Radiotherapy based on hadrons like protons or carbon ions is a promising treatment for improving cancer care. Hadrons target tumors and cancer cells with precision and minimal exit dose, reducing overall toxicity and the likelihood of secondary tumors caused by the treatment. In order to ensure safe treatment delivery during clinical practice, compact energy detection systems are of importance as they can provide for range verification, energy determination and hadron-based imaging.
Particularly, range uncertainty is an issue because when using high-dose from a particle beam a small uncertainty can greatly affect tumor control or cause normal-tissue complications. Inaccuracies and non-uniqueness of the calibration from computer tomography (CT) Hounsfield units to proton stopping powers affects the accuracy of the treatment planning system (TPS), therefore, it is desirable to verify proton range in vivo. Moreover, for QA applications, there is a need of detectors that can provide a comprehensive characterization of the incoming radiation, which requires the verification of the reproducibility of treatment delivery (energy, dose, position) within assumed dynamic range of measurement conditions.
However, current systems for range verification are based on a bulky detector to infer the energy of the hadrons, which proves unpractical for clinical application. Additionally, to fully characterize the incoming irradiation we usually use two or more different detectors for measuring dose, spatial characteristics and energy.
In this project, we propose a novel methodology to measure the residual energy of protons from first physical principles, without requiring their complete stop in the detector and heuristic calibration. The idea focuses on collecting the secondary electrons inevitably set in motion by the hadrons during their course in matter (water, PMMA). By passing hadrons through a magnetic field, it is possible to separate the electrons from the hadrons and follow their path. The electrons’ trajectory depends on their energy, which is strongly correlated with the hadron’s energy. Hence, characterizing the former provides a good surrogate of the latter. The goal of this project is to study the feasibility of this concept and to develop a prototype designed for measuring the secondary electrons.
The prototype will have two main applications
1) in proton therapy QA, where the prototype will measure both energy and, possibly, spatial resolution from monoenergetic and quasi-monoenergetic clinical proton beam;
2) in Proton tomography (pCT), where the prototype will assess the heterogeneities and multiple scattering of proton energies traversing the human body.(Deffet, 2018).
The PhD student will work closely with Monte Carlo simulations, instrumentation and measurements, using a proton beam at the therapy centre in Leuven on Gasthuisberg campus.