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

The decay characteristics of radionuclides in PET studies can impact image reconstruction. ^44gSc 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 ¹⁸F and two prominent radiometals: ⁶⁴Cu and ⁶⁸Ga METHODS: Three phantoms filled with ¹⁸F, ⁶⁴C, ⁶⁸Ga, and ^44gSc 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).

Image quality parameters were measured for ¹⁸F, ⁶⁴Cu, ⁶⁸Ga, and ^44gSc 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 ^44gSc increased at a slower rate than ¹⁸F and ⁶⁸Ga as a function of activity in the field of view.

^44gSc demonstrates intermediate behavior relative to ¹⁸F and ⁶⁸Ga with regard to RC and contrast measurements. It is a promising radionuclide for preclinical imaging.