Determining optimal gel sensitivity in optical CT scanning of gel dosimeters.
Determining optimal gel sensitivity in optical CT scanning of gel dosimeters.
复制标题
确定凝胶剂量计光学 CT 扫描的最佳凝胶灵敏度。
DOI：
10.1118/1.1593837
复制
发表时间：
2003
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：
Xua,Y;Wuu,Cheng-Shie;Maryanski,MarekJ
提出了一种测定凝胶剂量计光学CT扫描中获得最佳图像对比度所必需的凝胶灵敏度的方法。分析了OCTOPUS‐ONE™研究扫描仪（MGS research, Inc., Madison， CT）的有效动态范围。根据聚合物凝胶的光学特性和来自商业处理计划系统（Cadplan, Varian Corporation, Palo Alto， CA）的剂量分布，计算要扫描的凝胶圆柱体上选定直线路径的光密度增量。通过在一组不同旋转角度的横向平面上搜索凝胶柱，可以获得整个凝胶的最大光密度增量。通过对两种具有代表性的治疗方案的剂量验证，论证了该量作为优化CT光学扫描质量的标准的应用。当治疗方案的剂量分布的MU依赖关系为线性时，如静态场照射的情况，则可以对治疗方案进行缩放，使光电探测器接收到的信号的强度变化跨越其整个动态范围。对于可能是非线性的治疗计划，例如IMRT计划，修改凝胶材料的敏感性是必要的，以便以一定的信噪比收集高剂量信号。将优化后的CT扫描结果与治疗计划系统和膜测量结果进行了比较。
A method for determining the gel sensitivity that is necessary for obtaining optimal image contrast in optical CT scanning of gel dosimeters is presented. The effective dynamic range of the OCTOPUS‐ONE™ research scanner (MGS Research, Inc., Madison, CT) is analyzed. Optical density increments for selected straight‐line paths across a gel cylinder to be scanned are calculated based on the optical properties of the polymer gel and the dose distribution from a commercial treatment planning system (Cadplan, Varian Corporation, Palo Alto, CA). Maximum optical density increment across the entire gel is obtained by searching the gel cylinder over a set of transverse planes at different rotational angles. The application of this quantity as a criterion for optimizing the quality of the optical CT scanning is demonstrated through dose verification of two representative treatment plans. When the MU dependence of the dose distribution for a treatment plan is linear, as is the case for static field irradiation, it is possible to scale the treatment plan such that the intensity variation of the signals received by the photodetector spans its entire dynamic range. For treatment plans that are possibly nonlinear, IMRT plans, for example, modification of the sensitivity of the gel material is necessary for the high‐dose signals to be collected at a certain signal‐to‐noise ratio. Results obtained using the optimized CT scanning approach are compared with those from the treatment planning system and the film measurement.