Efficient simulation of voxelized phantom in GATE with embedded SimSET multiple photon history generator

Area of Science:

• Medical Imaging Physics
• Computational Science
• Nuclear Medicine

Background:

• GEANT4 Application for Tomographic Emission (GATE) is a Monte Carlo simulator for emission tomography, but detailed physical modeling of voxelized phantoms is computationally intensive.
• Existing workflows integrating GATE with SimSET improve speed but limit the simulation of complex radioactive decays and time-dependent processes.
• The SimSET photon history generator (PHG) requires large storage for temporal photon history files, posing practical challenges.

Purpose of the Study:

• To develop and implement a multiple photon emission history generator (MPHG) within GATE to improve the efficiency of voxelized phantom simulations.
• To support a wider range of medically relevant positron emitters and eliminate the need for large temporal photon history files.
• To validate the performance and accuracy of the new GATE/MPHG code against established simulation methods.

Main Methods:

• Developed a multiple photon emission history generator (MPHG) based on SimSET/PHG.
• Integrated the MPHG codes into the GATE simulation platform.
• Validated the GATE/MPHG system using a MicroPET R4 scanner with (124)I and (18)F isotopes and mouse-like/rat-like phantoms.
• Compared simulation results with standard GATE/GEANT4, including energy spectra, spatial resolution, scatter fraction, and count rate performance.

Main Results:

• The GATE/MPHG code demonstrated significant acceleration factors (3.1x to 9.5x) compared to standard GATE methods for voxelized phantom simulations.
• Validation showed good agreement in spatial resolution, scatter fraction, and count rate performance between GATE/MPHG and GATE/GEANT4.
• A slight difference in energy spectra below 50 keV was observed due to the lack of x-ray simulation from (124)I decay in the new code.

Conclusions:

• The implementation of MPHG in GATE substantially improves the efficiency of voxelized phantom simulations for emission tomography.
• The GATE/MPHG system effectively simulates complex decay schemes and eliminates the need for temporal photon history files, addressing previous workflow limitations.
• This enhanced simulation tool is suitable for both clinical and preclinical emission tomography studies, offering a balance of speed and accuracy.