Collimator choice in cardiac SPECT with I-123-labeled tracers

Background. Septal penetration of high-energy photons may degrade the quality of single photon emission computed tomography (SPECT) of the heart with iodine 123-labeled tracers. We investigated the impact of collimator choice on cardiac SPECT with I-123. Methods and Results. SPECT of a thoracic phantom containing I-123 solution was performed with a low-energy high-resolution (LEHR) collimator, special LEHR (SLEHR) collimator, and medium-energy (ME) collimator, and the cavity-to-myocardium contrast, wall thickness, and defect contrast were compared among the collimators. For all indices, use of the SLEHR collimator yielded the best results. Comparison between the LEHR and ME collimators revealed that the cavity-to-myocardium contrast and contrast for large defects were better with the ME collimator, whereas wall thickness and contrast for small defects were similar. Scatter correction by the triple-energy window method improved the indices examined; however, the superiority of the SLEHR collimator was still observed after correction. Conclusions. Collimator choice substantially influences the quality of cardiac SPECT with I-123-labeled agents, and an appropriate collimator needs to be selected in consideration of septal penetration and spatial resolution.