Example of a multimodal (F-18 ML-10 PET and sodium MRI), multitime-point (BL and ETA) assessment of GBM therapy response. Subject 4's ETA contrast-enhanced MRI (A) was used to define an ROI around the tumor. The ROI was applied to the same-time coregistered sodium (Na) MR and F-18 ML-10 PET scans at the BL and ETA time points. A scatterplot was used to evaluate multiparameter change for the contrast-enhanced MRI-guided ROI (B). Differences were represented in a four-quadrant scatterplot by assigning each voxel within the tumor ROI a particular color corresponding to scatterplot class (class I, blue; class II, green; class III, yellow; and class IV, red). To spatially localize changes, color-coded change maps were generated for the ROI volume and fused to the ETA contrast-enhanced MRI. Plate (C) shows a contrast-enhanced MRI section with the color-coded change parameters (color code is same as in B). Plate (D) shows a zoomed-in version of C.