Enhanced RBE of Particle Radiation Depends on Beam Size in the Micrometer Range

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61389005%3A_____%2F24%3A00599796" target="_blank" >RIV/61389005:_____/24:00599796 - isvavai.cz</a>

Result on the web

<a href="https://doi.org/10.1667/RADE-23-00217.1" target="_blank" >https://doi.org/10.1667/RADE-23-00217.1</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1667/RADE-23-00217.1" target="_blank" >10.1667/RADE-23-00217.1</a>

Result language

angličtina

Original language name

Enhanced RBE of Particle Radiation Depends on Beam Size in the Micrometer Range

Original language description

High-linear energy transfer (LET) radiation, such as heavy ions is associated with a higher relative biological effectiveness (RBE) than low-LET radiation, such as photons. Irradiation with low- and high-LET particles differ in the interaction with the cellular matter and therefore in the spatial dose distribution. When a single high-LET particle interacts with matter, it results in doses of up to thousands of gray (Gy) locally concentrated around the ion trajectory, whereas the mean dose averaged over the target, such as a cell nucleus is only in the range of a Gy. DNA damage therefore accumulates in this small volume. In contrast, up to hundreds of low-LET particle hits are required to achieve the same mean dose, resulting in a quasi-homogeneous damage distribution throughout the cell nucleus. In this study, we investigated the dependence of RBE from different spatial dose depositions using different focused beam spot sizes of proton radiation with respect to the induction of chromosome aberrations and clonogenic cell survival. Human-hamster hybrid (AL) as well as Chinese hamster ovary cells (CHO-K1) were irradiated with focused low LET protons of 20 MeV (LET = 2.6 keV/mu m) beam energy with a mean dose of 1.7 Gy in a quadratic matrix pattern with point spacing of 5.4 x 5.4 mu m(2) and 117 protons per matrix point at the ion microbeam SNAKE using different beam spot sizes between 0.8 mu m and 2.8 mu m (full width at half maximum). The dose-response curves of X-ray reference radiation were used to determine the RBE after a 1.7 Gy dose of radiation. The RBE for the induction of dicentric chromosomes and cell inactivation was increased after irradiation with the smallest beam spot diameter (0.8 mu m for chromosome aberration experiments and 1.0 mu m for cell survival experiments) compared to homogeneous proton radiation but was still below the RBE of a corresponding high LET single ion hit. By increasing the spot size to 1.6-1.8 mu m, the RBE decreased but was still higher than for homogeneously distributed protons. By further increasing the spot size to 2.7-2.8 mu m, the RBE was no longer different from the homogeneous radiation. Our experiments demonstrate that varying spot size of low-LET radiation gradually modifies the RBE. This underlines that a substantial fraction of enhanced RBE originates from inhomogeneous energy concentrations on the mu m scale (mean intertrack distances of low-LET particles below 0.1 mu m) and quantifies the link between such energy concentration and RBE. The missing fraction of RBE enhancement when comparing with high-LET ions is attributed to the high inner track energy deposition on the nanometer scale. The results are compared with model results of PARTRAC and LEM for chromosomal aberration and cell survival, respectively, which suggest mechanistic interpretations of the observed radiation effects.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

30224 - Radiology, nuclear medicine and medical imaging

Project

—

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2024

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Radiation Research

ISSN

0033-7587

e-ISSN

1938-5404

Volume of the periodical

201

Issue of the periodical within the volume

2

Country of publishing house

US - UNITED STATES

Number of pages

10

Pages from-to

140-149

UT code for WoS article

001208541800005

EID of the result in the Scopus database

2-s2.0-85184656637