TY  - JOUR
AU  - Marot, Mathieu
AU  - Surla, Sonja
AU  - Burke, E.
AU  - Brons, S.
AU  - Runz, A.
AU  - Greilich, S.
AU  - Karger, Christian
AU  - Jäkel, Oliver
AU  - Burigo, Lucas Norberto
TI  - Proton beam dosimetry in the presence of magnetic fields using Farmer-type ionization chambers of different radii.
JO  - Medical physics
VL  - 50
IS  - 7
SN  - 0094-2405
CY  - College Park, Md.
PB  - AAPM
M1  - DKFZ-2023-00569
SP  - 4590-4599
PY  - 2023
N1  - #EA:E040#LA:E040# / 2023 Jul;50(7):4590-4599
AB  - Magnetic resonance-guided proton therapy is promising, as it combines high-contrast imaging of soft tissue with highly conformal dose delivery. However, proton dosimetry in magnetic fields using ionization chambers is challenging since the dose distribution as well as the detector response are perturbed.This work investigates the effect of the magnetic field on the ionization chamber response, and on the polarity and ion recombination correction factors, which are essential for the implementation of a proton beam dosimetry protocol in the presence of magnetic fields.Three Farmer-type cylindrical ionization chambers, the 30013 with 3 mm inner radius (PTW, Freiburg, Germany) and two custom built chambers 'R1' and 'R6' with 1 and 6 mm inner radii respectively were placed at the center of an experimental electromagnet (Schwarzbeck Mess - Elektronik, Germany) 2 cm depth of an in-house developed 3D printed water phantom. The detector response was measured for a 3×10 cm2 field of mono-energetic protons 221.05 MeV/u for the three chambers, and with an additional proton beam of 157.43 MeV/u for the chamber PTW 30013. The magnetic flux density was varied between 0.1 and 1.0 Tesla in steps of 0.1 Tesla.At both energies, the ionization chamber PTW 30013 showed a non-linear response as a function of the magnetic field strength, with a decrease of the ionization chamber response of up to 0.27±0.06
KW  - MR-guided Proton therapy (Other)
KW  - dosimetry (Other)
KW  - ionization chamber (Other)
KW  - magnetic fields (Other)
LB  - PUB:(DE-HGF)16
C6  - pmid:36940235
DO  - DOI:10.1002/mp.16368
UR  - https://inrepo02.dkfz.de/record/274367
ER  -