CCI Cerebrovascular Duplex Examinations 3 — Questions and Answers
Question 1: In transcranial Doppler (TCD), the middle cerebral artery (MCA) is most commonly insonated through which acoustic window?
- Suboccipital window
- Transorbital window
- Transtemporal window (Correct answer)
- Submandibular window
Correct answer: Transtemporal window
The transtemporal window, located superior to the zygomatic arch, provides the primary access for MCA insonation in TCD.
Question 2: A normal vertebral artery waveform is best described as:
- High-resistance with absent diastolic flow
- Low-resistance with continuous antegrade flow throughout diastole (Correct answer)
- Bidirectional with equal systolic and diastolic components
- Monophasic with broad systolic peak
Correct answer: Low-resistance with continuous antegrade flow throughout diastole
The vertebral artery supplies the low-resistance posterior circulation, producing a low-resistance waveform with continuous forward diastolic flow.
Question 3: Which condition would cause a unilateral increase in common carotid artery diastolic flow velocity?
- Ipsilateral ICA occlusion
- Contralateral ICA high-grade stenosis
- Ipsilateral external carotid artery stenosis
- Ipsilateral ICA high-grade stenosis (Correct answer)
Correct answer: Ipsilateral ICA high-grade stenosis
Ipsilateral ICA stenosis increases downstream resistance demand, elevating the diastolic component of the CCA waveform feeding it.
Question 4: What is the primary purpose of using power Doppler (energy Doppler) instead of color flow Doppler during carotid duplex?
- To determine flow direction
- To measure peak systolic velocity
- To detect very slow flow in a near-total occlusion (Correct answer)
- To assess spectral waveform morphology
Correct answer: To detect very slow flow in a near-total occlusion
Power Doppler is highly sensitive to slow flow and is used to differentiate near-occlusion from complete occlusion where color Doppler may miss a trickle of flow.
Question 5: Intima-media thickness (IMT) measurement on carotid duplex is performed at which arterial wall layer?
- Inner edge of intima to inner edge of adventitia
- Leading edge of intima to leading edge of media
- Trailing edge of intima to leading edge of adventitia (Correct answer)
- Outer edge of media to outer edge of adventitia
Correct answer: Trailing edge of intima to leading edge of adventitia
IMT is measured from the trailing (far) wall's intima-lumen interface to the media-adventitia interface on B-mode imaging.
Question 6: A patient with complete ICA occlusion would most likely show which waveform pattern in the ipsilateral CCA?
- Normal low-resistance biphasic waveform
- High-resistance pattern with reduced or absent diastolic flow (Correct answer)
- Markedly elevated PSV with spectral broadening
- Retrograde flow throughout the cardiac cycle
Correct answer: High-resistance pattern with reduced or absent diastolic flow
ICA occlusion eliminates the low-resistance contribution from the ICA, leaving only the high-resistance ECA component in the CCA, reducing diastolic flow.
Question 7: During evaluation of the carotid bifurcation, the carotid bulb normally demonstrates which flow pattern?
- Laminar high-velocity flow
- A zone of flow separation and reversal along the outer wall (Correct answer)
- Turbulent flow with spectral broadening throughout
- Monophasic low-velocity flow
Correct answer: A zone of flow separation and reversal along the outer wall
The carotid bulb's geometry causes a normal zone of boundary layer separation and helical flow reversal along the outer wall opposite the flow divider.
CCI Cerebrovascular Duplex Examinations 3
In transcranial Doppler (TCD), the middle cerebral artery (MCA) is most commonly insonated through which acoustic window?