Left panel (true progression [TP]): the axial postcontrast T1-weighted image demonstrates a nodular contrast-enhancing lesion in the left temporal lobe. The square box overlaid on the enhancing lesion is a combination of 16 voxels (nominal voxel size = 4.3 × 4.3 × 5.6 mm3). Corresponding summed 1H MRS spectrum from these 16 voxels exhibiting various metabolites. Right panel (pseudoprogression [PsP]): the axial postcontrast T1-weighted image shows a heterogeneously enhancing lesion in the right more than left frontal lobes involving the genu and body of corpus callosum. The square box overlaid on the enhancing lesion is a combination of 16 voxels (nominal voxel size = 4.3 × 4.3 × 5.6 mm3). Corresponding summed 1H MRS spectrum from these 16 voxels exhibiting various metabolites. Please note the presence of higher Cho/NAA and Cho/Cr ratios in TP than in PsP. Both these patients were scanned on a 3-T MR system after the completion of maximal resection of tumor followed by standard-of-care chemoradiation therapy and were exhibiting new contrast-enhancing lesion in the resection bed within 6 months of standard treatment. The whole-brain 1H MRS was acquired using a three-dimensional echoplanar spectroscopic imaging sequence (a modified spin-echo sequence with GRAPPA). The typical sequence parameters were: repetition time/echo time = 1700/17.6 ms; scanning time = ~17 min that included interleaved acquisition of metabolite and water reference scans. Cho, choline; Cr, creatine; Glx, glutamate + glutamine; mI, myo-inositol; NAA, N-acetylaspartate