Sharpening the edge in pencil-beam proton therapy: an aftermarket collimation system to better spare normal tissue during radiation treatment

项目概要/摘要： 目前在笔形束扫描（PBS）质子治疗中存在技术差距，导致过量的 辐射剂量溢出到预期靶组织之外。这一差距的存在是一个重要的 问题，因为在技术解决方案开发出来之前，接受PBS质子治疗的患者将 暴露于不需要的辐射剂量和正常组织并发症。长期目标是增加 治疗效果和降低与PBS质子治疗相关的副作用的风险。整体 本项目的目标是翻译和验证一种新的准直器技术，称为动态准直 系统（DCS），与现有的商业PBS质子治疗输送系统在临床设置，以限制 剂量溢出。DCS使用四个独立控制的修剪刀片， 与PBS输送期间扫描的质子束同步。通过在光束到达 在肿瘤的侧边界，剂量分布可以被锐化并且剂量到周围正常 结构可以大大减少。与其他建议的解决方案不同，DCS可以提供独特的 用于PBS质子治疗治疗的每个能量层的准直和足够小的覆盖区， 靠近患者表面的位置。进行这项工程计划的理据是， 现有的PBS设备，仅是3000万美元质子治疗中心成本的一小部分， 转化为更好的临床护理服务。在我们的计算机模拟治疗的强大初步数据的指导下 区域供冷系统的发展将按三个具体目标进行：1）设计，建造， 并根据我们的广泛建模验证DCS原型，2）最大限度地减少治疗时间损失 与DCS相关，以及3）为中心提供使用DCS的适当方法。根据具体 目标1，现有的计算机设计模型将驱动集成原型的物理构造 系统和剂量测定性能将根据系统模型进行确认。在具体目标2下， 将开发和测试一种修剪机排序算法，该算法允许修剪机叶片的动态运动 与光束扫描同时进行。该算法的目的是使治疗时间损失最小化 与DCS相关，每次治疗的目标治疗时间损失小于2分钟。 在具体目标3下，将制定质量保证和试运行方法，以促进安全和 放射肿瘤学界对DCS的有效临床使用。这项研究提出， 应用是创新的，因为它代表了一个新的和实质性的偏离目前的准直 技术，并引入了一个紧凑的准直器，具有动态运动，用于成形单个笔 一层一层的光束。预期这一贡献将是显著的，因为准直系统将减少 剂量的目标周围的健康组织，导致改善患者的结果。最终，这样的设备 具有减少接受PBS质子治疗的患者的正常组织并发症的潜力。

Project Summary/Abstract: There is currently a technological gap in pencil beam scanning (PBS) proton therapy that is resulting in excess spillage of radiation dose outside of the intended target tissue. Existence of this gap represents an important problem because, until a technological solution is developed, patients undergoing PBS proton therapy will be exposed to unwanted radiation dose and the normal tissue complications. The long-term goal is to increase therapeutic efficacy and reduce the risk of side effects associated with PBS proton therapy. The overall objective of this project is to translate and validate a new collimator technology, called the dynamic collimation system (DCS), with an existing commercial PBS proton therapy delivery system in a clinical setting to limit the dose spillage. The DCS makes use of four independently controlled trimmer blades that are designed to move in synchrony with the scanned proton beam during PBS delivery. By intercepting the beam as it arrives at the lateral boundaries of the tumor, the dose distribution can be sharpened and dose to surrounding normal structures can be substantially reduced. Unlike other proposed solutions, the DCS can provide unique collimation for each energy layer of a PBS proton therapy treatment and a footprint small enough to allow placement near the surface of the patient. The rationale for the project is that the addition of the DCS to existing PBS equipment, at only a small fraction of the cost of a $30M+ proton therapy center, can rapidly translate to improved clinical care delivery. Guided by strong preliminary data from our in-silico treatment planning studies, development of the DCS will be carried out by pursing three specific aims: 1) Design, build, and validate a DCS prototype based on our extensive modeling, 2) Minimize the treatment time penalty associated with the DCS, and 3) Provide appropriate methodologies for centers to use the DCS. Under specific aim 1, an existing computer designed model will drive the physical construction of an integrated prototype system and the dosimetric performance will be validated against a model of the system. Under specific aim 2, a trimmer sequencing algorithm will be developed and tested that allows dynamic motion of trimmer leaves simultaneously with beam scanning. The purpose of this algorithm is to minimize the treatment time penalty associated with the DCS, with a target treatment time penalty of less than 2 minutes per treatment session. Under specific aim 3, a quality assurance and commissioning approach will be developed to facilitate safe and effective clinical use of the DCS by the radiation oncology community. The research proposed in this application is innovative because it represents a new and substantial departure from current collimation technologies with the introduction of a compact collimator with dynamic motion for shaping individual pencil beams layer-by-layer. This contribution is expected to be significant as the collimation system will decrease the dose to healthy tissue surrounding the target, leading to improved patient outcomes. Ultimately, such a device has the potential to reduce normal tissue complications for patients undergoing PBS proton therapy.