Source distribution in adjoint Monte Carlo calculation

Keh-Shih Chuang ,Hong-Long Tzeng

With the popularity of intensity modulated radiation therapy (IMRT), inverse treatment planning (Oldham et al 1995) becomes more important than before. One way to perform inverse treatment planning is to use adjoint Monte Carlo simulation (Chen and Chou 1998, Difilippo 1998). The paper ‘Monte Carlo-based inverse treatment planning’ by Jeraj and Keall (1999) appeared to be an interesting work. In the paper, photons in the target volume were transported, using an adjoint Monte Carlo method, to outside the patient surface to build up an intensity distribution which was then used as an initial input to an optimization algorithm. However, the source distribution in the target volumewas not properly handled in theirwork. In this letter, we would like to address the following viewpoints regarding the source distribution.