Metrology Guided Radiotherapy

放射疗法通过重复地以小剂量的“部分”辐射靶向肿瘤来治疗局部癌症。虽然健康组织受到辐射，但图像辅助治疗前计划将其保持在最低限度。CT扫描可以看到身体表面、肿瘤和重要器官的比例，从而可以计算出一组辐射束的最佳形状和方向。这些是每天使用的治疗方案，可能持续数周。相应的剂量分布估计和放射生物学可以用来预测治愈和并发症的概率。患者在治疗期间将如何移动或改变尚不清楚。因此，专家指定肿瘤周围的公差范围，并假设其他一切都将保持在治疗前CT扫描中所见。在这种简化的基础上，患者在治疗的每一天都被定位。当治疗正在进行时，放射线正指向肿瘤，没有对患者的位置或内部解剖结构的监测。因此，以有效盲的方式提供精确计划的治疗。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“锥形束”成像（CBI），这是研究人员帮助开发的。IGRT辐射剂量和CBI的实际限制是新的关注原因。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。研究了基于光电传感器的无创、无辐射、实时三维病人位置监测，利用结构光映射人体表面。一个原型系统，具有无与伦比的性能，已成功地试点的研究人员在治疗室。这将被开发为包括多色、自适应感测的激进概念，其中投射到身体表面上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细化。MEGURATH传感器将与新型低辐射剂量CBI同步，基于在治疗射束之间采集患者图像。这种方法已经由研究者沿着创新的CBI准直器设计进行了试验，该设计有可能将患者剂量减半，但改善了重建体积图像的对比度。在反馈回路中，CBI然后将针对不一定是周期性的测量运动被最佳地校正。然后将重建成像与动态变形建模相结合，以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计划的试点工作。将这种方法扩展到身体的受照射部分，将使描述患者在照射期间发生的形状变化成为可能。这将是第一次在治疗过程中通过实时测量构建患者的逐点模型。反过来，这将最终使使用放射生物学来计算肿瘤治愈的概率和实际提供的治疗的并发症，并将其与计划的治疗进行比较成为可能。MEGURATH具有强大的，多样化的理论组成部分。它还有一个雄心勃勃的计划，将科学和技术转化为英国第一个专门建造的IGRT研究设施。它得到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移动的疾病部位的癌症治疗，尤其是乳腺、肺和骨盆。

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.