Main Session
Sep
29
PQA 05 - Physics
3186 - Optimizing Left Breast Cancer Tomotherapy with Repetitive Abdominal DIBH: Achieving Both Dosimetric and Efficiency Gains
Presenter(s)
Yongheng Yan, MD, PhD - The First affiliated Hospital Zhejiang University School of Medicine, Hangzhou, Zhejiang
Y. Yan, G. Yao, Z. Sun, J. Yang, K. Dong, Z. Lu, F. Zhao, and S. Yan; Department of Radiation Oncology, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
Purpose/Objective(s):
Despite the clinical promise of integrating DIBH with helical tomotherapy (HT), a fundamental incompatibility remains between gated-DIBH and HT. This study integrated Abdominal DIBH (ADIBH) and HT to facilitate continuous beam delivery while preserving the dosimetric advantages.
Materials/Methods:
The dosimetric superiority of HT-ADIBH relative to HT-free-breathing (HT-FB) and Linear Accelerator (LA)-DIBH was validated through a comparative analysis of 50 treatment plans. An optical surface monitoring system was employed to analyze real-time positional variations of the breast/chest wall surface. Breath-hold performance among 20 volunteers and the impact of respiratory motion on continuous dose delivery were quantified to evaluate the clinical feasibility of the proposed strategy.
Results:
HT-ADIBH yielded the lowest ipsi lateral lung V5 and heart Dmean among the compared techniques. Gated-DIBH increased treatment duration and numbers of breath-holds by over 47% compared to continuous delivery, rendering it impractical for HT. Intra-DIBH stability and intrafractional reproducibility remained within 5mm, with audio-visual feedback further enhancing breath-hold stability. The mean duty cycle was 67.82±14.12%, close to the 2/3 threshold which provides the optimal balance between dosimetric accuracy and clinical feasibility.
Conclusion:
The proposed ADIBH strategy overcomes the barrier between HT and DIBH by enabling continuous beam delivery with stable target positioning inherently provided by ADIBH. This paradigm represents an effective and clinically feasible solution for cardiac sparing in left-sided breast cancer. The integration of audio-visual feedback and pre-treatment assessment further enhance respiratory stability, allowing for safe margin reduction.