Planar and SPECT Monte Carlo acceleration using a variance reduction technique in I131 imaging

Background: various variance reduction techniques such as forced detection (fd) have been implemented in monte carlo (mc) simulation of nuclear medicine in an effort to decrease the simulation time while keeping accuracy. however most of these techniques still result in very long mc simulation times for being implemented into routine use. materials and methods: convolution-based forced detection (cfd) method as a variance reduction technique was implemented into the well known simind mc photon simulation software. a variety of simulations including point and extended sources in uniform and non-uniform attenuation media, were performed to compare differences between fd and cfd versions of simind modeling for i131 radionuclide and camera configurations. experimental measurement of system response function was compared to fd and cfd simulation data. results: different simulations using the cfd method agree very well with experimental measurements as well as fd version. cfd simulations of system response function and larger sources in uniform and non-uniform attenuated phantoms also agree well with fd version of simind. conclusion: cfd has been modeled into the simind mc program and validated. with the current implementation of cfd, simulation times were approximately 10-15 times shorter with similar accuracy and image quality compared with fd mc.