Proton Therapy Unit, S. Chiara Hospital - Azienda Provinciale per I Servizi Sanitari (APSS), Trento, Italy.
Proton Therapy Unit, S. Chiara Hospital - Azienda Provinciale per I Servizi Sanitari (APSS), Trento, Italy.
Radiother Oncol. 2022 Apr;169:43-50. doi: 10.1016/j.radonc.2022.02.015. Epub 2022 Feb 18.
To comprehensively describe the treatment of mediastinal lymphoma by pencil beam scanning (PBS) proton therapy.
Fourteen patients underwent PBS proton treatment in a supine position in deep inspiration breath-hold (DIBH). Three DIBH computed tomography (CT) scans were acquired for each patient to delineate the Internal Target Volume (ITV). Intensity-modulated proton therapy (IMPT) was planned by min-max robust optimization on the ITV, with a 6 mm setup and 3.5% range uncertainties. Robustness analysis was performed and dose coverage was visually inspected on the corresponding voxel-wise minimum map. Layer repainting was set equal to 5 to compensate for cardiac motion. Intra-fraction reproducibility during treatment was assessed by repeated daily DIBH X-ray imaging. Finally, an additional CT was acquired at half treatment to estimate the impact of inter-fraction dosimetric reproducibility.
IMPT guaranteed robust mediastinal target coverage and organs-at-risk sparing. However, visual voxel-wise robustness evaluation showed that in five patients a second optimization with focused objectives in the cost-function was necessary to achieve a robust coverage of the target regions at the interface between lungs and soft tissue. In six patients, repainting was not used due to excessive treatment time length and poor patient compliance. Intra-fraction average reproducibility was within 1 mm/1degree. On repeated CT scans, inter-fraction setup errors and/or anatomical changes showed minimal dosimetric differences in CTV coverage.
IMPT in DIBH is effective and reproducible to treat mediastinal lymphomas. Caution is recommended to guarantee robust dose delivery to high-risk regions at the interface between lungs and soft tissue.
全面描述铅笔束扫描（PBS）质子治疗纵隔淋巴瘤的治疗方法。
14 名患者在深吸气屏气（DIBH）的仰卧位接受 PBS 质子治疗。每位患者采集 3 次 DIBH 计算机断层扫描（CT）以描绘内部靶区（ITV）。在 ITV 上通过 min-max 鲁棒优化进行强度调制质子治疗（IMPT），设置和 3.5%范围不确定度为 6mm。进行稳健性分析，并在相应的体素最小图上进行剂量覆盖的视觉检查。层重绘设置为 5，以补偿心脏运动。通过重复每日 DIBH X 射线成像评估治疗过程中的分次内可重复性。最后，在治疗进行到一半时获取额外的 CT 以估计分次间剂量学可重复性的影响。
IMPT 保证了纵隔靶区的稳健覆盖和危及器官的保护。然而，直观的体素稳健性评估表明，在五名患者中，需要在成本函数中进行重点目标的二次优化，以实现肺部和软组织交界处靶区的稳健覆盖。在六名患者中，由于治疗时间过长和患者顺应性差，未使用重绘。分次内平均可重复性在 1mm/1 度以内。在重复 CT 扫描中，分次间的设置误差和/或解剖变化显示CTV 覆盖的剂量学差异最小。
DIBH 中的 IMPT 对于治疗纵隔淋巴瘤是有效且可重复的。建议谨慎操作，以保证在肺部和软组织交界处高风险区域的稳健剂量传递。
