Semiautomated Segmentation and Volume Measurements of Cervical Carotid High-Signal Plaques Using 3D Turbo Spin-Echo T1-Weighted Black-Blood Vessel Wall Imaging: A Preliminary Study

Figures

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  Figure 1. Flow chart of semiautomated segmentation of high-signal plaque (HSP) using custom-designed software. Region growing process consists of the 3 steps. In process 1, initial threshold value is given by the highest voxel value in the 7 × 7 × 7 region centered on the seed point. In process 2, neighboring voxels with voxel values higher than the threshold value are added to the plaque region. In process 3, addition to plaque region is repeated while reducing the threshold value by one until one of the end conditions is satisfied. Then, extraction of plaque region is achieved on 3D TSE T1-BB VWI images.

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  Figure 2. Correlation of HSP volumes measured by the manual and semiautomated segmentation methods (r = 0.965).

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  Figure 3. Bland–Altman analysis shows bias between the manual and semiautomated methods is very small (bias: −15.5 mm3).

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  Figure 4. Bland–Altman plots of inter-rater (a) and intra-rater (b) HSP volumes measured using the manual method. Each plot represents the percentage difference between the measurements by the two readers (a) and between the measurements of the two reading sessions by a single rater (b). The intraclass correlation coefficients were 0.959 for inter-raters (a) and 0.979 for intra-raters (b).

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  Figure 5. Bland–Altman plots of inter-rater (a) and intra-rater (b) HSP volume measured using the semiautomated method. Each plot represents the percentage difference between the measurements by the two readers (a) between the measurements of the two reading sessions by a single rater (b). The intraclass correlation coefficients were 0.998 for inter-raters (a) and 0.998 for intra-raters (b).

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  Figure 6. The segmentation times using the semiautomated method were shorter than segmentation times using the manual method (81.7 ± 7.8 s versus 189.5 ± 49.6 s; p < 0.01).

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  Figure 7. The manual method exhibited a wide range of segmentation times (124 to 307 s) and a linear relationship between HSP volume and segmentation times (p < 0.01, r = 0.789).