Arab Board Radiology Final Written key terms

A calculated image derived from diffusion-weighted MRI that quantifies how freely water molecules move in each voxel. Low values indicate restricted diffusion, typical of acute infarction, dense cellular tumours, and abscess pus.

Cell swelling caused by failure of membrane ion pumps, drawing water into cells and shrinking the extracellular space. On MRI it produces restricted diffusion with low ADC, seen earliest in acute ischaemic stroke.

An MRI sequence that weights signal by microscopic water motion, making highly cellular or ischaemic tissue appear bright at high b-values. It is the most sensitive sequence for acute stroke and helps distinguish abscess from tumour.

Abnormal contrast uptake along the pia and arachnoid, following the brain surface into sulci and gyri. It suggests meningitis, leptomeningeal metastasis, or subarachnoid spread of tumour and requires CSF analysis.

Thickened enhancing dura that spares the sulci and follows the inner skull vault or falx. Causes include intracranial hypotension, dural metastasis, empyema, and granulomatous disease such as tuberculosis.

Increased T2 signal within the cord indicating oedema, demyelination, ischaemia, or tumour. Its length, location, and enhancement pattern help distinguish compressive myelopathy, transverse myelitis, and intramedullary neoplasm.

Occlusion of pulmonary arteries by thrombus, usually embolised from leg veins. CT pulmonary angiography shows an intraluminal filling defect; right heart strain and elevated D-dimer support the diagnosis and guide anticoagulation or thrombectomy.

Contrast-enhanced chest CT timed to opacify the pulmonary arteries, the first-line test for suspected pulmonary embolism. It directly visualises thrombus and can reveal alternative diagnoses such as pneumonia or pneumothorax.

Clustered thick-walled cystic airspaces in subpleural lung, usually 3 to 10 mm, representing end-stage fibrosis. It is a hallmark of usual interstitial pneumonia and implies a poor prognosis with limited reversibility.

A CT pattern of basal, peripheral reticulation with honeycombing, traction bronchiectasis, and minimal ground-glass change. When idiopathic it defines idiopathic pulmonary fibrosis; it may also occur in connective tissue disease.

Dilated, irregular airways caused by surrounding fibrotic lung retracting the bronchial walls. Seen in fibrosing interstitial lung disease, it indicates irreversible architectural distortion rather than simple airway infection.

A non-contrast CT measurement of calcified coronary plaque, expressed as an Agatston score. It estimates atherosclerotic burden and cardiovascular risk, and a score of zero carries a very low short-term event rate.

A computational estimate of lesion-specific coronary flow limitation derived from CT angiography data. Values below about 0.8 suggest haemodynamically significant stenosis and help select patients for invasive angiography or revascularisation.

Cardiac MRI technique that nulls normal myocardium so that scar or fibrosis appears bright. Its pattern distinguishes ischaemic scar, which follows a coronary territory, from non-ischaemic cardiomyopathies.

Echocardiographic or MRI measurement of myocardial deformation, reported as percentage shortening or lengthening. Global longitudinal strain detects subclinical ventricular dysfunction earlier than ejection fraction, notably after cardiotoxic chemotherapy.

A standardised scheme for interpreting liver observations in patients at risk of hepatocellular carcinoma. Categories range from definitely benign to definitely malignant, based on arterial enhancement, washout, capsule, and size.

Loss of enhancement of a liver lesion on portal venous or delayed phases relative to surrounding liver. Combined with arterial hyperenhancement it supports hepatocellular carcinoma in a cirrhotic liver.

A liver lesion becoming brighter than background liver during the hepatic arterial phase. It reflects predominantly arterial supply and is a major criterion for hepatocellular carcinoma and other hypervascular tumours.

Simultaneous dilatation of the common bile duct and pancreatic duct, usually from a pancreatic head or ampullary mass. Its presence on imaging prompts urgent evaluation for obstruction, often with endoscopic ultrasound.

A heavily T2-weighted MRI technique that renders static fluid in bile and pancreatic ducts bright, giving a non-invasive cholangiogram. It is used for stones, strictures, and ductal anatomy without iodinated contrast or ionising radiation.

