The long term aim of this research is to develop techniques for in vivo quantification of radioisotope localization in small animals in order to speed and simplify the design and evaluation of new radiolabeled pharmaceuticals. As part of another project we are completing construction of a high-resolution single photon ring tomograph modeled after SPRINT, but specifically designed for imaging 99mTc, 123I, and 131I in mice and rats with millimeter resolution. The focus of this new proposal is development and evaluation of data acquisition strategies, lower bounds, and image reconstruction algorithms for the following taskspecific objectives related initially to small animals: 1. Total organ or tumor uptake. 2. Tumor and organ dose distribution. Performance limits and estimation strategies will be developed for these tasks both for the case where there is side information available, e.g. in the form of accurate estimates of organ and tumor boundaries, and where no such information is available. Unlike the task of unconstrained image reconstruction, these tasks involve a much smaller number of task-specific parameters to be estimated and therefore better estimator statistical stability can be expected. Estimates of these parameters will initially be calculated from complete images reconstructed using constrained E-M and generalized Landweber iterative algorithms. Projection-data based lower bounds on minimum achievable estimator mean-square- error will be used to optimize data acquisition so as to provide the best tradeoff between collimator resolution and sensitivity relative to the performance of a specific estimation task.
