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Title: SU-F-T-211: Evaluation of a Dual Focusing Magnet System for the Treatment of Small Proton Targets

Abstract

Purpose: To investigate magnetic focusing for small volume proton targets using a doublet combination of quadrupole rare earth permanent magnet Halbach cylinder assemblies Methods: Monte Carlo computer simulations were performed using the Geant4 toolkit to compare dose depositions of proton beams transported through two focusing magnets or in their absence. Proton beams with energies of 127 MeV and initial diameters of 5, 8 and 10 mm were delivered through two identical focusing magnets similar to those currently in experimental use at Loma Linda University Medical Center. Analogous experiments used optimized configurations based on the simulation results. Dose was measured by a diode detector and Gafchromic EBT3 film and compared to simulation data. Based on results from the experimental data, an additional set of simulations was performed with an initial beam diameter of 18 mm and a two differing length magnets (40mm & 68mm). Results: Experimental data matched well with Monte Carlo simulations. However, under conditions necessary to produce circular beam spots at target depth, magnetically focused beams using two identical 40 mm length magnets did not meet all of our performance criteria of circular beam spots, improved peak to entrance (P/E) dose ratios and dose delivery efficiencies. The simulations usingmore » the longer 68 mm 2nd magnet yielded better results with 34% better P/E dose ratio and 20–50% better dose delivery efficiencies when compared to unfocused 10 mm beams. Conclusion: While magnetic focusing using two magnets with identical focusing power did not yield desired results, ongoing Monte Carlo simulations suggest that increasing the length of the 2nd magnet to 68 mm could improve P/E dose ratios and dose efficiencies. Future work includes additional experimental validation of the longer 2nd magnet setup as well as experiments with triplet magnet systems. This project was sponsored with funding from the Department of Defense (DOD# W81XWH-BAA-10-1).« less

Authors:
; ; ;  [1];  [1];  [2]
  1. Loma Linda University, Loma Linda, CA (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
22648828
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; COMPUTERIZED SIMULATION; EFFICIENCY; LENGTH; MEV RANGE 100-1000; MONTE CARLO METHOD; PERFORMANCE; PRODUCTIVITY; PROTON BEAMS; RADIATION DOSES

Citation Formats

Nguyen, TT, McAuley, GA, Heczko, S, Slater, J, Wroe, A, and Loma Linda University Medical Center, Loma Linda, CA. SU-F-T-211: Evaluation of a Dual Focusing Magnet System for the Treatment of Small Proton Targets. United States: N. p., 2016. Web. doi:10.1118/1.4956349.
Nguyen, TT, McAuley, GA, Heczko, S, Slater, J, Wroe, A, & Loma Linda University Medical Center, Loma Linda, CA. SU-F-T-211: Evaluation of a Dual Focusing Magnet System for the Treatment of Small Proton Targets. United States. doi:10.1118/1.4956349.
Nguyen, TT, McAuley, GA, Heczko, S, Slater, J, Wroe, A, and Loma Linda University Medical Center, Loma Linda, CA. Wed . "SU-F-T-211: Evaluation of a Dual Focusing Magnet System for the Treatment of Small Proton Targets". United States. doi:10.1118/1.4956349.
@article{osti_22648828,
title = {SU-F-T-211: Evaluation of a Dual Focusing Magnet System for the Treatment of Small Proton Targets},
author = {Nguyen, TT and McAuley, GA and Heczko, S and Slater, J and Wroe, A and Loma Linda University Medical Center, Loma Linda, CA},
abstractNote = {Purpose: To investigate magnetic focusing for small volume proton targets using a doublet combination of quadrupole rare earth permanent magnet Halbach cylinder assemblies Methods: Monte Carlo computer simulations were performed using the Geant4 toolkit to compare dose depositions of proton beams transported through two focusing magnets or in their absence. Proton beams with energies of 127 MeV and initial diameters of 5, 8 and 10 mm were delivered through two identical focusing magnets similar to those currently in experimental use at Loma Linda University Medical Center. Analogous experiments used optimized configurations based on the simulation results. Dose was measured by a diode detector and Gafchromic EBT3 film and compared to simulation data. Based on results from the experimental data, an additional set of simulations was performed with an initial beam diameter of 18 mm and a two differing length magnets (40mm & 68mm). Results: Experimental data matched well with Monte Carlo simulations. However, under conditions necessary to produce circular beam spots at target depth, magnetically focused beams using two identical 40 mm length magnets did not meet all of our performance criteria of circular beam spots, improved peak to entrance (P/E) dose ratios and dose delivery efficiencies. The simulations using the longer 68 mm 2nd magnet yielded better results with 34% better P/E dose ratio and 20–50% better dose delivery efficiencies when compared to unfocused 10 mm beams. Conclusion: While magnetic focusing using two magnets with identical focusing power did not yield desired results, ongoing Monte Carlo simulations suggest that increasing the length of the 2nd magnet to 68 mm could improve P/E dose ratios and dose efficiencies. Future work includes additional experimental validation of the longer 2nd magnet setup as well as experiments with triplet magnet systems. This project was sponsored with funding from the Department of Defense (DOD# W81XWH-BAA-10-1).},
doi = {10.1118/1.4956349},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = {Wed Jun 15 00:00:00 EDT 2016},
month = {Wed Jun 15 00:00:00 EDT 2016}
}