Fig. 4
T-site (1-T) with low FLT-uptake: FDG-PET (axial (a), coronal (b), sagittal (c)), FLT-PET (axial (d), coronal (e), sagittal (f)), and DW-MRI (transversal (g), coronal (h), sagittal (i)), and voxel-by-voxel scatterplot of FDG-SUV vs. FLT-SUV (j). This T-site was clearly detectable on FDG-PET (SUVpeak 16.6); almost indistinguishable from background on FLT-PET (SUVpeak 1.6); and detectable on DW-MRI (ADCmedian 1.22 × 10−3 mm2/s). The low tumor-to-background ratio causes PTV70 to be less convincing, visually. MTV70 and DWTV50 had a partial overlap. The voxel-by-voxel scatter plot of FLT-SUV and FDG-SUV (j) showed an overall moderate positive correlation (r = 0.50), but the very low FLT-SUVs should be noticed, and the correlation may be a result of perfusion to the region rather than a correlation between metabolism and (a very low) proliferation. Voxel-by-voxel analysis was not feasible for FLT-SUV vs. ADC. This T-site had complete response to chemotherapy, and did not relapse during follow up