Abstract
The purpose of this study is to investigate the effectiveness of the HIPO planning and optimization algorithm for real‐time prostate HDR brachytherapy. This study consists of 20 patients who underwent ultrasound‐based real‐time HDR brachytherapy of the prostate using the treatment planning system called Oncentra Prostate (SWIFT version 3.0). The treatment plans for all patients were optimized using inverse dose‐volume histogram–based optimization followed by graphical optimization (GRO) in real time. The GRO is manual manipulation of isodose lines slice by slice. The quality of the plan heavily depends on planner expertise and experience. The data for all patients were retrieved later, and treatment plans were created and optimized using HIPO algorithm with the same set of dose constraints, number of catheters, and set of contours as in the real‐time optimization algorithm. The HIPO algorithm is a hybrid because it combines both stochastic and deterministic algorithms. The stochastic algorithm, called simulated annealing, searches the optimal catheter distributions for a given set of dose objectives. The deterministic algorithm, called dose‐volume histogram–based optimization (DVHO), optimizes three‐dimensional dose distribution quickly by moving straight downhill once it is in the advantageous region of the search space given by the stochastic algorithm. The PTV receiving 100% of the prescription dose (V100) was 97.56% and 95.38% with GRO and HIPO, respectively. The mean dose (Dmean) and minimum dose to 10% volume (D10) for the urethra, rectum, and bladder were all statistically lower with HIPO compared to GRO using the student pair t‐test at 5% significance level. HIPO can provide treatment plans with comparable target coverage to that of GRO with a reduction in dose to the critical structures.PACS number: 87.55.‐X
Highlights
Radiation therapy has been a primary treatment modality for the management of adenocarcinoma of the prostate either as a sole treatment or in combination with other treatment modalities like surgery and hormonal therapy.[1,2,3] The last decade has witnessed a dramatic improvement in the way radiation therapies are delivered.[4]
The V150 and V200 are both significantly bigger in plans optimized by graphical optimization (GRO), as compared to plans optimized by HIPO1 (Table 1 and Fig. 6)
Both Homogeneity Index (HI) and Conformal Index (COIN) are significantly higher in plans optimized by HIPO1 compared to plans optimized by GRO (Table 1 and Fig. 7)
Summary
Radiation therapy has been a primary treatment modality for the management of adenocarcinoma of the prostate either as a sole treatment or in combination with other treatment modalities like surgery and hormonal therapy.[1,2,3] The last decade has witnessed a dramatic improvement in the way radiation therapies are delivered.[4]. 97 Pokharel et al.: HIPO for HDR brachytherapy of prostate and minimize the normal tissue complication probability (NTCP) within a clinically reasonable amount of time These two objectives are in conflict with each other and cannot be ideally optimized simultaneously.[5]. The main concern is to deliver the prescription dose (PD) to the planning target volume (PTV) accurately, keeping dose to the surrounding critical structures as low as possible to prevent treatmentrelated complications. In such optimizations, biological aspects are understood to be implicitly embedded in the physician’s prescription
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