Radiation Field Modeling and Computerized Treatment Planning

我们使用的是一家商业供应商的视频处理器板（GPU），它比上一代定制体绘制板便宜得多，而且性能增长潜力更大。商业供应商还提供软件（CUDA），用于使用蒙特卡洛计算板，这进一步支持了我们的研究目标。我们已经从三维图像融合过渡到探索四维放射治疗成像。我们的研究已经建立了一个基本的三维外部躯干体积和内部器官，特别是肺的时间运动之间的关系。我们的研究已经开发出一种体积的方法，图像跟踪使用外部躯干体积变化，已申请专利。基于电子-γ簇射（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已集成到一个功能齐全的治疗计划系统中。现在的工作集中在相空间源模型的发展。目前，该系统用于研究小野立体定向放射外科。由于减小的场尺寸，边缘效应变得重要，并且用于访问辐射输出的检测器的尺寸影响测量结果。这些输出测量的Monte Carlo模拟极大地有助于选择最适合这些测量的探测器系统。Monte Carlo算法提供了良好的协议与实验测量小到4毫米的喷头。在一个相关的项目中，我们已经适应了代数和蒙特卡罗DCE来预测从诊断CT扫描收到的器官剂量。在儿童国家医疗中心用于临床扫描的GE CT扫描仪的X射线束的表征已经完成。我们还完成了绝对剂量测量，将计算机断层扫描剂量指数（CTDI）的标准诊断测量与实际吸收剂量联系起来。这包括传统CT剂量测定方法与新CTDS的直接比较，以突出个性化剂量测定的优势，并证明器官特异性剂量描述。我们的下一个目标是进行调试的螺旋扇形束CT扫描仪使用一个小的点剂量计，而不是传统的测量CTDI诊断放射学。希望该系统将为流行病学剂量反应研究提供对患者人群进行更完整剂量评估的框架。ROB已经开始与RRP，DCTD，NCI合作建造一台强大的计算机，该计算机将使用现场可编程网格阵列（FPGA）板来补充GPU卡，以将基础计算机的计算能力提高几个数量级。除了HPE Proliant DL-580 Gen 10服务器，ROB还收购了一台OSS（一站式系统）2U EOS服务器，该服务器保证支持多个PCIe扩展机箱，因为它们都来自同一家供应商。这个新系统（Colossus II）已经安装并正在测试中，目前配置为30个FPGA卡和2个GPU卡。最初的HP服务器（Colossus I）配置了一个PCIe扩展机箱（特伦顿系统），其中包含4个FPGA卡和2个GPU卡。服务器BIOS将支持单个PCIe机箱。该系统将用于软件开发和测试，然后再将最终产品输出到生产服务器。Colossus I上安装了双因素身份验证（2FA），允许经批准的外部人员访问，以便他们可以促进代码开发。由于电力过载造成不可逆转的损坏，我们已将OSS 2U EOS服务器更换为全新的设备（政府无需支付任何费用）。COVID-19的到来仍影响该项目的进度，员工最近才恢复全职内部工作。CBIIT已经失去了所有的Linux支持人员，这也抑制了现场支持的可用性，以协助解决问题。虽然已经招聘了一名新人，但仍有一个重要的学习曲线。此外，CBIIT授权的Linux操作系统（RHL 7）不支持多个FPGA板所需的驱动程序。我们刚刚得到许可升级到RHL 8。

We are using a commercial vendor of video processor boards (GPUs) which are both substantially less expensive than the previous generation of custom volume rendering boards as well as having a greater potential for growth in performance. The commercial vendor also provides software (CUDA) 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. Our research has developed a volumetric methodology for image tracking using external torso volume change for which a patent has been applied for. 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 4mm. 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. This includes a direct comparison of traditional CT dosimetry methodology versus the new CTDS to highlight the advantages of individualized dosimetry and demonstrate organ-specific dose descriptions. Our next goal is to undertake the commissioning of a helical fan-beam CT scanner using a small point-dosimeter, as opposed to the traditional measurement of CTDI employed in Diagnostic Radiology. It is hoped that this system will provide the framework for a more complete dose assessment of patient populations for epidemiological dose-response studies. ROB has embarked on a joint project with RRP, DCTD, NCI on the construction of a powerful computer that will make use of Field Programmable Grid Array (FPGA) boards to supplement the GPU cards to boost the computational power of the base computer by several orders of magnitude. In addition to the HPE Proliant DL-580 Gen 10 server, ROB has acquired an OSS (One Stop Systems) 2U EOS server, which is guaranteed to support multiple PCIe expansion chassis, since they are all from the same vendor. This new system (Colossus II) has been installed and is being tested and is currently configured for 30 FPGA cards and 2 GPU cards. The original HP server (Colossus I) has been configured with a single PCIe expansion chassis (Trenton Systems), which hosts 4 FPGA cards and 2 GPU cards. The server BIOS will support a single PCIe chassis. This system will be utilized for software development and testing prior to exporting the finalized product to the production server. Two factor authentication (2FA) has been installed on Colossus I, to permit access by approved extramural individuals so that they can facilitate code development. We have replaced the OSS 2U EOS server with an entirely new unit (at no cost to the Government) due to an electrical overload causing irreversible damage. The advent of COVID-19 is still impacting the progress of this project and staff have only recently returned to full time work in-house. CBIIT has lost all of its LINUX support staff, which also inhibits on-site support availability to assist with resolving issues. Although a new person has been recruited, there is still a significant learning curve involved. Additionally, the CBIIT-mandated LINUX operating system (RHL 7) does not support the drivers needed for multiple FPGA boards. We have only just received permission to upgrade to RHL 8.