Enhancing the capability of MAPS for radiotherapy verification

我们已经开发了一个薄的，上游设备的真实的时间二维验证调强放疗的基础上LASSENA单片有源像素传感器。在调强放射治疗中，射束由一堆薄的移动准直器成形，以尽可能多地保留健康组织。该设备非常薄，因此可以放置在光束和患者之间，因为其衰减小于1%。该设备以前所未有的精确度（我们的位置分辨率为146微米，使用仅在一秒的治疗中生成的数据）和积分信号报告每个准直器的真实的时间位置，这给出了光束强度的粗略估计。因此，治疗计划可以在没有先前测量的情况下被真实的验证。放射治疗的趋势之一是转向更短但更强烈的治疗。其中之一是扁平过滤器免费（FFF）治疗。这些治疗提供了高得多的剂量率，因此更重要的是真实的时间监测治疗，因为错误可能具有严重的后果。我们目前基于LASSENA的系统不适合FFF治疗。一种新的传感器已经开发出来，雅典娜。在本提案中，我们希望在临床环境中使用Athena，并证明其至少与LASSENA一样有效，即使是FFF治疗。在正常的临床操作中，我们的设备每年将接受约5kGy的综合辐射剂量。我们希望对Athena进行辐射测试，以确定其临床寿命，从而确保基于Athena的器械作为产品是可行的。LASSENA无法测量给予患者的剂量。这是因为设备中的信号是由治疗光子和污染电子产生的信号的结果。后者是由光子与放射治疗机中的空气和材料相互作用产生的。电子信号取决于许多部分未知的参数，因此不能以简单的方式去除。我们已经发明了一种方法来同时测量电子和光子的贡献分别通过图案化的传感器的基板。我们成功地完成了原理测量的证明，并证明了该方法的有效性。已经申请了专利。在这个项目中，我们希望优化设计，并确定剂量测量精度。LASSENA系统能够真实的实时报告准直器位置。整个算法在LASSENA传感器的前身Achilles的DAQ系统的固件中实现。在本项目中，我们将调整Achilles系统的固件到Athena系统。项目完成后，我们将生产出一个能够真实的实时监测准直器位置和患者剂量的系统。这显著提高了患者的安全性，因为如果测量的治疗不符合计划的治疗，则可以在几秒钟内停止射束。这样的系统也将对NHS有很大的好处，因为在实际治疗之前不需要测量（体模运行）。因此，可以在同一时间内安全地治疗更多的患者。

We have developed a thin, upstream device for real time 2D verification of intensity modulated radiotherapy based on the LASSENA monolithic active pixel sensor. In intensity modulated radiotherapy, the beam is shaped by a stack of thin moving collimators to spare as much of the healthy tissue as possible. The device is very thin and can therefore be placed between the beam and the patient as its attenuation is less than 1%. The device reports the position of each of the collimators in real time with unprecedented precision (our position resolution is 146 micron using the data generated in only one second of treatment) and an integrated signal, which gives a crude estimate of the beam intensity. Thus the treatment plan can be verified in real time without prior measurements. One of the trends in radiotherapy is to move to shorter but more intense treatments. One strand of this is Flattening Filter Free (FFF) treatments. These treatments provide a much higher dose rate and therefore it is even more important to monitor the treatment in real time as errors can have grave consequences. Our current LASSENA-based system is not suitable for FFF treatments. A new sensor has been developed, the Athena. In this proposal we want to characterise the Athena in a clinical setting and demonstrate that it works at least as well as the LASSENA, even for FFF treatments. In normal clinical operation our device would receive an integrated radiation dose of around 5kGy per year. We want to perform a radiation test of the Athena to find its clinical lifetime to ensure that the Athena based device is viable as a product. The LASSENA is not able to measure the dose administrated to the patient. This is because the signal in the device is the result of signal generated by the therapeutic photons and contamination electrons. The latter are generated by interactions of the photons with air and materials in the radiotherapy machine. The electron signal is dependent on many and partly unknown parameters and thus cannot be removed in a simple way. We have invented a way to measure simultaneously the electron and the photon contribution separately by patterning the substrate of the sensor. We successfully completed proof of principle measurements and showed that the method works. A patent application has been made. In this project we want to optimise the design and determine the dose measurement precision. The LASSENA system is able to report the collimator positions in real time. The whole algorithm was implemented in the firmware for the DAQ system for a predecessor of the LASSENA sensor, the Achilles. In this project we will adapt the firmware from the Achilles system to the Athena system.After completion of the project, we will have produced a system that can monitor the collimator positions and the dose administered to the patient in real time. This significantly enhances patient safety as the beam can be stopped within seconds if the measured treatment is not conform the planned treatment. Such a system would also be of great benefit for the NHS as there is no need for measurements (phantom runs) before the actual treatment. Hence, more patients can be safely treated in the same time.