Metrology Guided Radiotherapy

放射治疗通过反复使用小剂量的分次放射治疗肿瘤来治愈局部癌症。虽然健康的组织受到辐射，但图像辅助的治疗前计划将这种情况保持在最低限度。CT扫描可以看到体表、肿瘤和关键器官的比例，从而可以计算出一组辐射束的最佳形状和方向。这些药物每天都会在可能持续数周的治疗方案中使用。相应的剂量分布被估计，放射生物学可以用来预测治愈和并发症的概率。患者在治疗过程中会如何移动或变化，目前尚不清楚。因此，专家指定肿瘤周围的耐受范围，并假设其他一切都将保持治疗前的CT扫描所见。在这种简化的基础上，患者在治疗的每一天都进行定位。当治疗进行中，放射指向肿瘤时，没有对患者的位置或内部解剖进行监测。因此，精确计划的治疗是以一种有效的盲目方式提供的。这种情况仍然存在，尽管研究人员帮助开发了复杂的新治疗方法和图像引导放射治疗(IGRT)，其中现在包括“锥束”成像(CBI)。IGRT辐射剂量和CBI的实际限制是新的令人担忧的原因。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。它研究基于光电传感器的非侵入性、无辐射、实时的三维患者位置监测，使用结构光来绘制体表。一个性能无与伦比的原型系统已经在治疗室由研究人员成功地进行了试验。这将被开发为包括多颜色、自适应传感的基本概念，其中投射到身体表面的结构光首先预先适应患者CT计划扫描中提供的形状信息，然后在使用过程中进行细化。MEGURATH传感器将基于在治疗光束之间获取患者的图像而与新型低辐射剂量CBI同步。这一方法已经由研究人员与创新的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。在反馈环路中，CBI将针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，以量化肿瘤及其附近器官的形状和位置的变化。调查人员报告了使用传感器测量来变形治疗计划的试点工作。将这一方法推广到身体受辐射的部分，将有可能描述患者在照射期间发生的形状变化。这将是第一次从现场测量中构建治疗期间患者的逐点模型。反过来，这将最终使使用放射生物学来计算实际提供的治疗的肿瘤治愈和并发症的概率，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大力支持。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流动的疾病部位的癌症治疗问题，尤其是乳房、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.