TAC1 and neoplasm: Ninety minutes p.i., the tumor to blood ratio values ranged from 14–23 for 68Ga-RGD peptides and 2.8 for 68Ga-substance P. Similarly, the tumor to blood ratio 30 min and 90 min p.i. for 18F-FDG was 2.0 for both time points and 1.1 and 2.4, respectively, for 18F-FLT.