Accuracy of tumor motion compensation algorithm from a robotic respiratory tracking system: A simulation study
Accuracy of tumor motion compensation algorithm from a robotic respiratory tracking system: A simulation study
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DOI：
10.1118/1.2739811
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发表时间：
2007-07-01
期刊：
影响因子：
3.8
通讯作者：
Heijmen, Ben
中科院分区：
文献类型：
--
作者：
Seppenwoolde, Yvette;Berbeco, Ross I.;Heijmen, Ben
同步（TM）呼吸跟踪系统（RTS）是射波刀机器人治疗设备的一种治疗选择，用于照射因呼吸而移动的颅外肿瘤。RTS的优点是患者可以正常呼吸，并且不存在诸如门控治疗的直线加速器占空比损失。跟踪基于内部肿瘤运动和外部（胸部/腹部）标记运动之间测量的对应模型（线性或多项式）。辐射束通过连续测量的外部标记运动跟随肿瘤运动。为了在治疗开始时建立对应模型，通过在两个正交X射线图像中自动检测植入的金基准点，在15个离散时间点确定3D内部肿瘤位置;同时，测量外部标记的位置。在治疗过程中，内部和外部标记位置之间的关系被持续说明，并定期检查和更新。在这里，我们使用计算机模拟的基础上连续和同时记录的内部和外部标记的位置，调查肿瘤跟踪的RTS的有效性。射波刀不允许连续采集X射线图像以跟踪移动的内部标记（典型成像频率为每分钟一次）。因此，对于模拟，我们使用了8名接受呼吸门控治疗的肺癌患者的数据。所有这些患者都同时和连续记录了内部肿瘤运动和外部腹部运动。这些患者的内部和外部标志物之间的可用连续关系允许研究RTS采集频率较低的后果。通过使用RTS，所有研究患者在治疗时间内因呼吸运动引起的模拟治疗错误大幅减少且一致。一个简单的线性模型已经可以达到治疗误差的最大减少的相当大的一部分。在滞后的情况下，多项式模型增加了一些额外的减少。对应模型的更频繁更新仅导致相对于当前X射线更新频率具有快速时间趋势的少数记录的误差略小。在一般情况下，模拟表明，内部和外部标记的应用组合使用允许机器人准确地跟踪肿瘤运动，即使在呼吸模式不规则的情况下。(C)2007年美国医学物理学家协会。
The Synchrony (TM) Respiratory Tracking System (RTS) is a treatment option of the CyberKnife robotic treatment device to irradiate extra-cranial tumors that move due to respiration. Advantages of RTS are that patients can breath normally and that there is no loss of linac duty cycle such as with gated therapy. Tracking is based on a measured correspondence model (linear or polynomial) between internal tumor motion and external (chest/abdominal) marker motion. The radiation beam follows the tumor movement via the continuously measured external marker motion. To establish the correspondence model at the start of treatment, the 3D internal tumor position is determined at 15 discrete time points by automatic detection of implanted gold fiducials in two orthogonal x-ray images; simultaneously, the positions of the external markers are measured. During the treatment, the relationship between internal and external marker positions is continuously accounted for and is regularly checked and updated. Here we use computer simulations based on continuously and simultaneously recorded internal and external marker positions to investigate the effectiveness of tumor tracking by the RTS. The Cyberknife does not allow continuous acquisition of x-ray images to follow the moving internal markers (typical imaging frequency is once per minute). Therefore, for the simulations, we have used data for eight lung cancer patients treated with respiratory gating. All of these patients had simultaneous and continuous recordings of both internal tumor motion and external abdominal motion. The available continuous relationship between internal and external markers for these patients allowed investigation of the consequences of the lower acquisition frequency of the RTS. With the use of the RTS, simulated treatment errors due to breathing motion were reduced largely and consistently over treatment time for all studied patients. A considerable part of the maximum reduction in treatment error could already be reached with a simple linear model. In case of hysteresis, a polynomial model added some extra reduction. More frequent updating of the correspondence model resulted in slightly smaller errors only for the few recordings with a time trend that was fast, relative to the current x-ray update frequency. In general, the simulations suggest that the applied combined use of internal and external markers allow the robot to accurately follow tumor motion even in the case of irregularities in breathing patterns. (C) 2007 American Association of Physicists in Medicine.