PET digitization chain for Monte Carlo simulation in GATE.

Area of Science:

• Medical Imaging Physics
• Computational Science
• Nuclear Medicine Technology

Background:

• Accurate modeling of Positron Emission Tomography (PET) systems is crucial for quantitative imaging.
• Monte Carlo simulations, particularly using Geant4 application for tomographic emission (GATE), are powerful tools for PET system modeling.
• The digitizer component in GATE plays a key role in emulating real system count rates.

Purpose of the Study:

• To introduce a versatile methodology for accurate PET system modeling using Monte Carlo simulations.
• To optimize the GATE digitizer to replicate the detection chain of real PET systems.
• To validate the methodology by comparing simulation results with experimental data from state-of-the-art PET scanners.

Main Methods:

• A two-step approach was developed: (1) modeling the digitizer using all available parameters and (2) estimating remaining parameters (noise, efficiency, pile-up) via optimization.
• Optimization was based on experimental single and prompt event rates.
• The method was validated using NEMA count loss tests on three SiPM-based TOF-PET systems (Philips Vereos, Siemens Biograph Vision 600, GE Discovery MI).

Main Results:

• The optimized digitizer accurately reproduced experimental count rates (true, scatter, random) without further adjustments.
• Simulations showed good agreement with experimental data for the three tested PET systems.
• Absolute relative discrepancies were below 3-12% for various count rates within a typical activity concentration range.

Conclusions:

• The proposed digitizer optimization method effectively reproduces count rates and Noise Equivalent Count Rate (NECR) for modern SiPM-based TOF-PET systems.
• This methodology enhances the accuracy of Monte Carlo simulations for PET imaging.
• The approach is versatile and can be applied to other PET scanner designs.