RPVI flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Doppler angle correction

Velocity equals Doppler shift times sound speed divided by twice the transmitted frequency times the cosine of the angle; angles above 60 degrees cause unacceptable velocity error.

Resistive index formula

RI equals peak systolic velocity minus end-diastolic velocity, divided by peak systolic velocity; higher values indicate greater downstream resistance.

Nyquist limit

The maximum Doppler shift that can be unambiguously displayed, equal to half the pulse repetition frequency; exceeding it produces aliasing on the spectral display.

Spectral broadening

Widening of the spectral waveform caused by a range of velocities within the sample volume, often reflecting turbulence or nonuniform flow.

Color Doppler meaning

Color encodes mean velocity and direction within the region of interest, not peak velocity, so color alone cannot grade stenosis severity.

Bernoulli pressure gradient

The pressure gradient across a stenosis is estimated as four times the square of peak velocity, so 4 m/s corresponds to about 64 mmHg.

Wall filter function

A high-pass filter that removes low-frequency, high-amplitude signals from vessel wall motion; set too high, it obscures slow flow.

ICA stenosis velocity criteria

Peak systolic velocity above roughly 230 to 250 cm/s with elevated end-diastolic velocity supports a 70 percent or greater internal carotid artery stenosis.

ICA to CCA ratio

Internal carotid peak systolic velocity divided by common carotid peak systolic velocity; a ratio above about 4.0 supports a 70 percent or greater stenosis.

Near-occlusion string sign

Markedly reduced or absent flow with high distal resistance in a nearly occluded internal carotid artery; standard velocity criteria do not apply.

Ophthalmic artery direction

Normally flow is toward the probe; reversed flow suggests severe ipsilateral internal carotid disease with external carotid collateral supply.

Subclavian steal waveform

Vertebral artery flow reversal or a high-resistance damped waveform indicating proximal subclavian stenosis or occlusion.

TCD acoustic windows

Transtemporal, transorbital, foraminal, and suboccipital approaches used to insonate intracranial arteries; the temporal window is absent in some adults.

Microembolic signal

A brief, high-intensity, unidirectional signal on transcranial Doppler occurring randomly, distinct from the lower-intensity background flow signal.

Ankle-brachial index formula

Highest ankle pressure from dorsalis pedis or posterior tibial divided by the higher of the two brachial pressures.

ABI interpretation thresholds

Above 1.40 noncompressible; 1.00 to 1.40 normal; 0.91 to 0.99 borderline; 0.90 or less abnormal; 0.50 or less severe.

Toe-brachial index use

Toe pressure divided by brachial pressure; useful when medial calcinosis falsely elevates ankle pressure, with values below about 0.70 considered abnormal.

Segmental pressure gradient

A drop of 20 to 30 mmHg between adjacent cuff levels localizes hemodynamically significant disease to the intervening arterial segment.

Pulse volume recording

Pneumoplethysmographic waveform showing damping and loss of the dicrotic notch distal to a hemodynamically significant stenosis.

Exercise ABI testing

Post-exercise ankle-brachial index drop of 20 percent or more, or 30 mmHg or more, increases diagnostic yield when resting ABI is normal.

Triphasic waveform

Normal peripheral arterial spectral pattern with forward systolic, early diastolic reversal, and late forward diastolic components.

TcPO2 threshold

Transcutaneous oxygen pressure below about 30 to 40 mmHg suggests impaired wound healing potential in critical limb ischemia assessment.

Normal venous flow features

Spontaneous, phasic with respiration, and augmentable with distal compression; loss of these features suggests obstruction or valve failure.

Venous reflux thresholds

Reflux duration greater than 0.5 seconds in superficial veins and greater than 1.0 second in deep veins after distal augmentation.

Acute DVT findings

Noncompressibility of the vein with hypoechoic luminal material, vein distension, and absent spontaneous or phasic flow.

Valsalva maneuver use

Assesses proximal venous valve competency by provoking reflux in the femoral and iliac segments during a sustained increase in intra-abdominal pressure.

Continuous venous flow

Loss of respiratory phasicity with continuous, nonpulsatile flow suggests proximal venous obstruction; pulsatile flow suggests right heart dysfunction.

Renal-aortic ratio

Renal artery peak systolic velocity divided by aortic peak systolic velocity; a ratio above about 3.5 suggests significant renal artery stenosis.

Tardus-parvus waveform

Delayed systolic upstroke with low resistive index distal to a stenosis, reflecting dampened flow transmission through the narrowed segment.

SMA waveform variation

Superior mesenteric artery flow is low resistance with high diastolic flow and changes after a meal, so fasting status should be documented.

Median arcuate ligament syndrome

Focal celiac artery stenosis with a characteristic hook and velocity increase that varies with respiration, caused by ligament compression.

Aortic aneurysm definition

Infrarenal aortic diameter of 3.0 cm or greater measured outer wall to outer wall on ultrasound.

Endoleak detection

Color flow within the aneurysm sac outside the stent graft after endovascular repair, indicating persistent perfusion of the sac.