Quantification and assessment of carotid artery lesions: Degree of stenosis and plaque volume

Various methods were developed for the quantification of the degree of stenosis: B‐mode imaging, CW Doppler with spectral analysis, PW‐duplex, and colorflow imaging. The degree of stenosis can be evaluated using transverse views of the carotid in conventional B‐mode imaging. The diameters of the residual lumen (Ds) and the external diameter (De) of the artery at the same level are measured and the degree of stenosis (in area) is calculated. Two different Doppler methods have been designed and validated for the quantification of the stenosis degree. The first one is based on the determination of the maximal velocity inside the stenosis and requires the use of a duplex device. The second one, based on the quantification of the hemodynamic disturbances at the outlet of the stenosis, can be used either with a duplex system or with a continuous‐wave Doppler system (pencil probe). The color display mode facilitates the determination of the residual lumen and therefore contributes to making the B‐mode method more accurate. Moreover, it provides a visualization of the blood flow which avoids most of the misinterpretations of B‐mode or Doppler data. Several classification systems based on subjective or semi‐quantitative criteria (morphological or hemodynamic) were used to identify different grades of stenosis (