title: An improved method for rebinning kernels from cylindrical to Cartesian coordinates.
abstract: This paper describes the errors in rebinning photon dose point spread functions and pencil beam kernels (PBKs) from cylindrical to Cartesian coordinates. An area overlap method, which assumes that the fractional energy deposited per unit volume remains constant within cylindrical voxels, provides large deviations (up to 20%) in rebinned Cartesian voxels while conserving the total energy. A modified area overlap method is presented that allows the fractional energy deposited per unit volume within cylindrical voxels to vary according to an interpolating function. This method rebins the kernels accurately in each Cartesian voxel while conserving the total energy. The dose distributions were computed for a partially blocked beam of uniform fluence using the Cartesian coordinate kernel and the kernels rebinned by both methods. The kernel rebinned by the modified area overlap method provided errors less than 1.7%, while the kernel rebinned by the area overlap method gave errors up to 4.4%.
authors.affiliation: Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Rathee
authors.forename: B A
authors.initials: BA
authors.lastname: McClean
authors.forename: C
authors.initials: C
authors.lastname: Field
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D003198:Computer Simulation; D006801:Humans; D008962:Models, Theoretical; D009010:Monte Carlo Method; D017785:Photons; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods* / Q000706:statistics & numerical data