A single-optical kernel for a phosphor-screen-based geometric QA system (RavenQA™) as a tool for patient-specific IMRT/VMAT QA
A single-optical kernel for a phosphor-screen-based geometric QA system (RavenQA™) as a tool for patient-specific IMRT/VMAT QA
复制标题
用于基于荧光屏的几何 QA 系统 (RavenQA™) 的单光学内核，作为患者特定 IMRT/VMAT QA 的工具
DOI：
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发表时间：
2018
影响因子：
3.5
通讯作者：
B. Yi
中科院分区：
文献类型：
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作者：
Minsik Lee;K. Ding;B. Yi
它已被证明，门户剂量测定可以来自基于反射镜的荧光EPID系统，通过应用多个内核的位置依赖。本研究的目的是表明，患者特定的IMRT/VMAT验证与一个单一的内核，这是从一系列的输出测量的几个字段大小是可行的，使用市售的荧光屏为基础的几何QA系统。RavenQA™（德国吕讷堡激光应用有限公司（Lüneberg，Germany））中的光学散射分量通过用二维（2D）空间不变的单个光学散射核（OSK）进行去卷积来校正。我们假设OSK是一个2D各向同性点扩散函数，其随着与散射中心的距离而减小。OSK是通过比较各种字段大小的输出因子来确定的。我们报告的性能测试系统使用12个调强放射治疗和三个体积调制弧治疗的情况下。可以采用单个空间不变的OSK，因为OSK在图像板上的形状几乎相同。15例患者的平均3%/3 mm伽马通过率为97.6% ± 1.1%。所有患者的通过率>95%。根据AAPM TG-142，使用市售的基于荧光屏的机械QA设备，使用单个内核执行患者特定IMRT/VMAT验证是可行的。由于只需测量几个方形场的场中心的光强即可获得OSK，因此也很实用。
It has been proven that portal dosimetry can be derived from a mirror-based fluorescent EPID system by applying multiple kernels that are position dependent. The purpose of this study is to show that patient-specific IMRT/VMAT verification with a single kernel which is acquired from a series of output measurements of a few field sizes is feasible using a commercially available phosphor-screen–based geometric QA system. The optical scatter component in the RavenQA™ (LAP GmbH Laser Applications; Lüneberg, Germany) is corrected by deconvolution with a two-dimensional (2D) spatially invariant single optical scatter kernel (OSK). We assume that the OSK is a 2D isotropic point spread function that decreases as a function of distance from the scatter center. The OSK is determined by comparing output factors of various field sizes. We report on performance testing of the system using 12 intensity-modulated radiation therapy and three volumetric-modulated arc therapy cases. A single spatially invariant OSK can be employed, because the shapes of the OSK across the image plate are almost identical. The average 3%/3 mm gamma passing rate for 15 patients was 97.6% ± 1.1%. The passing rate was >95% for all patients. It is feasible to perform the patient-specific IMRT/VMAT verification with a single kernel using a commercially available phosphor-screen-based mechanical QA device in accordance with AAPM TG-142. It is also practical to implement since it only requires to measure the optical intensities of the field centers of several square fields, in order to obtain the OSK.