Open AccessInvestigating the effect of a magnetic field on dose distributions at phantom-air interfaces using PRESAGE®3D dosimeter and Monte Carlo simulations
Author(s) -
Francisco Costa,
Simon J. Doran,
I. Hanson,
Simeon Nill,
Ilias Billas,
D R Shipley,
S Duane,
J Adamovics,
Uwe Oelfke
Publication year - 2018
Publication title -
physics in medicine and biology/physics in medicine and biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.312
H-Index - 191
eISSN - 1361-6560
pISSN - 0031-9155
DOI - 10.1088/1361-6560/aaaca2
Subject(s) - imaging phantom , dosimeter , linear particle accelerator , monte carlo method , dosimetry , physics , quality assurance , nuclear medicine , radiation treatment planning , computational physics , radiation therapy , optics , mathematics , medicine , beam (structure) , statistics , radiology , external quality assessment , pathology
Dosimetric quality assurance (QA) of the new Elekta Unity (MR-linac) will differ from the QA performed of a conventional linac due to the constant magnetic field, which creates an electron return effect (ERE). In this work we aim to validate PRESAGE ® dosimetry in a transverse magnetic field, and assess its use to validate the research version of the Monaco TPS of the MR-linac. Cylindrical samples of PRESAGE ® 3D dosimeter separated by an air gap were irradiated with a cobalt-60 unit, while placed between the poles of an electromagnet at 0.5 T and 1.5 T. This set-up was simulated in EGSnrc/Cavity Monte Carlo (MC) code and relative dose distributions were compared with measurements using 1D and 2D gamma criteria of 3% and 1.5 mm. The irradiation conditions were adapted for the MR-linac and compared with Monaco TPS simulations. Measured and EGSnrc/Cavity simulated profiles showed good agreement with a gamma passing rate of 99.9% for 0.5 T and 99.8% for 1.5 T. Measurements on the MR-linac also compared well with Monaco TPS simulations, with a gamma passing rate of 98.4% at 1.5 T. Results demonstrated that PRESAGE ® can accurately measure dose and detect the ERE, encouraging its use as a QA tool to validate the Monaco TPS of the MR-linac for clinically relevant dose distributions at tissue-air boundaries.