On the automated definition of mobile target volumes from 4D-CT images for stereotactic body radiotherapy
On the automated definition of mobile target volumes from 4D-CT images for stereotactic body radiotherapy
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DOI：
10.1118/1.2106448
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发表时间：
2005-11-01
期刊：
影响因子：
3.8
通讯作者：
Tomé, WA
中科院分区：
文献类型：
--
作者：
Zhang, TZ;Orton, NP;Tomé, WA
立体定向体部放射治疗（SBRT）可用于治疗胸部的小病灶。基于真空的固定系统在我们的诊所用于SBRT，并在治疗计划中使用运动包络。本研究的目的是利用4D-CT图像的可变形图像配准自动获得运动包络，并评估腹部压力对运动包络的影响。在使用包括腹部压力枕的基于真空的固定系统进行自由和限制呼吸治疗之前，在10个阶段采集4D-CT扫描。为了研究治疗过程中运动包络的稳定性，在输送第三部分后，对两名患者进行了治疗中期4D-CT扫描。在全呼气阶段的图像集上定义不包括呼吸运动的计划目标体积（PTVex），并使用来自可变形图像配准的位移图将其转换为所有其他阶段。运动包络被获得为所有相位的PTVex掩模的联合。运动包络与PTVex体积的比值范围为1.3至2.5。当施加压力时，与自由呼吸相比，一些患者的比率降低了29%，但其他患者的比率增加了9%。腹压枕对肺的前/下区域具有更多的运动限制作用。对于在治疗中期重复4D-CT扫描的两名患者中的一名，运动包络是可再现的。然而，对于另一名患者，由于治疗过程中肿瘤周围解剖结构的变化，肿瘤位置和肺部运动模式发生了显著变化，这表明SBRT的图像引导方法可能会提高该治疗的疗效。(c)2005年美国医学物理学家协会。
Stereotactic body radiotherapy (SBRT) can be used to treat small lesions in the chest. A vacuum-based immobilization system is used in our clinic for SBRT, and a motion envelope is used in treatment planning. The purpose of this study is to automatically derive motion envelopes using deformable image registration of 4D-CT images, and to assess the effect of abdominal pressure on the motion envelopes. 4D-CT scans at ten phases were acquired prior to treatment for both free and restricted breathing using a vacuum-based immobilization system that includes an abdominal pressure pillow. To study the stability of the motion envelope over the course of treatment, a mid-treatment 4D-CT scan was obtained after delivery of the third fraction for two patients. The planning target volume excluding breathing motion (PTVex) was defined on the image set at full exhalation phase and transformed into all other phases using displacement maps from deformable image registration. The motion envelope was obtained as the union of PTVex masks of all phases. The ratios of the motion envelope to PTVex volume ranged from 1.3 to 2.5. When pressure was applied, the ratios were reduced by as much as 29% compared to free breathing for some patients, but increased by up to 9% for others. The abdominal pressure pillow has more motion restriction effects on the anterior/inferior region of the lung. For one of the two patients for whom the 4D-CT scan was repeated at mid-treatment, the motion envelope was reproducible. However, for the other patient the tumor location and lung motion pattern significantly changed due to changes in the anatomy surrounding the tumor during the course of treatment, indicating that an image-guided approach to SBRT may increase the efficacy of this treatment. (c) 2005 American Association of Physicists in Medicine.