Cerebral blood volume analysis in glioblastomas using dynamic susceptibility contrast-enhanced perfusion MRI: a comparison of manual and semiautomatic segmentation methods

Abstract

Purpose: To compare the reproducibilities of manual and semiautomatic segmentation method for the measurement of normalized cerebral blood volume (nCBV) using dynamic susceptibility contrast-enhanced (DSC) perfusion MR imaging in glioblastomas.

Materials and methods: Twenty-two patients (11 male, 11 female; 27 tumors) with histologically confirmed glioblastoma (WHO grade IV) were examined with conventional MR imaging and DSC imaging at 3T before surgery or biopsy. Then nCBV (means and standard deviations) in each mass was measured using two DSC MR perfusion analysis methods including manual and semiautomatic segmentation method, in which contrast-enhanced (CE)-T1WI and T2WI were used as structural imaging. Intraobserver and interobserver reproducibility were assessed according to each perfusion analysis method or each structural imaging. Interclass correlation coefficient (ICC), Bland-Altman plot, and coefficient of variation (CV) were used to evaluate reproducibility.

Results: Intraobserver reproducibilities on CE-T1WI and T2WI were ICC of 0.74-0.89 and CV of 20.39-36.83% in manual segmentation method, and ICC of 0.95-0.99 and CV of 8.53-16.19% in semiautomatic segmentation method, repectively. Interobserver reproducibilites on CE-T1WI and T2WI were ICC of 0.86-0.94 and CV of 19.67-35.15% in manual segmentation method, and ICC of 0.74-1.0 and CV of 5.48-49.38% in semiautomatic segmentation method, respectively. Bland-Altman plots showed a good correlation with ICC or CV in each method. The semiautomatic segmentation method showed higher intraobserver and interobserver reproducibilities at CE-T1WI-based study than other methods.

Conclusion: The best reproducibility was found using the semiautomatic segmentation method based on CE-T1WI for structural imaging in the measurement of the nCBV of glioblastomas.

Figure 1. Flowchart of patient selection and inclusion criteria.

MR = magnetic resonance; WHO = World Health Organization.

Figure 2. Flowchart of manual and semiautomatic segmentation analysis.

Structural imaging (CE-T1WI or T2WI) and nCBV maps were coregistered using the manual segmentation method, and then the ranges of tumors were manually depicted by each observer using an ROI (right row). Structural imaging (CE-T1WI or T2WI) and nCBV maps were coregistered using the semiautomatic segmentation method; then, the ranges of tumors were depicted by each observer using a VOI. Finally, an appropriate combination of clusters from the various clusters was determined by each observer (left row). CE-T1WI = contrast enhanced T1-weighted imaging; T2WI = T2-weighted imaging; nCBV = normalized cerebral blood volume; ROI = region of interest; VOI = volume of interest.

Figure 3. Bland-Altman plots show intraobserver reproducibility between the first and second measurement with observer 1 (a) and observer 2 (b) with the manual method and observer 1 (c) and observer 2 (d) with the semiautomatic segmentation method.

Intraobserver reproducibility with the semiautomatic segmentation method was better than that of the manual method for both CE-T1WI- and T2WI-based evaluations. CE-T1WI = contrast enhanced T1-weighted imaging; T2WI = T2-weighted imaging.

Figure 4. Bland-Altman plots show interobserver reproducibility according to structural imaging technique for both CE-T1WI (a) and T2WI (b) with the manual method and CE-T1WI (c) and T2WI (d) with the semiautomatic segmentation method.

Interobserver reproducibility using the semiautomatic segmentation method was better than with the manual method for CE-T1WI-based evaluation and lower than with the manual method for T2WI-based evaluation. CE-T1WI = contrast enhanced T1-weighted imaging; T2WI = T2-weighted imaging.