PET quantitation and imaging of the non-pure positron-emitting iodine isotope 124I

A series of PET studies using phantoms is presented to characterize the imaging and quantitative performance of the positron-emitting iodine isotope 124I. Measurements were performed on the 2D-PET scanner GE 4096+ as well as on the Siemens PET scanner HR+ operated in both 2D and 3D modes. No specific correction was applied for the γ-rays emitted together with the positrons. As compared to 18F, in studies with 124I there is a small loss of image resolution and contrast, and an increase in background. The quantitative results varied between different scanners and various acquisition as well as reconstruction modes, with an average relative difference of −6±13% (mean±SD) in respect of the phantom radioactivity as measured with γ-ray spectroscopy. We conclude that quantitation of a radiopharmaceutical labelled with 124I is feasible and may be improved by the development of specific corrections.