Dosimetry by Radioluminescence of GaN for in vivo real time patient dose assessment for radiotherapy and interventional radiology – DoRGaN

Context
In external beam radiotherapy and brachytherapy, verification of the delivered dose at the target volume during each radiotherapy session and for the whole treatment is a key issue for quality assurance. To be reliable, this dosimetric monitoring must be independent and obtained in real-time. In interventional radiology, long and complex procedures require the skin entrance dose to be determined directly in real-time since doses of several Gy are not rarely observed. Also for emerging external radiotherapy modalities such as IMRT or hadrontherapy with proton or carbon ions beams require reliable punctual and robust (radiation hardness) dosimetry.

Program
To meet these application requirements, the DoRGaN project proposes to develop a multi-channel dosimetry system based on the use of GaN scintillator as transducer. The proposed studies are:
- Monte-Carlo simulations and Modeling of GaN energy response to therapeutic photon/electron beams, with implementation of a compensation/correction method for over-response effects of GaN scintillator.
- Design and realization of a new GaN-based dosimetric probe prototype, for head & neck IMRT radiotherapy treatments. This task includes development and integration of a specific calibration method.
- Design and realization of a multi-channel bundle probe and an associated photodetection module for brachytherapy. This task includes implementation of calibration bench for continuous or pseudo continuous irradiation operation.
- Design and realization of a multi-probe network dosimetry system providing probe geometric mapping, for interventional radiology. This task includes implementation of calibration bench.
- Phantom testing of GaN-based dosimetry probe in clinical protontherapy conditions, and spectral photoluminescence analysis of GaN after irradiation to evaluate clinical hadrons hardness.
- Development of system interface (SW/HW) (DICOM RT standard, PDR brachytherapy triggering,) … Implementation of patients files management allowing real-time control of the treatment and recording.
- Tests of dosimetry systems for External Beam Radiotherapy, Interventional Radiology, Brachytherapy, and Protontherapy for characterization and calibration, including ergonomics, reliability and accuracy.

Expected results
By the end of the DoRGaN project, pre-industrial dosimetry system prototypes will be available for Brachytherapy, External Beam Radiotherapy and Interventional Radiology. These prototypes will include optimized probes and associated instrumentation, with implementation of innovative methods and signal processing for efficient GaN energy dependence compensation, for optical transmission monitoring and probe failure detection. These prototypes will have been characterized on laboratory equipments and on clinical routinely used installations. The targeted accuracy of dose measurements is within +/-2% (1SD) for radiotherapy (electron and photon beams therapy and brachytherapy) and +/-10% (1SD) for interventional radiology.