or mediastinal in origin and supports an airspace process.

A noncontrast CT measurement of calcified coronary plaque, commonly reported as an Agatston score. Higher values indicate greater atherosclerotic burden and independently predict cardiovascular events, helping refine risk assessment beyond clinical scores.

A computational estimate of lesion-specific coronary flow limitation derived from CT angiography data using computational fluid dynamics. It adds functional information to anatomic stenosis assessment and may reduce invasive angiography in selected stable patients.

The site where dilated proximal bowel abruptly changes to collapsed distal bowel on CT. Identifying it helps determine the cause, such as adhesion, hernia, or mass, and distinguishes mechanical obstruction from ileus.

Free intraperitoneal gas, usually detected on CT as gas outside the bowel lumen, often anteriorly in the supine patient. It may indicate perforation and is a surgical emergency when accompanied by peritonitis or instability.

Particulate material resembling stool within dilated small bowel, seen on CT in obstruction. It results from stasis and altered absorption and supports a diagnosis of significant small bowel obstruction, often at a distal level.

A system for stratifying cystic renal masses by CT or MRI features such as septation, nodularity, and enhancement. Categories range from benign simple cysts to clearly malignant lesions, guiding surveillance versus surgical management.

Apparent increase in renal cyst attenuation after contrast administration caused by beam hardening and reconstruction effects rather than true vascularity. It can falsely suggest a solid or enhancing lesion, especially in small cysts.

A standardized reporting system for prostate MRI that scores the likelihood of clinically significant cancer on a scale from 1 to 5. Scores combine findings on T2-weighted, diffusion-weighted, and dynamic contrast-enhanced sequences to guide biopsy decisions.

A calculated image derived from diffusion-weighted MRI that quantifies water molecule mobility. Low values indicate restricted diffusion, which is typical of highly cellular tumors, abscesses, and acute infarction, aiding lesion characterization.

A system for describing fractures involving the growth plate in children, graded by which physeal and metaphyseal or epiphyseal components are involved. Higher grades carry greater risk of growth disturbance and require closer orthopedic follow-up.

A primary malignant bone tumor producing osteoid, most common in adolescents and typically arising in the metaphysis of long bones around the knee. Radiographs show aggressive destruction, periosteal reaction, and sometimes a sunburst pattern.

Thickening and enhancement of dura adjacent to an extra-axial mass, most often a meningioma. It reflects reactive dural change rather than tumor invasion, so it is helpful but not specific for diagnosis.

Displacement of midline intracranial structures caused by mass effect from hemorrhage, edema, or tumor. Significant shift suggests impending herniation and may require urgent decompression or neurosurgical consultation.

A standardized lexicon and final assessment category system for breast imaging reports, ranging from category 0 for incomplete assessment to category 6 for known malignancy. It communicates suspicion level and recommends management such as routine screening, short-interval follow-up, or biopsy.

Three-dimensional breast imaging that acquires multiple low-dose projection images and reconstructs thin slices. It reduces tissue overlap compared with standard mammography, improving cancer detection and lowering recall rates, especially in dense breasts.

A prenatal or neonatal finding of two gas- or fluid-filled structures representing the stomach and a dilated proximal duodenum. It suggests duodenal atresia or stenosis and is often associated with other congenital anomalies.

Telescoping of one bowel segment into another, usually ileocolic in young children, causing obstruction and ischemia. Ultrasound shows a target or pseudokidney sign, and air or contrast enema is often both diagnostic and therapeutic.

A semiquantitative measure of radiotracer accumulation in a lesion on PET, normalized to injected activity and patient size. It helps assess malignancy, treatment response, and inflammatory activity, though it varies with technique and biology.

Correction of PET emission data for photon absorption within the body, usually using a CT or transmission scan. Accurate correction is essential for valid SUV measurements and for reliable lesion detection and comparison over time.

A method of gaining vascular or cavity access by needle puncture, passage of a guidewire, removal of the needle, and insertion of a catheter over the wire. It is fundamental to angiography, drainage, and many interventional procedures.

A self-limited constellation of fever, pain, and nausea occurring after embolization, caused by tissue ischemia and inflammatory response. It is common after liver or tumor embolization and must be distinguished from infection or abscess.

Acute decline in renal function after intravascular iodinated contrast administration, typically occurring within days. Risk is increased by pre-existing renal impairment, diabetes, dehydration, and high contrast volume, and prevention focuses on hydration and minimizing dose.

Paramagnetic agents used in MRI that shorten T1 and T2 relaxation times, producing enhancement on T1-weighted images. Risks include hypersensitivity and, rarely, nephrogenic systemic fibrosis in severe renal impairment with certain linear agents.

A structured method for investigating a serious adverse event by tracing contributing system factors rather than blaming individuals. Findings feed into process changes and monitoring to reduce recurrence, supporting a culture of safety.

A communication pattern in which a request is acknowledged, repeated back, and confirmed before action. In radiology it reduces errors in handoffs, critical result reporting, and procedural team coordination.

A quality assurance process in which radiologists review each other's studies and reports against defined criteria. It identifies discrepancies, supports education, and contributes to departmental quality metrics and improvement activities.