A method for determination of radionuclide S values for any voxel size for dosimetry of nonuniform activity distribution

The most widely extended method to determine the macroscopic nonuniform dose distribution is the dose-point convolution method because is less demanding of computational requirements than Monte Carlo Transport (MCT) method and the limited availability of S values for any voxel size. The use of S values at voxel level offers a convenient tool for absorbed dose estimation similar to the MIRD schema for organ dosimetry. In this work, we present a method for rapid determination of radionuclide S values for any voxel size based on 3D Discrete Fourier Transform (3D-DFT) convolution method. The dose calculation using these S voxel values was validated by comparison with the radial dose profile obtained from Monte Carlo Transport (MTC) method based on MCNP4B code for mathematical phantoms consisted of spheres of different size containing uniform and nonuniform cumulated activity distribution. Our results demonstrated that the dose calculation based on S voxel values generated by 3D-DFT convolution is as accurate as MCT method and is computationally much more efficient and hence can be used as the method of choice to provide S values that correspond to the voxel geometry of any imaging data in clinical routine