Geant4-Simulations for cellular dosimetry in nuclear medicine.

Area of Science:

• Radiobiology
• Medical Physics
• Computational Biology

Background:

• Unsealed radionuclides in radiobiological experiments cause intracellular uptake and increased absorbed dose.
• Accurate dose quantification is essential for assessing radiobiological effects.
• Direct dose measurement at the cellular level is impossible due to small dimensions.

Purpose of the Study:

• To demonstrate the application of Monte Carlo simulations for accurate dose calculation in radiobiological experiments.
• To validate dose calculations with experimental data.
• To highlight the necessity of precise dose assessment for unsealed radionuclide applications.

Main Methods:

• Utilized the Geant4 Monte Carlo toolkit for dose calculations.
• Simulated dose distributions within wells for various radionuclides.
• Modeled S values for spherical cells and cell monolayers of different sizes.
• Conducted cellular experiments using the PC Cl3 cell line with mediated radionuclide uptake.
• Measured cellular survival rates for different activity distributions.

Main Results:

• Generated S values for dose distribution within wells.
• Calculated S values for single cells showed good agreement with literature (0.87-1.07 ratio).
• Observed cross-dose effects up to ten times higher for Yttrium-90 (Y-90).
• Experimental cellular survival data corroborated the dose calculations.
• Demonstrated the feasibility and accuracy of using Geant4 for dose calculations.

Conclusions:

• Monte Carlo simulations with Geant4 are feasible and accurate for calculating absorbed doses from unsealed radionuclides at the cellular level.
• Precise dose calculation is imperative for reliable assessment of radiobiological effects.
• Cross-dose contributions can be significant, particularly for certain radionuclides like Y-90.
• The study validates the computational approach against experimental findings, enhancing confidence in simulation-based dosimetry.