MOSFET dose measurements for proton SOBP beam

Chun-Hui Hsing; Luu Dang Hoang Oanh; Tsi-Chian Chao; Chung-Chi Lee; Ji-Hong Hong; Chun-Chi Cheng; Chien-Kai Tseng; Chuan-Jong Tung

doi:10.1016/j.ejmp.2020.12.007

MOSFET dose measurements for proton SOBP beam

Phys Med. 2021 Jan:81:185-190. doi: 10.1016/j.ejmp.2020.12.007. Epub 2021 Jan 16.

Authors

Chun-Hui Hsing¹, Luu Dang Hoang Oanh², Tsi-Chian Chao³, Chung-Chi Lee³, Ji-Hong Hong⁴, Chun-Chi Cheng⁵, Chien-Kai Tseng⁵, Chuan-Jong Tung⁶

Affiliations

¹ Medical Physics Research Center, Institute for Radiological Research, Chang Gung University and Chang Gung Memorial Hospital, Guishan Dist., Taoyuan City 333, Taiwan; Particle Physics and Beam Delivery Core Laboratory, Institute for Radiological Research, Chang Gung University/Chang Gung Memorial Hospital, Guishan, Taoyuan 333, Taiwan.
² Department of Medical Imaging and Radiological Sciences, Chang Gung University, Guishan Dist., Taoyuan City 333, Taiwan.
³ Medical Physics Research Center, Institute for Radiological Research, Chang Gung University and Chang Gung Memorial Hospital, Guishan Dist., Taoyuan City 333, Taiwan; Department of Medical Imaging and Radiological Sciences, Chang Gung University, Guishan Dist., Taoyuan City 333, Taiwan.
⁴ Department of Radiation Oncology, Chang Gung Memorial Hospital, Guishan, Taoyuan 333, Taiwan.
⁵ National Space Organization, 8F, No.9, Prosperity 1st Rd., Hsinchu Science Park, Hsinchu 33378, Taiwan.
⁶ Medical Physics Research Center, Institute for Radiological Research, Chang Gung University and Chang Gung Memorial Hospital, Guishan Dist., Taoyuan City 333, Taiwan; Department of Medical Imaging and Radiological Sciences, Chang Gung University, Guishan Dist., Taoyuan City 333, Taiwan. Electronic address: cjtung@mail.cgu.edu.tw.

PMID: 33465755
DOI: 10.1016/j.ejmp.2020.12.007

Abstract

Purpose: The aim of this work was to develop a computational scheme for the correction of the LET dependence on the MOSFET response in water phantom dose measurements for a spread-out Bragg peak (SOBP) proton beam.

Methods: The LET dependence of MOSFET was attributed to the stopping power ratio of SiO₂ to H₂O and to the fractional hole yield in the SiO₂ layer. Using literature values for the stopping powers of the continuous slowing down approximation and measured fractional hole yields vs. electric field and LET, formulas were derived for the computation of a dose-weighted correction factor of a SOBP beam.

Results: Dose-weighted correction factors were computed for a clinical 190-MeV proton SOBP beam in a high-density polyethylene phantom. By applying correction factors to the SOBP beam, which consisted of weighted monoenergetic Bragg peaks, the MOSFET outputs were predicted and agreed well with the measured MOSFET responses.

Conclusion: By applying LET dependent correction factors to MOSFET data, quality assurance of dose verification based on MOSFET measurements becomes possible for proton therapy.

Keywords: Dose-weighted correction factor; LET dependence; MOSFET dosimeter; Recombination effect; Residual range.

MeSH terms

Phantoms, Imaging
Proton Therapy*
Protons
Radioactivity*
Radiometry
Silicon Dioxide

Substances

Protons
Silicon Dioxide