RD7.3 | Imaging in Internal Medicine — Glossary

A higher D-dimer exclusion threshold for patients over 50 years (age × 10 ng/mL in fibrinogen-equivalent units) that increases specificity and reduces unnecessary imaging, validated by the ADJUST-PE study.

A serum tumour marker that may be raised in hepatocellular carcinoma; used, with or without ultrasound, in HCC surveillance and as an adjunct to imaging.

Recombinant tissue plasminogen activator (rt-PA) used for IV thrombolysis in acute ischaemic stroke; dose 0.9 mg/kg IV (maximum 90 mg) within 4.5 hours of onset, after haemorrhage is excluded by NCCT.

Bilateral perihilar air-space opacification on chest radiograph caused by fluid flooding the alveoli; the sign of severe acute cardiogenic pulmonary oedema.

The diagnostic multiphasic-imaging pattern of HCC: avid enhancement in the arterial phase followed by relative hypoenhancement (washout) in the portal-venous/delayed phases, reflecting the tumour's predominantly arterial blood supply.

Alberta Stroke Program Early CT Score; a 10-point scale where one point is deducted for each of 10 MCA-territory regions showing early ischaemic change on CT; ASPECTS ≤6 indicates large established infarct core with high haemorrhagic transformation risk.

CT artefact caused by the petrous bones of the posterior fossa absorbing lower-energy photons preferentially, creating streak artefacts that degrade image quality of the brainstem and cerebellum — the main reason MRI is preferred for posterior-fossa stroke.

Magnetic resonance imaging of the heart; the reference standard for ventricular volumes and ejection fraction and the best modality for myocardial tissue characterisation (myocarditis, infiltration, scar/viability).

On an erect PA chest radiograph, the ratio of the maximum transverse cardiac diameter to the maximum internal thoracic diameter; a value greater than 0.5 indicates cardiomegaly.

The end stage of chronic liver injury with diffuse fibrosis and regenerative nodules; on imaging it shows a nodular surface, coarse echotexture and segmental change (caudate hypertrophy, right-lobe atrophy).

CT performed with intravenous iodinated contrast during the arterial phase to image the intracranial and cervical vessels; used in acute stroke to detect large-vessel occlusion for thrombectomy planning.

Dynamic CT acquired during contrast first-pass through the brain to generate perfusion maps (CBF, CBV, MTT); used to distinguish salvageable penumbra from irreversible infarct core, especially in the extended treatment window (6–24 h).

Contrast-enhanced CT of the pulmonary arteries timed to peak arterial opacification; the first-line / modality of choice for diagnosing PE in haemodynamically stable patients, directly visualising the clot as a filling defect.

A fibrin degradation product that rises with active clot formation and breakdown; a sensitive but non-specific test used to exclude PE in low pre-test-probability patients, never to confirm it.

2018 RCT (Nogueira et al, NEJM) demonstrating benefit of mechanical thrombectomy up to 24 hours after onset in patients with LVO and clinical-imaging mismatch (small infarct core relative to clinical deficit).

2018 RCT (Albers et al, NEJM) demonstrating benefit of mechanical thrombectomy up to 16 hours after onset in patients with LVO and CT perfusion or MRI perfusion-diffusion mismatch.

The liver's blood supply from both the portal vein (~75%) and the hepatic artery (~25%); the physiological basis of multiphasic contrast imaging used to characterise liver lesions.

MRI sequence that detects restriction of water diffusion in acutely ischaemic brain tissue; positive (bright) within minutes of onset and remains the most sensitive tool for early infarct, including posterior-fossa strokes.

The degree to which a tissue reflects ultrasound; hyperechoic tissues appear brighter and hypoechoic darker. Increased liver echogenicity (a 'bright liver') is the hallmark of fatty infiltration.

A peripheral, wedge-shaped, pleural-based opacity on chest radiograph representing pulmonary infarction secondary to PE.

The structured programme of abdominal ultrasound every 6 months (with or without serum AFP) in patients with cirrhosis, designed to detect hepatocellular carcinoma while it is small and curable.

A clinical syndrome in which the heart cannot pump or fill adequately to meet the body's needs, producing congestion (breathlessness, oedema) and reduced perfusion; classified by ejection fraction.

Accumulation of fat within hepatocytes; on ultrasound it produces a diffusely bright (hyperechoic) liver with loss of the normal hepatorenal echo contrast and posterior beam attenuation.

The commonest primary liver cancer, usually arising in cirrhosis; characteristically shows arterial-phase hyperenhancement with portal-venous/delayed washout on multiphasic imaging, allowing imaging diagnosis without biopsy.

The normal slight difference in brightness between the liver and the adjacent right renal cortex; its loss (the liver becoming brighter than the kidney) is a key ultrasound sign of fatty liver.

Heart failure with mildly reduced ejection fraction, defined as an LVEF of 41–49%, intermediate between HFrEF and HFpEF.

Heart failure with preserved ejection fraction, defined as an LVEF of 50% or more with symptoms/signs of failure and evidence of diastolic dysfunction or raised filling pressures.

Heart failure with reduced ejection fraction, defined as an LVEF below 40%; the category with the strongest evidence for the four foundational mortality-reducing drug classes and device therapy.

Pulmonary embolism causing sustained hypotension or shock with right-ventricular strain; the category that warrants urgent reperfusion (thrombolysis, catheter-directed therapy, or surgical embolectomy).

Spontaneous hyperdensity (high HU) of the proximal middle cerebral artery on non-contrast CT, representing acute thrombus; indicates large-vessel occlusion and predicts large-territory MCA infarction.

