Chi Pai-Chun Melinda, Balter Peter, Luo Dershan, Mohan Radhe, Pan Tinsu
Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030, USA.
Med Phys. 2006 Sep;33(9):3116-23. doi: 10.1118/1.2241993.
The accuracy of delivering gated-radiation therapy to lung tumors using an external respiratory surrogate relies on not only interfractional and intrafractional reproducibility, but also a strong correlation between external motion and internal tumor motion. The purpose of this work was to use the cine images acquired by four-dimensional computed tomography acquisition protocol to study the relation between external surface motion and internal tumor motion. The respiratory phase information of tumor motion and chest wall motion was measured on the cine images using a proposed region-of-interest (ROI) method and compared to measurement of an external respiratory monitoring device. On eight lung patient data sets, the phase shifts were measured between (1) the signal of a real-time positioning-management (RPM) respiratory monitoring device placed in the abdominal region and four surface locations on the chest wall, (2) the RPM signal in the abdominal region and tumor motions, and (3) chest wall surface motions and tumor motions. Respiratory waveforms measured at different surface locations during the same respiratory cycle often varied and had significant phase shifts. Seven of the 8 patients showed the abdominal motion leading chest wall motion. The best correlation (smallest phase shift) was found between the abdominal motion and the superior-inferior (S-I) tumor motion. A wide range of phase shifts was observed between external surface motion and tumor anterior-posterior (A-P)/lateral motion. The result supported the placement of the RPM block in the abdominal region and suggested that during a gated therapy utilizing the RPM system, it is necessary to place the RPM block at the same location as it is during treatment simulation in order to reduce potential errors introduced by the position of the RPM block. Correlations between external motions and lateral/A-P tumor motions were inconclusive due to a combination of patient selection and the limitation of the ROI method.
使用外部呼吸替代物对肺部肿瘤进行门控放射治疗的准确性不仅依赖于分次间和分次内的可重复性，还依赖于外部运动与内部肿瘤运动之间的强相关性。本研究的目的是利用四维计算机断层扫描采集协议获取的电影图像来研究胸壁表面运动与内部肿瘤运动之间的关系。使用一种提议的感兴趣区域（ROI）方法在电影图像上测量肿瘤运动和胸壁运动的呼吸相位信息，并与外部呼吸监测设备的测量结果进行比较。在八个肺部患者数据集上，测量了以下三者之间的相位偏移：（1）放置在腹部区域的实时定位管理（RPM）呼吸监测设备的信号与胸壁上四个表面位置之间；（2）腹部区域的RPM信号与肿瘤运动之间；（3）胸壁表面运动与肿瘤运动之间。在同一呼吸周期内，不同表面位置测量的呼吸波形经常变化且有显著的相位偏移。8名患者中有7名显示腹部运动领先于胸壁运动。在腹部运动与肿瘤的上下（S-I）运动之间发现了最佳相关性（最小相位偏移）。在胸壁表面运动与肿瘤的前后（A-P）/侧向运动之间观察到了广泛的相位偏移范围。该结果支持将RPM传感器放置在腹部区域，并表明在利用RPM系统进行门控治疗期间，有必要将RPM传感器放置在与治疗模拟期间相同的位置，以减少由RPM传感器位置引入的潜在误差。由于患者选择和ROI方法的局限性，外部运动与肿瘤侧向/A-P运动之间的相关性尚无定论。
