A Fast Dosimetric Optimization Method of Intensity Modulated Brachytherapy(IMBT) Treatment Plans for Cervical Cancer
Abstract
Purpose
Intensity-modulated brachytherapy (IMBT) is an innovative technique aimed at achieving anisotropic dose distributions in brachytherapy. This study develops a fast dosimetric optimization method specifically for IMBT plans in cervical cancer.
Methods
The method combines GPU-based dose matrix calculations with a conjugate gradient (CG) algorithm to optimize dwell times. Dose matrices are computed using ARCHER-IMBT, a high-speed Monte Carlo (MC) code, validated against the well-established MC code--TOPAS. Optimization tests using Ir-192 and 50 kVp X-ray sources were conducted on six intracavitary brachytherapy (IC-BT) cases by approximating TG-43(WA) and TG-186 methods. Furthermore, the feasibility of reducing needle use was evaluated by assessing IMBT plans without needles for an intracavitary/interstitial (IC/IS-BT) case.
Results
ARCHER-IMBT demonstrated high dosimetric consistency with TOPAS while achieving substantial speedup factors exceeding 350x for clinical ICBT cases. For WA dose calculations, CG optimization require 53.4±26.5s on average. Compared with clinical IC-BT plans, IMBT plans reduce bladder and rectum D2cc by 6.2% and 30.2% for Ir-192, and by 4.7% and 47.9% for 50 kVp X-rays with TG-186 results showing minimal relative differences (−0.86% to −4.72%) from WA. For the IC/IS-BT case, both X-ray IMBT plans meet prescription goals. However, the 50 kVp plan exhibits a notable rise in CTV V200%, which the 80 kVp plan effectively mitigates, producing a smaller high-dose region.
Conclusion
In this study, we proposed and validated a comprehensive workflow for IMBT treatment plan optimization by integrating a newly developed MC engine, ARCHER-IMBT, with the conjugate gradient (CG) method. This method enables high-quality IMBT plan generation for cervical cancer with clinically acceptable speeds, exhibiting the dosimetric characteristics of IMBT and suggesting its potential as a non-invasive alternative to costly interstitial needle insertions.