Move up to MRI guided Gamma Knife radiosurgery: A Monte Carlo study on dose distribution changes

Abstract

This study explores the feasibility of integrating Magnetic Resonance Imaging (MRI) with the Gamma Knife Icon (GKI™) for real-time monitoring during radiosurgery. The use of MRI could improve treatment accuracy and safety, but combining it with GKI™ poses dosimetric challenges due to the Lorentz force exerted by the MR scanner Magnetic Field (MF). A comprehensive GKI™ Monte Carlo (MC) simulation was conducted to investigate the changes induced by MF on the dose distribution of GKI™. The simulation was validated using profile curves and output factors (OFs). Five MF intensities were applied for different collimator sizes, and changes in physical penumbra width and Full Width at Half Maximum (FWHM) were calculated. The study found that the effect of MF on the dose distribution of the GKI™ is more prominent in high-intensity fields and smaller collimator sizes. The observed lateral displacement of up to 1 mm is significant, considering the device's nominal 0.25 mm precision. The results indicate that a 7 T magnetic field is the most suitable choice for the hypothetical MR-GK device, considering the penumbra width reduction and potential improvements in image quality. However, significant engineering and cost-related challenges are associated with integrating these two devices, and further research is necessary to investigate the feasibility and safety of combining these two technologies in clinical settings.