Improving the Safety and Quality of Eye Plaque Brachytherapy by Assembly with Intensity Modulated Loading

项目摘要/摘要 眼内癌的最佳治疗方法是眼球斑块近距离放射治疗(EPB)，包括手术植入 在肿瘤基底部上方的巩膜表面上的装载有放射源(称为种子)的载体(“斑块”)。 虽然确保放射性种子的强度和准确位置对于准确治疗至关重要， 根据AAPM任务组(TG)报告129的当前质量保证(QA)实践仅规定 由于缺乏有效和实用的技术来测量斑块组件，因此需要目视检查斑块组件 种子放射性分布。在临床上，这通常限制了治疗只能使用均匀的种子强度，否则 我们必须在没有验证的情况下假定装货正确。这对于预加载的斑块来说尤其不理想。 由于不同活动的种子不能在视觉上区分，因此不能由供应商进行识别。因此，不同于普通的 在体外放射治疗中采用强度调制的做法，我们不能进一步优化 通过使用不同的种子强度提供更个性化的剂量治疗，基于肿瘤本身和 正常器官的位置。克服这一阻碍环保事业发展的根本性问题，解决 针对以往EPB QA设计存在的问题，我们的目标是开发一套快速、准确、低成本的QA系统，让 安全集成不同载荷的EPB。我们构建了一个概念验证系统，该系统由一个 闪烁片和安装在一起的镜头/相机系统，旨在定量测量差异 从最初计划的分布到斑块组件的放射性/剂量分布 伽玛评价是调强放射治疗质量保证的常用方法。放射发光 由闪烁体附近的加载斑块产生的信号将由相机收集并在实时处理- 是时候验证种子的装载是否正确了。测量和分析只需要几分钟， 大大缩短了化验物理学家必须执行的额外验证种子的时间 由TG129推荐。我们的初步数据是有希望的，同时我们假设性能可以 通过使用半球形闪烁体使斑块内表面共形来增强系统 敏感度和识别斑块中的每一颗种子。我们最初的蒙特卡罗(MC)模拟演示了 可行性。具体目标：设计和构建一个新颖的、具有关联功能的QA系统原型 使我们能够为眼部肿瘤患者提供种子加载调制的软件，以及 通过广泛的体模实验和MC模拟来委托/评估/验证系统。学习 设计：在建造改进的设备之前，将进行系统的MC模拟以优化设计。 将开发软件工具来分析数据并记录测量结果。广泛性 将进行体模测量，以比较和调整MC和光学系统模型。因素 将研究影响质量保证的不确定因素。与健康相关：这项提案旨在解决未得到满足的人 根据病变的形状和关键结构的保留，需要进行强度调节的个性化EPB。

Project summary / Abstract Intraocular cancers are optimally treated with eye plaque brachytherapy (EPB), involving surgical implantation of a carrier (“plaque”) loaded with radioactive sources (called seeds) on the scleral surface over the tumor base. While it is critical to ensure the strength and exact positions of the radioactive seeds for accurate treatment, current quality assurance (QA) practice according to the AAPM Task Group (TG) report 129 only dictates the plaque assembly be visually inspected due to the lack of an effective and practical technique to measure the seed radioactivity distribution. Clinically, this often limits treatments to using uniform seed intensity, otherwise we have to assume the correct loading without verification. This is especially suboptimal for plaques preloaded by the vendor, as seeds with different activities cannot be distinguished visually. Therefore, unlike the common practice of employing intensity modulation in external beam radiation therapy, we cannot further optimize treatment by using differential seed strengths to provide more personalized dosing based on the tumor itself and the location of normal organs. To overcome this fundamental issue hindering EPB advancement and solve the problems of previous EPB QA designs, our goal is to develop a fast, accurate, and low-cost QA system to allow safe integration of differentially loaded EPB. We constructed a proof-of-concept system consisting of a flat scintillator sheet and a lens/camera system mounted together, aiming to quantitatively measure the discrepancy in radioactivity/dose distribution of the plaque assembly from the originally planned distribution through the gamma evaluation commonly used for the QA of intensity modulated radiotherapy. The radioluminescence signal generated by a loaded plaque near the scintillator will be collected by the camera and processed in real- time to verify correct loading of the seeds. The measurement and analysis only require a few minutes, significantly shorter than the time to assay the extra verification seeds the physicist already must perform as recommended by TG129. Our preliminary data are promising, while we hypothesize that the performance can be improved by using a hemispherical scintillator conformal the plaque inner surface to enhance the system sensitivity and identify each individual seed in the plaque. Our initial Monte Carlo (MC) simulation demonstrated the feasibility. Specific aims: Design and construct a novel, functional prototype QA system with associated software enabling us to offer seed loading modulation to patients with ocular tumors, and commission/evaluate/validate the system through extensive phantom experiments and MC simulation. Study design: Systematic MC simulations will be performed to optimize the design before building the improved device. Software tools will be developed to analyze the data and document the measurement results. Extensive phantom measurements will be performed to compare and tune the MC and optical system models. Factors affecting the QA uncertainties will be studied. Health relatedness: This proposal aims to address the unmet need of intensity modulated, personalized EPB delivery based on the lesion shape and critical structure sparing.