OPTIma: Optimising Proton Therapy through Imaging

在英国，每年确诊的癌症病例超过35万例，其中约40%的患者接受放射治疗作为治疗的一部分。大多数放射治疗采用直线加速器产生的外部x射线束。然而，人们对使用高能质子束进行放射治疗越来越感兴趣。在英国，两家NHS中心和几家私人中心将在未来几年内开业。质子束疗法对头颈部肿瘤、某些脑肿瘤、靠近危险器官的肿瘤和儿童癌症最有用。质子失去能量的方式与x射线（光子）非常不同，因为它们在组织中有一个有限的范围，大部分能量沉积在这个范围的末端。因此，质子可以用集中剂量靶向肿瘤，而健康组织较少暴露于辐射中。很明显，挑战在于准确地预测质子将把大部分能量储存在何处——在目标肿瘤而不是邻近的健康组织中。目前的治疗计划是基于x射线CT图像，但这在将基于低能x射线的图像转换为高能质子范围时产生了不可避免的不确定性。答案是使用相同的辐射类型来治疗和成像——“同一尺子”的概念。质子成像已被证明是困难的，因为必须在质子穿过病人或幻影时跟踪单个质子，并记录每个质子相应的剩余能量。我们之前的项目PRaVDA为宽束质子奠定了基础。目前的质子束治疗设施使用小直径的光束，在目标区域上进行电磁扫描。这意味着一个完全不同的仪器概念和设计，但基于我们对PRaVDA的经验。其理念是提供一个强大的、交钥匙的（对于尖端仪器来说尽可能可行），可以被更广泛的社区利用。该项目将在曼彻斯特克里斯蒂质子束治疗中心独特的研究室提供一个国家设施，用于探索质子成像与最先进的扫描铅笔束传输系统。这将为研究界开辟一种新的医学成像方式-放射治疗中的带电粒子成像。主要的项目目标是：探索质子CT和x线摄影的能力，将范围不确定性降低到不影响最佳治疗计划的水平。为复杂的生物样品开发算法，以计算效率高的方式提供满意和可量化的图像。结合不同模式的质子CT与其他影像（x线CT、PET等），提供更多临床信息，改善影像。为其他质子治疗中心提供设备及方法，以准确校正质子幻像。了解质子CT如何成功地整合到治疗工作流程中，从计划到治疗过程中的监测。进一步发展质子成像龙门系统，鼓励商业化开发。

Over 350,000 cancer cases are diagnosed annually in the UK with some 40% of patients receiving radiotherapy as part of their curative treatment. Most radiotherapy treatments employ external x-ray beams generated by linacs. However, there is a growing interest in the use of high-energy proton beams for radiotherapy. Within the UK, two NHS centres and several private ones will open in the next few years. Proton Beam Therapy is most useful for tumours in the head/neck region, some brain tumours, tumours near to organs at risk and childhood cancers. Protons lose their energy in a very different way to x-rays (photons) as they have a finite range in tissue with most of their energy being deposited near the end of this range. So protons can target a tumour with a focused dose with less exposure of healthy tissue to radiation. The challenge is, clearly, predicting accurately where the protons will deposit the bulk of their energy - in the target tumour and not in neighbouring healthy tissue. Treatment planning is currently based on x-ray CT imagery but this gives rise to unavoidable uncertainties in translating from images based on low energy x-rays to the ranges of high energy protons. The answer is to use the same radiation type to treat and to image - the concept of the 'same ruler'. Imaging with protons has proved difficult as it is necessary to track individuals protons as they pass through a patient or phantom and record the corresponding residual energy of each proton. Our previous project, PRaVDA, laid the foundations of this for a broad beam of protons. Current Proton Beam Therapy facilities use small diameter beams that are electromagnetically scanned over the target region. This implies a radically different instrument concept and design, but based on our experience with PRaVDA. The philosophy is to provide a robust, turn-key (as far as feasible for a cutting-edge instrument) that can be exploited by a wider community.This project will provide a national facility in the unique Research Room at The Christie Proton Beam Therapy Centre, Manchester, for exploring proton imaging with a state-of-the-art scanning pencil-beam delivery system. This will open up to the research community a new medical imaging modality - charged-particle imaging in radiotherapy. The main project aims are:Explore the capabilities of proton CT and radiography in reducing range uncertainties to a level that do not influence optimum treatment planning.Develop algorithms for complex biological samples that provide in a computationally efficient manner satisfactory and quantifiable imagery.Combining different modes of proton CT and other imagery (x-ray CT, PET, etc) to provide more clinical information and improved imagery.Providing a facility and a methodology for the accurate calibration of phantoms for other proton therapy centres.Understanding how proton CT can be successfully integrated in treatment workflows from planning to in and between treatment monitoring. Further the development of proton imaging for gantry systems and encourage commercial exploitation.