Performance of a commercial optical CT scanner and polymer gel dosimeters for 3-D dose verification.
Performance of a commercial optical CT scanner and polymer gel dosimeters for 3-D dose verification.
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用于 3D 剂量验证的商用光学 CT 扫描仪和聚合物凝胶剂量计的性能。
DOI：
10.1118/1.1803674
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发表时间：
2004
期刊：
影响因子：
3.8
通讯作者：
Maryanski,MarekJ
中科院分区：
文献类型：
--
作者：
Xu,Y;Wuu,Cheng-Shie;Maryanski,MarekJ
提出了基于聚合物凝胶光学 CT 扫描的商用三维 (3-D) 剂量测绘系统的性能分析。该系统由聚合物凝胶（MGS Research, Inc.，麦迪逊，康涅狄格州）、OCTOPUS™ 激光 CT 扫描仪（MGS Research, Inc.，麦迪逊，康涅狄格州）和内部开发的软件组成，用于光学 CT 图像重建以及凝胶、胶片测量和放射治疗计划之间的 3D 剂量分布比较。分析了扫描仪产生的各种图像噪声源（数字化、电子、光学和机械）以及聚合物凝胶的光学均匀性。扫描仪的性能进一步根据数据采集过程的再现性、每单位长度重建光密度的不同水平的不确定性以及扫描参数的影响进行评估。事实证明，对于装在圆柱形塑料容器中的凝胶体模，扫描仪可以再现相对剂量分布，在容器半径的约 75% 内，总体不确定度约为 3%。然而，在靠近容器壁的区域，扫描仪会产生错误的光密度值，这是由于激光射线在凝胶和容器之间的界面处的反射和折射而产生的。通过将凝胶/OCT 衍生的剂量分布与胶片测量和商用治疗计划系统（Cadplan，Varian Corporation，Palo Alto，CA）针对单场 X 射线和 3-D 适形放射治疗 (3DCRT) 计划的剂量分布进行比较，举例说明了聚合物凝胶剂量计的准确性分析。在整个可用的、无伪影的凝胶体积中心区域，凝胶测量结果与治疗计划和胶片测量结果一致，符合“3%或”标准。分析三个数据集之间的差异。
Performance analysis of a commercial three‐dimensional (3‐D) dose mapping system based on optical CT scanning of polymer gels is presented. The system consists of polymer gels (MGS Research, Inc., Madison, CT), OCTOPUS™ laser CT scanner (MGS Research, Inc., Madison, CT), and an in‐house developed software for optical CT image reconstruction and 3‐D dose distribution comparison between the gel, film measurements and the radiation therapy treatment plans. Various sources of image noise (digitization, electronic, optical, and mechanical) generated by the scanner as well as optical uniformity of the polymer gel are analyzed. The performance of the scanner is further evaluated in terms of the reproducibility of the data acquisition process, the uncertainties at different levels of reconstructed optical density per unit length and the effects of scanning parameters. It is demonstrated that for gel phantoms held in cylindrical plastic containers, the relative dose distribution can be reproduced by the scanner with an overall uncertainty of about 3% within approximately 75% of the radius of the container. In regions located closer to the container wall, however, the scanner generates erroneous optical density values that arise from the reflection and refraction of the laser rays at the interface between the gel and the container. The analysis of the accuracy of the polymer gel dosimeter is exemplified by the comparison of the gel/OCT‐derived dose distributions with those from film measurements and a commercial treatment planning system (Cadplan, Varian Corporation, Palo Alto, CA) for a single field of x rays and a 3‐D conformal radiotherapy (3DCRT) plan. The gel measurements agree with the treatment plans and the film measurements within the “3%‐or‐” criterion throughout the usable, artifact‐free central region of the gel volume. Discrepancies among the three data sets are analyzed.