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Updated: Jun 5, 2026
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Dosimetry for Cell Irradiation using Orthovoltage (40-300 kV) X-Ray Facilities
Published on: February 20, 2021
For ultra-high dose rate carbon-ion irradiation, comparable beam parameters induce the equivalent cell sparing
Kento Tsubouchi1, Yukari Yoshida2, Masashi Yagi3,4
1Department of Carbon Ion Radiotherapy, The University of Osaka Graduate School of Medicine, 2‑2 Yamada‑oka, Suita, Osaka 565-0871, Japan.
Journal of Radiation Research
|June 3, 2026
Summary
Ultra-high dose rate (uHDR) irradiation demonstrates a cell-sparing effect, reducing normal tissue damage without impacting tumor control. This effect depends on beam parameters, not the specific irradiation device, advancing FLASH therapy research.
Area of Science:
- Medical Physics
- Radiation Oncology
- Cell Biology
Background:
- Ultra-high dose rate (uHDR) irradiation exhibits the FLASH effect, reducing normal tissue damage while maintaining antitumor efficacy compared to normal dose rate (NDR) irradiation.
- The cell-sparing effect, observed in vitro, is a protective response to uHDR irradiation, previously demonstrated with carbon-ion beam systems.
Purpose of the Study:
- To reproduce and evaluate the cell-sparing effect using comparable irradiation conditions on a different machine and facility.
- To assess the influence of beam parameters, specifically dose-averaged linear energy transfer (LETd), on the cell-sparing effect.
Main Methods:
- Used identical cell lines (HSGc-C5, HDF, Nuli-1) and beam settings (7 Gy, 100 Gy/s uHDR vs. 1 Gy/s NDR, LETd 16.3 and 50 keV/μm).
- Assessed cell survival via colony formation assay and DNA damage using γH2AX immunofluorescence staining.
- Verified comparable physical dose, average dose rates (ADR), and field flatness through measurements.
Main Results:
- Human dermal fibroblasts (HDF) and Nuli-1 cells showed significant cell-sparing effects (increased survival, reduced DNA damage), enhanced by higher LET.
- Human salivary gland cells (HSGc-C5) exhibited a diminished cell-sparing effect, absent at low LET.
- Results were consistent with previous studies, confirming reproducibility across different facilities.
Conclusions:
- The cell-sparing effect in carbon-ion irradiation is primarily dependent on beam parameters (like LETd and dose rate) rather than the specific irradiation device.
- These findings support the acceleration of FLASH research and the clinical implementation of carbon-ion uHDR irradiation.
