Carotid Doppler

Plaque Characterization

Grayscale plaque characterization:

type I: Predominantly hypoechoic with thin echogenic rim
type II: Echogenic plaque with >50% hypoechoic areas
type III: Echogenic plaque with <50% hypoechoic areas
type IV: Uniformly echogenic plaque

Refer to plaque as:

Homogenous (type III and IV)
Heterogenous (type I and II)

Society of Radiologists in Ultrasound (SRU) Consensus

This consensus developed recommendations for the diagnosis and stratification of ICA stenosis.
[PSV = peak systolic velocity; EDV = end diastolic velocity; ICA = internal carotid artery; CCA = common carotid artery]

Normal:

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 colour 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 colour or power Doppler ultrasound

Total occlusion of the ICA:

no detectable patent lumen at gray-scale US and no flow with spectral, power, and colour 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:

deceleration spectral broadening with a peak systolic velocity (PSV) <125 cm/s

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