Ultrasound assessment of carotid arterial atherosclerotic disease

Last revised by Dr Yuranga Weerakkody on 02 Aug 2021

Ultrasound assessment of carotid arterial atherosclerotic disease has become the first choice for carotid artery stenosis screening, permitting the evaluation of both the macroscopic appearance of plaques as well as flow characteristics in the carotid artery.

This article focus on internal carotid artery (ICA) stenosis, reporting both criteria: the one published by Society of Radiologists in Ultrasound 2 and the Sonographic NASCET Index 1.

Please refer to the article on extracranial carotid artery stenosis for a general discussion involving carotid stenosis and other image modalities involved on it.

Society of Radiologists in Ultrasound (SRU) consensus

This consensus developed recommendations for the diagnosis and stratification of ICA stenosis 2.

[PSV = peak systolic velocity; EDV = end-diastolic velocity; ICA = internal carotid artery; CCA = common carotid artery]

  • normal
    • ICA PSV is <125 cm/sec and no plaque or intimal thickening is visible sonographically
    • additional criteria include ICA/CCA PSV ratio <2.0 and ICA EDV <40 cm/sec
  • <50% ICA stenosis
    • ICA PSV is <125 cm/sec and plaque or intimal thickening is visible sonographically
    • additional criteria include ICA/CCA PSV ratio <2.0 and ICA EDV <40 cm/sec
  • 50-69% ICA stenosis
    • ICA PSV is 125-230 cm/sec and plaque is visible sonographically
    • additional criteria include ICA/CCA PSV ratio of 2.0-4.0 and ICA EDV of 40-100 cm/sec
  • ≥70% ICA stenosis but less than near occlusion
    • ICA PSV is >230 cm/sec and visible plaque and luminal narrowing are seen at gray-scale and color Doppler ultrasound (the higher the Doppler parameters lie above the threshold of 230 cm/sec, the greater the likelihood of severe disease)
    • additional criteria include ICA/CCA PSV ratio >4 and ICA EDV >100 cm/sec
  • near occlusion of the ICA
    • velocity parameters may not apply, since velocities may be high, low, or undetectable
    • diagnosis is established primarily by demonstrating a markedly narrowed lumen at color or power Doppler ultrasound
  • total occlusion of the ICA:
    • no detectable patent lumen at gray-scale ultrasound and no flow with spectral, power, and color Doppler ultrasound
    • there may be compensatory increased velocity in the contralateral carotid
Sonographic NASCET Index

This study proposed the incorporation of distal ICA flow velocity information on the conventional carotid Doppler study improving the diagnostic accuracy of PSV 1.

  • <15% stenosis
  • 16-49% stenosis
    • pansystolic spectral broadening with a PSV <125 cm/s
  • 50-69% stenosis
    • pansystolic spectral broadening with a PSV of >125 cm/s
      and
    • end diastolic velocity (EDV) <110 cm/s or ICA/CCA PSV ratio >2 but <4
  • 70-79% stenosis
    • pansystolic spectral broadening with PSV >270 cm/s
      • or
      • EDV >110 cm/s
        or
      • ICA/CCA PSV ratio >4
  • 80-99% stenosis: EDV >140 cm/s
  • complete occlusion: no flow; terminal thump

Proposed revised version (ASUM) 2015 reference required

  • < 50 stenosis
    • peak systolic velocity (PSV) < 150 cm/s
  • 50-59 stenosis
    • peak systolic velocity (PSV) < 150 cm/s
    • end diastolic velocity (EDV) < 70 cm/s
  • 60-69 stenosis
    • peak systolic velocity (PSV) < 180-220 cm/s
    • end diastolic velocity (EDV) > 70 cm/s
    • ICA:CCA PSV ratio < 3 
  • 70-79 stenosis
    • peak systolic velocity (PSV) < 225-260 cm/s
    • end diastolic velocity (EDV) > 80-90 cm/s
    • ICA:CCA PSV ratio > 3 
  • 80-89 stenosis
    • peak systolic velocity (PSV) < 270-320 cm/s
    • end diastolic velocity (EDV) > 100-140 cm/s
    • ICA:CCA PSV ratio > 3.7
  • > 90 stenosis 
    • peak systolic velocity (PSV) > 325 cm/s
    • end diastolic velocity (EDV) > 140 cm/s

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Cases and figures

  • Case 1: 50-69 % R-ICA stenosis
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  • Case 2: CCA occlusion and reversed flow in ECA
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  • Case 3
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  • Case 4
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  • Case 5
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  • Case 6: markedly narrowed lumen
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  • Case 7: ICA PSV 367 cm/s
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  • Case 8: ICA PSV 631 cm/s
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  • Case 9
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