Monte Carlo calculated and experimentally determined output correction factors for small field detectors in Leksell Gamma Knife Perfexion beams

2015 ◽  
Vol 60 (10) ◽  
pp. 3959-3973 ◽  
Author(s):  
H Benmakhlouf ◽  
J Johansson ◽  
I Paddick ◽  
P Andreo
Keyword(s):  
Monte Carlo ◽  
Gamma Knife ◽  
Small Field ◽  
Correction Factors ◽  
Gamma Knife Perfexion

Monte carlo determination of correction factors for dosimetric measurements in gamma knife perfexion small fields

2016 ◽  
Vol 32 ◽  
pp. 237 ◽  
Author(s):  
E. Zoros ◽  
E.P. Pappas ◽  
A. Moutsatsos ◽  
E. Pantelis ◽  
C. Paraskevopoulou ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Gamma Knife ◽  
Correction Factors ◽  
Small Fields ◽  
Gamma Knife Perfexion

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

2020 ◽  
Vol 65 (1) ◽  
pp. 54-58
Author(s):  
T. Medjadj ◽  
A. Ksenofontov ◽  
A. Dalechina
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Phase Space ◽  
Gamma Knife ◽  
Homogeneous Medium ◽  
Planning System ◽  
Monte Carlo Code ◽  
Output Factors ◽  
Gamma Knife Perfexion ◽  
Conical Form

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.

scholarly journals EP-1438: Experimental determination of correction factors for reference dosimetry in Gamma Knife Perfexion

2017 ◽  
Vol 123 ◽  
pp. S767 ◽  
Author(s):  
E. Zoros ◽  
E.P. Pappas ◽  
K. Zourari ◽  
E. Pantelis ◽  
A. Moutsatsos ◽  
...  
Keyword(s):  
Experimental Determination ◽  
Gamma Knife ◽  
Correction Factors ◽  
Gamma Knife Perfexion

scholarly journals Estimation of Dosimetric Parameters based on KNR and KNCSF Correction Factors for Small Field Radiation Therapy at 6 and 18 MV Linac Energies using Monte Carlo Simulation Methods

2019 ◽  
Vol 9 (1Feb) ◽  
Author(s):  
S A Rahimi ◽  
B Hashemi ◽  
S R Mahdavi
Keyword(s):  
Monte Carlo ◽  
Correction Factor ◽  
Reference Conditions ◽  
Field Size ◽  
Monte Carlo Code ◽  
Small Field ◽  
Correction Factors ◽  
Photon Beams ◽  
Small Field Dosimetry ◽  
Circular Field

Background: Estimating dosimetric parameters for small fields under non-reference conditions leads to significant errors if done based on conventional protocols used for large fields in reference conditions. Hence, further correction factors have been introduced to take into account the influence of spectral quality changes when various detectors are used in non-reference conditions at different depths and field sizes.Objective: Determining correction factors (KNR and KNCSF) recommended recently for small field dosimetry formalism by American Association of Physicists in Medicine (AAPM) for different detectors at 6 and 18 MV photon beams.Methods: EGSnrc Monte Carlo code was used to calculate the doses measured with different detectors located in a slab phantom and the recommended KNR and KNCSF correction factors for various circular small field sizes ranging from 5-30 mm diameters. KNR and KNCSF correction factors were determined for different active detectors (a pinpoint chamber, EDP-20 and EDP-10 diodes) in a homogeneous phantom irradiated to 6 and 18 MV photon beams of a Varian linac (2100C/D).Results: KNR correction factor estimated for the highest small circular field size of 30 mm diameter for the pinpoint chamber, EDP-20 and EDP-10 diodes were 0.993, 1.020 and 1.054; and 0.992, 1.054 and 1.005 for the 6 and 18 MV beams, respectively. The KNCSF correction factor estimated for the lowest circular field size of 5 mm for the pinpoint chamber, EDP-20 and EDP-10 diodes were 0.994, 1.023, and 1.040; and 1.000, 1.014, and 1.022 for the 6 and 18 MV photon beams, respectively.Conclusion: Comparing the results obtained for the detectors used in this study reveals that the unshielded diodes (EDP-20 and EDP-10) can confidently be recommended for small field dosimetry as their correction factors (KNR and KNCSF) was close to 1.0 for all small field sizes investigated and are mainly independent from the electron beam spot size.

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