Question 1: The correct answer is B) PSV > 230 cm/sec
A peak systolic velocity (PSV) greater than 230 cm/sec in the ICA is a well-established Doppler criterion for identifying a hemodynamically significant stenosis of 70-99%. The increase in PSV is due to the accelerated blood flow through a narrowed vessel lumen, which is a hallmark of high-grade stenosis. Additionally, this criterion is often supported by an increased ICA/CCA (internal carotid artery/common carotid artery) ratio and elevated end diastolic velocity (EDV) in severe stenosis. These combined metrics enhance diagnostic accuracy and aid in stratifying the degree of stenosis.

Question 2: The correct answer is B) Retrograde vertebral artery flow
Subclavian steal syndrome occurs when a significant stenosis or occlusion of the proximal subclavian artery leads to a reversal of flow in the ipsilateral vertebral artery. Instead of delivering blood to the posterior circulation of the brain, the vertebral artery supplies the arm, resulting in a "steal" of blood flow. This phenomenon is often identified by spectral Doppler imaging showing reversed (retrograde) flow direction in the vertebral artery and is associated with symptoms of vertebrobasilar insufficiency, such as dizziness and syncope during arm exertion.

Question 3: The correct answer is C) Takayasu's Arteritis
Takayasu's arteritis is a large-vessel vasculitis that predominantly affects the aorta and its main branches, including the subclavian and carotid arteries. It commonly presents in young women, particularly those of Asian and Hispanic descent. Ultrasound findings often show concentric, homogeneous wall thickening due to chronic inflammation and fibrosis of the arterial wall. Unlike atherosclerosis, which typically presents with heterogeneous and eccentric plaque, Takayasu’s arteritis shows a smooth, uniform appearance. Early recognition is crucial for initiating immunosuppressive therapy to prevent progression to stenosis or occlusion.

Question 4: The correct answer is A) Peak systolic velocity (PSV)
The Society of Radiologists in Ultrasound (SRU) criteria emphasize peak systolic velocity (PSV) as the most reliable parameter for grading internal carotid artery stenosis. The PSV correlates directly with the degree of luminal narrowing; as stenosis increases, blood flow velocity rises significantly within the narrowed segment. While plaque characterization and end diastolic velocity (EDV) also contribute to assessment, PSV remains the primary measurement. Additionally, when PSV findings are borderline or conflicting, clinicians often integrate the ICA/CCA ratio and EDV to refine the diagnosis.

Question 5: The correct answer is B) String sign with markedly low flow velocities. The "string sign" refers to a thin, thread-like residual lumen with very low flow velocities, typically seen in near-total occlusion of the ICA. This finding suggests a critically narrowed artery that allows minimal flow, distinguishing it from complete occlusion where no flow would be detected.

2025 NAVIX Vascular Interpretation Preceptorship (40 CME)

VIP Lecture 6 - Extremity Arterial Protocols, Criteria, and Documentation