Measurement of the Internal Carotid Artery Cross-Sectional Area: Systematic Differences Depending on Grayscale, Power Doppler, and Color Doppler Techniques.

Abstract

To determine how measurements of the internal carotid artery (ICA) cross-sectional area will differ systematically when obtained by grayscale, color Doppler, and power Doppler imaging. A total of 451 patients had greater than 40% diameter stenosis in at least a single ICA. Anteroposterior and transverse luminal diameters were measured in 609 arteries on grayscale, color, and power Doppler transverse images of the carotid bulb and proximal and distal ICAs. Cross-sectional areas were calculated and compared by a repeated-measures analysis of variance model to assess for significant differences. Mean ICA cross-sectional areas ± SDs as measured by grayscale, power Doppler, and color Doppler imaging were 122 ± 81, 122 ± 79, and 125 ± 79 mm2 , respectively. The mean ICA area estimated by color Doppler imaging was significantly greater than that estimated by power Doppler imaging (P < .0001) and grayscale imaging (P = .02). Area estimates on grayscale and power Doppler images were not significantly different (P = .99). After accounting for the correlation of repeated measurements within single vessels, color Doppler estimates of the luminal area were on average 3.44 and 9.5 mm2 greater than grayscale and power Doppler estimates. Relative cross-sectional area estimates were on average 9.4% greater with color Doppler imaging at smaller luminal diameters (<60 mm2 ) compared with larger luminal diameters. Measurements of the ICA cross-sectional area by color Doppler imaging were significantly greater than those obtained by power Doppler or grayscale imaging. This difference should be considered when stenosis estimates are confirmed or graded by luminal measurements.