A Proton Tomography System for Optimization of Proton Therapy

摘要 质子疗法正在美国迅速发展。目前，质子中质子射程的计算 治疗患者是基于患者组织的CT Hounsfield单位转换为质子相对停顿 权力。这一转换的不确定性需要更大的近端和远端计划目标销量利润率。 这些更大的利润率增加了对附近健康组织的剂量，导致了不必要的和可以避免的毒性。 质子计算机断层扫描(PCT)通过直接测量质子阻止能力避免了这些不确定性， 而这可以大幅减少计划的靶标体积，从而直接降低毒性。质子射线照相 (PRAD)能够准确地将患者与质子束对准，并对解剖结构进行量化 治疗前治疗位置的一致性和质子范围，这将导致更多 始终如一的目标覆盖，改善了患者的预后。临床质子成像系统必须提供 PCT以及PRAD能力。该项目旨在实现先进的，将确保完整的功能 在临床环境中的质子成像，并展示质子成像系统与FDA的路径 通行证。质子治疗方面的这些关键改进是辐射领域的基本要求 肿瘤学走向低分馏(以更少的分数给予更高剂量的治疗)。 ProtonVDA(https://www.protonvda.com/)，)与最近的第二阶段SBIR赠款一起，已经充分展示了第一个 一种能够用临床质子拍摄并快速显示准确PRAD图像的系统的功能原型 使用极低强度的铅笔束扫描系统来分析单个质子。虽然功能齐全的 PCT系统尚不存在，该项目将涉及来自洛马林达大学的联合调查人员 具有临床前PCT系统的丰富经验。ProtonVDA的技术将用于开发一种完全 功能PCT原型。而PRAD使用单波束方向，而PCT则需要一套完整的角度 在对象参考系中至少跨越180度。这可以通过使用固定的百分比来实现 在旋转对象时或在沿PCT系统旋转时与固定对象一起旋转时的系统和质子束 用质子束。在这两种情况下，梁内任何机械运动的精确信息 传输、成像和对象参考帧是必不可少的，因为轴未对齐或 机械下垂会显著降低图像质量。因此，原型将包含一个光学 跟踪系统，以测量和纠正这些移动。Provision中的项目协作者 (https://provisionhealthcare.com/)之前曾演示过对患者使用光学跟踪 定位。在PCT系统开发后，使用PCT计划的质子束应用于模体进行测试 包含剂量学胶片将验证PCT的临床相关准确性。

Abstract Proton therapy is rapidly expanding in the United States. Currently, the calculation of proton range in proton therapy patients is based on a conversion of CT Hounsfield Units of patient tissues to proton relative stopping power. Uncertainties in this conversion necessitate larger proximal and distal planned target volume margins. These larger margins increase the dose to nearby healthy tissues, causing unwanted and avoidable toxicities. Proton computed tomography (pCT) avoids these uncertainties by directly measuring proton stopping power, and this can drastically reduce the planned target volume, thus directly reducing toxicity. Proton radiography (pRad) has the capability to accurately align the patient to the proton beam and quantify anatomical consistency and proton range in the treatment position just prior to treatment, which will lead to more consistent target coverage, yielding improved patient outcomes. Clinical proton imaging systems must provide pCT as well as pRad capability. This project aims to achieve the advances that will ensure the full functionality of proton imaging in a clinical environment and demonstrate a proton imaging system with a path to FDA clearance. These key improvements in proton therapy are an essential requirement as the field of radiation oncology moves toward hypofractionation (higher dose treatments given in fewer fractions). ProtonVDA (https://www.protonvda.com/), with a recent Phase II SBIR grant, has demonstrated the first fully functional prototype of a system able to take and promptly display accurate pRad images with clinical proton pencil beam scanning systems using very low intensity to analyze individual protons. While a fully functional pCT system does not yet exist, this project will involve co-investigators from Loma Linda University with extensive experience with a preclinical pCT system. ProtonVDA’s technology will be used to develop a fully functional pCT prototype. Whereas pRad uses a single beam direction, pCT requires a complete set of angles spanning at least 180 degrees in the object reference frame. This can be achieved either with a fixed pCT system and proton beam while rotating the object or with a fixed object while rotating the pCT system along with the proton beam. In both cases, precise information on any mechanical movements within the beam delivery, imaging, and object reference frames is essential, because effects from axis misalignment or mechanical sagging can significantly degrade image quality. Therefore, the prototype will incorporate an optical tracking system to measure and correct for these movements. Project collaborators from Provision (https://provisionhealthcare.com/) have previously demonstrated the use of optical tracking for patient positioning. After development of the pCT system, tests using pCT-planned proton beams applied to phantoms containing dosimetric films will verify the clinically relevant accuracy of pCT.