Lee Young Kyu, Seol Yunji, Kim Byeong Jin, Choi Kyu Hye, Hong Ji Hyun, Park Chan-Beom, Kim Sun Hwa, Park Hyeong Wook, Cheon Wonjoong, Kang Young Nam, Choi Byung-Ock
Department of Radiation Oncology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea.
Department of Biomedicine & Health Sciences, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea.
Front Oncol. 2025 Jan 14;14:1495216. doi: 10.3389/fonc.2024.1495216. eCollection 2024.
This study aimed to provide quantitative information for implementing Lattice radiotherapy (LRT) using a medical linear accelerator equipped with the Millennium 120 multi-leaf collimator (MLC). The research systematically evaluated the impact of varying vertex diameters and separations on dose distribution, peak-to-valley dose ratio (PVDR), and normal tissue dose.
A cylindrical Virtual Water™ phantom was used to create LRT treatments using the Eclipse version 16.0 treatment planning system (Varian, Palo Alto, USA). The plans were optimized employing a 3 × 3 × 3 lattice structure with vertex diameters ranging from 0.5 to 2.0 cm and separations from 1.0 to 5.0 cm. The prescribed dose was 20.0 Gy to 50% of the vertex volume in a single fraction. Peak-to-valley dose ratio (PVDR) was calculated along three orthogonal axes, and normal tissue dose and monitor units (MU) were analyzed. Additionally, the modulation complexity score (MCS) was calculated for each plan to quantitatively assess treatment plan complexity.
The PVDR analysis demonstrated heterogeneous dose distribution, with optimal values below 30% in all directions for 5.0 cm separation. PVDR in the superior-inferior direction was consistently lower than in other directions. Normal tissue dose analysis revealed increasing mean dose with larger diameters and separations, while the volume receiving high doses decreased. MU analysis showed significant contributions from collimator angles of 315.0° and 45.0°. MCS values ranged from 0.02 to 0.17 for 0.5 cm vertex diameter and 0.08 to 0.20 for larger diameters (1.0-2.0 cm) across different separations, respectively.
This study demonstrates the technical feasibility of implementing LRT using a medical linear accelerator with Millennium 120 MLC. The findings provide insights into optimizing LRT treatment plans, offering a comprehensive quantitative reference for achieving desired dose heterogeneity while maintaining normal tissue protection.
本研究旨在为使用配备 Millennium 120 多叶准直器（MLC）的医用直线加速器实施点阵放射治疗（LRT）提供定量信息。该研究系统评估了不同顶点直径和间距对剂量分布、峰谷剂量比（PVDR）和正常组织剂量的影响。
使用圆柱形虚拟水模体，通过 Eclipse 版本 16.0 治疗计划系统（美国瓦里安公司，帕洛阿尔托）创建 LRT 治疗计划。采用 3×3×3 点阵结构进行计划优化，顶点直径范围为 0.5 至 2.0 厘米，间距范围为 1.0 至 5.0 厘米。单次分割中，规定剂量为顶点体积的 50%接受 20.0 戈瑞。沿三个正交轴计算峰谷剂量比（PVDR），并分析正常组织剂量和监测单位（MU）。此外，计算每个计划的调制复杂性评分（MCS）以定量评估治疗计划的复杂性。
PVDR 分析显示剂量分布不均匀，对于 5.0 厘米的间距，所有方向上的最佳值均低于 30%。上下方向的 PVDR 始终低于其他方向。正常组织剂量分析表明，直径和间距越大，平均剂量越高，而接受高剂量的体积则减小。MU 分析显示 315.0°和 45.0°的准直器角度贡献显著。对于 0.5 厘米的顶点直径，不同间距下 MCS 值范围为 0.02 至 0.17，对于较大直径（1.0 - 2.0 厘米），MCS 值范围为 0.08 至 0.20。
本研究证明了使用配备 Millennium 120 MLC 的医用直线加速器实施 LRT 的技术可行性。研究结果为优化 LRT 治疗计划提供了见解，为在保持正常组织保护的同时实现所需的剂量不均匀性提供了全面的定量参考。
