SU‐DD‐A2‐04: Use of the Adjoint Analysis Based Greedy Heuristic Algorithms in Treatment Planning for LDR Brachytherapy of the Prostate and HDR Brachytherapy Using Multicatheter Breast Implant Technique

Abstract

Purpose: To demonstrate use of the adjoint analysis based Greedy Heuristic (GH) algorithms in treatment planning for LDR brachytherapy of the prostate using directional sources and multicatheter‐HDR breast implant. Method and Materials: Two adjoint analysis based GH treatment planning tools are developed; The first, for a directional LDR brachytherapy application and the second, for a HDR‐multicatheter brachytherapy application. Both the problems have an extra degree of freedom compared with conventional, binary LDR treatment planning — the seed rotational orientation in directional LDR brachytherapy and the variable dwell‐time in HDR brachytherapy. The greedy heuristic treatment planning algorithm uses adjoint‐based ROI‐sensitivity‐fields to search for the best available source type and orientation, or dwell time increment at a source‐location in steps to build either a seed‐needle‐source‐orientation distribution or dwell‐location‐dwell‐time distribution solution non‐iteratively. The GH treatment planning for LDR technique is based on dose‐distribution optimization and that for HDR technique is based on dose‐homogeneity optimization. Results: The treatment plans generated by the greedy heuristic algorithm using the directional sources resulted in target coverage with V100 >98% and remarkably better OAR‐sparing owing to the directional dose properties of the sources, as seen from the DVH analysis and evaluation parameters comparison on 6 prostate cases when compared with conventional LDR‐brachytherapy. The multicatheter‐HDR brachytherapy dwell‐time optimization generated treatment plan with a target coverage V100 >96%, skin‐sparing (D85=4.5%), few hot‐spots and a dose homogeneity index of 0.82. Conclusion: Greedy Heuristic algorithms coupled with greedy criterions based on ROI‐sensitivity fields of dose response and dose‐homogeneity response are utilized as efficient tools for fast and reproducible treatment planning solutions in LDR and HDR brachytherapy.