Correcting angular dependencies using non-polarized components of Cherenkov light in water during high-energy X-ray irradiation

Chihiro Toyonaga, Seiichi Yamamoto*, Takuya Yabe, Kuniyasu Okudaira, Katsunori Yogo, Yoshiyuki Hirano, Jun Kataoka

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Objective: Dose distribution measurements of high-energy X-rays from medical linear accelerators (LINAC) in water are important for quality control (QC) of the system. Although Cherenkov-light imaging is a useful method for measuring the high-energy X-ray dose distribution, depth profiles have an underestimated dose at increased depths due to the angular dependency of the Cherenkov light generated in water. In this study, we use a linear polarizer to separate the majority of polarized components from the majority of unpolarized components of Cherenkov-light images in water and then use this information to correct for angular dependencies. Methods: A water phantom, a cooled charge-coupled device (CCD) camera, and a polarizer were installed in a black box. Then, the water phantom was irradiated from the upper side with 6 or 10 MV X-rays, and the Cherenkov light generated in water was imaged with the polarizer axis at both parallel and perpendicular orientations to the beam. By using these images from the two orientations relative to the beam, we corrected the angular dependency of the Cherenkov light. Results: By subtracting the images measured with the polarizer perpendicular to the beams from the images measured with the polarizer parallel to the beams, we could obtain images with only the polarized components. Using these images, we could calculate the images with non-polarized components that had similar depth profiles to those calculated with a planning system. The average difference between corrected depth profiles and those calculated with the planning system was less than 1%, while that between uncorrected depth profiles and the planning system was more than 8.3% in depths of water from 20 to 100 mm. Conclusion: We conclude that the use of the polarizer has the potential to improve the accuracy of dose distribution in Cherenkov-light imaging of water using high-energy X-rays.

Original languageEnglish
JournalMedical Physics
DOIs
Publication statusAccepted/In press - 2022

Keywords

  • Cherenkov light
  • LINAC
  • optical imaging
  • polarizer
  • X-rays

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging

Fingerprint

Dive into the research topics of 'Correcting angular dependencies using non-polarized components of Cherenkov light in water during high-energy X-ray irradiation'. Together they form a unique fingerprint.

Cite this