J-F Adam (RSRM Université Grenoble Alpes) Radiothérapie et imagerie par rayonnement synchrotron

Tuesday 5 Mar 2019, 11:00 → 12:00 Europe/Paris

Amphithéâtre (LPSC)

Medical Physics in (bio)medical applications of synchrotron radiation JF Adam on behalf of the INSERM/UGA STROBE team The use of x-rays for medical purposes started almost immediately after Wilhelm Conrad Roëntgen's discovery of x-rays in November 1895. Since then, x-rays have played a central role in diagnostic imaging methods and in radiation therapy. The advent of synchrotron radiation (SR) has added a new dimension to the use of x-rays in imaging and therapy, and several beamlines currently have active research programs in medicine using high-flux coherent x-ray beams produced by a synchrotron source. These programs are covering a broad range of topics, from fundamental biomedical research to clinical trials on human patients. The aim of this presentation is to detail the medical physics issues in synchrotron imaging and radiotherapy programs that are developed in the INSERM-Grenoble-Alpes Research team based at the European synchrotron. High contrast in X-ray medical imaging, while maintaining acceptable radiation dose levels to the patient is the ultimate goal that should be achieved in diagnostic imaging. Synchrotron radiation offers two promising methods: spectral imaging, including K-edge subtraction imaging and phase contrast imaging which explores the phase signal potential, whereas conventional x-ray imaging uses the absorption signal. Besides conventional x-ray radiation sources, synchrotron radiation has also proven to offer significant advantages in external beam radiotherapy (RT) for further widening the therapeutic window (a better tumor control with reduced side effects). The relatively weak beam penetration is compensated by (i) high dose rate x-ray beams to take advantage of the so-called flash effect, (ii) high beam coherence allowing to produce submillimetric fields and a spatial fractionation of the dose to explore the limits of a concept called dose-volume effects; and (iii) the potential of combined therapies using synchrotron low-medium energies x-ray on high-atomic number radiosensitizers. This is of particular interest as 70% of cancer patients are treated using ionising radiation. The first phase I/II clinical study of Synchrotron RT ever realized has recently been performed at the European Synchrotron Radiation Facility (ESRF) in a dose escalation protocol on 15 patients to show the feasibility and safety of the technique. As this technique is still in its conception phase, it obviously requires extensive methodological and medical physics development for further implementation in clinics, in particular for in vivo dosimetry, which is the real-time assessment of the true dose delivered to targets and organs at risk during the treatment. The various medical physics aspects of synchrotron radiotherapy will also be covered in this seminar.