A seed specific dose kernel method for low‐energy brachytherapy dosimetry

We describe a method for independently verifying the dose distributions from pre‐ and post‐implant brachytherapy source distributions. Monte Carlo calculations have been performed to characterize the three‐dimensional dose distribution in water phantom from a low‐energy brachytherapy source. The calculations are performed in a voxelized, Cartesian coordinate geometry and normalized based upon a separate Monte Carlo calculation for the seed specific air‐kerma strength to produce an absolute dose grid with units of [Formula: see text]. The seed‐specific, three‐dimensional dose grid is stored as a text file for processing using a separate visual basic program. This program requires the coordinate positions of each seed in the pre‐ or post‐plan and sums the kernel file for a three‐dimensional composite dose distribution. A kernel matrix size of [Formula: see text] with a voxel size of [Formula: see text] was chosen as a compromise between calculation time, kernel size, and truncation of the stored dose distribution as a function of radial distance from the midpoint of the seed. Good agreement is achieved for a representative pre‐ and post‐plan comparison versus a commercial implementation of the TG‐43 brachytherapy dosimetry protocol. © 2003 American College of Medical Physics. PACS number(s): 87.53.‐j, 87.52.‐g