Development of novel sensors for radiotherapy verification

Lead Research Organisation: University of Bristol
Department Name: Physics

Abstract

The PhD project will address the development of novel dosimeters for conventional radiotherapy and novel treatments. The trend in conventional radiotherapy is to move towards shorter treatments, using fewer but more intense pulses with varying pulse rates and intensities. Hence, there is a clear need for real time, pulse by pulse dosimetry. Currently, systems integrate over the treatment. Hence, the delivered dose is only checked after treatment. We aim to develop novel, extremely thin silicon diode dosimetry systems exploiting modern silicon processing technology, which will not suffer from the tissue equivalence issue, do not display the angular dependence and measure the delivered dose, pulse by pulse, in real time. With the advent of Intensity Modulated Radiotherapy (IMRT), where the LINAC beam is dynamically shaped using multileaf collimators, it has become possible to deliver treatment with very high precision. High precision delivery is however more valuable when this information can be combined with the position of the tumour. To that effect, several consortia are developing integrated MRI-IMRT machines. This implies that the dosimetry needs to be done with high precision in a high magnetic field. We have already successfully tested the dosimetry system we developed for our NIHR-i4i project in a prototype MRI-IMRT in Utrecht. In this PhD we will further develop the detectors, the readout and the data analysis for both challenges. The work will also encompass a large Monte Carlo simulation program to optimize the designs. We aim to produce functional prototypes for both applications.

Publications

10 25 50

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509619/1 01/10/2016 30/09/2021
1942503 Studentship EP/N509619/1 18/09/2017 30/09/2021 Jordan Pritchard
 
Description The research which I have conducted to-date has focused on Multileaf collimator (MLC) leaf edge verification. Multileaf collimators (MLC) are an essential component in modern radiotherapy as they shape the X-ray treatment beam prior to interacting with the patient. The MLC is situated in the head of the Liner accelerator (LINAC) and consists of two opposing rows of tungsten leaves which move independently of each other to create complex spatial treatment geometries. These geometries ensure that the X-ray treatment beam irradiates cancerous tissue and spares healthy tissue being irradiated. The precise placement of these leaves is therefore of fundamental importance as poorly verified or misaligned leaves can cause errors within the patients delivered treatment. Current methods verify the MLC leaf positions to +/- 1mm pre-treatment and independent live-treatment monitoring is none existent.

I have conducted research using a Lassena Monolithic Active Pixel Sensor (MAPS) device and have shown that it is capable of monitoring MLC leaf edge positions, with resolutions ranging between 60.6 +/- 8 microns and 109 +/- 12 microns, accurate over a range of leaf displacements. These results show that MLC leaf edges can be verified at excellent resolutions using the Lassena device, which exceeds the current +/- 1 mm tolerance. Additionally, these results were obtained using 0.3 seconds of treatment beam and the algorithms developed can be implemented in an Field-Programmable Gate Array (FPGA), hence live-treatment monitoring is achievable. It has been demonstrated that this device is a working solution and is also clinically deployable.

The above-mentioned research was presented at the 2019 IEE NSS MIC conference (see 'engagement activities'), earlier research findings have been accepted to the 2019 IEE NSS MIC conference record (see 'publications') and the above-mentioned results have been submitted to the IEEE TRPMS journal for publication and are currently undergoing the review process.
Exploitation Route This award is still active, hence the research associated with this funding is still ongoing. The results described above however, provide an excellent foundation for a MAPS device to be used for the live-treatment monitoring of MLC leaf edges. Taking this forward, a live-treatment monitoring device can be developed for use in radiotherapy.
Sectors Electronics,Healthcare,Other

 
Description 2019 IEEE Nuclear Science Symposium and Medical Imaging Conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact I attended the 2019 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS MIC) and gave an oral presentation detailing my research, outlined in the "key findings" section of this submission. This conference is the leading annual international meeting for research regarding radiation detectors, related technologies and their applications. The purpose of this talk was to share my research with the wider scientific community who specialise in areas relating to my research. Outcomes from the talk included further discussions with academics afterwards and requests for further information regarding this research.
Year(s) Of Engagement Activity 2019
URL https://nssmic.ieee.org/2019/
 
Description University of Bristol - Particle Physics Group 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact I gave an oral presentation to postgraduates and staff members of the particle physics group at the University of Bristol in which I presented my PhD project. The purpose of this talk was to inform other members of the research group the details of my PhD project, and to demonstrate that I have a good understanding of the project. Outcomes from the talk included discussing research methods that were applicable to my research.
Year(s) Of Engagement Activity 2017
 
Description University of Bristol - School of Physics 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact I gave an oral presentation to postgraduates and staff members of the physics department at the University of Bristol in which I presented an overview of my research area. This talk was part of a series of postgraduate talks, in which students presented their research to a wider audience within the physics department. The purpose of this talk was to inform other research groups of other research taking place across the department. Outcomes from the talk included audience members having a more positive view of Radiotherapy.
Year(s) Of Engagement Activity 2018
 
Description University of Bristol - physics open days 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact The particle physics department at the University of Bristol has a series of open days, masterclasses and prospective PhD student introductions throughout the year. I have participated in these events on a number of occasions, and as part of these events I discuss my area of research with school, undergraduates and postgraduate students.
Year(s) Of Engagement Activity 2018,2019,2020