Calculation Algorithm of Three-dimensional Absorbed Dose Distribution in Non-water Equivalent Tissue Due to Administration of Radio-labeled Antibody

In radioimmunotherapy, an algorithm is proposed for the purpose of calculating three-dimensional absorbed dose distributions of non-water equivalent tissues. The three-dimensional absorbed dose distribution due to the algorithm, is given by convolution of the threedimensional dose matrix for a unit cubic voxel containing unit cumulated activity, with the three-dimensional matrix of the cumulated activity distribution given by the same voxel size above. The three-dimensional dose matrix for the unit voxel source, is calculated from the β- or photon-dose point kernel in the corresponding tissue. Present work theoretically showed that β- and photon-dose point kernels in non-water equivalent tissue can be calculated by applying a scaling factor on distance to each dose point kernel in water. In consequence, present calculation algorithm is essentially the same as the algorithm for water that authors have already developed. Computer simulations were performed using the MIRD lung phantom, and the agreement obtained between the results of present work and the MIRD method, supported the validity of the proposed calculation algorithm.