Comparison of scandium-44 g with other PET radionuclides in pre-clinical PET phantom imaging

Purpose The decay characteristics of radionuclides in PET studies can impact image reconstruction. 44g Sc has been the topic of recent research due to potential theranostic applications and is a promising radiometal for PET imaging. In this study, the reconstructed images from phantom measurements with scandium in a small-animal PET scanner are compared with 18 F and two prominent radiometals: 64 Cu and 68 Ga Methods Three phantoms filled with 18 F, 64 C, 68 Ga, and 44g Sc were imaged in the Siemens Inveon PET scanner. The NEMA image quality phantom was used to determine the recovery coefficients (RCs), spill-over ratios (SORs), and noise (%SD) under typical pre-clinical imaging conditions. Image contrast was determined using a Derenzo phantom, while the coincidence characteristics were investigated using an NEC phantom. Three reconstruction algorithms were used, namely filtered back projection (FBP), ordered subset expectation maximization (OSEM), and maximum a-posteriori (MAP). Results Image quality parameters were measured for 18 F, 64 Cu, 68 Ga, and 44g Sc respectively; using FBP, the %SD are 5.65, 5.88, 7.28, and 7.70; the RCs for the 5-mm rod are 0.849, 1.01, 0.615, and 0.825; the SORs in water are 0.0473, 0.0595, 0.141, 0.0923; and the SORs in air are 0.0589, 0.0484, 0.0525, and 0.0509. The contrast measured in the 2.5-mm rods are 0.674, 0.637, 0.196, and 0.347. The NEC rate with 44g Sc increased at a slower rate than 18 F and 68 Ga as a function of activity in the field of view. Conclusion 44g Sc demonstrates intermediate behavior relative to 18 F and 68 Ga with regard to RC and contrast measurements. It is a promising radionuclide for preclinical imaging.