Halle, Bo

Abstract Glioblastoma progression is spatially heterogeneous, but conventional imaging provides limited information about where subsequent tumor progression is likely to occur. We developed a directional magnetic resonance elastography (MRE) framework to test whether local post-treatment tumor–brain interface mechanics are associated with later spatial tumor progression. In a secondary analysis of a prospectively acquired glioblastoma cohort, wedge-level viscoelastic instability features were extracted from the first post-treatment MRE scan and related to novel tumor burden on the second post-treatment scan after excluding tumor already present on pretreatment or first post-treatment imaging. Nine patients had longitudinal imaging suitable for spatial comparison; six lesions showed net interval growth and were included in the primary wedge-level directional analysis, while three non-growing lesions were retained for descriptive comparison. In growing lesions, several directional mechanical features were descriptively associated with later novel tumor burden. In cluster-aware models accounting for within-patient dependence among wedges, mean Δtanδ showed the most consistent association with later wedge-level novel tumor fraction across mixed-effects and generalized estimating equation analyses. Associations were directionally stable across wedge-width sensitivity analyses. These findings provide proof of principle that post-treatment glioblastoma interface mechanics contain spatially resolved information related to where later tumor emergence occurs, supporting further validation of directional MRE as a framework for longitudinal mapping of progression geometry.

ABSTRACTBackgroundMagnetic resonance elastography (MRE) quantifies tissue viscoelasticity, offering insights into intracranial meningiomas. MRE‐derived parameters, including the storage modulus (G') and the magnitude of the complex modulus (|G*|), may aid neurosurgical planning, but their repeatability remains unexplored in brain tumors.Purpose/HypothesisTo evaluate the repeatability of G' and |G*| in meningiomas, the influence of tumor volume and spatial location on variability, and ranking stability across paired elastograms.Study TypeProspective.Population/SubjectsSeventeen paired MRE scans from 16 patients with meningiomas (mean age 64 ± 12 years, 10 females) scheduled for resection.Field Strength/SequenceMRE was performed on a 3 T system using a single‐shot spin‐echo echo‐planar imaging (SE‐EPI) sequence.AssessmentTumors were segmented on contrast‐enhanced T1‐weighted images; distance and volume metrics were extracted. Regions of interest were applied to G' and |G*| elastograms. Repeatability was evaluated using the coefficient of variation (CV%). Ranking stability was assessed by comparing median G' or |G*| values.Statistical TestsThe difference in CV% was assessed using the Wilcoxon signed rank test. Linear regression assessed the effect of tumor volume and distance from the external occipital protuberance (EOP) on CV%. The Wilcoxon signed‐rank test evaluated ranking stability and scan‐rescan CV%. Statistical significance was defined as p < 0.05.ResultsThe difference in CV% G' (14.89 ± 12.32) and CV% |G*| (13.88 ± 12.60) was not significant (p = 0.61). Tumor volume inversely correlated with CV% (G': β = −0.75 |G*|: β = −0.59). Tumor‐EOP distance had no significant effect (G': p = 0.58, |G*|: p = 0.23). Rankings remained stable (G': p = 0.82, |G*|: p = 0.71).Data ConclusionMRE‐derived parameters are repeatable in intracranial meningiomas, with G' and |G*| being equally stable. Larger tumors yielded more consistent estimates. Preserved ranking stability supports the use of MRE in preoperative planning.Evidence Level2.Technical EfficacyStage 2.