Accurate image reconstruction based on standard-Gaussian-model fitted system matrix in multipinhole small animal SPECT imaging

For multi-pinhole small animal SPECT imaging, system matrix (SM) is critical for accurate reconstruction. It is typically achieved by analytical calculation, experimental measurement, or Monte-Carlo (MC) simulation. MC simulation method is relatively accurate and avoids long-time measurements. However, to achieve high resolution for small animal reconstruction, SM should be extremely huge, and would have severe noise produced when simulation time is limited.