On the possibility of ‘real-time’ Monte Carlo calculations for the estimation of absorbed dose in radioimmunotherapy

Abstract

Dosimetry calculations of monoclonal antibodies (MABs) are made difficult because the focus of radioactivity is targeted for a nonstandard volume in a nonstandard geometry, precluding straighforward application of the MIRD formalism. The MABDOS software addresses this shortcoming by interactive placement of a spherical perturbation into the Standard Man geometry for each tumor focus. S tables are calculated by a Monte Carlo Simulation of photon transport for each organ system (including tumor) that localizes activity. Performance benchmarks are reported that measure the time required to simulate 60 000 photons for each penetrating radiation in the spectrum of 99mTc and 131I using the kidney as source organ. Results indicate that calculation times are probably prohibitive on current microcomputer platforms. Mini and supercomputers offer a realistic platform for MABDOS patient dosimetry estimates.