CCI Cerebrovascular Duplex Examinations 5 — Questions and Answers
Question 1: During TCD monitoring for microembolic signals (MES), an embolic signal is characterized by which property?
- Unidirectional, low-intensity, bidirectional signal lasting >300 ms
- Unidirectional, high-intensity, transient signal lasting <300 ms within the Doppler spectrum (Correct answer)
- Bidirectional artifact present in all gates simultaneously
- Persistent signal with constant intensity across the cardiac cycle
Correct answer: Unidirectional, high-intensity, transient signal lasting <300 ms within the Doppler spectrum
MES are unidirectional, high-intensity transient signals <300 ms duration occurring randomly within the cardiac cycle, distinct from artifacts.
Question 2: Which clinical scenario would MOST warrant a cerebrovascular duplex examination as the initial imaging study?
- Suspected aortic dissection
- Transient ischemic attack with hemispheric symptoms (Correct answer)
- Suspected mesenteric ischemia
- Lower extremity claudication
Correct answer: Transient ischemic attack with hemispheric symptoms
Carotid duplex is the first-line investigation for hemispheric TIA to identify treatable carotid stenosis as a potential embolic source.
Question 3: What is the clinical significance of identifying a carotid 'string sign' on duplex ultrasound?
- It represents a normal variant of the carotid bifurcation
- It indicates near-total occlusion with a thin trickle of residual flow (Correct answer)
- It confirms complete ICA occlusion requiring no further imaging
- It is pathognomonic for fibromuscular dysplasia
Correct answer: It indicates near-total occlusion with a thin trickle of residual flow
The string sign describes a thread-like trickle of flow through a near-total ICA occlusion, an important distinction from complete occlusion since it may still be treatable.
Question 4: Fibromuscular dysplasia (FMD) of the internal carotid artery most commonly involves which segment and appears as what pattern on duplex?
- Proximal ICA near the bifurcation; concentric calcified plaque
- Mid-to-distal ICA; alternating stenoses and dilations producing a 'string of beads' appearance (Correct answer)
- ICA origin; focal high-grade eccentric plaque
- Carotid siphon; diffuse wall thickening
Correct answer: Mid-to-distal ICA; alternating stenoses and dilations producing a 'string of beads' appearance
FMD characteristically affects the mid-to-distal cervical ICA, producing the classic angiographic and ultrasound 'string of beads' pattern of alternating stenoses and aneurysmal segments.
Question 5: During carotid duplex, spectral broadening is defined as filling in of which portion of the Doppler waveform?
- The systolic peak above the baseline
- The diastolic window below the spectral envelope
- The entire spectral window including the baseline
- The temporal window beneath the systolic peak (systolic window) (Correct answer)
Correct answer: The temporal window beneath the systolic peak (systolic window)
Normal laminar flow produces a clear systolic window (spectral window) under the waveform envelope; spectral broadening fills this window, indicating turbulent or disturbed flow.
Question 6: Which duplex finding is the BEST indicator to differentiate ICA occlusion from severe near-total occlusion when color Doppler shows no flow?
- Presence of calcification on B-mode at the ICA origin
- Detection of a trickle of flow using power Doppler or contrast-enhanced ultrasound (Correct answer)
- Absent temporal tap response in the ipsilateral ECA
- High-resistance waveform in the ipsilateral CCA
Correct answer: Detection of a trickle of flow using power Doppler or contrast-enhanced ultrasound
Power Doppler or CEUS can detect residual trickle flow in near-occlusion that conventional color Doppler misses, changing patient management.
Question 7: A patient undergoing carotid stenting has post-procedure duplex showing PSV of 240 cm/s at the stent. What is the most appropriate clinical interpretation?
- Normal in-stent velocities consistent with no restenosis
- In-stent restenosis ≥50% requiring close surveillance (Correct answer)
- Technical artifact from stent strut reflection requiring repeat imaging
- In-stent thrombosis requiring emergency intervention
Correct answer: In-stent restenosis ≥50% requiring close surveillance
Post-carotid stenting velocity criteria differ from CEA; PSV ≥220–240 cm/s within a stent generally indicates ≥50% in-stent restenosis requiring surveillance or re-intervention.
CCI Cerebrovascular Duplex Examinations 5
During TCD monitoring for microembolic signals (MES), an embolic signal is characterized by which property?