EDiR key terms

Hazy increase in lung attenuation in which the underlying bronchi and vessels remain visible. It reflects partial alveolar filling, interstitial thickening or increased capillary blood volume, and on its own is non-specific.

Small centrilobular branching nodules resembling a budding tree, produced when bronchioles are impacted with mucus, pus or fluid. It usually indicates infectious bronchiolitis and is best appreciated on thin-section CT.

Clusters of thick-walled cystic spaces 3-10 mm across, usually subpleural and basal, marking complete destruction of lung architecture. It is a hallmark of usual interstitial pneumonia and implies a poor prognosis.

Contrast-enhanced CT timed so that the pulmonary arteries are opacified, allowing emboli to be seen as intraluminal filling defects. Right ventricular enlargement on the same study indicates strain.

Increased myocardial signal on inversion-recovery MRI several minutes after gadolinium, marking fibrosis or scar. Its pattern, whether subendocardial, transmural, mid-wall or epicardial, points to the likely cause.

Loss of normal haustral folds with a smooth, rigid, tube-like colon on barium studies or CT, resulting from chronic mucosal damage and fibrosis in long-standing ulcerative colitis.

Accumulation of fat within hepatocytes, shown by liver attenuation lower than spleen on unenhanced CT or by signal loss on out-of-phase MRI. It may be diffuse or focal and can mimic a mass.

A swirl of bowel loops and mesenteric vessels on CT caused by twisting of the mesentery around its axis. It suggests volvulus and prompts urgent surgical assessment.

A standardised CT and MRI reporting system for liver observations in patients at risk of hepatocellular carcinoma, assigning categories from definitely benign to definitely malignant and guiding biopsy or treatment.

A scheme grading cystic renal masses on CT or MRI by septation, nodularity, wall thickness and enhancement, from category I (benign) to IV (malignant), which determines whether surgery is needed.

A five-point score expressing the probability that a prostate lesion on multiparametric MRI is a clinically significant cancer, combining T2-weighted, diffusion-weighted and dynamic contrast-enhanced findings to guide biopsy.

Twisting of the ovary and its pedicle that first obstructs venous outflow and later arterial supply. Ultrasound shows an enlarged, oedematous ovary with peripheral follicles, often with reduced or absent Doppler flow.

Spicules of new bone radiating perpendicular to the cortex, produced when periosteum is lifted rapidly by an aggressive process. It is classically seen in osteosarcoma but also in other malignancies and in infection.

A triangular cuff of periosteal new bone at the margin of an aggressive bone lesion, formed where the elevated periosteum meets the cortex. It indicates rapid growth rather than a specific tumour type.

On ultrasound, an abnormal hyperechoic line parallel to the surface of hyaline cartilage, representing deposited monosodium urate crystals. It is a specific finding in gout and may appear before erosions.

Increased marrow water content giving low T1 and high fluid-sensitive MRI signal, caused by trauma, infection, tumour or altered mechanical stress. It is a non-specific reaction pattern rather than a diagnosis.

A wedge-shaped impaction fracture of the posterolateral humeral head caused by the head striking the anterior glenoid rim during anterior dislocation. It is best seen on internal rotation views.

Increased density of the proximal middle cerebral artery on unenhanced CT, caused by acute thrombus. It is an early but insensitive sign of large-vessel ischaemic stroke and warrants urgent vascular imaging.

Ovoid demyelinating plaques oriented perpendicular to the lateral ventricles and centred on small veins, best seen on sagittal fluid-sensitive MRI. They are characteristic of multiple sclerosis.

A triangular area of absent enhancement within an enhancing dural venous sinus on contrast-enhanced CT, representing thrombus. It supports the diagnosis of cerebral venous sinus thrombosis.

A collection of keratinising squamous epithelium in the middle ear or mastoid that erodes adjacent bone. On MRI it does not enhance and shows restricted diffusion, distinguishing it from other middle-ear masses.

A standardised lexicon and final assessment scale, from category 0 to 6, used in mammography, ultrasound and breast MRI to communicate the likelihood of malignancy and the recommended next step.

Disruption of the normal arrangement of breast tissue strands without a central mass, which may be the only sign of a small invasive cancer or of a radial scar. It usually requires biopsy.

Breast calcifications smaller than about half a millimetre, assessed by their number, shape and distribution. Clustered pleomorphic or linear branching forms raise suspicion of ductal carcinoma in situ.

Two gas-filled bubbles on a neonatal abdominal radiograph, representing the stomach and a dilated proximal duodenum, with little gas distally. It indicates duodenal atresia or severe stenosis.

A five-part system describing fractures involving the growth plate by their extension into physis, metaphysis or epiphysis. Higher types carry a greater risk of premature physeal closure and growth disturbance.

An acquired inflammatory bowel disease of preterm infants, shown on radiographs by bowel distension, pneumatosis intestinalis, portal venous gas or pneumoperitoneum from perforation. It carries high mortality and needs urgent treatment.

A stent channel created between a hepatic vein and a portal vein branch to lower portal pressure. It controls variceal bleeding and refractory ascites but may cause encephalopathy or shunt stenosis.

Image-guided delivery of coils, particles, glue or sclerosants into a vessel to stop bleeding, occlude a malformation, or shrink a tumour by cutting off its blood supply.

Percutaneous access to a vessel or cavity by puncturing with a needle, passing a guidewire, removing the needle and advancing a catheter over the wire. It underpins most angiographic procedures.

A semi-quantitative PET measure of tracer accumulation in a region of interest, normalised to injected activity and body size. It helps characterise lesions, though it varies with scanner, timing and metabolic state.

Comparison of the distribution of an inhaled radioactive gas or aerosol with that of injected radiolabelled particles. Mismatched perfusion defects with preserved ventilation suggest pulmonary embolism.

Treatment with iodine-131 that destroys residual thyroid tissue or metastases after thyroidectomy for differentiated thyroid cancer, exploiting the cells' ability to take up iodine.

A scale expressing CT attenuation relative to water, set at 0, and air, set at about minus 1000. It allows tissues to be compared and window settings to be chosen for display.

In CT, the table distance travelled per gantry rotation divided by the total width of the collimated beam. Higher pitch reduces dose and scan time but can increase noise and artefact.

The principle that radiation exposure should be kept as low as reasonably achievable while still answering the clinical question, applied through protocol selection, shielding and avoidance of unnecessary repeat studies.

The radiofrequency power deposited per kilogram of tissue during MRI, measured in watts per kilogram. Regulatory limits prevent excessive heating, particularly with high-field strength or fast sequences.