From: Enrica Seravalli <>
Newsgroups: milano.seminari
Subject: 10-05-2010 2-D dosimetry using novel GEM scintillating detector for photon and particle beams
Date: Tue, 4 May 2010 13:55:26 +0000 (UTC)


                              Il giorno 10-05-2010
                        alle ore 10:00 in Aula Consiglio

                          La Dott.ssa Enrica Seravalli
                         Delft University of Technology

                        terra' un seminario dal titolo:

  2-D dosimetry using novel GEM scintillating detector for photon and particle

     When treating with charged particle beams, accurate knowledge of dose
  distributions in three-dimensions is critical. Ability to measure and verify
    quickly dose distributions in multiple dimensions is therefore extremely
 important. In this framework, we have developed a 10x10 cm2 position-sensitive
   scintillating gas detector for pre-treatment dose measurements in particle
 therapy. The primary electrons, created in the detector*s sensitive volume by
       the incoming beam, drift in an electric field towards two cascaded
 multiplicating structures (GEMs) where they undergo gas multiplication. During
   this process, photons are emitted by the excited Ar/CF4 gas molecules and
  detected by a mirror-lens-CCD camera system. The measured 2D light intensity
 distribution is proportional to the 2D distribution of the energy deposited in
   the sensitive volume by the beam. By placing an appropriate water bellows
   phantom in the beam in front of the detector a 3D dose distribution can be
reconstructed. The dosimetric properties of the detector that are of importance
 for verification of charged particle treatment plans were studied in a 150 MeV
proton beam, 360 MeV alpha particle and 250 MeV/u clinical carbon ion beam. The
main result of this work is that the energy dependence of the detector response
     in high LET (Linear Energy Transfer) beams is quite small compared to
          state-of-the-art 2D dosimeters with a millimetre resolution.

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