First year experience with newly developed Leksell Gamma Knife Perfexion.

A new model of Leksell Gamma Knife(R) (LGK), known as Perfexion (LGK PFX), was introduced by Elekta Instrument, AB, Sweden, in 2006. This model has a radically different design from the earlier models U, B, C and 4C. Dosimetric characteristics of LGK PFX, technical differences between LGK PFX and LGK 4C, experience gained with acceptance testing and commissioning of the LGK PFX, and comparison between LGK PFX and LGK 4C are presented in this study. Excellent agreement is found between the manufacturers recommended values of absorbed dose rate, relative output factors for 4 and 8 mm collimators, coincidence of mechanical and dosimetric isocenter, FWHM for beam profiles for various collimators and those reported in the present study. Excellent agreement is also found between the dosimetric characteristics of LGK PFX and LGK 4C for the 4 and 8 mm collimators. Examples of clinical cases treated with LGK PFX and impact of LGK PFX on workflow and dosimetric conformity of treatment planning is also given. The set up and treatment of patients on the LGK PFX is much more efficient since it is a fully automated system. The system also provides more options to generate plan with high dosimetric conformity.