Comparison of Two Inverse Planning Algorithms for Cervical Cancer Brachytherapy

Abstract

Purpose: To compare two methods, the hybrid inverse planning optimization (HIPO) algorithm and the inverse planning simulated annealing (IPSA) algorithm, for cervical cancer brachytherapy and provide suggestions for their usage.Material and methods: This study consisted of 24 cervical cancer patients treated with CT image-based high-dose-rate brachytherapy using various combinations of tandem/ovoid applicator and interstitial needles. For fixed catheter configurations, plans were retrospectively optimized with two methods: IPSA and HIPO. The dosimetric parameters with respect to target coverage, localization of high dose volume (LHDV), conformal index (COIN), and sparing of organs at risk (OARs) were evaluated. A plan assessment method which combines a graphical analysis and a scoring index was used to compare the quality of two plans for each case. The characteristics of dwell time distributions of the two plans were also analyzed.Results: Both IPSA and HIPO can produce clinically acceptable treatment plans. The rectum D2cc was slightly lower for HIPO as compared to IPSA (p=0.002). All other dosimetric parameters for targets and OARs were not significantly different between the two algorithms. The generated radar plots and scores intuitively presented the plan properties and enabled to reflect the clinical priorities for the treatment plans. Different characteristics were observed between the dwell time distributions generated by IPSA and HIPO. Conclusions: Despite significant difference in dwell time distributions, both the two algorithms could generate high-quality treatment plans. With the help of the plan assessment method, the clinical decision on the optimal plan can be made quickly and consistently for each patient.

Mathematical Models Used for Brachytherapy Treatment Planning Dose Calculation Algorithms

“…The application of an inverse planning algorithm 23 is to find the minimum value of a combined objective function based on a group of predefined objectives of the dose. As compared to forward planning, inverse planning has few benefits like less time required for treatment planning, good reproducibility, more target coverage, and less dose to organs at high risk.…”