Precise ex vivo histological validation of heightened cellularity and diffusion-restricted XXXX in regions of dark apparent diffusion coefficient in 7 cases of high-grade @entity11 .

@entity1 @entity39 @entity5 @entity1313 @entity4 @entity11 @entity1653 @entity204
BACKGROUND: Recent conflicting reports have found both @entity1313 hypercellularity and @entity39 in regions of restricted diffusion on MRI-derived apparent diffusion coefficient (ADC) images. This study precisely compares ADC and cell density voxel by voxel using postmortem @entity1 whole brain samples. METHODS: @entity1 with @entity1653 were evaluated to determine a normative ADC distribution within benign fluid attenuated inversion recovery (FLAIR) T2/hyperintensity surrounding @entity5 . This distribution was used to calculate a minimum ADC threshold to define regions of ADC-FLAIR mismatch (AFMM), where restricted diffusion presented in conjunction with T2/FLAIR hyperintensity. Contrast-enhancing voxels were excluded from this analysis. AFMM maps were generated using imaging acquired prior to @entity204 in 7 @entity1 with high-grade @entity11 who eventually donated their brains upon @entity204 . Histological samples were taken from numerous regions of abnormal FLAIR and AFMM. Each sample was computationally processed to determine cell density. Custom software was then used to downsample coregistered microscopic histology to the more coarse MRI resolution. A voxel-by-voxel evaluation comparing ADC and cellularity was then performed. RESULTS: An ADC threshold of 0.929   10(-3) mm(2)/s was calculated from @entity1653 -induced @entity4 and was used to define AFMM. Regions of AFMM showed significantly greater cell density in 6 of 7 high-grade @entity11 cases compared with regions of hyperintense FLAIR alone (P < .0001). Two @entity1 had small regions of diffusion-restricted @entity39 that had significantly lower ADC than nearby hypercellularity. CONCLUSIONS: Regions of AFMM contain hypercellularity except for regions with extremely restricted diffusion, where @entity39 is present.
