1. Estimation of diffuse Cherenkov optical emission from external beam radiation build-up in tissue
- Author
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Daniel A. Alexander, Rongxiao Zhang, David J. Gladstone, Brian W. Pogue, Rachael L. Hachadorian, Petr Bruza, and Savannah M. Decker
- Subjects
Paper ,Photon ,Astrophysics::High Energy Astrophysical Phenomena ,Physics::Medical Physics ,Biomedical Engineering ,Radiation ,Signal ,Biomaterials ,Optics ,Cherenkov ,Irradiation ,in-vivo dosimetry ,Cherenkov radiation ,Physics ,Photons ,Phantoms, Imaging ,Scattering ,business.industry ,X-Rays ,Emission intensity ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Intensity (physics) ,Therapeutic ,business ,surface dose - Abstract
Significance: Optical imaging of Cherenkov emission during radiation therapy could be used to verify dose delivery in real-time if a more comprehensive quantitative understanding of the factors affecting emission intensity could be developed. Aim: This study aims to explore the change in diffuse Cherenkov emission intensity with x-ray beam energy from irradiated tissue, both theoretically and experimentally. Approach: Derivation of the emitted Cherenkov signal was achieved using diffusion theory, and experimental studies with 6 to 18 MV energy x-rays were performed in tissue phantoms to confirm the model predictions as related to the radiation build-up factor with depth into tissue. Results: Irradiation at lower x-ray energies results in a greater surface dose and higher build-up slope, which results in a ∼46% greater diffusely emitted Cherenkov signal per unit dose at 6 MV relative to 18 MV x-rays. However, this phenomenon competes with a decrease in signal from less Cherenkov photons being generated at lower energies, a ∼44% reduction at 6 versus 18 MV. The result is an emitted Cherenkov signal that is nearly constant with beam energy. Conclusions: This study explains why the observed Cherenkov emission from tissue is not a strong function of beam energy, despite the known strong correlation between Cherenkov intensity and particle energy in the absence of build-up and scattering effects.
- Published
- 2021