TOPAS-imaging: extensions to the TOPAS simulation toolkit for medical imaging systems

Area of Science:

• Medical Physics
• Computational Imaging
• Radiation Oncology

Background:

• The TOol for PArticle Simulation (TOPAS) is a Geant4-based Monte Carlo software widely used in medical physics for radiotherapy research.
• Existing TOPAS applications primarily focus on radiotherapy delivery systems and patient dose calculations.
• There is a need for enhanced TOPAS capabilities to facilitate the modeling of medical imaging systems.

Purpose of the Study:

• To develop and present the first set of TOPAS extensions specifically designed for modeling medical imaging systems.
• To provide user-configurable geometry components and scorers for various imaging modalities.
• To enable easier simulation of medical imaging systems within the TOPAS framework.

Main Methods:

• Utilized the TOPAS extension system to implement pre-built, configurable geometry components (e.g., FlatImager, RingImager) for detectors.
• Developed pre-built, configurable scorers for medical imaging systems, including digitizer chains.
• Modeled cone-beam CT (CBCT), positron emission tomography (PET), and prompt gamma (PG) systems using the developed extensions.

Main Results:

• Successfully implemented and tested new TOPAS extensions for simulating medical imaging systems.
• Demonstrated the modeling of CBCT and PG systems using the FlatImager component, accurately capturing X-ray and prompt gamma signals.
• Modeled a PET system using the RingImager component, simulating positron-electron annihilation and coincidence detection with results in agreement with expectations.

Conclusions:

• The developed TOPAS extensions represent a significant advancement in simplifying the simulation of medical imaging systems.
• These extensions facilitate the integration of medical imaging simulations with existing radiotherapy simulation tools in TOPAS.
• This work paves the way for advanced image-guided radiotherapy research through integrated simulations.