%0 Journal Article
%A Frick, Stephan
%A Schneider, Moritz
%A Thorwarth, Daniela
%A Kapsch, Ralf-Peter
%T Determination of output correction factors in magnetic fields using two methods for two detectors at the central axis.
%J Physics in medicine and biology
%V 70
%N 6
%@ 0031-9155
%C Bristol
%I IOP Publ.
%M DKFZ-2025-00510
%P 065008
%D 2025
%X Objective.Commissioning an MR-linac treatment planning system requires output correction factors,kB→,Qclin,Qmsrfclin,fmsr, for detectors to accurately measure the linac's output at various field sizes. In this study,kB→,Qclin,Qmsrfclin,fmsrwas determined at the central axis using two methods: one that combines the corrections for the influence of the magnetic field and the small field in a single factor (kB→,Qclin,Qmsrfclin,fmsr), and a second that isolates the magnetic field's influence, allowing the use of output correction factors without a magnetic field,kQclin,Qmsrfclin,fmsr, from literature for determiningkB→,Qclin,Qmsrfclin,fmsr.Approach.To determinekB→,Qclin,Qmsrfclin,fmsrand examine its behaviour across different photon energies and magnetic flux densitiesBin small fields, measurements with an ionization chamber (0.07 cm3sensitive volume) and a solid-state detector were carried out at an experimental facility for both approaches. Changes in absorbed dose to water with field size were determined via Monte Carlo simulations. To evaluate clinical applicability, additional measurements were conducted on a 1.5 T MR-linac.Main results.Both methods determined comparablekB→,Qclin,Qmsrfclin,fmsrresults. For field sizes >3 × 3 cm2,Branging from -1.5 to 1.5 T and photon energies of 6 and 8 MV, no change ofkQclin,Qmsrfclin,fmsras a function of the magnetic field was observed. Comparison with measurement results from the 1.5 T MR-linac confirm this. For ⩽3 × 3 cm2,kB→,Qclin,Qmsrfclin,fmsrdepends on photon energy andB. For 1.5 T and 6 MV,BreduceskQclin,Qmsrfclin,fmsrup to 3
%K Magnetic Fields
%K Radiometry: instrumentation
%K Monte Carlo Method
%K Particle Accelerators: instrumentation
%K Magnetic Resonance Imaging: instrumentation
%K MR-guided radiation therapy (Other)
%K magnetic field correction factor (Other)
%K output correction factor (Other)
%K small field dosimetry (Other)
%F PUB:(DE-HGF)16
%9 Journal Article
%$ pmid:39983310
%R 10.1088/1361-6560/adb934
%U https://inrepo02.dkfz.de/record/299569