Inter-observer and intra-observer reliability between manual segmentation and semi-automated segmentation for carotid vessel wall volume measurements on three-dimensional ultrasonography

Fig. 1.. Schematic diagram showing the technical parameters of segmentation in carotid vessel wall volume measurement. The media-adventitia boundary (green lines) and lumen-intima boundary (blue lines) were segmented under an interslice distance of 0.5 mm, with the length of interest being 7.5 mm proximal to the carotid bifurcation for CCA and 5 mm distal to the carotid bifurcation for both ICA and ECA. CCA, common carotid artery; ICA, internal carotid artery; ECA, external carotid artery; ISD, interslice distance.

Fig. 2.. A 48-year-old healthy woman without previous stroke, transient ischemic attack and cardiovascular disease. The media-adventitia boundary (red lines) and lumen-intima boundary (green lines) were contoured for the corresponding vessel of interest in the transverse slices of the three-dimensional ultrasound volume. A-C. The left common carotid artery (arrowhead) without segmentation (A), with manual segmentation (B), and with semiautomated segmentation (C) are shown. D-H. An unsegmented left internal carotid artery (arrow) and an unsegmented left external carotid artery (arrowhead) are shown (D). The left internal carotid artery (arrow) with manual segmentation (E) and semi-automated segmentation (F), and the left external carotid artery (arrowhead) with manual segmentation (G) and semiautomated segmentation (H) are also shown correspondingly.

Fig. 3.. Flow diagram of generating carotid vessel wall volume by manual or semi-automated segmentation on three-dimensional ultrasonography. The input stage involved contouring the media-adventitia boundary and lumen-intima boundary on two-dimensional transverse slices manually or semi-automatically, depending on the approach under investigation. In the automatic processing stage, the areas enclosed by the two contours were subtracted from one another in each transverse slice; and the subtracted area was incrementally evolved across the interslice distance using the trapezoidal rule. In the output stage, carotid vessel wall volume values (red box) were generated. The entire process was repeated until all five observers performed manual segmentation and semi-automated segmentation five times each.

Fig. 4.. Bland-Altman plots for agreement between manual segmentation and semi-automated segmentation for carotid vessel wall volume (VWV) in the common carotid artery (A), internal carotid artery (B), external carotid artery (C), and total carotid VWV (D). SD, standard deviation.