A system for stratifying cystic renal masses by CT or MRI features such as septa, nodularity, and enhancement. Higher categories carry greater malignancy risk and guide decisions between surveillance and surgery.

Apparent increase in renal cyst density on contrast CT caused by beam hardening or partial volume effects rather than true vascularity. It can mimic a solid mass and may require MRI or ultrasound to resolve.

A structured scoring system for prostate MRI that grades the likelihood of clinically significant cancer from 1 to 5. It combines T2-weighted, diffusion-weighted, and dynamic contrast findings to guide targeted biopsy.

A risk-stratification lexicon for adnexal lesions on ultrasound and MRI, ranging from normal to highly malignant. It standardises reporting and links categories to recommended management and follow-up.

Increased T2 fluid-sensitive signal within marrow with low T1 signal, reflecting increased water content. It occurs with trauma, infection, tumour, and reactive stress and is not itself a specific diagnosis.

Death of bone from interrupted blood supply, typically affecting the femoral head, scaphoid, or talus. MRI shows a serpiginous low-signal line on T1 with surrounding oedema before collapse occurs.

On T2-weighted MRI of avascular necrosis, an inner bright line of granulation tissue bordered by an outer dark sclerotic rim. It indicates the reactive interface and helps confirm the diagnosis.

The Breast Imaging Reporting and Data System, a standard lexicon and final assessment scale from 0 to 6 for mammography, ultrasound, and MRI. It communicates malignancy likelihood and recommends management.

Three-dimensional mammography that acquires multiple low-dose projections and reconstructs thin breast slices. It reduces tissue overlap, improving cancer detection and lowering recall rates compared with standard two-dimensional mammography.

Disruption of normal breast tissue architecture by a radiating, spiculated lesion without a central mass. It is a suspicious mammographic finding often caused by invasive carcinoma or radial scar and warrants biopsy.

Acquired inflammatory bowel necrosis in premature neonates, presenting with feeding intolerance and bloody stools. Abdominal radiographs show pneumatosis intestinalis, portal venous gas, or pneumoperitoneum in severe cases.

Thickening of the pyloric muscle in infants causing non-bilious projectile vomiting. Ultrasound shows an elongated, thickened pylorus with a target sign; pyloromyotomy is curative.

Twisting of the midgut around the superior mesenteric artery, usually from malrotation, threatening bowel ischaemia. The upper gastrointestinal series shows a corkscrew duodenum; it is a surgical emergency.

Delivery of chemotherapy mixed with embolic material directly into a tumour's arterial supply, commonly for hepatocellular carcinoma. It causes ischaemic tumour necrosis while sparing normal liver parenchyma.

Catheter-directed infusion of radioactive microspheres into hepatic arteries supplying tumour, delivering internal brachytherapy. It is used for liver malignancy and requires pre-treatment mapping to prevent shunting to lung or gut.

A self-limiting constellation of pain, fever, nausea, and malaise occurring after tumour embolisation. It reflects ischaemic necrosis and must be distinguished from abscess or infection, which require different management.

A beta-emitting radioisotope with a half-life of about 64 hours used in radioembolisation of liver tumours. Its short tissue range confines the radiation dose to the treated territory.

The pairing of a diagnostic radionuclide imaging agent with a matching therapeutic radioligand targeting the same receptor. Examples include prostate-specific membrane antigen and somatostatin receptor analogues in nuclear oncology.

A semi-quantitative PET metric normalising tissue tracer concentration to injected dose and body size. It supports lesion characterisation and treatment response assessment but depends heavily on acquisition and reconstruction settings.

The principle that radiation doses should be kept as low as reasonably achievable, accounting for economic and social factors. It underpins protocol optimisation, shielding, and justification of every examination.

A benchmark dose value for a standard examination, derived from survey data, used to flag unusually high patient exposures. Values above the level prompt protocol review rather than indicating individual harm.

The regulatory and ethical requirement that each radiological exposure produce sufficient benefit to outweigh its risk. It applies at referral and again at the point of imaging, especially in children and pregnancy.