Gamma Knife Icon™ Single Source and Collimator Characterization Based on Monte Carlo Simulation

Gamma Knife Radiosurgery refers to surgery using radiation to destroy intracranial tissues or lesions elusive or unsuitable for open surgery. This study aimed to simulate the Gamma Knife Icon™ (GKI™) single sector to assess various attributes of the output beam and evaluate the EGSnrc C++ Monte Carlo code capabilities to perform a complete simulation of GKI™ for more investigations.

The single source is simulated, and the geometries of the 4 and 16 mm collimators are defined based on the manufacturer data. The phase space files (PSFs) are recorded at the end of each collimator, and dose distributions are saved for the final analysis process in the last step.

The beam spectrum has two energy peaks g1 =1.17 MeV and g2 = 1.33 MeV, and low energy photons from scattering are also evident. The Gamma Index (GI) values are less than 1 in comparing the dose profiles generated in simulation with reference data. The Full Width at Half Maximum (FWHM) is 4.55, 10.9, 5.13 (mm) and 16.7, 35.1, 17.65 (mm) for 4mm and 16 mm collimators along x, y, and z axes, respectively. The penumbra width (80%-20%) is also 1.48, 5.5, 1.54 (mm) and 3.76, 10.1, 2.78 (mm) for 4mm and 16 mm collimators along x, y, and z axes, respectively.

Results are in good agreement with what is expected, and it is possible to perform a complete simulation of the GKI™ system using egs++ for more investigations in phantoms and patients.