Description of an object in Monte Carlo simulations [SPECT application]

Object modeling is important for performing photon transport efficiently by means of a Monte Carlo method. The modeling includes a voxel-based approach which represents an object by a union of voxels of the same size and an octree based method which describes an object by using several sizes of cubic regions. The authors propose a new modeling method called the maximum rectangular region (MRR) method. In the MRR method, a maximum rectangular region for a given voxel is selected within a homogeneous, irregularly shaped region from a set of cross sections. The search is performed by checking the six sides of a box (MRR) including the voxel of interest. With the MRR representation of the object, high speed calculation of photon transport can be accomplished because one can describe the object by means of fewer regions than in the voxel-based method or the octree representation method.