Convolution technique in beta dosimetry for radioimmunotherapy

A computer simulation for treatment planning suitable to RIT has been studied. The new convolution technique we adopted in our calculational method has the advantage, comparing with the previous ones, of accepting any distribution of activity in source volume. For the electrons absorbed fraction calculation, the EGS (electron gamma shower) Monte Carlo code is used to generate point source kernel in the form of lookup tables. We present the dose rate profiles calculated for the radionuclides beta emitters used in radioimmunotherapy for various tumour shapes and sizes, and for different distributions of radioactivity. Radionuclide and radioactivity quantitation selections are governed by the need to deliver enough high doses to tumour regions (also to those regions which have less radioactivity accumulation) and to minimize the dose to the surrounding tissues and to critical organs. The time-dose fractionation modality is advanced with an approach based on the linear-quadratic model with repair rates, biological half-lives of antibodies, physical half-lives of the radionuclides, dose rates and total doses needed for a given biologically effective dose