A Geant4 shielding design for the first US carbon multi-ion hybrid synchrotron facility

Area of Science:

• Medical Physics
• Radiation Oncology
• Particle Therapy

Background:

• The Mayo Clinic Florida Integrated Oncology Building will house Hitachi, Ltd.'s first spot-scanning only carbon/proton hybrid therapy system.
• This advanced system will deliver proton beams up to 230 MeV and carbon beams up to 430 MeV n^-1 for clinical use.

Purpose of the Study:

• To quantify ambient dose equivalent (H*(10)) for photons and neutrons to ensure adequate radiation protection.
• To optimize shielding design for the new hybrid carbon/proton therapy facility.

Main Methods:

• Utilized the Geant4 (v10.6) Monte Carlo toolkit for radiation transport simulations.
• Imported detailed 3D CAD models of the facility and particle system components into Geant4.
• Performed analytical calculations for initial design checks and iterative optimization of shielding slabs using Geant4.

Main Results:

• The 430 MeV n^-1 carbon beams were the primary driver for concrete shielding thickness requirements.
• The primary wall thickness for the carbon fixed beam room was determined to be 4 meters.
• Proton gantry structure increased dose equivalent by ~67% at the maze entrance but decreased it in the beam transport corridor.

Conclusions:

• All shielding goals for clinical operations were successfully met, adhering to state regulations and national guidelines.
• Geant4 simulations proved effective in optimizing radiation shielding for advanced particle therapy facilities.