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Current Directions in Biomedical Engineering

Joint Journal of the German Society for Biomedical Engineering in VDE and the Austrian and Swiss Societies for Biomedical Engineering

Editor-in-Chief: Dössel, Olaf

Editorial Board: Augat, Peter / Buzug, Thorsten M. / Haueisen, Jens / Jockenhoevel, Stefan / Knaup-Gregori, Petra / Kraft, Marc / Lenarz, Thomas / Leonhardt, Steffen / Malberg, Hagen / Penzel, Thomas / Plank, Gernot / Radermacher, Klaus M. / Schkommodau, Erik / Stieglitz, Thomas / Urban, Gerald A.


CiteScore 2018: 0.47

Source Normalized Impact per Paper (SNIP) 2018: 0.377

Open Access
Online
ISSN
2364-5504
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Influence of a transverse magnetic field on the dose deposited by a 6 MV linear accelerator

A Monte Carlo study

Sebastian Richter
  • Corresponding author
  • University Hospital Tübingen, Department of Radiation Oncology, Section for Biomedical Physics, Hoppe-Seyler-Str. 3, 72076 Tübingen, Germany
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/ Stefan Pojtinger
  • University Hospital Tübingen, Department of Radiation Oncology, Section for Biomedical Physics, Hoppe-Seyler-Str. 3, 72076 Tübingen, Germany
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ David Mönnich
  • University Hospital Tübingen, Department of Radiation Oncology, Section for Biomedical Physics, Hoppe-Seyler-Str. 3, 72076 Tübingen, Germany
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/ Oliver S. Dohm
  • University Hospital Tübingen, Department of Radiation Oncology, Division for Medical Physics, Hoppe-Seyler-Str. 3, 72076 Tübingen, Germany
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/ Daniela Thorwarth
  • University Hospital Tübingen, Department of Radiation Oncology, Section for Biomedical Physics, Hoppe-Seyler-Str. 3, 72076 Tübingen, Germany
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Published Online: 2017-09-07 | DOI: https://doi.org/10.1515/cdbme-2017-0058

Abstract

An integrated system of a linear accelerator and a magnetic resonance imaging (MRI) device may provide real-time imaging during radiotherapy treatments. This work investigated changes affecting the dose deposition caused by a magnetic field (B-field) transverse to the beam direction by means of Monte Carlo simulations. Two different phantoms were used: A water phantom (Ph1) and a water-air phantom (Ph2) with a 4-2-4 cm water-air-water cross section. Dose depositions were scored for B-field values of 0 T, 0.35 T, 0.5 T, 1.5 T, 3 T and 5 T. Beams were based on a precalculated photon spectrum taken from an earlier simulated Elekta 6 MV FFF accelerator. All lateral profiles in Ph1 showed a Lorentz force driven shift w.r.t. the B-field strength, presenting a steeper penumbra in the shift's direction. Depositions were shifted up to 0.3 cm for 5 T, showing a constant central axis plateau-dose or an increase by 2.3 % for small fields. Depth-dose curves in Ph1 showed a shift of the dose maximum towards the beam entrance direction for increasing B-field of up to 1.1 cm; the maximum dose was increased by 6.9 %. In Ph2, an asymmetric dose increase by up to 36.9 % was observed for 1.5 T at the water-air boundary, resulting from the electron return effect (ERE). In our scenario, B-field dependent dose shifts and local build-ups were observed, which consequently affect the resulting dose distribution and need to be considered in magnetic resonance guided radiotherapy treatment planning.

Keywords: radiotherapy; magnetic field; Monte Carlo simulation; dose deposition; ERE; linear accelerator; MRgRT; MR-Linac

About the article

Published Online: 2017-09-07


Citation Information: Current Directions in Biomedical Engineering, Volume 3, Issue 2, Pages 281–285, ISSN (Online) 2364-5504, DOI: https://doi.org/10.1515/cdbme-2017-0058.

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©2017 Sebastian Richter et al., published by De Gruyter, Berlin/Boston. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. BY-NC-ND 4.0

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