Evaluating Measurement Stability in Glioblastomas Using Magnetic Resonance Elastography: Repeatability and Interobserver Agreement.

Background: Magnetic resonance elastography (MRE) has demonstrated potential in characterizing intracranial tumors, including glioblastoma. The influence of pathology on measurement consistency and interobserver agreement needs evaluation to promote MRE implementation as a quantitative biomarker.

Purpose: To assess repeatability and interobserver agreement of absolute and normalized magnitude of the complex shear modulus (|G*|), storage modulus (G'), and loss modulus (G″) in glioblastoma.

Study type: Prospective.

Population: Thirteen adults (5 male, 8 female, mean age 66.23 years) with histopathologically confirmed glioblastoma.

Field strength/sequence: 3 T MRI, modified single-shot spin-echo echo-planar imaging.

Assessment: Two same-session MRE acquisitions were performed with patient repositioning. The solid tumor component was independently segmented by 2 observers on contrast-enhanced T1-weighted images co-registered to MRE maps.

Statistical tests: Repeatability was assessed using the repeatability coefficient, coefficient of variation, and Bland-Altman plots, and interobserver agreement by the intraclass correlation coefficient. The Wilcoxon signed-rank test compared parameters and coefficients of variation between tumor-normal-appearing white matter and absolute and normalized measurements. Significance was set at 0.05.

Results: Tumor |G*| and G' showed repeatability coefficients of 0.07-0.08 kPa and 0.05 kPa, compared with 0.13 kPa (|G*|) and 0.15-0.16 kPa (G') for normalized measurements. Coefficients of variation in tumor regions were 1.42% ± 1.12%-1.60% ± 1.41% for |G*| and 1.19% ± 0.96%-2.08% ± 2.22% for G', significantly lower than normalized values (4.82% ± 4.49%-4.21% ± 4.27% for |G*|; 5.12% ± 5.04%-5.45% ± 4.53% for G'). Tumor |G*| and G' showed excellent interobserver agreement (intraclass correlation coefficients 0.97 and 0.95). Tumor G″ demonstrated higher variability than |G*| and G' (coefficients of variation 8.58% ± 7.69%-7.51% ± 6.73%), with no significant difference between absolute and normalized measurements (p = 0.14).

Data conclusion: Tumor |G*| and G' are the most repeatable metrics in glioblastoma. Normalization reduces measurement repeatability due to normal-appearing white matter variability. The small sample size (n = 13) limits generalizability.

Evidence level: 2.

Technical efficacy: Stage 2.