Monte Carlo Simulation of High Energy Photon Imaging

描述（由申请人提供）： 这项工作的广泛的长期目标是大大改善成像，定量和剂量测定的高能量单光子发射器与伽马相机成像。一个特定的长期目标是验证两种放射性核素疗法1）1-131抗B1放射免疫疗法（RIT）和2）1-131间碘苄胍（MIBG）疗法中肿瘤消退与计算的肿瘤辐射吸收剂量之间高度显著相关性的假设。在我们的机构，II期1-131标记的抗B1 RIT试验滤泡性淋巴瘤，显示了97%的反应率和63%的完全反应率。1-131 RIT和MIBG治疗的成功重新引起了人们对1-131成像的兴趣，以准确估计内部剂量。在前一阶段，优化和验证了用于模拟I-131单光子成像的Monte Carlo代码。模拟研究表明，目前的局限性，准确的I-131活性定量使用单光子计算机断层扫描（SPECT）。下一阶段的重点将是使用Monte Carlo开发高度患者特异性的方法，这将显着改善肿瘤/器官剂量测定的两个主要步骤：活性定量和吸收剂量计算。患者特异性方法将通过整合SPECT和共配准CT的信息来实现。具体而言，我们建议实现1）患者特异性部分体积校正; 2）基于蒙特卡罗的前向投影仪，其包括患者特异性散射; 3）3-D患者特异性剂量估计。此外，我们将继续评价3D OSEM重建，其中包括探测器响应，我们将生成用于共轭视图活动量化方法的多中心评价的数据。这项工作将最终与体模研究，建立1-131 SPECT定量和剂量估计的最佳方法，并与现有的RIT患者数据的方法的应用，可能揭示剂量和肿瘤体积减少之间的统计学显着关系。此外，我们将尝试从3-D剂量学，如剂量不均匀性和最小剂量，与肿瘤体积缩小的新的可用参数相关。在任何1-131 RIT临床研究中尚未证明强剂量-反应关系，可能是由于剂量估计不佳。在这里，我们建议联合收割机和扩展许多工具，以显着提高估计和个性化治疗计划的进展。

DESCRIPTION (provided by applicant): The broad long-term objective of this work is to substantially improve imaging, quantification and dosimetry of high-energy single-photon emitters imaged with gamma cameras. A specific long-term objective is to verify the hypothesis of a highly significant correlation between tumor regression and calculated tumor radiation absorbed dose in two radionuclide therapies 1) 1-131 anti-B1 radioimmunotherapy (RIT), and 2) 1-131 metaiodobenzylguanidine (MIBG) therapy. At our institution, a phase II 1-131 labeled anti-B1 RIT trial for follicular lymphoma, showed a 97% response rate and a 63% complete response rate. The success of 1-131 RIT and MIBG therapy has renewed interest in 1-131 imaging for accurate internal dose estimates. During the previous period a Monte Carlo code for modeling single-photon imaging of I-131 was optimized and validated. Simulation studies demonstrated the current limitations to accurate I-131 activity quantification using single photon computed tomography (SPECT). The focus for the next period will be on using Monte Carlo to develop highly patient-specific methods that will significantly improve the two main steps in tumor/organ dosimetry: activity quantification and absorbed dose calculation. The patient-specific methods will be implemented by integrating information from SPECT and co-registered CT. Specifically we propose to implement 1) patient-specific partial volume correction; 2) a Monte Carlo based forward projector, which includes patient-specific scatter; 3) 3-D patient-specific dose estimation. In addition, we will continue evaluation of a 3D OSEM reconstruction, which includes detector response and we will generate data for a multi-center evaluation of conjugate-view activity quantification methods. The work will culminate with phantom studies that establish the optimum methods for 1-131 SPECT quantification and dose estimation and with the application of the methods to existing RIT patient data to possibly reveal a statistically significant relationship between dose and tumor volume reduction. In addition, we will attempt to correlate newly available parameters from the 3-D dosimetry, such as dose non-uniformity and minimum dose, with tumor volume reduction. A strong dose-response relationship has not yet been demonstrated in any 1-131 RIT clinical study possibly due to poor dose estimation. Here we propose to combine and expand many tools to significantly improve the estimate and make advances towards individualized treatment planning.