Carotid

a. Primary parameters for quantifying a significant stenosis are the PSV and the presence of plaque. Ratio and EDV are used when ICA PSV may not be representative of degree of stenosis due to the following factors:

• Presence of tandem lesions

• Contralateral high-grade stenosis (>70%)

• Discrepancy between visual assessment of plaque and ICA PSV

• Elevated CCA velocity

• Hyperdynamic cardiac state

• Low cardiac output

* Report should state rationale for making diagnostic choice to rely more heavily on ratio. 

b. The ICA/ CCA ratio uses the highest PSV obtained in the proximal 3 cm of the ICA divided by the CCA PSV obtained approximately 2 cm proximal to the flow divider/bifurcation of the ICA and ECA. If significant CCA disease is present, the ICA/CCA ratio is to be used with caution or not at all.

*  Plaque estimate (diameter reduction) with gray-scale and color Doppler US.