IPIP: A New Approach to Inverse Planning for HDR Brachytherapy by Directly Optimizing Dosimetric Indices

摘要

Purpose: Many planning methods for high dose rate (HDR) brachytherapytreatment planning require an iterative approach. A set of computationalparameters are hypothesized that will give a dose plan that meets dosimetriccriteria. A dose plan is computed using these parameters, and if any dosimetriccriteria are not met, the process is iterated until a suitable dose plan isfound. In this way, the dose distribution is controlled by abstract parameters.The purpose of this study is to improve HDR brachytherapy planning bydeveloping a new approach that directly optimizes the dose distribution basedon dosimetric criteria. Method: We develop Inverse Planning by Integer Program (IPIP), anoptimization model for computing HDR brachytherapy dose plans and a fastheuristic for it. We used our heuristic to compute dose plans for 20 anonymizedprostate cancer patient image data sets from our clinic database. Dosimetry wasevaluated and compared to dosimetric criteria. Results: Dose plans computed from IPIP satisfied all given dosimetriccriteria for the target and healthy tissue after a single iteration. Theaverage target coverage was 95%. The average computation time for IPIP was 30.1seconds on a Intel(R) CoreTM2 Duo CPU 1.67 GHz processor with 3 Gib RAM. Conclusion: IPIP is an HDR brachytherapy planning system that directlyincorporates dosimetric criteria. We have demonstrated that IPIP has clinicallyacceptable performance for the prostate cases and dosimetric criteria used inthis study, both in terms of dosimetry and runtime. Further study is requiredto determine if IPIP performs well for a more general group of patients anddosimetric criteria, including other cancer sites such as GYN.