RVT key terms

A branch of the common carotid bifurcation, usually lying lateral and posterior to the external carotid, that supplies the anterior brain and eye. It has no normal cervical branches and shows a low-resistance waveform.

The branch of the common carotid that supplies the face, scalp, and neck. It typically gives off cervical branches, lies medial and anterior to the internal carotid, and shows a higher-resistance waveform.

A ring of interconnected arteries at the base of the brain that joins the internal carotid and vertebrobasilar circulations through communicating arteries, allowing collateral flow when one supply route is compromised.

A cervical artery, usually arising from the subclavian, that ascends through the transverse foramina of the spine and joins its partner to form the basilar artery, supplying the posterior circulation.

A low-frequency Doppler technique, usually about 2 MHz, that insonates intracranial arteries through acoustic windows in the skull to measure velocities in the circle of Willis and its branches.

Retrograde vertebral artery flow caused by a significant stenosis or occlusion of the proximal subclavian artery, which reverses the pressure gradient and diverts blood away from the posterior circulation, especially during arm exertion.

Reversal of the normal direction of ophthalmic artery flow on orbital Doppler, a finding that suggests severe ipsilateral internal carotid stenosis or occlusion with collateral supply through external carotid branches.

Widening or filling-in of the Doppler spectral waveform caused by a broad range of red cell velocities within the sample volume, typical of post-stenotic turbulence or of an overly large sample gate.

The ratio of the higher ankle systolic pressure, from the dorsalis pedis or posterior tibial artery, to the higher brachial systolic pressure; used to detect and grade lower-extremity arterial obstruction.

Systolic pressures obtained with cuffs at several levels of the limb, such as thigh, calf, and ankle, so that pressure gradients between adjacent segments localize and quantify arterial occlusive disease.

A plethysmographic method that records volume changes in a limb segment during each cardiac cycle using pneumatic cuffs, producing a waveform whose amplitude and contour reflect arterial perfusion.

A normal peripheral arterial spectral waveform with three phases: forward systolic flow, brief early diastolic reversal, and late diastolic forward flow, reflecting a compliant, high-resistance vascular bed.

A damped arterial Doppler waveform with a slow systolic upstroke and a low, rounded peak, seen distal to a severe stenosis or occlusion because of reduced pulsatility and delayed systolic arrival.

The ratio of toe systolic pressure to brachial systolic pressure, measured with a small digital cuff and plethysmograph, useful when ankle pressures are falsely elevated by medial calcinosis.

A provocative study in which the patient walks on a treadmill and post-exercise ankle pressures are compared with resting values; a fall in pressure indicates hemodynamically significant arterial disease.

Advanced peripheral arterial disease producing ischemic rest pain, nonhealing ulceration, or gangrene from inadequate limb perfusion, carrying a high risk of limb loss without revascularization.

Retrograde venous flow through incompetent valves, provoked by Valsalva or distal compression and timed on duplex; prolonged reflux in deep or superficial veins indicates venous insufficiency.

A forced expiration against a closed glottis that raises intra-abdominal pressure and challenges venous valves; used during duplex to provoke and time reflux in the common femoral and proximal veins.

A brief increase in the venous Doppler signal produced by squeezing the limb distal to the sample site; an absent or weak response suggests obstruction between the compression point and the probe.

The duration of retrograde flow after a provocative maneuver before the valve closes; commonly used thresholds are greater than about 0.5 seconds in superficial veins and 1 second in deep veins.

Clot formation within the deep veins, most often of the legs, identified on duplex by failure of vein compression, intraluminal echogenic material, and absent or abnormal flow and augmentation.

An optical technique that detects changes in skin blood volume using reflected infrared light, applied with calf exercise and tourniquets to measure venous refilling time and assess insufficiency.

The muscular and valvular mechanism in the calf that propels venous blood toward the heart during walking; its failure contributes to ambulatory venous hypertension and chronic venous disease.

The ratio of peak systolic velocity in the renal artery to that in the adjacent abdominal aorta; a value of about 3.5 or greater supports a hemodynamically significant renal artery stenosis.

Ultrasound evaluation of the renal arteries and kidneys using velocity criteria, waveform analysis, and kidney size to detect stenosis and judge its hemodynamic effect on the kidney.

A focal dilation of the abdominal aorta, generally defined as a diameter of 3 cm or more, most often located below the renal arteries, with rupture risk rising as the diameter increases.

Persistent blood flow within an aortic aneurysm sac after endovascular repair, classified by its source such as attachment site, branch vessel, fabric defect, graft porosity, or endotension, and often requiring reintervention.

Abnormally high pressure in the portal venous system, often from cirrhosis, suggested on ultrasound by portal vein dilation, slowed or reversed flow, splenomegaly, ascites, and portosystemic collaterals.

Compression of the origin of the celiac artery by the median arcuate ligament of the diaphragm, producing a focal hook-like narrowing with accelerated velocity that typically varies with respiration.

The angle between the ultrasound beam and the direction of blood flow; velocity calculation requires angle correction, and the cosine of this angle strongly affects the measured frequency shift, ideally keeping it at 60 degrees or less.

An ambiguous Doppler display that occurs when the frequency shift exceeds the Nyquist limit, causing wrap-around of the spectral waveform or color inversion; corrected by raising PRF, lowering transducer frequency, or adjusting the baseline.

The rate at which ultrasound pulses are transmitted, which determines the Nyquist limit and therefore the highest velocity that can be measured without aliasing; higher PRF allows higher velocities but shortens the usable depth.

A high-pass filter that removes low-frequency, high-amplitude Doppler signals arising from vessel wall motion and slow tissue movement, allowing the weaker signals from flowing blood to be displayed.

The adjustable depth and length along the ultrasound beam from which pulsed Doppler echoes are processed, determining exactly where along the vessel the velocity measurement is obtained.

A test object containing fluid-filled vessels and blood-mimicking fluid pumped at known velocities, used to verify Doppler accuracy, sensitivity, and depth penetration during routine quality assurance.

Sensitivity is the proportion of diseased patients correctly identified by a test, while specificity is the proportion of healthy patients correctly identified as normal; both express accuracy against a reference standard.

A nonprofit organization that accredits vascular laboratories through peer review of case studies, personnel credentials, equipment, and quality assurance practices; accreditation is frequently required for reimbursement.

Quality control covers day-to-day checks of equipment and test performance, while quality assurance is the broader program that includes protocols, personnel competency, correlation with outcomes, and continuous improvement.

As Low As Reasonably Achievable: the practice of minimizing ultrasound exposure for patients and sonographers by limiting dwell time and output while still obtaining the diagnostic information needed.

Compression of the brachial plexus or subclavian vessels at the thoracic outlet, assessed with provocative maneuvers and duplex or plethysmographic monitoring of subclavian artery flow and waveform changes.