1. A method for tissue classification comprising the steps of: acquiring MRI image of a tissue to be classified; acquiring PET image of said tissue; superimposing a voxel grid on said acquired MRI and/or PET images; determining, for each voxel of said grid, at least cerebral blood volume (rCBV) parameter value, and Choline/Creatine ratio (Cho/Cr) parameter value, and apparent diffusion coefficient (ADC) parameter value based on said MRI image; determining, for each said voxel of said grid, at least maximum standardized uptake value (SUV Max) parameter value based on said PET image; comparing, for each said voxel of said grid, rCBV parameter value, Cho/Cr parameter value, ADC parameter value, and SUV Max parameter value with respective threshold values to determine parameter values that are above respective threshold values; associating a color with each said voxel of said grid based on said comparison; and classifying said tissue based on color association to each voxel of said grid, wherein each of said rCBV parameter value, said Cho/Cr parameter value, said ADC parameter value, and said SUV Max parameter value has an importance weight; and color association to each said voxel of said tissue is based on a combination of parameter values being greater than respective threshold and the importance weight of each parameter value.