Characterization of plaques

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  Uniformly echolucent or predominantly echolucent; fatty or fibrofatty; ↑ risk of embolization

  
  
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  Uniformly/mildly echogenic and predominantly echogenic; fibrous; ↓ risk of embolization

  
  
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  Highly echogenic with distal shadowing, focal/diffuse; calcified; ↓ risk of embolization

  
  
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  Ulcerated: Focal crypt in plaque with sharp or overhanging edges; ↑ risk of embolization

Grading of internal carotid artery (ICA) stenosis

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  < 50% stenosis: Peak systolic velocity (PSV) < 125 cm/s; PSV ratio (PSVR) < 2.0

  
  
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  50-69% stenosis: PSV 125-229 cm/s; PSVR 2.0-3.9

  
  
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  ≥ 70% stenosis: PSV ≥ 230 cm/s; PSVR ≥ 4.0

  
  
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  Near occlusion: High-/low-velocity (trickle) flow

  
  
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  Occlusion: Absent flow

Common carotid artery and external carotid artery stenosis

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  No well-established Doppler criteria for grading stenosis

  
  
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  Measuring stenosis on color-coded images may underestimate degree of stenosis

Diagnostic pitfalls

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  Trickle flow at near occlusion may be undetected

  
  
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  ICA stenosis may be underestimated due to poor cardiac function or tandem stenoses

  
  
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  Contralateral ICA stenosis may be overestimated due to crossover collateral flow

  
  
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  Moderate carotid stenosis may be underestimated due to normalization of flow at bulb

Correlate grayscale, color Doppler, and spectral Doppler findings when evaluating carotid stenosis

Obtain color Doppler view of stenotic area during systole, because aliasing (indicative of stenosis) may not be seen during diastole

Power Doppler is more sensitive than color Doppler in depicting trace flow in stenotic areas and should be used as supplement to color Doppler when needed

Do not set scale too low, which will result in aliasing throughout vessel

Small parts/high-frequency probes (10-15MHz) can better delineate grayscale detail of ulcerated plaques, but color and power Doppler will have limited steering angles