Integration of a real-time tumor monitoring system into gated proton spot-scanning beam therapy: An initial phantom study using patient tumor trajectory data
Integration of a real-time tumor monitoring system into gated proton spot-scanning beam therapy: An initial phantom study using patient tumor trajectory data
复制标题
DOI：
10.1118/1.4810966
复制
发表时间：
2013-07-01
期刊：
影响因子：
3.8
通讯作者：
Shirato, Hiroki
中科院分区：
文献类型：
--
作者：
Matsuura, Taeko;Miyamoto, Naoki;Shirato, Hiroki
目的：在点扫描质子治疗中，肿瘤运动和射束输送之间的相互作用导致剂量分布恶化。为了减轻肿瘤运动的影响，门控结合重绘是已提出的最有前途的方法之一。本研究的重点是基于同步加速器的点扫描质子治疗系统与实时肿瘤监测集成。作者通过对患者的运动数据进行模拟，研究了门控在输送剂量分布和照射时间方面的有效性。探讨了可调辐照控制参数的临床可接受范围。方法：利用水模体进行模拟研究。门控质子束照射到5 x 5 x 5 cm（3）的临床靶体积（CTV），与肺癌患者的肿瘤轨迹数据同步。通过改变门宽、点间距和单点剂量等参数，计算了78例患者的397个肿瘤轨迹数据的剂量均匀性和照射时间。此外，作者在体模上游放置了一个能量吸收器，并改变了厚度，以检查改变布拉格峰大小和所需能量层数量的影响。95%的肿瘤轨迹数据符合我们定义的标准的参数是可接受的。接下来，相关系数计算之间的最大剂量误差和肿瘤的运动特性，从肿瘤的轨迹data.Results提取：与假设的CTV，最大的百分比的数据满足标准时，门宽度为+/- 2毫米。较大的点间距是首选，因为它增加了绘画的数量。在规定剂量为2戈伊的情况下，由于布拉格峰的尖锐性，很难满足有效深度非常小（假设的能量吸收体厚度与体模中目标深度之和）的目标的标准。然而，即使是浅的目标也可以通过使用足够数量的涂料和放置足够厚度的能量吸收器来成功地照射，以使有效目标深度超过12厘米。作者还观察到，在束方向的运动是剂量失真的主要原因，其次是运动在横向平面垂直于扫描direction.Conclusions：结果表明，通过适当调整照射控制参数，门控质子点扫描束治疗可以强大的目标运动。这是在真实的患者几何结构中建立治疗计划的重要的第一步。(C)2013年美国医学物理学家协会。
Purpose: In spot-scanning proton therapy, the interplay effect between tumor motion and beam delivery leads to deterioration of the dose distribution. To mitigate the impact of tumor motion, gating in combination with repainting is one of the most promising methods that have been proposed. This study focused on a synchrotron-based spot-scanning proton therapy system integrated with real-time tumor monitoring. The authors investigated the effectiveness of gating in terms of both the delivered dose distribution and irradiation time by conducting simulations with patients' motion data. The clinically acceptable range of adjustable irradiation control parameters was explored. Also, the relation between the dose error and the characteristics of tumor motion was investigated.Methods: A simulation study was performed using a water phantom. A gated proton beam was irradiated to a clinical target volume (CTV) of 5 x 5 x 5 cm(3), in synchronization with lung cancer patients' tumor trajectory data. With varying parameters of gate width, spot spacing, and delivered dose per spot at one time, both dose uniformity and irradiation time were calculated for 397 tumor trajectory data from 78 patients. In addition, the authors placed an energy absorber upstream of the phantom and varied the thickness to examine the effect of changing the size of the Bragg peak and the number of required energy layers. The parameters with which 95% of the tumor trajectory data fulfill our defined criteria were accepted. Next, correlation coefficients were calculated between the maximum dose error and the tumor motion characteristics that were extracted from the tumor trajectory data.Results: With the assumed CTV, the largest percentage of the data fulfilled the criteria when the gate width was +/- 2 mm. Larger spot spacing was preferred because it increased the number of paintings. With a prescribed dose of 2 Gy, it was difficult to fulfill the criteria for the target with a very small effective depth (the sum of an assumed energy absorber's thickness and the target depth in the phantom) because of the sharpness of the Bragg peak. However, even shallow targets could be successfully irradiated by employing an adequate number of paintings and by placing an energy absorber of sufficient thickness to make the effective target depth more than 12 cm. The authors also observed that motion in the beam direction was the main cause of dose distortion, followed by motion in the lateral plane perpendicular to the scan direction.Conclusions: The results suggested that by properly adjusting irradiation control parameters, gated proton spot-scanning beam therapy can be robust to target motion. This is an important first step toward establishing treatment plans in real patient geometry. (C) 2013 American Association of Physicists in Medicine.