Online control of the beam range during Hadrontherapy
Résumé
One of the advantages of hadrontherapy with respect to conventional radiotherapy is the fact that ions deposit a large fraction of their dose at the end of their path (Bragg peak), which allows a maximization of the dose to the tumor and a minimization in haelthy tissues. The lateral dose distribution is also quite narrow. Another advantage is the higher relative biological effectiveness. Due to sharp falloff, one of the major issues for quality control during the treatment with ion beams is the control of the Bragg peak position and its conformation to the tumor volume. A mispositioning would lead to an over-dosage of healthy tissue and/ or an under-dosage in the target volume.Since no primary radiation is emerging from the patient during traetment, secondary radiation arising from nuclear reactions is used for in vivo monitoring purposes. Several types of radiation are being investigated in the frame of WP1 of the LabEx PRIMES and WP4 of France Hadron:- the detection of the two 511 KeV gammas following a beta+ decay via a PET scanner,- prompt secondary radiation following inelastic nuclear interactions, either prompt gamma rays via a collimated gamma or Compton camera, or secondary proton vertex imaging.Proton radiography and computed tomography (CT) is also under investigation for quality assurance prior to the irradiation: this could reduce the uncertainty of the proton therapy planning due to the lack of accuracy in the proton stopping power of tissues computed from photon CT images.