Fundamental study for SPECT imaging with 123I produced by (p, 5n) reaction

The effects of higher-energy photon from 123I (p, 5n) on the SPECT image quality were evaluated. The quality was evaluated by image contrast and %rms. Image contrast had similar tendency to planar and SPECT FWHM value. %rms was affected by septal penetration. Using 140 keV high resolution collimator (140 keV HR), image contrast was superior to that for 300 keV medium energy collimator (300 keV ME), but septal penetration rate (SPR) was 18% and %rms was 10.5. When quantitation is required, the collimator with less SPR than 18% is recommended for SPECT imaging. Using 300 keV ME, SPR was 0.05%, but spatial resolution and image contrast were inferior to that for 140 keV HR.