Monte Carlo simulation of the Leksell Gamma Knife$reg$: I. Source modelling and calculations in homogeneous media

Abstract

The Monte Carlo code PENELOPE has been used to simulate photon flux from the Leksell Gamma Knife, a precision method for treating intracranial lesions. Radiation from a single 6OCo assembly traversing the collimator system was simulated, and phase space distributions at the output surface of the helmet for photons and electrons were calculated. The characteristics describing the emitted final beam were used to build a two-stage Monte Carlo simulation of irradiation of a target. A dose field inside a standard spherical polystyrene phantom, usually used for Gamma Knife dosimetry, has been computed and compared with experimental results, with calculations performed by other authors with the use of the EGS4 Monte Carlo code, and data provided by the treatment planning system Gamma Plan. Good agreement was found between these data and results of simulations in homogeneous media. Owing to this established accuracy, PENELOPE is suitable for simulating problems relevant to stereotactic radiosurgery.

MAGAT gel and EBT2 film‐based dosimetry for evaluating source plugging‐based treatment plan in Gamma Knife stereotactic radiosurgery

“…Previously, numerous studies were done to analyze the accuracy of plugging in Gamma Knife 7 , 8 , 9 , 10 . There are a set of Monte Carlo (MC) studies which were successfully used for simulating Gamma Knife sources and units itself, including plugging patterns 2 , 7 , 10 , 11 , 12 , 13 , 14 , 15 . Cheung et al (7) employed Monte Carlo general‐purpose code EGS4 implementing PRESTA (parameter reduced electron‐step transport algorithm) algorithm and GAFCHROMIC films (Type MD 55) 16 , 17 to verify the accuracy of LGP TPS when plugged collimators were used.…”

“…A 9% methacrylic‐based gel was found to give linear doses response up to 40 Gy and is ideal for performing radiosurgery verification (31) . Several studies exist for Gamma Knife verification with polymer gel dosimetry 3 , 13 , 31 , 32 , 33 , 34 , 35 , 36 . Interestingly, 3D measurement based on gel dosimetry has not been used so far for plug planning verification which is the goal of this study.…”

A simplified model of the source channel of the Leksell Gamma Knife®: testing multisource configurations with PENELOPE

“…Most of the simulations performed (Cheung et al 1998, 1999a, 1999b, Xiaowei and Chunxiang 1999, Moskvin et al 2002 have pointed out a good agreement with the GP predictions in the case of a homogeneous phantom. However, differences reaching 25% are found for phantoms with inhomogeneities, near tissue interfaces and dose edges (Cheung et al 2001).…”

“…In addition to the dose profiles around the isocenter of the GK, the output factors for the 4, 8 and 14 mm helmets have been obtained. Our findings have been compared with various results obtained with other MC codes, such as EGS4 (Cheung et al 1999a, 1999b, Xiaowei and Chunxiang 1999 or PENELOPE (Moskvin et al 2002), predicted with GP (Elekta 1992, 1998 or measured with different techniques (Ma et al 2000, Tsai et al 2003. Figure 1 shows a scheme of the simplified model of the source channel of the GK.…”

Development of a Monte Carlo model for treatment planning dose verification of the Leksell Gamma Knife Perfexion radiosurgery system

“…It is important that the electronic inequilibrium and secondary scattering are taken into account properly. Studies on MC simulations are mainly for the prior LGK systems because the collimator system for prior LGK models is relatively simpler to implement 5 , 6 , 7 , 8 , 9 . To simulate prior LGK, only one dataset of the phase space of photon beams at the distal source channel is needed since this phase space is identical for all 201 sources.…”