Mesoscopic Assessment of Microstructure in Glioblastomas and Metastases by Merging Advanced Diffusion Imaging with Immunohistopathology

Representative MR images of patients with left insular GBM (A, T1WI post-Gd; C, FA; E, OD) and a large callosal melanoma metastasis (B, T1 post-Gd; D, FA; F, OD). Representative Bielschowsky silver staining to demonstrate nerve fibers and neurofibrillary tangles (G and H) and immunohistochemical labeling for GFAP (I and J). Scale bar = 100 μm. As illustrated by parametric maps for FA (C and D, arrows) and OD (E and F, arrows), values in contrast-enhancing solid tumor components (A and B, arrows) approximate normal-appearing white matter in GBM. This finding is accompanied by abundant axonal structures visualized by Bielschowsky silver staining (G) and high GFAP expression (I) in GBM compared with melanoma metastasis (H and J). Scale = 100 μm.

DTI, NODDI, and DMI metrics in contrast-enhancing tumor areas in patients with GBM (n = 22) and metastases (n = 21). Compared with metastases, GBM showed a significant shift toward increased FA and decreased OD, whereas no significant differences were found regarding microFA. Four asterisks indicate P ≤ .001. NAWM indicates normal-appearing white matter.

The Spearman rank correlation demonstrates a positive association of FA with GFAP and Bielschowsky scores (upper row) and a negative association of OD with GFAP and Bielschowsky scores (middle row). No association between microFA with GFAP and Bielschowsky scores can be detected (lower row). Open circles indicate metastasis cases; filled circles, GBM cases.