Catheters and dose optimization using a modified CVT algorithm and multi‐criteria optimization in prostate HDR brachytherapy

Abstract

Purpose: Currently, in high-dose rate (HDR) brachytherapy planning, the catheter's positions are often selected by the planner, which involves the planner's experience. The catheters are then inserted using a template that helps to guide the catheters. For certain applications, it is of interest to choose the optimal location and number of catheters needed for dose coverage and potential decrease of the treatment's toxicity. Hence, it is of great importance to develop patient-specific algorithms for catheters and dose optimization. Methods: A modified Centroidal Voronoi tessellation (CVT) algorithm is implemented and merged with a graphics processing unit (GPU)-based multi-criteria optimization algorithm (gMCO). The CVT algorithm optimizes the catheters' positions,and the gMCO algorithm optimizes the dwell times and dwell positions. The CVT algorithm can be used simultaneously for insertion with or without a template. Some improvements to the CVT algorithm are presented such as a new way of considering the area that needs to be covered. One hundred eight previously treated prostates HDR cases using real-time ultrasound are used to evaluate the different optimization procedures. The plan robustness is evaluated using two types of errors:deviations (random) in the insertion and deviation (systematic) in the reconstruction of the catheters. Results: Using gMCO on clinically inserted catheter increases the acceptance rate by 37% for Radiation Therapy Oncology Group (RTOG) criteria. Our results show that all the patients respect RTOG criteria with 11 catheters using CVT+gMCO with a template of 5 mm. The number of catheters needed for all patients to respect RTOG criteria with the freehand technique is 10 catheters using CVT+gMCO. When deviations are introduced, using a template, the acceptance rate goes to 85% with 3 mm deviations using 11 catheters. This decrease is less significant when the number of catheters is higher, decreasing by less than 5% with a 3 mm deviation using 13 catheters or more. In conclusion, it is feasible to decrease the number of catheters needed to treat most patients. Conclusions: Some cases still need a high number of catheters to reach the plan's criteria. Using gMCO allows an increase in the plan quality, while using CVT reduces the number of catheters. A higher number of catheters equates to plans that are more robust to deviations.

Simultaneous catheter and multicriteria optimization for HDR cervical cancer brachytherapy with a complex intracavity/interstitial applicator

“…First, most of studies in HDR prostate involved parallel catheter configurations (template-based or freehand). 9,11,13,17,19 Siauw et al proposed non-parallel catheter optimization with integer programming for HDR prostate (purely geometric optimization), 16 but did not implement simultaneous dose and catheter optimization as proposed in this study. With the Venezia applicator, non coplanar catheter configurations need to be optimized (i.e., perineal template, and parallel and oblique ring catheters are not in the same plane); the results show that the proposed sparse method can handle these types of complex configurations.…”

“…Similar conclusions were also observed in a previous study involving a modified CVT algorithm combined with MCO for HDR prostate. 19 Nonetheless, the design of the SC+MCO algorithm is flexible and offers different catheter configurations (number and position) for the user to choose from. Using more catheters increases plan quality (i.e., EMBRACE II acceptance rate in soft constraints in Figure 3), but with the trade-off of increased risk of inducing more pain, bleeding, and infections.…”

“…These algorithms includes genetic algorithm, 9 compressed sensing-based (or sparse) methods, 10,11 mixed integer linear programming (MILP), 12,13 heuristics such as variable neighborhood search (VNS) 14 or hybrid inverse planning optimization (HIPO). 15 Purely geometric methods such as needle planning by integer programming (NPIP) 16 and centroidal voronoi tessalation (CVT) [17][18][19] have also been proposed.…”

“…Catheter optimization also enables the possibility to reduce the number of catheters while maintaining high plan quality. 19 This could be advantageous given that higher pain scores and larger volume of vaginal bleeding were observed with increased number of IS catheters. 29 A lower number of catheters could also reduce the risk of errors, and reduce the overall procedure time and cost.…”

Robust stochastic optimization of needle configurations for robotic HDR prostate brachytherapy

“…Including the optimization of needle configurations in the inverse treatment planning problem has been proposed before. [14][15][16][17][18][19] However, a major unaddressed challenge in the context of prostate BT is the tissue deformation and displacement during the insertion which may influence the position and shape of the prostate and OARs. 20 Additionally, the deviation between the planned and actually inserted needle position can influence the dose distribution.…”