IPIP: A new approach to inverse planning for HDR brachytherapy by directly optimizing dosimetric indices

Abstract

Purpose: Many planning methods for high dose rate (HDR) brachytherapy treatment planning require an iterative approach. A set of computational parameters are hypothesized that will give a dose plan that meets dosimetric criteria. A dose plan is computed using these parameters, and if any dosimetric criteria are not met, the process is iterated until a suitable dose plan is found. In this way, the dose distribution is controlled by abstract parameters. The purpose of this study is to improve HDR brachytherapy planning by developing a new approach that directly optimizes the dose distribution based on dosimetric criteria.Method: We develop Inverse Planning by Integer Program (IPIP), an optimization model for computing HDR brachytherapy dose plans and a fast heuristic for it. We used our heuristic to compute dose plans for 20 anonymized prostate cancer patient image data sets from our clinic database. Dosimetry was evaluated and compared to dosimetric criteria.Results: Dose plans computed from IPIP satisfied all given dosimetric criteria for the target and healthy tissue after a single iteration. The average target coverage was 95%. The average computation time for IPIP was 30.1 seconds on a Intel(R) Core T M 2 Duo CPU 1.67 GHz processor with 3 Gib RAM.Conclusion: IPIP is an HDR brachytherapy planning system that directly incorporates dosimetric criteria. We have demonstrated that IPIP has clinically acceptable performance for the prostate cases and dosimetric criteria used in this study, both in terms of dosimetry and runtime. Further study is required to determine if IPIP performs well for a more general group of patients and dosimetric criteria, including other cancer sites such as GYN.

Initial experiments toward automated robotic implantation of skew-line needle arrangements for HDR brachytherapy

“…There has been studies in automating each of these steps. For example, there has been extensive effort in developing planning systems for computing optimal dose distributions for both PPI-and HDR-BT [17,18,19,20,21,22]. These dose planning systems allow physicians to compute dose distributions without directly adjusting the dwell times to meet treatment objectives.…”

“…Dose plans were optimized to a given needle arrangement using Inverse Planning by Integer Program (IPIP), a dose planning optimization model that directly optimizes dosimetric indices. The IPIP model and optimization parameters were the same as in [22]. A prescription dose of 950 cGy was applied to all planning cases, which is a common prescription dose for prostate HDR-BT.…”

Robot-Guided Open-Loop Insertion of Skew-Line Needle Arrangements for High Dose Rate Brachytherapy

“…Existing research has explored planning systems for computing optimal dose distributions for both PPI-and HDR-BT [20], [21], [22], [23], [24], [11]. Since the set of possible dose distributions depends on the implanted needle arrangement, planning systems like Prostate Implant Planning Engine for Radiotherapy (PIPER) [20] and Hybrid Inverse Planning and Optimization (HIPO) [24] incorporate the positioning of needles into their dose planning model.…”

“…AND DOSE DISTRIBUTIONS To plan skew-line needle arrangements and dose plans, we modified the NPIP needle planning algorithm [12] to use a more comprehensive sample set of candidate needles and we incorporated it with the IPIP dose planning algorithm [11]. These references include details on these planners with experiments and sensitivity analysis.…”

“…In previous work, we developed the IPIP algorithm to compute HDR-BT dose plans [11] and the NPIP algorithm for computing skew-line needle arrangements [12]. In simulation we have shown that these algorithms can generate patient-specific skew-line needle arrangements that avoid sensitive organs and meet treatment dose objectives.…”