Aperture Optimization in Emission Imaging Using Optimal LROC Observers

Optimal decision strategies for detection tasks using mathematical ideal observers are useful in system optimization in emission imaging. For the familiar 2-class detection problem (signal present/absent), ideal (and approximately ideal) observers have been applied to optimization of pinhole and collimator parameters in planar emission imaging. Such experiments, albeit with rather simple imaging systems, yield insights as to the roles played by Poisson data noise and object noise (i.e. stochastic background and signal variabilities) in system design. In this work, we consider a fundamentally different task in which the observer is required to both detect and localize a signal. This task is more clinically realistic than detection only, and it is natural to inquire whether the addition of a localization requirement changes conclusions on system design. We have previously formulated an optimal decision strategy and associated ideal observer for this joint detection/localization task, and here we apply it to the classic problem of determining an optimal pinhole diameter in a planar imaging system. We conclude that as the allowed search tolerance on the localization task decreases, the optimal pinhole size shrinks from that required by detection alone. However, as background variability increases, the optimal pinhole sizes for detection only and detection + localization approach one another.