B-mode estimate of carotid stenosis: Planimetric measurements complement the velocity estimate of internal carotid stenosis

Aims. Velocity criteria for diagnosis of carotid stenosis are subject to flow phenomenon such as contralateral stenosis or occlusion. Duplex tri-axial diameter and cross sectional area measurements are potentially more accurate because they are anatomic. Methods. As part of a prospective study on triplanar ultrasound carotid stenosis measurements, 30 consecutive patients were studied by 3 independent operators to assess variability of the technique. PSV and EDV were recorded at the common and internal carotid arteries and Duplex B-mode long-axis and diameter views were obtained using color and/or power Doppler. Cross-sectional area (CSAS), minimal luminal diameter (MLD), and triaxial diameter measurements, based on the NASCET criteria were performed at the narrowest lumen. Results. The CSAS, MLD and triaxial diameter measurements were not significantly different in the 3 measurements and that was true for the 3 operators (ANOVA, P=0.1 for both). There were 4 patients where the velocity measurements differed by one stenosis grade, when compared to diameter. The triaxial diameter stenosis correlated well with the percent area reduction for all three measurements. Other than having a very good linear relationship (R2=0.95, R2=0.96, R2=0.93). The MLD was reduced with increasing grades of stenosis and provided a clear separation between the 50-69% and 80-99% grades with only a small overlap in the 70-79% grade. Conclusion. The present analysis demonstrates that CSAS and triaxial diameter can be performed by experienced investigators with low variability and good reproducibility. Velocity and planimetric measurements are complimentary in the assessment of carotid artery stenosis.