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

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.

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.

Prospective.

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

3 T MRI, modified single-shot spin-echo echo-planar imaging.

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.

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.

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).

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.

2.

Stage 2.