Radiation Field Modeling and Computerized Treatment Planning

今年的主要变化是摆脱了我们与一家供应商的长期合作关系， 体积渲染硬件，而选择高性能视频的商业供应商 图形加速器这些单元提供与旧板相当的性能，但 两者都基本上较便宜并且具有更大的性能增长潜力。的 商业供应商还提供软件，用于利用蒙特卡罗电路板 计算，这进一步支持了我们的研究目标。我们已经从 3-三维图像融合，探索四维放射治疗成像。我们的研究 建立了一个基本的关系之间的时间运动的三维 外部躯干体积和内部器官的体积，特别是肺。这可以作为 剂量门控或剂量跟踪方法的验证基础， 外部基准。基于EGS-4的蒙特卡罗剂量计算 引擎（DCE）已在Linux和Windows环境中完全实现。在 Windows环境下，DCE已集成到功能齐全的治疗计划中 系统现在的工作集中在相空间源模型的发展。目前这款 系统用于研究小野立体定向放射外科。由于磁场减小， 尺寸、边缘效应变得重要，并且用于访问辐射的检测器的尺寸 输出影响测量结果。这些输出测量的蒙特卡罗模拟 这大大有助于选择最适合这些检测器系统， 测量.蒙特卡罗算法提供了良好的协议与实验测量 小至5毫米的涂抹器。在一个相关的项目中，我们采用了代数和 蒙特卡罗DCE预测从诊断CT扫描接收的器官剂量。的 用于临床扫描的GE CT扫描仪的X射线束表征 国家儿童医疗中心已建成。我们还完成了绝对剂量测定 计算机断层扫描剂量指数的标准诊断测量 （CTDI）与实际吸收剂量的比值。

The major change this year was to move away from our long association with a vendor of volume rendering hardware and select instead a commercial vendor of high performance video graphics accelerators. These units offer comparable performance to the old boards, but are both substantially less expensive and have a greater potential for growth in performance. The commercial vendor also provides software for utilizing the boards for Monte Carlo calculations, which further supports our research objectives. We have transitioned from 3-dimensional image fusion to exploring 4-dimensional radiotherapy imaging. Our research has established a fundamental relationship between the temporal motion of the 3-dimensional external torso volume and those of internal organs, especially the lungs. This can serve as the basis for the validation of dose gating or dose tracking methodologies that rely on external fiducials. The Electron-Gamma Shower (EGS-4)-based Monte Carlo Dose Calculation Engine (DCE) has been fully implemented in both a LINUX and Windows environment. In the Windows environment, the DCE has been integrated into a full featured treatment planning system. Work is now centered on the development of phase-space source models. Currently, this system is used to investigate small field stereotactic radiosurgery. Due to the reduced field size, edge effects become important and the size of detectors used to access the radiation output affect the measurement results. Monte Carlo simulation of these output measurements greatly assisted in the selection of the detector system that is most suitable for these measurements. The Monte Carlo algorithm provided good agreement with experimental measurements down to applicators as small as 5mm. In a related project, we have adapted both algebraic and Monte Carlo DCEs to predict organ doses received from diagnostic CT scans. The characterization of the x-ray beam from a GE CT Scanner used for clinical scanning at Children's National Medical Center is complete. We have also completed absolute dosimetry measurements linking the standard diagnostic measurement of Computer Tomography Dose Index (CTDI) to actual absorbed dose.