Year: 2026 | Month: July | Volume: 13 | Issue: 7 | Pages: 216-223
DOI: https://doi.org/10.52403/ijrr.20260725
Characterization of Energy Spectra and DNA Damage Induced by Secondary Electrons from Gadolinium Neutron Capture Therapy at Various Subcellular Locations Using Geant4-DNA and MCDS
Sri Hasniah Ashara1, Catur Edi Widodo2, Qidir Maulana Binu Soesanto3
1Department of Physics, Diponegoro University, Semarang, Indonesia.
Corresponding Author: Sri Hasniah Ashara
ABSTRACT
This study characterized the energy spectra of secondary electrons reaching the nuclear surface and evaluated the resulting DNA damage from three different source locations: cell membrane, cytoplasm, and nucleus. Monte Carlo simulations were conducted using Geant4-DNA to model the isotropic emission of 10,000 secondary electrons from each compartment in a spherical cell geometry (nuclear radius = 3 μm). The energy spectra of electrons reaching the nuclear surface were subsequently analyzed for DNA damage using the Monte Carlo Damage Simulation (MCDS) code under normoxic conditions (21% O₂). Results showed that only 1.37% and 2.91% of electrons emitted from the cell membrane and cytoplasm, respectively, reached the nuclear surface, due to the very short range of Auger electrons (average energy 4.19 keV, range ≈ 12.5 nm). In contrast, higher-energy IC electrons (average 45.9 keV, range ≈ 38 μm) contributed significantly from peripheral locations. Nuclear localization produced the highest DNA damage, with double-strand break (DSB) yield increasing from 49.59 Gy⁻¹ cell⁻¹ (cell membrane) to 50.16 Gy⁻¹ cell⁻¹ (cytoplasm) and 53.27 Gy⁻¹ cell⁻¹ (nucleus), representing a 7.41% enhancement. Complex lesions (DSB+, DSB++, DSBcb) were also significantly higher in the nucleus. Normalized per gigabase pair, the nuclear source yielded 8.87 DSBs Gy⁻¹ Gbp⁻¹. These findings confirm that GdNCT efficacy strongly depends on the proximity of the source to nuclear DNA. The combination of Geant4-DNA and MCDS offers a reliable framework for predicting subcellular dose deposition and DNA damage complexity in GdNCT.
Keywords: Neutron Capture Therapy, GdNCT, MCDS, Geant4-DNA
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