移动性肺肿瘤IMAT治疗期间的运动管理——MLC跟踪与门控递送的比较
Motion management during IMAT treatment of mobile lung tumors--a comparison of MLC tracking and gated delivery.
作者信息
Falk Marianne, Pommer Tobias, Keall Paul, Korreman Stine, Persson Gitte, Poulsen Per, Munck af Rosenschöld Per
机构信息
Department of Radiation Oncology, Rigshospitalet, Copenhagen University Hospital, Copenhagen DK-2100, Denmark and Niels Bohr Institute, University of Copenhagen, Copenhagen DK-2100, Denmark.
Radiation Physics Laboratory, Sydney Medical School, University of Sydney, Sydney NSW 2006, Australia.
出版信息
Med Phys. 2014 Oct;41(10):101707. doi: 10.1118/1.4896024.
PURPOSE
To compare real-time dynamic multileaf collimator (MLC) tracking, respiratory amplitude and phase gating, and no compensation for intrafraction motion management during intensity modulated arc therapy (IMAT).
METHODS
Motion management with MLC tracking and gating was evaluated for four lung cancer patients. The IMAT plans were delivered to a dosimetric phantom mounted onto a 3D motion phantom performing patient-specific lung tumor motion. The MLC tracking system was guided by an optical system that used stereoscopic infrared (IR) cameras and five spherical reflecting markers attached to the dosimetric phantom. The gated delivery used a duty cycle of 35% and collected position data using an IR camera and two reflecting markers attached to a marker block.
RESULTS
The average gamma index failure rate (2% and 2 mm criteria) was <0.01% with amplitude gating for all patients, and <0.1% with phase gating and <3.7% with MLC tracking for three of the four patients. One of the patients had an average failure rate of 15.1% with phase gating and 18.3% with MLC tracking. With no motion compensation, the average gamma index failure rate ranged from 7.1% to 46.9% for the different patients. Evaluation of the dosimetric error contributions showed that the gated delivery mainly had errors in target localization, while MLC tracking also had contributions from MLC leaf fitting and leaf adjustment. The average treatment time was about three times longer with gating compared to delivery with MLC tracking (that did not prolong the treatment time) or no motion compensation. For two of the patients, the different motion compensation techniques allowed for approximately the same margin reduction but for two of the patients, gating enabled a larger reduction of the margins than MLC tracking.
CONCLUSIONS
Both gating and MLC tracking reduced the effects of the target movements, although the gated delivery showed a better dosimetric accuracy and enabled a larger reduction of the margins in some cases. MLC tracking did not prolong the treatment time compared to delivery with no motion compensation while gating had a considerably longer delivery time. In a clinical setting, the optical monitoring of the patients breathing would have to be correlated to the internal movements of the tumor.
目的
比较在调强弧形放疗（IMAT）期间实时动态多叶准直器（MLC）跟踪、呼吸幅度和相位门控以及对分次内运动管理不进行补偿的情况。
方法
对4例肺癌患者评估了采用MLC跟踪和门控的运动管理。将IMAT计划施用于安装在执行患者特异性肺肿瘤运动的三维运动体模上的剂量学体模。MLC跟踪系统由一个光学系统引导，该光学系统使用立体红外（IR）摄像机和附着在剂量学体模上的五个球形反射标记。门控递送使用35%的占空比，并使用IR摄像机和附着在标记块上的两个反射标记收集位置数据。
结果
所有患者采用幅度门控时平均伽马指数失败率（2%和2毫米标准）<0.01%，4例患者中有3例采用相位门控时<0.1%，采用MLC跟踪时<3.7%。其中1例患者采用相位门控时平均失败率为15.1%，采用MLC跟踪时为18.3%。在不进行运动补偿的情况下，不同患者的平均伽马指数失败率在7.1%至46.9%之间。剂量学误差贡献评估表明，门控递送主要在靶区定位方面存在误差，而MLC跟踪还存在MLC叶片拟合和叶片调整方面的贡献。与采用MLC跟踪（不延长治疗时间）或不进行运动补偿的递送相比，门控时平均治疗时间大约长三倍。对于其中2例患者，不同的运动补偿技术允许减少大致相同的边界，但对于另外2例患者，门控比MLC跟踪能够更大程度地减少边界。
结论
门控和MLC跟踪均降低了靶区运动的影响，尽管门控递送显示出更好的剂量学准确性，并且在某些情况下能够更大程度地减少边界。与不进行运动补偿的递送相比，MLC跟踪不会延长治疗时间，而门控的递送时间则长得多。在临床环境中，对患者呼吸的光学监测必须与肿瘤的内部运动相关联。
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