A smart imaging sensor for real time transit dosimetry in radiotherapy

Radiotherapy treatment is delivered to over half of cancer patients, and due to the ageing population and lifestyle factors the prevalence of cancer is rising. EPIDs (electronic portal imaging devices) are used during the treatment delivery process to control patient set-up and positioning. The demand for accurate treatment verification has led to the possibility of using EPIDs to acquire dosimetric information.
Recent government guidelines require that each radiotherapy centre should have protocols for in vivo dosimetry monitoring and that it should be used at the beginning of treatment for most patients. Within the radiotherapy physics community EPID dosimetry is widely seen to have the potential to become an accurate and efficient means of large-scale patient specific in-vivo dose verification for Intensity Modulated RadioTherapy at any radiotherapy department.
Current EPID technology is based upon passive amorphous silicon flat panel imagers. In this proposal we plan to investigate the application of next generation sensor technology, developed by the STFC CMOS Sensor Design Group, which has both superior image quality and active functionality.
We propose to carry out a feasibility study with a long-term view to developing the following transit dosimetry technology: a large area, ultra high image quality flat panel imager displaying real-time, calibrated dose map updates throughout treatment delivery. The core of the system will be an STFC developed CMOS Active Pixel Sensor. It will not only introduce large area, radiation hard CMOS technology to EPID systems but will go a significant step further and introduce next generation Active Pixel Sensor technology.

Who will benefit from this research and how?

Department of Health policy makers - The department of health have made recommendations to all radiotherapy departments in the UK to implement in-vivo dosimetry methods. One recommendation is that IMRT would benefit from transit dosimetry and that research into this field should be encouraged and supported. This proposal aims to do exactly that and so will help to work towards safer radiotherapy for the UK and beyond.

Radiotherapy community - The radiotherapy community is actively implementing in-vivo dosimetry methods, including transit dosimetry. Currently centres are implementing methodologies which uses EPID technology that was designed and built for a different purpose, namely patient set-up and localisation. Consequently, the performance of current EPIDs is not matched to that required for transit dosimetry and there is a complete absence of any built-in functionality or programmable features that lend themselves to developing an automated, efficient technology that operates with minimal disruption to the clinical workflow. It is a common problem in radiotherapy that as the demand for more sophisticated radiotherapy increases and more technological solutions are introduced then it has a negative impact on patient throughput. We aim to counter this by introducing new technology with a programmable interface and built-in functionality to enable self-calibration, automated procedures, continuously updating display presenting the information needed in the most appropriate format without the need for post treatment analysis, and so on.

Patient groups - The Department of Health aim in recommending the introduction of in-vivo dosimetry and research into transit dosimetry was to make radiotherapy safer for the patient. The Case for Support refers to a report from the Netherlands whereby 17 serious errors were detected using transit dosimetry in the treatment delivery plan within a cohort of just over 4000 patients. Our aim is to introduce technology with superior performance and an application specific set of features and functionality to enable easy integration of such systems into the clinic.

Academic community - Novel large area, radiation hard, functional, sensor technology is applicable to a wide range of academic communities beyond radiotherapy, from medical imaging and monitoring, through to space science, particle physics and industrial imaging. Via wide dissemination we hope to introduce the technology to other disciplines and stimulate further research into such technological solutions. A key interest of the project consortium is to promote extensive research into solving the issues currently facing in-vivo dosimetry and work towards a verifiable radiotherapy solution.