Intraobserver and Interobserver Consistency Evaluation of Carotid Plaque Volume Measured by Different 3-Dimensional Ultrasound Methods

This study aims to evaluate the accuracy of the semiautomatic planimetric measurement (SAPM) method and the necessity of manually adjusted boundary measurement in 3-dimensional ultrasound measurement of plaque volume. A total of 50 patients with 82 plaques in the common carotid arteries between December 2020 and March 2021 were included in this study. Two observers measured the 3-dimensional volume of plaque for each patient in 3 different methods (contour tracing method [CTM], SAPM method without manually adjusted boundary [SAPM1], and SAPM method with manually adjusted boundary [SAPM2]). The difference in measurement time between the 3 methods was evaluated by Kruskal-Wallis H test. Intraclass correlation coefficient and 95% confidence interval were used to evaluate the intraobserver and interobserver reliability of the 3 measurement modes. The Bland-Altman analysis was used to assess the agreement, which was expressed as the mean difference with the 95% limits of agreement (LOA). The difference in measurement time between the 3 methods was statistically significant ( P < 0.001). Both observers' intraobserver and interobserver reliability showed well in the 3 methods (all of the intraclass correlation coefficients were >0.75). The mean differences of the plaque volume measurement were 38.17, 26.42, and 11.75 mm 3 , respectively. The agreement between CTM and SAPM2 was the best, and LOA was -57.00 to 80.51. The agreement between SAPM1 and SAPM2 and the agreement between SAPM1 and CTM were similar, and the LOAs were -126.10 to 202.40 and -158.00 to 210.80, respectively. The SAPM method may be recommended to measure plaque volume in clinical practice.