An empirical method to build up a model of proton dose distribution for a radiotherapy treatment-planning package

An empirical method has been developed to build up a three-dimensional proton dose model in a water phantom. The proton beam delivering this dose distribution is constructed as a group of parallel, broad monoenergetic beams. The mean and the standard deviation of their ranges are input to fit the resulting central-axis depth-dose distribution to a pre-specified shape. The model has been used in a radiotherapy treatment-planning package for comparing proton and photon plans. This dose model is approximate and adequate for comparative treatment planning, and is also usable when locally measured proton dose distribution data are not available.