Dynamic high resolution imaging of rats: quantitative potentials

Finite spatial resolution and low annihilation photon detection sensitivity are studied in order to evaluate the design parameters for positron emission tomography (PET) systems built to image tracer biodistribution in rats. Simulations were run to determine the maximum dynamic counting rates likely during a typical rat blood flow study. For a tomograph with a 7.5-cm detector ring radius and 5-mm axial collimation, count densities of approximately 600 counts/voxel/s were calculated for 3-mm voxels of the brain, assuming a 10 mCi injection of /sup 15/O water. Simulations were also run to estimate recovery coefficient (RC) values for rat structures of imaging interest. For tomography with 4-mm full width at half maximum (FWHM) image resolution, RC values were approximately 1.0 for the whole brain (assuming uniform activity), approximately 1.0 for the whole heart (assuming uniform activity and no motion), and approximately 0.5 for a 2.3-mm radius spherical tumor. The limiting factor in the quantitative potential for dynamic rat imaging is the image resolution of the tomography, and this design parameter must be stringently optimized. Two high-resolution detector decoding strategies were evaluated for implementation of a two-layer BGO block detector module for use in a dedicated rat tomograph.<>