Applications of particle physics techniques for proton computed tomography

Granado-González, Marc (2023). Applications of particle physics techniques for proton computed tomography. University of Birmingham. Ph.D.

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Abstract

Proton beam therapy can potentially offer improved treatment for head and neck cancers and paediatric patients. There has been a sharp uptake of proton beam therapy in recent years as improved delivery techniques and patient benefits are observed. However, treatments are currently planned using conventional X-ray CT images due to the absence of devices able to perform high-quality proton computed tomography (pCT) under realistic clinical conditions. The rise of new technologies such as the Depleted Monolithic Active Pixel Sensors (DMAPS), developed for the inner tracker upgrades at the High Luminosity Large Hadron Collider (HL-LHC) or the plastic scintillators detectors used at the Fine Grained Detector at the Tamioka to Kamio (T2K) experiment, could imply a big step forward in the field. This thesis aims to show the potential of both technologies by providing a proof of concept on the capabilities of these technologies. First, by building a tracker with two TJ-Monopix sensors and testing it at Birmingham's MC40 cyclotron and the proton minibeam radiotherapy centre at the Curie Institue under real clinical conditions, and second by simulating a full pCT system consisting in a DMAPS as proton trackers and a novel range telescope ASTRA (designed during the thesis). The simulation and consequent analysis aimed to obtain a pCT image of a phantom with 7 different materials. Using a set of classic algorithms and demonstrating later the enhancement obtained by using Convoluted Neural Networks (CNN). For the first part, the TJ-Monopix chip is used. The chip presents an excellent response up to a fluency of $\sim~$1~M $\frac{particles}{s}$ with no area coverage dependence, allowing flux above $\sim~$13.3~M $\frac{particles}{s*cm^2}$ with a fast detection rate of 40~MHz. Thus, the TJ-Monopix properties allow it also to be used as a beam monitoring device for micro-beam therapy and to improve the knowledge of the clinical beam's behaviour at low currents. ASTRA is the new plastic-scintillator-based range telescope concept designed to simulate a full proton CT system, it was first presented in the peer-reviewed paper \cite{MGranado} and it was used here to measure the proton’s energy loss in a pCT system. Simulations conducted using GEANT4 yield an expected energy resolution of 0.7$\%$. When calorimetric information is used in combination with Boosted Decision Trees (BDT) techniques the energy resolution could be further improved to about 0.5$\%$. In addition, the ability of ASTRA to track multiple protons simultaneously is presented, first with classic algorithms that do not use the energy-deposited information and then with the use of this information combined with a Comboluted Neural Network of the type U-Net using a novel in-pixel Multi-Label analysis. Due to its fast components, ASTRA is expected to reach unprecedented data collection rates around 10$^8$ protons/s. The performance of ASTRA has also been tested by simulating the imaging of phantoms The results show excellent image contrast and relative stopping power reconstruction.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):