Spontaneous haemorrhage within the brain parenchyma; appears as hyperdense on NCCT; hypertensive ICH classically affects the putamen, thalamus, or posterior fossa; an absolute contraindication to thrombolysis.

The direct, diagnostic CTPA sign of PE: a low-attenuation clot surrounded by bright contrast within a pulmonary artery, giving the polo-mint (cross-section) and railway-track (longitudinal) appearances.

The rim of dysfunctional but structurally viable brain surrounding the irreversibly infarcted core; it is salvageable if perfusion is restored — this is the target of both thrombolysis and mechanical thrombectomy.

Short, horizontal, peripheral lines at the lung bases on chest radiograph representing fluid within the interlobular septa; a sign of interstitial pulmonary oedema.

Occlusion of a proximal intracranial artery (M1/M2 MCA, ICA, basilar artery) detectable on CT angiography; the primary indication for mechanical thrombectomy.

The proportion of end-diastolic blood volume ejected by the left ventricle per beat (normally ~55–70%); measured by echocardiography and used to classify heart failure.

The Liver Imaging Reporting and Data System; a standardised scheme for reporting and diagnosing hepatocellular carcinoma on multiphasic CT/MRI based on features such as arterial hyperenhancement and washout.

Early CT sign of ischaemia in which cytotoxic oedema reduces the attenuation of grey matter toward white-matter density, making the cortical ribbon indistinct; particularly prominent at the insular cortex (insular ribbon sign).

Vertical comet-tail artefacts arising from the pleural line on lung ultrasound; multiple B-lines indicate interstitial pulmonary congestion and allow rapid bedside monitoring of decongestion.

Endovascular procedure to mechanically retrieve a thrombus from a large intracranial vessel; indicated for LVO within 6 hours (standard) or up to 24 hours (extended, with CT perfusion or MRI penumbra mismatch criteria).

A lung segment that is normally ventilated but shows absent or reduced perfusion on a V/Q scan; the hallmark scintigraphic pattern of pulmonary embolism.

Contrast-enhanced CT or MRI acquired in arterial, portal-venous and delayed phases, exploiting the liver's dual blood supply to characterise focal lesions such as hepatocellular carcinoma.

Hormones released by stretched ventricular myocardium; a normal level makes heart failure unlikely and a raised level supports the diagnosis, helping to prioritise echocardiography.

CT brain performed without intravenous contrast; the first-line investigation in acute stroke to exclude intracranial haemorrhage before thrombolysis.

Pulmonary oedema due to increased capillary permeability rather than raised hydrostatic pressure; characterised by a normal heart size, peripheral opacities and a normal ejection fraction, distinguishing it from cardiogenic oedema.

A V/Q study performed with the perfusion phase alone, often used in pregnancy with a normal chest radiograph because it delivers a lower breast radiation dose than CTPA while still detecting perfusion defects.

Thickening of the soft tissue around the bronchi seen end-on on chest radiograph, caused by peribronchial interstitial fluid in pulmonary congestion.

Raised pressure in the portal venous system, most often from cirrhosis; imaging signs include splenomegaly, ascites, portosystemic collaterals, portal vein dilatation and reversed (hepatofugal) Doppler flow.

An indirect measure of left atrial pressure; its elevation in left heart failure drives the staged radiographic signs of pulmonary venous congestion.

Obstruction of a pulmonary artery, usually by a thrombus that has embolised from a deep vein thrombosis; the pulmonary end of the venous thromboembolism (VTE) spectrum.

A reopened portosystemic collateral vein along the falciform ligament seen in portal hypertension; an ultrasound/Doppler sign of decompressing portal flow.

The ratio of right-to-left ventricular short-axis diameters measured on CTPA (or echo); a value >1.0 indicates right-ventricular strain/dilatation and helps identify higher-risk PE.

A large pulmonary embolus straddling the bifurcation of the main pulmonary artery, indicating a central and potentially high-risk PE.

Haemorrhage into the subarachnoid space, most commonly from a ruptured berry aneurysm; presents as thunderclap headache; CT shows hyperdensity in basal cisterns and sulci; LP for xanthochromia if CT negative.

Intravenous administration of a fibrinolytic agent to rapidly dissolve clot; indicated in high-risk (massive) PE with haemodynamic instability and right-ventricular strain, when not contraindicated.

A non-invasive technique that measures liver stiffness as a surrogate for fibrosis, allowing fibrosis to be staged and monitored without liver biopsy in many patients.

Ultrasound imaging of the heart through the chest wall; the key functional modality in heart failure, measuring ejection fraction, chamber size, wall motion, valves and filling pressures.

Real-time imaging using high-frequency sound; the first-line, radiation-free, contrast-free modality for diffuse liver parenchymal disease and for hepatocellular carcinoma surveillance.

Redistribution of pulmonary blood flow so that upper-zone vessels become as prominent as or more prominent than lower-zone vessels; an early chest-radiograph sign of rising pulmonary venous pressure.

Nuclear scintigraphic study comparing regional lung ventilation and perfusion; the principal alternative to CTPA when iodinated contrast is contraindicated, with a mismatched (ventilated but non-perfused) defect indicating PE.

The three contributors to venous thrombosis — venous stasis, endothelial injury, and hypercoagulability — that underlie the deep vein thrombosis from which most pulmonary emboli arise.

A validated clinical prediction rule estimating the pre-test probability of PE; in the two-tier model a score >4 classifies PE as 'likely' (proceed to CTPA) and ≤4 as 'unlikely' (perform D-dimer first).

A chest-radiograph sign of PE: regional oligaemia (reduced vascular markings) distal to an occluded pulmonary artery; insensitive and rarely seen.