Simple quality assurance based on filtered back projection for geometrical/irradiation accuracy in single-isocenter multiple-target stereotactic radiotherapy
Simple quality assurance based on filtered back projection for geometrical/irradiation accuracy in single-isocenter multiple-target stereotactic radiotherapy
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DOI：
10.1007/s12194-022-00683-1
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发表时间：
2022-10-19
影响因子：
1.6
通讯作者：
Yasui，Keisuke
中科院分区：
文献类型：
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作者：
Hayashi，Naoki;Kurata，Shun;Yasui，Keisuke
在单等中心多靶点立体定向放射治疗（SIMT-SRT）中，离等中心靶点照射的几何精度和吸收剂量的测量是一个难点。本研究旨在开发一种简单的质量保证（QA）方法来评估SIMT-SRT中的离等中心照射位置精度，并将其可行性与商业设备进行比较。首先，我们创建了两种类型的插入物和直径为5 mm的金属球，以插入市售体模（SIMT体模）中。其次，我们使用Python开发了一个专用的分析软件，用于Winston-Lutz测试（WLT）。第三，一个图像处理软件，包括滤波反投影算法，被开发用于分析使用电子射野成像设备（EPID）获得的图像。第四，我们的方法的可行性进行了评估，通过比较它与WLT的结果，使用两个市售的phantomy：WL-QA和MultiMet-WL立方体。值得注意的是，92%的一维偏差结果在0.26 mm（EPID像素宽度）内。左右、上下和前后方向的相关系数分别为0.52、0.92和0.96。在WLT中，在我们的方法中检测到的最大二维偏差为0.70 mm，而在另一种方法中的偏差在0.5 mm以内。我们的方法的优点是，它可以评估在任何机架角度的几何精度在动态旋转照射使用过滤反投影算法，即使目标位于等中心。我们的方法可以在任意位置进行WLT，适用于使用EPID的动态旋转照射的QA。
In single-isocenter multiple-target stereotactic radiotherapy (SIMT-SRT), it is difficult to evaluate both the geometrical accuracy and absorbed dose measurement when irradiating off-isocenter targets. This study aimed to develop a simple quality assurance (QA) method to evaluate off-isocenter irradiation position accuracy in SIMT-SRT and compare its feasibility with that of a commercial device. First, we created two types of inserts and metallic balls with a diameter of 5 mm to be inserted into a commercially available phantom (SIMT phantom). Second, we developed a dedicated analysis software using Python for the Winston–Lutz test (WLT). Third, an image processing software, including the filtered back-projection algorithm, was developed to analyze the images obtained using an electronic portal imaging device (EPID). Fourth, the feasibility of our method was evaluated by comparing it with the results of WLT using two commercially available phantoms: WL-QA and MultiMet-WL cubes. Notably, 92% of the results in one-dimensional deviations were within 0.26 mm (EPID pixel width). The correlation coefficients were 0.52, 0.92, and 0.96 in the left–right, superior-inferior, and anterior–posterior directions, respectively. In the WLT, a maximum two-dimensional deviation of 0.70 mm was detected in our method, while the deviation in the other method was within 0.5 mm. The advantage of our method is that it can evaluate the geometrical accuracy at any gantry angle during dynamic rotation irradiation using a filtered back-projection algorithm, even if the target is located off the isocenter. Our method can perform WLT at arbitrary positions and is suitable for the QA of dynamic rotation irradiation using an EPID.