Deep learning-based in vivo dose verification from proton-induced secondary-electron-bremsstrahlung images with various count level

Takuya Yabe; Mitsutaka Yamaguchi; Chih-Chieh Liu; Toshiyuki Toshito; Naoki Kawachi; Seiichi Yamamoto

doi:10.1016/j.ejmp.2022.05.013

Deep learning-based in vivo dose verification from proton-induced secondary-electron-bremsstrahlung images with various count level

Phys Med. 2022 Jul:99:130-139. doi: 10.1016/j.ejmp.2022.05.013. Epub 2022 Jun 9.

Authors

Takuya Yabe¹, Mitsutaka Yamaguchi², Chih-Chieh Liu³, Toshiyuki Toshito⁴, Naoki Kawachi², Seiichi Yamamoto⁵

Affiliations

¹ Department of Integrated Health Science, Nagoya University Graduate School of Medicine, Aichi, Japan; Department of Medical Technology, Nagoya University Hospital, Aichi, Japan. Electronic address: yabe.takuya@qst.go.jp.
² Takasaki Advanced Radiation Research Institute, Quantum Beam Science Research Directorate, National Institutes for Quantum Science and Technology (QST), Gunma, Japan.
³ Department of Biomedical Engineering, University of California, Davis, USA.
⁴ Department of Proton Therapy Physics, Nagoya Proton Therapy Center, Nagoya City University West Medical Center, Aichi, Japan.
⁵ Department of Integrated Health Science, Nagoya University Graduate School of Medicine, Aichi, Japan; Faculty of Science and Engineering, Waseda University, Tokyo, Japan.

PMID: 35689979
DOI: 10.1016/j.ejmp.2022.05.013

Abstract

Purpose: Proton-induced secondary-electron-bremsstrahlung (SEB) imaging is a promising method for estimating the ranges of particle beam. However, SEB images do not directly represent dose distributions of particle beams. In addition, the ranges estimated from measured images were deviated because of limited spatial resolutions of the developed x-ray camera as well as statistical noise in the images. To solve these problems, we proposed a method for predicting high-resolution dose images from SEB images with various count level using a deep learning (DL) approach for range and width verification.

Methods: In this study, we adopted the double U-Net model, which is a previously proposed deep convolutional network model. The first U-Net model in the double U-Net model was used to denoise the SEB images with various count level. The first U-Net model for denoising was trained on 8000 pairs of SEB images with various count level and noise-free images which were created by a sophisticated in-house developed model function. The second U-Net model for dose prediction was trained using 8000 pairs of denoised SEB images from the first U-Net model and high-resolution dose images generated by Monte Carlo simulation.

Results: For both simulation and measurement data, the trained DL model could successfully predict high-resolution dose images which showed a clear Bragg peak and no statistical noise. The difference of the range and width was less than 2.1 mm, even from the SEB images measured with a decrease in the number of irradiated protons to less than 11% of 3.2 × 10¹¹ protons.

Conclusions: High-resolution dose images from measured and simulated SEB images were successfully predicted by using the trained DL model for protons. Our proposed DL model was feasible to predict dose images accurately even with smaller number of irradiated protons.

Keywords: deep learning; dose prediction; proton therapy; secondary-electron-bremsstrahlung.

MeSH terms

Deep Learning*
Electrons
Monte Carlo Method
Proton Therapy*
Protons

Substances

Protons