Welsh James S, Bradley Kristin, Ruchala Kenneth J, Mackie Thomas R, Mañon Rafael, Patel Rakesh, Wiederholt Peggy, Lock Michael, Hui Susanta, Mehta Minesh P
Department of Human Oncology, University of Wisconsin School of Medicine, Madison, USA.
Clin Lung Cancer. 2004 Mar;5(5):303-6. doi: 10.3816/CLC.2004.n.010.
Helical tomotherapy is an innovative means of delivering intensity-modulated radiation therapy (IMRT) using a device that merges features of a linear accelerator and a helical computed tomography (CT) scanner. The tomotherapy unit can generate CT images from the megavoltage radiation it uses for treatment as often as needed during a course of radiation therapy. These megavoltage CT (MVCT) images offer verification of patient position prior to and potentially during radiation therapy, and provide considerably more anatomical detail than the conventional radiation therapy port films used for patient set-up verification. Also, MVCT imaging may enable reconstruction of the radiation dose delivered, thereby providing unprecedented verification of the actual treatment. These key features of helical tomotherapy distinguish it from other IMRT approaches. We report results from a pilot feasibility trial of 10 patients with non-small-cell lung cancer (NSCLC) on whom we obtained MVCT images using a prototype helical tomotherapy system. All patients underwent conventional CT imaging for radiation therapy treatment planning. Specific aims were to subjectively compare MVCT and conventional CT images and then to objectively compare the 2 modalities by contouring tumors and performing a volumetric comparison. Seven patients had disease located primarily in the lung parenchyma, 2 primarily in the mediastinum, and 1 in both. When evaluated by location, all 7 patients with lesions primarily in the lung parenchyma had subjectively high-quality MVCT images. Objectively, the volumetric agreement between conventional and MVCT for parenchymal lesions was excellent in 5 of the 7 patients. Megavoltage CT imaging via the helical tomotherapy prototype provided adequate information for use in verification of patient position and dose reconstruction for lesions within the pulmonary parenchyma, but presently appears suboptimal for primarily mediastinal disease. Further studies are ongoing to optimize MVCT imaging and better define its utility in patients with NSCLC.
螺旋断层放射治疗是一种创新的调强放射治疗（IMRT）方式，它使用一种融合了直线加速器和螺旋计算机断层扫描（CT）扫描仪功能的设备。在放射治疗过程中，断层放射治疗装置可根据需要，利用其用于治疗的兆伏级射线生成CT图像。这些兆伏级CT（MVCT）图像可在放射治疗前及治疗过程中对患者体位进行验证，并且比用于患者定位验证的传统放射治疗定位片提供了更多的解剖细节。此外，MVCT成像可能使所给予的放射剂量得以重建，从而为实际治疗提供前所未有的验证。螺旋断层放射治疗的这些关键特性使其有别于其他IMRT方法。我们报告了一项针对10例非小细胞肺癌（NSCLC）患者的初步可行性试验结果，我们使用一台螺旋断层放射治疗系统原型为这些患者获取了MVCT图像。所有患者均接受了用于放射治疗计划的传统CT成像。具体目标是主观比较MVCT和传统CT图像，然后通过勾勒肿瘤轮廓并进行体积比较来客观比较这两种成像方式。7例患者的病变主要位于肺实质，2例主要位于纵隔，1例两者均有。按病变位置评估时，所有7例主要病变位于肺实质的患者的MVCT图像主观质量较高。客观上，7例患者中有5例肺实质病变的传统CT与MVCT体积一致性极佳。通过螺旋断层放射治疗原型进行的兆伏级CT成像为肺实质内病变的患者体位验证和剂量重建提供了足够的信息，但目前对于主要为纵隔病变的情况似乎并不理想。正在进行进一步研究以优化MVCT成像并更好地确定其在NSCLC患者中的效用。
