TY  - JOUR
AU  - Dal Bello, Riccardo
AU  - Magalhaes Martins, Paulo Jorge
AU  - Brons, Stephan
AU  - Hermann, German
AU  - Kihm, Thomas
AU  - Seimetz, Michael
AU  - Seco, Joao
TI  - Prompt gamma spectroscopy for absolute range verification of 12C ions at synchrotron based facilities.
JO  - Physics in medicine and biology
VL  - 65
IS  - 9
SN  - 1361-6560
CY  - Bristol
PB  - IOP Publ.
M1  - DKFZ-2020-00464
SP  - 095010
PY  - 2020
N1  - 2020 May 11;65(9):095010#EA:E041#LA:E041#
AB  - The physical range uncertainty limits the exploitation of the full potential of charged particle therapy. In this work we face this issue aiming to measure the absolute Bragg peak position in the target. We investigate p,4He,12C and16O beams accelerated at the Heidelberg Ion-Beam Therapy Center. The residual range of the primary12C ions is measured using the prompt gamma spectroscopy method, which was demonstrated for proton beams accelerated by cyclotrons and is developed here for the first time for heavier ions accelerated by a synchrotron. We develop a detector system that includes (i) a spectroscopic unit based on cerium(III) bromide and bismuth germanium oxide scintillating crystals, (ii) a beam trigger based on an array of scintillating fibers and (iii) a data acquisition system based on a FlashADC. We test the system in two different scenarios. In the first series of experiments we detect and identify 19 independent spectral lines over a wide gamma energy spectrum in presence of the four ion species for different targets, including also a water target with a titanium insert. In the second series of experiments we introduce a collimator aiming to relate the spectral information to the range of the primary particles. We perform extensive measurements for a12C beam and demonstrate submillimetric precision for the measurement of its Bragg peak position in the experimental setup. The features of the energy and time spectra for gamma radiation induced by p,4He and16O are investigated upstream and downstream the Bragg peak position. We conclude the analysis extrapolating the required future developments, which would be needed to achieve range verification with a 2 mm accuracy during a single fraction delivery of D = 2 Gy physical dose.
LB  - PUB:(DE-HGF)16
C6  - pmid:32092707
DO  - DOI:10.1088/1361-6560/ab7973
UR  - https://inrepo02.dkfz.de/record/153798
ER  -