技术说明：动态轨迹放射治疗的门控可行性——机械精度和剂量学性能。

Technical note: Feasibility of gating for dynamic trajectory radiotherapy - Mechanical accuracy and dosimetric performance.

机构信息

Division of Medical Radiation Physics and Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern, Bern, Switzerland.

Institute for Biomedical Engineering, ETH Zürich and PSI, Villigen, Switzerland.

出版信息

Med Phys. 2023 Oct;50(10):6535-6542. doi: 10.1002/mp.16533. Epub 2023 Jun 20.

DOI:10.1002/mp.16533

PMID:37338935

Abstract

BACKGROUND

Dynamic trajectory radiotherapy (DTRT) extends state-of-the-art volumetric modulated arc therapy (VMAT) by dynamic table and collimator rotations during beam-on. The effects of intrafraction motion during DTRT delivery are unknown, especially regarding the possible interplay between patient and machine motion with additional dynamic axes.

PURPOSE

To experimentally assess the technical feasibility and quantify the mechanical and dosimetric accuracy of respiratory gating during DTRT delivery.

METHODS

A DTRT and VMAT plan are created for a clinically motivated lung cancer case and delivered to a dosimetric motion phantom (MP) placed on the table of a TrueBeam system using Developer Mode. The MP reproduces four different 3D motion traces. Gating is triggered using an external marker block, placed on the MP. Mechanical accuracy and delivery time of the VMAT and DTRT deliveries with and without gating are extracted from the logfiles. Dosimetric performance is assessed by means of gamma evaluation (3% global/2 mm, 10% threshold).

RESULTS

The DTRT and VMAT plans are successfully delivered with and without gating for all motion traces. Mechanical accuracy is similar for all experiments with deviations <0.14° (gantry angle), <0.15° (table angle), <0.09° (collimator angle) and <0.08 mm (MLC leaf positions). For DTRT (VMAT), delivery times are 1.6-2.3 (1.6- 2.5) times longer with than without gating for all motion traces except one, where DTRT (VMAT) delivery is 5.0 (3.6) times longer due to a substantial uncorrected baseline drift affecting only DTRT delivery. Gamma passing rates with (without) gating for DTRT/VMAT were ≥96.7%/98.5% (≤88.3%/84.8%). For one VMAT arc without gating it was 99.6%.

CONCLUSION

Gating is successfully applied during DTRT delivery on a TrueBeam system for the first time. Mechanical accuracy is similar for VMAT and DTRT deliveries with and without gating. Gating substantially improved dosimetric performance for DTRT and VMAT.

摘要

背景

动态轨迹放射治疗（DTRT）通过在射束开启时动态地旋转治疗床和准直器，扩展了最先进的容积调强弧形治疗（VMAT）。在 DTRT 治疗过程中，分次内运动的影响尚不清楚，特别是在存在额外动态轴的情况下，患者和机器运动之间可能存在相互作用。

目的

实验评估在 DTRT 治疗中使用呼吸门控的技术可行性，并量化其机械和剂量学准确性。

方法

为一个临床相关的肺癌病例创建 DTRT 和 VMAT 计划，并使用 Developer Mode 将其传送到置于 TrueBeam 系统治疗台上的剂量学运动体模（MP）。MP 再现了四种不同的 3D 运动轨迹。使用外部标记块触发门控，该标记块置于 MP 上。从日志文件中提取 VMAT 和 DTRT 有无门控的机械精度和传输时间。通过伽玛评估（3%全局/2mm，10%阈值）评估剂量学性能。

结果

对于所有运动轨迹，DTRT 和 VMAT 计划均成功地在有或没有门控的情况下传输。对于所有实验，机械精度均相似，偏差均<0.14°（旋转机架角度）、<0.15°（治疗床角度）、<0.09°（准直器角度）和<0.08mm（多叶准直器叶片位置）。对于 DTRT（VMAT），对于所有运动轨迹，有门控时的传输时间比无门控时长 1.6-2.3（1.6-2.5）倍，只有一个运动轨迹除外，由于基线漂移未得到充分校正，仅影响 DTRT 传输，DTRT（VMAT）的传输时间延长了 5.0（3.6）倍。对于有门控和无门控的 DTRT/VMAT，伽玛通过率分别为≥96.7%/98.5%（≤88.3%/84.8%）。对于一个没有门控的 VMAT 弧，伽玛通过率为 99.6%。