Imaging Characteristics of $^{124}$I Between 3D and 2D on Siemens ECAT HR${+}$ PET Scanner

124I has a complex decay scheme with high gamma energy and low positron abundance. In this study, comparative performance measurements of 124I were performed in terms of spatial resolution, sensitivity, and image quality. All measurements were performed using both 2D and 3D PET in both brain mode and whole body mode. The transverse and axial spatial resolutions at 1 cm were 5.56 and 6.07 mm for 124I, and were 4.58 and 4.77 mm and for 18F, respectively. Sensitivities were 0.5 kcps/MBq (2D) and 3.4 kcps/MBq (3D) for 124I, and 1.8 kcps/MBq (2D) and 9.8 kcps/MBq (3D) for 18F. The %contrast of 3D was higher than that of 2D in 124I. For 124I PET imaging, 3D acquisition with brain mode was highest achievable imaging acquisition mode with finer spatial resolution and higher contrast. This result will be useful for 124I PET imaging.