Dedicated modeling for tumor microstructure. A: Electron microscopy (EM) images of glioma guide the modeling as uncrowded spheres and the derivation of time-dependent diffusivity in this geometry. B: Estimates of extra-cellular space (ECS) in glioma using the POMACE model and correspondence to light microscopy slides. C: Discriminating between meningioma and glioma based on tumor cell shape (sticks for the former, spheres for the latter) using combined linear and spherical tensor encoding. Illustrations adapted from Reynaud, Front. Physics (A) (Reynaud, 2017), Reynaud et al., NMR in Biomed 2016 (Reynaud et al., 2016) (B) and Szczepankiewicz et al., NeuroImage 2016 (Szczepankiewicz et al., 2016) (C), with permission.