Lecture 6B: Arterial Testing & Carotid Duplex Ultrasound

Carotid Duplex Ultrasound

A noninvasive technique that combines 2D ultrasound with Doppler imaging to evaluate the extracranial cerebrovascular system.

Arteries Examined

• CCA

• ICA

• ECA

• VA

Applications

• Detect and quantify carotid stenosis.

• Monitor disease progression.

• Patient-RelatedEvaluate collateral circulation.

Patient-Related limitations

• Body habitus (affects penetration).

• Motion and breathing patterns.

• Tortuous vessels causing velocity variations.

Technical Limitations

• Calcified plaque can obscure imaging.

• Operator dependency and improper Doppler angle may lead to misinterpretation.

• Disease process and collateral flow can affect velocity readings.

Patient Positioning

supine or semi-supine with head hyperextended and rotated 45° away from the examined side.

transducer

High-frequency linear transducer (>7.5 MHz)

<0.9 mm

normal Intima-Media Thickness (IMT)

perpendicular

angle provides the best resolution

45°-60°

Angle correction

avoid aliasing

PRF scale

Waveform Interpretation

Assess peak systolic velocity (PSV) and end-diastolic velocity (EDV)

color Doppler

to locate high velocities within stenotic areas.

ICA

Low resistance, continuous diastolic flow

ECA

High resistance, sharp systolic upstroke.

VA

cephalic flow

B-mode

Smooth intima-media, no plaque

Color Doppler

Laminar flow with higher velocity at the center.

Subclavian Steal Syndrome

Retrograde VA flow.

Tortuous Vessels

Aliasing or velocity fluctuations

Dicrotic Notch

Closure of aortic valve seen in spectral waveforms.

Temporal Tap Maneuver

Helps differentiate ECA from ICA.