DEVELOPING A DOSE-VOLUME HISTOGRAM COMPUTATION PROGRAM FOR BRACHYTHERAPY

A dose-volume histogram (DVH) computation program was developed for br achytherapy treatment planning in an attempt to benefit from the DVH's ability to present graphically information on 3D dose distributions. The program is incorporated into a planning system that utilizes a pai r of orthogonal radiographs to localize the radiation sources. DVHs ar e calculated for the volume of tissue enclosed by an isodose sur-face (e.g. half the value of the reference isodose). The calculation algori thm is I,based on a non-uniform random sampling that gives a denser po int distribution at the centre of the implants. Our program was tested and proved to be fast enough for clinical use and sufficiently accura te (i.e. computation time of 20 s and less than 2% relative error for one point source, for 100000 calculation points). The accuracy improve s when a larger calculation point number is used, but the computation time also increases proportionally. The DVH is presented in the form o f a simple graph or table, or as Anderson's 'natural' DVH graph. The c umulative DVH tables can be used to extract a series of indexes charac terizing the homogeneity and the dose levels of the distribution in th e treatment volume and the surrounding tissues. If a reference plan is available, the DVH results can be assessed relative to the reference plan's DVH.