Monte Carlo-based inverse treatment planning

A Monte Carlo-based inverse treatment planning system (MCI) has been develo ped which combines arguably the most accurate dose calculation method (Mont e Carlo particle transport) with a 'guaranteed' optimization method (simula ted annealing). A distribution of photons is specified in the tumour volume; they are trans ported using an adjoint calculation method to outside the patient surface t o build up an intensity distribution. This intensity distribution is used a s the initial input into an optimization algorithm. The dose distribution f ront each beam element From a number of fields is pre-calculated using Mont e Carlo transport. Simulated annealing optimization is then used to find th e weighting of each beam element, to yield the optimal dose distribution Fo r the given criteria and constraints. MCI plans have been generated in various theoretical phantoms and patient g eometries. These plans show conformation of the dose to the target volume a nd avoidance of critical structures. To verify the code, an experiment was performed on an anthropomorphic phantom.