Toward fully automated pre-implantation planning for cervical cancer brachytherapy: a template-guided multi-criteria optimization framework for catheter placement and dose distribution

<i>Background and purpose.</i>Image-guided intracavitary/interstitial brachytherapy is standard for locally advanced cervical cancer (LACC), yet the lack of pre-implantation planning often leads to suboptimal catheter placement and dose distribution. A template-guided, multi-criteria optimization-based pre-implantation planning system was thus proposed, which integrates dosimetric, radiobiological, and geometric objectives.<i>Materials and methods.</i>The developed system employs an improved wish-list optimization strategy featuring a tighten-relax mechanism with hybrid constraints to enhance robustness and resolve conflicts from impractical wish-lists. It incorporates dose-volume indices, the generalized equivalent uniform dose, and a novel total conformity index, while supporting oblique catheter insertions for improved dose conformation. Dosimetric performance was benchmarked against clinical approved plans in 40 LACC cases, focusing on target coverage, conformity, and organ-at-risk sparing.<i>Results.</i>Compared to the catheter configurations in clinically approved plans, the proposed method resulted in catheter displacement exceeding 5 mm in 11 out of 40 LACC cases and catheter angular deviation greater than 10°in 7 cases. Correspondingly, the proportion of new plans meeting the<i>D</i>₉₀> 100% criterion was 100% with template guidance versus 92.5% without, both significantly higher than the 82.5% achieved by original clinical plans. The method also increased<i>V</i>₉₀and<i>V</i>₁₀₀by 3.4% and 4.9% (both<i>p</i>< 0.001), improved dose conformity from 0.59 to 0.61 (<i>p</i>< 0.001), while maintaining OAR<i>D</i>_2ccwithin clinical limits.<i>Conclusion.</i>The proposed pre-implantation planning method reduces reliance on operator experience and offers a robust, automated solution for high-conformity brachytherapy.