Monte Carlo N-Particle Transport Code Simulation
of Leksell Gamma Knife Using Disk 1 Sources of
Polystyrene, PMMA, Plastic Water and Head Phantom

Ma. Vanessa Francheska P. Perianes, Dorren Alexis F. Villanueva,
and Jade R. Dungao

Physics Department, De La Salle University
Taft Avenue, Manila, Philippines

*Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.


Stereotactic Radiosurgery (SRS) has become a standard modality for the treatment of benign and metastatic brain lesions that were deemed medically unsuitable for surgery. The Leksell Gamma Knife (LGK), a type of SRS that was used in this study, has 201 Cobalt-60 sources distributed in a hemisphere whose radiation intersects at the isocenter. The relative dose at the isocenter was verified using Monte Carlo N-Particle Simulation (MCNP). This study uses disk sources, an alternative for the full geometry collimator system of the LGK, to simulate a 160-mm water phantom made of different materials: polystyrene, plastic water, and PMMA (Polymethyl methacrylate). In addition, the simulation of a head phantom was also included in this study. Relative dose distributions were calculated and were compared to the relative dose distributions from the cited literatures. As a result, no significant differences have been found. In conclusion, the use of disk sources provides a simpler method of simulating the LGK instead of using the full geometry collimator system in the MCNP Visual Editor.

Stereotactic Radiosurgery (SRS) is one of the treatment modalities used to treat benign and metastatic brain lesions. It is a specialized technique where a uniform dose, with highly conformal radiation, is delivered to the target.
The type of SRS that was used in this study was the Leksell Gamma Knife (LGK). LGK was developed by Swedish neurosurgeon Lars Leksell and Physicist Borje Larson. The LGK, manufactured by Elekta Instruments Inc., uses 201 Co-60 sources distributed on a hemisphere. The diameter of the beams of the ionizing radiation was defined by the collimator system and the shape of the target can be varied by changing the size of the collimator helmets:  4 mm, 8 mm, 14 mm and 18 mm. . . . . read more

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