Medical Radiology and Radiation Safety. 2020. Vol. 65. No. 1. P. 54–58

T. Medjadj1, A.I. Ksenofontov1, A.V. Dalechina2

An Effective Method of Simulation for the Leksell Gamma Knife Perfexion by Rotating Particles in the Phase Space File

1. National Research Nuclear University (Moscow Engineering Physics Institute) MEPhI, Moscow, Russia;
2. OJSC Neurosurgery Business Center, Moscow GammaKnife Center, Moscow, Russia
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Purpose: To develop an effective method of Monte Carlo simulation of the GammaKnife Perfexion system by rotating particles in the phase space file (PSF). This method does not require simulating of all 192 sources that are distributed in the conical form of the Perfexion collimator. The simulation was performed only for 5 out of 192 sources for each collimator size.

Material and methods: Monte Carlo simulation of dose distribution for previous models of GammaKnife system requires phase space file for only one source, since this phase space is identical for all the 201 sources. The Perfexion model is more complex due to the non-coaxial positions of the sources and the complexity of the collimator system itself.
In this work, we present an effective method to simulate the Perfexion model using a phase space file. Penelope Monte Carlo code was used to perform this simulation. In this method, the PSF was obtained for one source in each ring, resulting in five files for each collimator size. PSF for other sources were created by azimuthal redistribution of particles, in the obtained PSF, by rotation around the Z-axis. The phase space files of the same ring were then stored together in a single file.

Results: The paper presented MC simulation using the azimuthal redistribution of particles in the phase space file by rotation around the Z-axis. The simulation has been validated comparing the dose profiles and output factors with the data of the algorithm TMR10 planning system Leksell Gamma Plan (LGP) in a homogeneous environment. The acceptance criterion between TMR10 and Monte Carlo calculations for the profiles was based on the gamma index (GI). Index values more than one were not detected in all cases, which indicates a good agreement of results. The differences between the output factors obtained in this work and the TMR10 data for collimators 8 mm and 4 mm are 0.74 and 0.73 %, respectively.

Conclusion: In this work successfully implemented an effective method of simulating the Leksell Gamma knife Perfexion system. The presented method does not require modeling for all 192 sources distributed in the conical form of the Perfexion collimator. The simulation was performed for only five sources for each collimator and their files PSF were obtained. These files were used to create the PSF files for other sources by azimuthal redistribution of particles, in these files, by rotation around the Z-axis providing correct calculations of dose distributions in a homogeneous medium for 16, 8 and 4 mm collimators.

Ключевые слова: Gamma-Knife Perfexion, Monte Carlo simulation, file phase field

Для цитирования: Medjadj T, Ksenofontov AI, Dalechina AV. An Effective Method of Simulation for the Leksell Gamma Knife Perfexion by Rotating Particles in the Phase Space File. Medical Radiology and Radiation Safety. 2020;65(1):54-8. (In Russ.).

DOI: 10.12737/1024-6177-2020-65-1-54-58

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Conflict of interest. The authors declare no conflict of interest.

Financing. The study had no sponsorship.

Contribution. Article was prepared with equal participation of the authors.

Article received: 08.04.2019. Accepted for publication: 11.12.2019.