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Use of Beam Spoiler to Improve Build-up of Photon Beam Using Low Strength Magnetic Field
Journal of Magnetics, Volume 22, Number 4, 31 Dec 2017, Pages 709-714
Abstract
The purpose of this study is to propose the use of a beam spoiler for improving the build-up region of photon beam by using external magnetic field with a low strength of 0.5 T (Tesla) outside the human body. A homemade
magnet device which can apply a transverse magnetic field to photon beam was developed. The effect of dose enhancement on build-up region was investigated by the beam spoiler-to-magnet distance (BMD), the
magnet-to-magnet distance (MMD), and the magnet-to-surface distance (MSD). Build-up regions of 6 MV photon beam with and without the magnetic field were measured for the field size to 5 × 5 cm2. When applying the
low magnetic field with MMD of 10 cm, D0mm, D2mm, D5mm and D10mm at BSD of 13 cm and MSD of 5 cm were increased by approximately 3.2%, 3.9%, 1.7% and 0.4%, respectively, compared to the build-up of the existing 6 MV photon beam without the magnetic field. The dose reduction was 5.1% compared to skin dose for 4 MV photon beam without the magnetic field. It is expected that use of a beam spoiler in the magnet device
designed in this study could provide improved dose distributions in build-up regions while maintain similar surface dose to the existing 6 MV photon beam without the magnetic field.
magnet device which can apply a transverse magnetic field to photon beam was developed. The effect of dose enhancement on build-up region was investigated by the beam spoiler-to-magnet distance (BMD), the
magnet-to-magnet distance (MMD), and the magnet-to-surface distance (MSD). Build-up regions of 6 MV photon beam with and without the magnetic field were measured for the field size to 5 × 5 cm2. When applying the
low magnetic field with MMD of 10 cm, D0mm, D2mm, D5mm and D10mm at BSD of 13 cm and MSD of 5 cm were increased by approximately 3.2%, 3.9%, 1.7% and 0.4%, respectively, compared to the build-up of the existing 6 MV photon beam without the magnetic field. The dose reduction was 5.1% compared to skin dose for 4 MV photon beam without the magnetic field. It is expected that use of a beam spoiler in the magnet device
designed in this study could provide improved dose distributions in build-up regions while maintain similar surface dose to the existing 6 MV photon beam without the magnetic field.
Keywords: magnetic field; 6 MV photon beam; build-up region; beam spoiler
DOI: https://doi.org/10.4283/JMAG.2017.22.4.709
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