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Title: TU-H-CAMPUS-TeP1-03: Magnetically Focused Proton Irradiation of Small Volume Radiosurgery Targets

Abstract

Purpose: To investigate the use of magnetic focusing for small volume proton radiosurgery targets using a triplet combination of quadrupole rare earth permanent magnet Halbach cylinder assemblies Methods: Fourteen quadrupole magnets consisting of 24 segments of radiation hard samarium-cobalt adhered into k=3 Halbach cylinders with various field gradients (100 to 250 T/m) were designed and manufactured. Triplet combinations of the magnets were placed on a positioning track on our Gantry 1 treatment table. Unmodulated 127 MeV proton beams with initial diameters of 3 to 20 mm were delivered to a water tank using single-stage scattering. Depth and transverse dose distributions were measured using a PTW PR60020 diode detector and EBT3 film, respectively. This data was compared with unfocused passively collimated beams. Monte Carlo simulations were also performed - both for comparison with experimental data and to further investigate the potential of triplet magnetic focusing. Results: Experimental results using 150 T/m gradient magnets and 15 to 20 mm initial diameter beams show peak to entrance dose ratios that are ∼ 43 to 48 % larger compared with spot size matched 8 mm collimated beams (ie, transverse profile full-widths at 90% maximum dose match within 0.5 mm of focused beams). In addition,more » the focusing beams were ∼ 3 to 4.4 times more efficient per MU in dose to target delivery. Additional results using different magnet combinations will also be presented. Conclusion: Our results suggest that triplet magnetic focusing could reduce entrance dose and beam number while delivering dose to small (∼≤ 10 mm diameter) radiosurgery targets in less time compared to unfocused beams. Immediate clinical applications include those associated with proton radiosurgery and functional radiosurgery of the brain and spine, however other treatment sites can be also envisioned. 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:
22654054
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 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:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; COMPUTERIZED SIMULATION; DEPTH DOSE DISTRIBUTIONS; EXPERIMENTAL DATA; FOCUSING; MEV RANGE 100-1000; MONTE CARLO METHOD; PARTICLE TRACKS; PROTON BEAMS; RADIOTHERAPY; SURGERY

Citation Formats

McAuley, GA, Slater, JM, Wroe, AJ, and Loma Linda University Medical Center, Loma Linda, CA. TU-H-CAMPUS-TeP1-03: Magnetically Focused Proton Irradiation of Small Volume Radiosurgery Targets. United States: N. p., 2016. Web. doi:10.1118/1.4957676.
McAuley, GA, Slater, JM, Wroe, AJ, & Loma Linda University Medical Center, Loma Linda, CA. TU-H-CAMPUS-TeP1-03: Magnetically Focused Proton Irradiation of Small Volume Radiosurgery Targets. United States. doi:10.1118/1.4957676.
McAuley, GA, Slater, JM, Wroe, AJ, and Loma Linda University Medical Center, Loma Linda, CA. Wed . "TU-H-CAMPUS-TeP1-03: Magnetically Focused Proton Irradiation of Small Volume Radiosurgery Targets". United States. doi:10.1118/1.4957676.
@article{osti_22654054,
title = {TU-H-CAMPUS-TeP1-03: Magnetically Focused Proton Irradiation of Small Volume Radiosurgery Targets},
author = {McAuley, GA and Slater, JM and Wroe, AJ and Loma Linda University Medical Center, Loma Linda, CA},
abstractNote = {Purpose: To investigate the use of magnetic focusing for small volume proton radiosurgery targets using a triplet combination of quadrupole rare earth permanent magnet Halbach cylinder assemblies Methods: Fourteen quadrupole magnets consisting of 24 segments of radiation hard samarium-cobalt adhered into k=3 Halbach cylinders with various field gradients (100 to 250 T/m) were designed and manufactured. Triplet combinations of the magnets were placed on a positioning track on our Gantry 1 treatment table. Unmodulated 127 MeV proton beams with initial diameters of 3 to 20 mm were delivered to a water tank using single-stage scattering. Depth and transverse dose distributions were measured using a PTW PR60020 diode detector and EBT3 film, respectively. This data was compared with unfocused passively collimated beams. Monte Carlo simulations were also performed - both for comparison with experimental data and to further investigate the potential of triplet magnetic focusing. Results: Experimental results using 150 T/m gradient magnets and 15 to 20 mm initial diameter beams show peak to entrance dose ratios that are ∼ 43 to 48 % larger compared with spot size matched 8 mm collimated beams (ie, transverse profile full-widths at 90% maximum dose match within 0.5 mm of focused beams). In addition, the focusing beams were ∼ 3 to 4.4 times more efficient per MU in dose to target delivery. Additional results using different magnet combinations will also be presented. Conclusion: Our results suggest that triplet magnetic focusing could reduce entrance dose and beam number while delivering dose to small (∼≤ 10 mm diameter) radiosurgery targets in less time compared to unfocused beams. Immediate clinical applications include those associated with proton radiosurgery and functional radiosurgery of the brain and spine, however other treatment sites can be also envisioned. This project was sponsored with funding from the Department of Defense (DOD# W81XWH-BAA-10-1).},
doi = {10.1118/1.4957676},
journal = {Medical Physics},
issn = {0094-2405},
number = 6,
volume = 43,
place = {United States},
year = {2016},
month = {6}
}