Figure 4.

Average pH_e values across all animals in ROIs positioned at increasing distances from the tumor center. The T₂ map for each animal was used to mask the tumor and determine its center of mass. The brain was then segmented into ROIs (A) defined by the distance from the corresponding voxel to the center of mass of the tumor. Each ROI was defined as the area bounded by two circles of radius n-1 mm to n mm from the center of mass of the tumor (n = 1 to 10). The average pH_e value for each animal was calculated from the pH_e values from all voxels inside each ROI. Then, the average pH_e values and the corresponding SDs (indicated as the error bar) across animals were calculated for each ROI (B). The boundaries between the intratumoral and the peritumoral regions (shown with white and black arrows for the treated and untreated groups, respectively) were calculated from the average tumor volume obtained from the anatomical MR images (Fig. 1B), assuming a spherical tumor shape.