A fast dosimetric optimization method of intensity modulated brachytherapy (IMBT) treatment plans for cervical cancer

Objective.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.Approach.ARCHER-IMBT was validated against TOPAS in both water phantoms and clinical geometries. Optimization was performed for six intracavitary (IC-BT) cases and one intracavitary/interstitial (IC/IS-BT) case, comparing 50 kVp x-ray and Ir-192 sources. The study also explored the potential of IMBT to achieve comparable dosimetry to IC/IS-BT using only intracavitary applicators. Furthermore, a stochastic uncertainty analysis (200 Monte Carlo scenarios) was conducted to evaluate plan robustness against positional (0.3 mm) and angular (0.2°) perturbations.Main results.ARCHER-IMBT achieved speedup factors exceeding 50× for water phantoms and 350× for clinical cases, with gamma passing rates >98%. The entire optimization process was completed within one minute. Compared to IC-BT, IMBT plans reduced bladder and rectumD_2ccby 3.1% and 15.1% for Ir-192, and by 23.4% and 22.8% for 50 kVp x-rays, respectively. In the IC/IS-BT case, IMBT plans achieved comparable target coverage while potentially eliminating the need for invasive needles. However, uncertainty analysis revealed that the 50 kVp source is highly sensitive to sub-millimeter translational errors (0.3 mm) due to its steep dose gradients, whereas Ir-192 exhibited greater robustness.Significance.This study demonstrates a computationally efficient IMBT optimization platform. The findings highlight the dosimetric benefits of IMBT and its potential to simplify complex IC/IS-BT procedures, while underscoring the stringent mechanical precision required for clinical implementation.