Emission-associated energy deposition and Cherenkov-dose proportionality in megavoltage photon beams
Abstract
Background: Quantitative Cherenkov-to-dose conversion depends on beam spectrum, field size, depth, and material properties. Purpose: To distinguish dose contributions with and without accompanying Cherenkov production and assess their implications for calibration. Methods: Geant4 simulations paired dose and local Cherenkov distributions in water for flattened 6, 10, and 15 MV and flattening-filter-free (FFF) 6 and 10 MV beams with 3 × 3 and 10 × 10 cm2 fields. Energy deposition was tagged by whether its transport step produced at least one Cherenkov photon. Component fractions were calculated over the phantom. Distributions were independently normalized within a shared reference region and compared using voxelwise ratios, lateral profiles, and spatial partitioning. Results: Emission-tagged fractions were 37%-61%, increasing with beam energy and lower for FFF beams. Fractions differed by less than 1.3 percentage points between field sizes. Emission-tagged ratios clustered near unity, with 98.4%-99.9% between 0.95 and 1.05 across the evaluated regions, whereas total and non-emission-tagged ratios varied with depth and lateral position. Emission-tagged profiles generally showed smaller residual differences. Conclusions: Emission-tagged deposition closely tracked local Cherenkov production. Departures of the total Cherenkov-to-dose ratio followed spatial variations in the emission-tagged dose fraction, indicating where calibration needs correction. The classification reflects actual photon production and depends on transport settings; dedicated electron-energy scoring is needed to isolate sub-threshold contributions.
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BibTeX
@misc{he2026emissionassociated,
title = {{Emission-associated energy deposition and Cherenkov-dose proportionality in megavoltage photon beams}},
author = {Xianghuan He and Yao Hao and Changyu Sun and Andy N. Wiles and Gregory B. Biedermann and Brian W. Pogue and Rongxiao Zhang},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.05700},
eprint = {2611.05700},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.05700},
}
RIS
TY - UNPB
TI - Emission-associated energy deposition and Cherenkov-dose proportionality in megavoltage photon beams
AU - Xianghuan He
AU - Yao Hao
AU - Changyu Sun
AU - Andy N. Wiles
AU - Gregory B. Biedermann
AU - Brian W. Pogue
AU - Rongxiao Zhang
PY - 2026
DA - 2026/11/03
PB - arXiv
DO - 10.48550/arxiv.2611.05700
UR - https://arxiv.org/abs/2611.05700
AB - Background: Quantitative Cherenkov-to-dose conversion depends on beam spectrum, field size, depth, and material properties. Purpose: To distinguish dose contributions with and without accompanying Cherenkov production and assess their implications for calibration. Methods: Geant4 simulations paired dose and local Cherenkov distributions in water for flattened 6, 10, and 15 MV and flattening-filter-free (FFF) 6 and 10 MV beams with 3 × 3 and 10 × 10 cm^2 fields. Energy deposition was tagged by whether its transport step produced at least one Cherenkov photon. Component fractions were calculated over the phantom. Distributions were independently normalized within a shared reference region and compared using voxelwise ratios, lateral profiles, and spatial partitioning. Results: Emission-tagged fractions were 37%-61%, increasing with beam energy and lower for FFF beams. Fractions differed by less than 1.3 percentage points between field sizes. Emission-tagged ratios clustered near unity, with 98.4%-99.9% between 0.95 and 1.05 across the evaluated regions, whereas total and non-emission-tagged ratios varied with depth and lateral position. Emission-tagged profiles generally showed smaller residual differences. Conclusions: Emission-tagged deposition closely tracked local Cherenkov production. Departures of the total Cherenkov-to-dose ratio followed spatial variations in the emission-tagged dose fraction, indicating where calibration needs correction. The classification reflects actual photon production and depends on transport settings; dedicated electron-energy scoring is needed to isolate sub-threshold contributions.
ER -