Metrology Guided Radiotherapy

放射治疗通过反复用小剂量的“部分”辐射靶向肿瘤来治疗局部癌症。虽然对健康组织进行照射，但图像辅助的预处理计划将其保持在最低限度。CT扫描可以让人体表面、肿瘤和关键器官按比例显示出来，这样就可以计算出一组辐射束的最佳形状和方向。这些都是每天使用的治疗方案，可能持续数周。估计相应的剂量分布，放射生物学可以用来预测治愈和并发症的概率。在治疗过程中，病人会如何移动或改变是未知的。因此，专家指定肿瘤周围的容忍度，并假设其他一切都将保持在治疗前的CT扫描中。在这个简化的基础上，病人在治疗的每一天被定位。在治疗过程中，对肿瘤进行放射治疗时，对患者的体位或内部解剖结构没有监测。因此，精确计划的治疗以一种有效的盲目方式进行。这种情况仍然存在，尽管复杂的新治疗和图像引导放射治疗（IGRT），现在包括“锥束”成像（CBI），这是研究人员帮助开发的。IGRT辐射剂量和CBI的实际限制是引起关注的新原因。MEGURATH引入了计量引导放射治疗（MGRT），在治疗过程中对患者进行测量、成像和建模。研究基于光电传感器的无创、无辐射、实时三维患者位置监测，利用结构光绘制体表。研究人员在治疗室成功试验了一个性能无与伦比的原型系统。这将发展为包括多色、自适应传感的基本概念，其中投射到体表的结构光首先预先适应患者CT计划扫描中可用的形状信息，然后在使用过程中进行改进。MEGURATH传感器将与基于获取治疗光束之间患者图像的新型低辐射剂量CBI同步。这种方法已经被研究人员与创新的CBI准直器设计一起进行了试验，该设计有可能将患者剂量减半，同时提高重建体积图像的对比度。在反馈回路中，CBI将对不一定是周期性的测量运动进行最佳校正。然后，重建成像将与动态变形建模相结合，量化肿瘤和附近器官的形状和位置的变化。研究人员报告了使用传感器测量来改变治疗方案的试点工作。将这种方法扩展到身体的辐照部位，将有可能描述患者在辐照期间发生的形状变化。这将是第一次从现场测量中构建患者在治疗期间的逐点模型。反过来，这将最终使利用放射生物学计算实际治疗中肿瘤治愈和并发症的概率成为可能，并将其与计划的治疗进行比较。MEGURATH具有强大而多样的理论组成部分。它还有一个雄心勃勃的计划，将科学技术转化为英国第一个专门建造的IGRT研究设施。它得到了IGRT和治疗计划设备制造商的物质支持。因此，它提供了一个独特的机会，将临床实践从IGRT推进到MGRT，并利用科学家、数学家和临床医生的技能来解决一些最重要和最易移动的疾病部位的癌症治疗问题，尤其是乳房、肺部和骨盆。

Radiotherapy cures local cancer by repeatedly targeting a tumour with small doses of radiation in 'fractions'. Though healthy tissues are irradiated, image assisted pre-treatment planning keeps this to a minimum. CT scans allow the body surface, tumour and critical organs to be seen to scale, so that the optimum shapes and directions of a set of radiation beams can be calculated. These are used daily in a treatment regime that may last weeks. The corresponding dose distribution is estimated and radiobiology can be used to predict the probabilities of cure and complications. How a patient will move or change during treatment itself, is unknown. Hence, an expert specifies a tolerance margin around the tumour and assumes everything else will stay as seen in the pre-treatment CT scan. On this simplified basis the patient is positioned on each day of the treatment.When treatment is in progress, and radiation is being directed at the tumour, there is no monitoring of the patient's position or internal anatomy. Hence, a precisely planned treatment is delivered in a manner that is effectively blind. This situation persists, despite complex new treatments and image guided radiotherapy (IGRT) that now includes 'cone beam' imaging (CBI), which the investigators helped to develop. IGRT radiation dose and CBI practical limitations are new causes for concern. MEGURATH introduces metrology guided radiotherapy (MGRT), where the patient is measured, imaged and modelled during treatment delivery. It researches non-invasive, radiation-free, real-time 3D patient positional monitoring based on optoelectronic sensors using structured light to map the body surface. A prototype system, with unrivalled performance, has been successfully piloted by the investigators in the treatment room. This will be developed to include radical concepts of multi-colour, adaptive sensing, where the structured light projected onto the body surface is first pre-adapted to the shape information available in patient's CT planning scan and then refined during use. The MEGURATH sensors will be synchronised with novel low radiation dose CBI based on acquiring images of the patient between treatment beams. This approach has been piloted by the investigators along with an innovative CBI collimator design that has the potential to halve patient dose, yet improve contrast in the reconstructed volume image. In a feedback loop, the CBI will then be optimally corrected for measured motion that is not necessarily periodic. Reconstructive imaging will then be combined with dynamic deformation modelling, to quantify changes in the shapes and positions of the tumour and nearby organs. Pilot work using sensor measurements to deform treatment plans has been reported by the investigators. Extending this approach across the irradiated part of the body will make it possible to describe the shape changes that occurred in the patient during irradiation. This will be the first time that a point by point model of the patient during treatment has been constructed from live measurements. In turn, this will finally make it possible to use radiobiology to calculate the probabilities of tumour cure and complications for the treatment actually delivered, and to compare this with the treatment that was planned.MEGURATH has strong, diverse theoretical components. It also has an ambitious programme for the translation of science and technology into the first purpose built IGRT research facility in the UK. It is materially supported by the manufacturers of IGRT and treatment planning equipment. Hence, it offers a unique opportunity to advance clinical practice beyond IGRT to MGRT and to use the skills of scientists, mathematicians and clinicians to address cancer treatment at some of the most significant and mobile disease sites, not least breast, lung and pelvis.