Methods for measuring stenosis
Society of Radiologists in Ultrasound (SRU) consensus
PSV = peak systolic velocity
EDV = end diastolic velocity
ICA = internal carotid artery
CCA = common carotid artery
normal:
ACI PSV <125 cm/sec
and no plaque or intimal thickening is visible sonographically
ACI/ACC PSV ratio <2.0 and ACI EDV <40 cm/sec
<50% ACI stenosis:
ACI PSV <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% ACI stenosis:
ACI PSV is 125-230 cm/sec and plaque is visible sonographically
additional criteria include ACI/ACC PSV ratio of 2.0-4.0 and ICA EDV of 40-100 cm/sec
>/= 70% ICA stenosis but less than near occlusion:
ACI PSV is >230 cm/sec and visible plaque and luminal narrowing are seen at gray-scale and colour Doppler ultrasound
additional criteria include ACI/ACC PSV ratio >4 and ACI EDV >100 cm/sec
near occlusion of the ACI:
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 ACI/ACC PSV ratio >2 but <4
70-79% stenosis:
pansystolic spectral broadening with PSV >270 cm/s
or
EDV >110 cm/s or ACI/ACC PSV ratio >4
80-99% stenosis: EDV >140 cm/s
complete occlusion: no flow; terminal thump