Technical Note: The development of a multi-physics simulation tool to estimate the background dose by systemic...

Area of Science:

• Nuclear Medicine
• Radiopharmaceutical Dosimetry
• Computational Modeling

Background:

• Targeted alpha therapy (TAT) relies on precise dosimetry for predicting biological effects.
• Radionuclide distribution in vivo is complex, influenced by circulation and decay, leading to non-uniform sources.
• Current dosimetry often assumes homogeneous and static emitter distributions, which may not reflect reality.

Purpose of the Study:

• To develop and apply a multi-physics model for predicting biological effects of TAT in preclinical studies.
• To account for the dynamic and non-uniform distribution of radionuclides due to transport phenomena.
• To provide an alternative to direct measurement of micro-level emitter distributions.

Main Methods:

• A multi-physics model integrating Monte Carlo microdosimetry and computational fluid dynamics (CFD) was developed.
• The CFD model simulates radionuclide transport (convection and diffusion) within biological systems.
• The dose model evaluates time-dependent absorbed doses to target tissues.

Main Results:

• The model successfully handles complex, non-uniform irradiation sources in vasculature.
• Simulations revealed that conventional homogeneous distribution assumptions can lead to significant over or underestimation of absorbed doses.
• The impact of radionuclide transport on dosimetry was quantified across various scenarios.

Conclusions:

• Modeling in vivo radionuclide transport enhances the accuracy of TAT dose estimates.
• This approach represents a foundational step towards a comprehensive simulation toolkit for TAT.
• Future applications include predicting absorbed doses to tumors and normal tissues, and biological responses.