Medical Physics Unit, Gemelli Molise Hospital, Università Cattolica del Sacro Cuore, Campobasso, Italy.
Radiation Oncology Unit, Gemelli Molise Hospital, Università Cattolica del Sacro Cuore, Campobasso, Italy.
J Appl Clin Med Phys. 2023 Jun;24(6):e13922. doi: 10.1002/acm2.13922. Epub 2023 Feb 27.
The aim of this study was to evaluate the reproducibility and stability of left breast positioning during spirometer-guided deep-inspiration breath-hold (DIBH) radiotherapy using an optical surface imaging system (AlignRT). The AlignRT optical tracking system was used to monitor five left-sided breast cancer patients treated using the Active Breathing Coordinator spirometer with DIBH technique. Treatment plans were created using an automated hybrid-VMAT technique on DIBH CTs. A prescribed dose of 60 Gy to the tumor bed and 50 Gy to the breast in 25 fractions was planned. During each treatment session, the antero-posterior (VRT), superior-inferior (LNG), and lateral (LAT) motion of patients was continuously recorded by AlignRT. The intra-breath-hold stability and the intra- and inter-fraction reproducibility were analyzed for all breath-holds and treatment fractions. The dosimetric impact of the residual motion during DIBH was evaluated from the isocenter shifts amplitudes obtained from the 50%, 90%, and 100% cumulative distribution functions of intra-fractional reproducibility. The positional variations of 590 breath-holds as measured by AlignRT were evaluated. The mean intra-breath-hold stability during DIBH was 1.0 ± 0.4 mm, 2.1 ± 1.9 mm, and 0.7 ± 0.5 mm in the VRT, LNG, and LAT directions, with a maximal value of 8.8 mm in LNG direction. Similarly, the mean intra-breath-hold reproducibility was 1.4 ± 0.8 mm, 1.7 ± 1.0 mm, and 0.8 ± 0.5 mm in the VRT, LNG, and LAT directions, with a maximal value of 4.1 mm in LNG direction. Inter-fractional reproducibility showed better reliability, with difference in breathing levels in all fractions of 0.3 mm on average. Based on tolerance limits corresponding to the 90% cumulative distribution level, gating window widths of 1 mm, 2 mm, and 5 mm in the LAT, VRT, and LNG directions were considered an appropriate choice. In conclusion, despite the use of a dedicated spirometer at constant tidal volume, a non-negligible variability of the breast surface position has been reported during breath-holds. The real-time monitoring of breast surface using surface-guided optical technology is strongly recommended.
本研究旨在评估使用光学表面成像系统（AlignRT）引导的肺活量计指导下深吸气屏气（DIBH）放疗过程中左侧乳房定位的可重复性和稳定性。采用光学跟踪系统监测 5 例左侧乳腺癌患者，采用主动呼吸控制仪配合 DIBH 技术进行治疗。在 DIBH CT 上使用自动化混合-VMAT 技术制定治疗计划。计划给予肿瘤床 60Gy 和乳房 50Gy（25 次分割）。在每次治疗过程中，AlignRT 连续记录患者的前后（VRT）、上下（LNG）和左右（LAT）运动。分析所有屏气和治疗分次的屏气内稳定性以及分次内和分次间的可重复性。从 50%、90%和 100%累积分布函数中获得的等中心点移位幅度，评估 DIBH 期间残留运动对剂量的影响。通过 AlignRT 测量了 590 次屏气的位置变化。在 DIBH 期间，左右方向的平均屏气内稳定性为 1.0±0.4mm、2.1±1.9mm 和 0.7±0.5mm，LNG 方向的最大位移为 8.8mm。同样，左右方向的平均屏气内可重复性为 1.4±0.8mm、1.7±1.0mm 和 0.8±0.5mm，LNG 方向的最大位移为 4.1mm。分次间可重复性具有更好的可靠性，各分次的呼吸水平差异平均为 0.3mm。基于对应 90%累积分布水平的容限限制，LAT、VRT 和 LNG 方向的门控窗宽度分别为 1mm、2mm 和 5mm，被认为是合适的选择。总之，尽管使用了专用的肺活量计保持潮气量恒定，但在屏气期间仍报告了乳房表面位置的显著变化。强烈建议使用表面引导的光学技术实时监测乳房表面。
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