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.