Description du sujet de thèse

The thesis project described below is a collaboration between the 4 partners LPSC-Grenoble, CREATIS-Lyon, IP2I-Lyon and CAL-Nice. It is funded by the Interdisciplinarity Mission of CNRS.
Context, state of the art and objectives:
The measurement of gamma radiation following nuclear reactions was proposed 20 years ago to perform on-line and in vivo monitoring of proton therapy treatments (Stichelbaut and Jongen, 2003). Indeed, the emission sites of these secondary radiations are correlated to the path of the primary protons, and the weak absorption of the gamma radiations of a few MeV by the soft tissues allows their detection outside the patient. Various imaging techniques (collimated camera or Compton), spectroscopy, time-of-flight measurement, or more simply integral counting, have been proposed (Krimmer et al., 2018). However, the use of a monitoring system under routine clinical conditions still faces challenges, associated in particular with the need to obtain real-time information, regardless of the irradiation conditions, with the necessary sensitivity and significance for the detection of deviations from a treatment plan at the scale of the percent for dose, or the millimeter for positioning. In other words, statistically significant information must be obtained with a detection or imaging system that is compatible with the clinical irradiation system.
In particular, the proton beams delivered by the Proteus-One synchro-cyclotron accelerator at CAL-Nice have a structure with pulses of a few microseconds every millisecond, with a very low duty cycle, of the order of 1/1000, and therefore a very high peak intensity. A first challenge is therefore to acquire a sufficient number of gamma-ray photons associated with these short pulses, with a detection system having a sufficient dynamic range. A second issue is related to the ability to predict and model by fast Monte Carlo simulations the emitted radiation with their temporal and energy distribution (Kanawati et al, 2015). Finally, a third issue lies in the comparison between the signal obtained with a prediction from a treatment planning on the CAL-Nice irradiator, if possible in a very short time in order to consider a possible adaptation of the treatment in case of detected deviation.
We propose to adapt the so-called Prompt Gamma Peak Integral method (Krimmer et al., 2017) that was developed in a joint project between the partners of this project. This method is based on photon-counting by a small number of detectors positioned around the patient, such that the comparison of the detection rates of each detector provides information on both the position of the beam path in the patient, and the length of this path. An indirect information on the dose can thus be extracted.
At the beginning of the thesis, he or she will have to develop a beam model with time structure in the Monte Carlo Geant4/Gate simulations, model the detection system and the acquisition signal formation, and carry out numerous laboratory tests with detectors and gamma sources on the benches available at the LPSC and/or the IP2I. Then, from the second year, the selected person will need to be reactive in order to maximize the opportunities of available beam time outside the patient treatment hours, which will require a presence on site at the Centre Antoine Lacassagne in Nice. This presence on site will allow comparisons between measurements and treatment plans, and the analysis of the gamma prompt emission map under clinical conditions.

Contexte de travail

The Grenoble Laboratory of Subatomic Physics and Cosmology (LPSC) (http://lpsc.in2p3.fr) is a joint research unit involving the CNRS-IN2P3, the University of Grenoble Alpes (UGA) and the Grenoble INP school, with an average staff of about 230 people. The person recruited will be assigned to the Nuclear Physics and Medical Applications Team composed of 7 researchers/teaching researchers, 1 post-doctoral student and 5 doctoral students of the LPSC.
Travel to Lyon and Nice is expected during the thesis.

Contraintes et risques

The person will have to obtain a certificate of no contraindication to work in the presence of ionizing radiation

Informations complémentaires

Knowledge (M2 level) in physics of particle matter interaction and radiation detection
Motivation for Monte Carlo simulation, instrumentation and experimentation in nuclear physics
Knowledge in medical physics will be an asset

-Requested documents for application :
-Undergraduate marks
-(Optional) recommendation letters