Collimator optimization for In-111 SPECT using performance on a detection/localization task

In SPECT, the collimator is an important component in determining reconstructed image quality. We evaluate a family of parallel-hole collimators used in In-111 octreotide imaging of neuroendocrine tumors. The evaluation is with respect to task performance on jointly detecting and localizing the tumors. In our approach, we apply on ideal observer to collimator images formed by the SIMIND Monte Carlo Program and evaluate performance without respect to a reconstruction algorithm. We show that for In-111, which radiates at 171 and 247 keV, septal penetration and septal scatter play an important role and the best performance is attained with a collimator that allows a moderate amount of penetration and scatter.