SU-E-J-38: Comparison of 6MV Photon Dose in a Perpendicular and Parallel Magnetic Field
Abstract
Purpose: Integrating a linac with an MRI system would allow for real time tumour tracking however the patient will be irradiated in the presence of a magnetic field. The present study experimentally investigates the magnetic field effects on entrance, exit, and interface dose for both transverse and parallel magnetic fields. Methods: Polystyrene was used to construct a set of phantoms for Gafchromic film measurements. One phantom had an adjustable air gap and four other phantoms had one surface at various angles. The linac-MR prototype consisting of a biplanar permanent magnet coupled to a linac was used for the transverse magnetic field measurements. A couple of solenoid electromagnets, stacked on top of each other and irradiated along their bore, were used for the parallel field measurements. Results: All doses are relative to no magnetic field. The transverse magnetic field reduced the entrance dose for all surface angles by strongly deflecting the contaminant electrons. The exit dose in a transverse magnetic field was found to be significantly higher. The entrance dose with a parallel magnetic field present is higher due to the contaminant electrons being concentrated within the beam area. The air gap phantom measurements, done in a transverse magnetic field, showmore »
- Authors:
-
- Cross Cancer Institute, Edmonton, AB (Canada)
- Publication Date:
- OSTI Identifier:
- 22325300
- Resource Type:
- Journal Article
- Journal Name:
- Medical Physics
- Additional Journal Information:
- Journal Volume: 41; Journal Issue: 6; Other Information: (c) 2014 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-2405
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 60 APPLIED LIFE SCIENCES; AIR; COMPUTERIZED SIMULATION; CONCENTRATION RATIO; ELECTRONS; LINEAR ACCELERATORS; MAGNETIC FIELDS; MONTE CARLO METHOD; NMR IMAGING; PHANTOMS; PHOTONS; POLYSTYRENE; RADIATION DOSES; SOLENOIDS
Citation Formats
Ghila, A, Fallone, B, and Rathee, S. SU-E-J-38: Comparison of 6MV Photon Dose in a Perpendicular and Parallel Magnetic Field. United States: N. p., 2014.
Web. doi:10.1118/1.4888090.
Ghila, A, Fallone, B, & Rathee, S. SU-E-J-38: Comparison of 6MV Photon Dose in a Perpendicular and Parallel Magnetic Field. United States. https://doi.org/10.1118/1.4888090
Ghila, A, Fallone, B, and Rathee, S. 2014.
"SU-E-J-38: Comparison of 6MV Photon Dose in a Perpendicular and Parallel Magnetic Field". United States. https://doi.org/10.1118/1.4888090.
@article{osti_22325300,
title = {SU-E-J-38: Comparison of 6MV Photon Dose in a Perpendicular and Parallel Magnetic Field},
author = {Ghila, A and Fallone, B and Rathee, S},
abstractNote = {Purpose: Integrating a linac with an MRI system would allow for real time tumour tracking however the patient will be irradiated in the presence of a magnetic field. The present study experimentally investigates the magnetic field effects on entrance, exit, and interface dose for both transverse and parallel magnetic fields. Methods: Polystyrene was used to construct a set of phantoms for Gafchromic film measurements. One phantom had an adjustable air gap and four other phantoms had one surface at various angles. The linac-MR prototype consisting of a biplanar permanent magnet coupled to a linac was used for the transverse magnetic field measurements. A couple of solenoid electromagnets, stacked on top of each other and irradiated along their bore, were used for the parallel field measurements. Results: All doses are relative to no magnetic field. The transverse magnetic field reduced the entrance dose for all surface angles by strongly deflecting the contaminant electrons. The exit dose in a transverse magnetic field was found to be significantly higher. The entrance dose with a parallel magnetic field present is higher due to the contaminant electrons being concentrated within the beam area. The air gap phantom measurements, done in a transverse magnetic field, show a significant increase of the dose at the proximal side of the air gap and a decrease at the distal side. The measurements, done in the parallel magnetic field, show the concentration of secondary electrons in the air gap. Conclusion: The radiation dose measurements of a 6MV beam in a parallel and transverse magnetic field presented here are currently being replicated using Monte Carlo simulations. This verified Monte Carlo system could provide the dose calculation basis for future linac-MR systems.},
doi = {10.1118/1.4888090},
url = {https://www.osti.gov/biblio/22325300},
journal = {Medical Physics},
issn = {0094-2405},
number = 6,
volume = 41,
place = {United States},
year = {Sun Jun 01 00:00:00 EDT 2014},
month = {Sun Jun 01 00:00:00 EDT 2014}
}