Optimizing collimator resolution/sensitivity in SPECT iterative reconstruction

We present a simulations study of the collimator sensitivity/resolution compromise as it affects the image quality of hot lesions in SPECT iterative reconstruction. We investigate three parallel-beam hexagonal-hole collimators with resolution in the center of the field of view equal to 11 mm, 15 mm, and 19 mm. We scan the Esser hot-rod phantom with 60 views and we reconstruct the images using MLEM iterative reconstruction with no regularization or filtering. As the image-quality figure of merit we use the reconstructed-image contrast vs noise. We repeat the study for three levels of object-contrast (2.3, 4, and 9). We conclude that the higher-sensitivity collimator (15-mm in resolution) offers an improvement (lower noise for same contrast or higher contrast for same noise) in the reconstruction of medium-sized lesions (12-mm and 16-mm), at medium to low contrasts (4, 2.3). At high contrast (9) and low lesions sizes (8-mm) the higher resolution (11-mm) collimator is still favorable. The conclusions are task-dependent, and apply to hot lesions of the particular sizes and contrasts. Similar studies can be performed to address a range of realistic clinical problems. We intend to repeat this study for cold lesions in a cardiac anthropomorphic phantom.