A Monte Carlo approach to calculate dose distribution around the lineal brachytherapy sources

Monte Carlo means the statistical methods used to solve stochastic or deterministic physical or mathematical problems. The use of this technique for solving deterministic problems is indicated whenever there is no analytical solution for the problem or when this solution is very difficult or when the use of numerical methods requires an excessive amount of CPU-time. This paper describes the application of Monte Carlo methods using a computer program, called ISODOSE, which calculates isodose curves around linear radioactive sources to be used in brachytherapy treatment-planning. Brachytherapy is a special form of cancer treatment in which the radioactive source is placed near or inside the tumor, in order to produce cancer tissue necrosis. The program is written in C language, and the results will be compared to similar data obtained from a commercially available program at Hospital do Cancer de Recife (Brazil), radiation therapy institute. The use of Monte Carlo techniques in the ISODOSE program allows for plotting isodose curves around linear sources, and it is especially more precise near the borders of the source (singularities), taking less time than it would be possible by using deterministic methods. The ISODOSE program can be used for brachytherapy planning in small clinics in Recife and adjacent areas.