Development of a methodology to study the effect of magnetic field on dose distributions in an MR-linac, using PRESAGE? and Monte Carlo calculations

9th International Conference on 3D Radiation Dosimetry

Costa, F.^1 ; Doran, S.^2 ; Nill, S.^1 ; Duane, S.^3 ; Shipley, D.^3 ; Billas, I.^3 ; Adamovics, J.^4 ; Oelfke, U.^1

Joint Department of Physics, Institute of Cancer Research, Royal Marsden NHS Foundation Trust, London

SM2 5NG, United Kingdom^1

CRUK and EPSRC Cancer Imaging Centre, Institute of Cancer Research, London

SM2 5NG, United Kingdom^2

Acoustics and Ionising Radiation Team, National Physical Laboratory, Hampton Road, Teddington

TW11 0LW, United Kingdom^3

Department of Chemistry and Biology, Rider University, Lawrenceville

NJ

08648, United States^4

关键词: Cancer research;    Cylindrical samples;    Different-magnetic fields;    Dose distributions;    Effect of magnetic field;    Monte Carlo calculation;    Poly(methyl methacrylate) (PMMA);    Secondary electrons;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/847/1/012058/pdf
DOI  :  10.1088/1742-6596/847/1/012058

来源: IOP

【 摘 要 】

At the Royal Marsden Hospital (RMH) and the Institute of Cancer Research (ICR) a new MR-linac is being installed and commissioned. Modifications to absorbed dose patterns will occur, because the paths of secondary electrons are deflected by Lorentz forces. In this paper, we describe a methodology to measure the effects of magnetic field on dose distributions, using the PRESAGE® 3D dosimeter and Monte Carlo (MC) simulations. A poly(methyl methacrylate) (PMMA) phantom has been developed to be positioned between the poles of an electromagnet and accommodate cylindrical samples of PRESAGE®. This phantom will be used to study the influence of different magnetic field strengths on radiation deposition from a Cobalt-60 (60Co) beam. Both the orientation of the samples with respect to the magnetic field and radiation beam, and the size of the air gap can be changed. Preliminary MC simulations with two PRESAGE® cylinders separated by an air gap, gave a good insight about the dosimetric effects that can be obtained with our newly-developed phantom.