Anthony Redpath1. 1. Department of Oncology Physics, Clinical Oncology Department, Lothian Hospitals University NHS Trust, Crewe Road South, Edinburgh, UK.
Abstract
BACKGROUND AND PURPOSE: Brachytherapy using 125I Rapid Strand as a permanent implant is now widely used for the treatment of prostate cancer. Manual treatment planning can be time-consuming and has provided the incentive to develop a computer planning algorithm for automatically determining the needle positions and source loading required to produce a clinically acceptable dose distribution. MATERIALS AND METHODS: The algorithm uses a method analogous to that used in simulated annealing. A needle with associated source positions is selected randomly from those possible. A number of source positional and dose volume histogram constraints for the prostate, rectum and urethra have to be satisfied before an objective function is evaluated that provides a measure of the dose distribution to the prostate. The objective function is gradually improved using an iterative process until a final solution is reached. RESULTS AND CONCLUSION: The algorithm is used to plan six patients which have previously been manually planned and which are selected to represent the range of prostate volumes encountered in practice. A clinically acceptable dose distribution is obtained that is shown to be as good as manual planning in all cases.
BACKGROUND AND PURPOSE: Brachytherapy using 125I Rapid Strand as a permanent implant is now widely used for the treatment of prostate cancer. Manual treatment planning can be time-consuming and has provided the incentive to develop a computer planning algorithm for automatically determining the needle positions and source loading required to produce a clinically acceptable dose distribution. MATERIALS AND METHODS: The algorithm uses a method analogous to that used in simulated annealing. A needle with associated source positions is selected randomly from those possible. A number of source positional and dose volume histogram constraints for the prostate, rectum and urethra have to be satisfied before an objective function is evaluated that provides a measure of the dose distribution to the prostate. The objective function is gradually improved using an iterative process until a final solution is reached. RESULTS AND CONCLUSION: The algorithm is used to plan six patients which have previously been manually planned and which are selected to represent the range of prostate volumes encountered in practice. A clinically acceptable dose distribution is obtained that is shown to be as good as manual planning in all cases.