Browsing by Author "Yegin G."

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    A new approach to geometry modeling for Monte Carlo particle transport: An application to the EGS code system
    (2003) Yegin G.
    A new technique has been developed for Monte Carlo particle transport calculations to handle the geometry for systems having complex structure. In this technique, the geometry of a problem is determined as a superposition of many simple geometries in the same space. The actual geometry of a region is determined by picking between these geometries based upon which one is real and which are virtual at a particular point in space. This method was applied in the EGS code system. The effect of this method on computation time and accuracy of the results are discussed. © 2003 Elsevier B.V. All rights reserved.
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    Improving the resolution of beta scattering spectroscopy
    (2004) Celiktas C.; Selvi S.; Yegin G.
    We have examined the performance of a modified beta-ray spectrometer using a pulse shape analyzer/timing single channel analyzer and related electronics, thereby preserving the low energy electron tail in measurement of the scattered electron spectra from an n-type Si wafer target. Comparison of measurements with the scattering spectra calculated by the Monte Carlo program EGS4 indicates good agreement across a significant part of the spectrum, an exception being for the energy region 30-100keV. Re-evaluation of existing scattering cross-sections would be useful, as would possible geometrical effects of the scattering arrangement used herein. Present efforts seek to contribute to the evaluation of electron scattering cross-sections and improvement in theoretical models. © 2004 Elsevier Ltd. All rights reserved.
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    SU‐GG‐T‐77: Effect of Mobile Seed Components on Dosimetry of Theragenic Model 200 Pd‐103 Seed Source
    (2010) Yegin G.; Duman S.; Aydogdu G.; Camgoz B.; Aras S.; Kumru M.
    Purpose: To investigate the influence of mobile internal source components of Theragenic Model 200 seed source on its dose rate distribution and TG‐43 parameters. Method and Materials : By using BrachyDose Monte Carlo code, the geometry of Theragenic Model 200 seed source was modeled in five different configurations. In each configuration, internal components are located at different positions in order to take into account the effect of gravitational force on the seed geometry. Physical dimensions of seed components are identical in all seed models. Air kerma strenghts and dose per unit activitiy were determined separately for each seed design on a plane which is in a direction where dose variations are expected to be maximum. Calculated data were used to produce TG‐43 parameters. Results: Comparison of TG‐43 dosimetric parameters for each seed configuation showed that dose rate constant varies up to 11% due to the position of internal source elements. For radial dose fuction, there are significant differences increasing up to 40% at distances 0.1≤ r <0.5 cm and for radial distances r >0.5 discrepancies are negligible (i.e. about 1–2%). Anisotropy functions were calculated at radial distances of 0.25, 0.5, 1.0 and 5.0 cm. It is observed that anisotropy function changes adruptly (up to 40%) for polar angels θ<15° and θ>165° at all radial distances. Differences are less than 5% for all other angles and decreases with increasing radial distance. Conclusions: The geometry variation effects investigated in this study are ignored in the TG‐43 formalism. This work indicates that these effects may change absorbed dose values significantly at some points around the Theragenic Model 200 seed source. This investigation was supported by Celal Bayar University (Project number: 2009/138) and ULAKBIM High Performance and Grid Computing Center (TR‐grid). © 2010, American Association of Physicists in Medicine. All rights reserved.
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    Sci—Sat AM(2): Brachy — 05: Fast Monte Carlo Dose Calculations for Brachytherapy with BrachyDose
    (2010) Thomson R.M.; Yegin G.; Taylor R.; Sutherland J.; Rogers D.
    A fast dose calculation algorithm called BrachyDose has been developed for brachytherapy applications. BrachyDose is based on the EGSnrc code system for simulating radiation transport. Complex geometries are modelled through the superposition of basic geometric entities (spheres, cuboids, cylinders, and cones) using Yegin's multi‐geometry package; the phantom geometry may be defined using a CT dataset. A database of brachytherapy sources has been developed and benchmarked, as has a database of eye plaque applicators. BrachyDose scores collision kerma, which is equivalent to absorbed dose for most situations of interest, using a tracklength estimator. The phase space of particles emitted from brachytherapy sources may be generated with BrachyDose and used in subsequent simulations to avoid the repeated simulation of particle transport within sources. A particle recycling feature has been implemented for multisource configurations in which the first source acts as a particle generator; particles emitted from this source are reinitiated at each source location. Dose calculations for prostate permanent implants achieving 2% average uncertainty in the prostate region take less than 30 seconds in (2 mm)3 voxels on a single 3.0 GHz Woodcrest core; calculation times for eye plaque therapy are on the order of three minutes in (0.5 mm)3 voxels. These calculation times are sufficiently fast for routine clinical treatment planning. A graphical user interface (GUI) for BrachyDose has been developed. Working towards clinical implementation, efforts are underway to integrate data in the DICOM‐RT format with BrachyDose. © 2010, American Association of Physicists in Medicine. All rights reserved.
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    Estimation of bremsstrahlung photon fluence from aluminum by artificial neural network
    (Novim Medical Radiation Institute, 2012) Akkurt I.; Gunoglu K.; Tekin H.O.; Demirci Z.N.; Yegin G.; Demir N.
    Background: As bremsstrahlung photon beam fluence is important parameter to be known in a photonuclear reaction experiment as the number of produced particle is strongly depends on photon fluence. Materials and Methods: Photon production yield from different thickness of aluminum target has been estimated using artificial neural network (ANN) model. Target thickness and incoming electron energy has been used as input in ANN model and the photon fluence was output. Results: The results were estimated using ANN model for three different thickness and compared with the results obtained by EGS (Electron Gamma Shower) simulation. Conclusion: It can be concluded from this work that the bremsstrahlung photon fluence can be obtained using ANN model.
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    Comment on 'egs-brachy: A versatile and fast Monte Carlo code for brachytherapy'
    (Institute of Physics Publishing, 2018) Yegin G.
    In a recent paper (Chamberland et al 2016 Phys. Med. Biol. 61 8214) develop a new Monte Carlo code called egs-brachy for brachytherapy treatments. It is based on EGSnrc, and written in the C++ programming language. In order to benchmark the egs-brachy code, the authors use it in various test case scenarios in which complex geometry conditions exist. Another EGSnrc based brachytherapy dose calculation engine, BrachyDose, is used for dose comparisons. The authors fail to prove that egs-brachy can produce reasonable dose values for brachytherapy sources in a given medium. The dose comparisons in the paper are erroneous and misleading. egs-brachy should not be used in any further research studies unless and until all the potential bugs are fixed in the code. © 2018 Institute of Physics and Engineering in Medicine.
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    Evaluation of BrachyDose Monte Carlo code for HDR brachytherapy: Dose comparison against Acuros®BV and TG-43 algorithms
    (Cambridge University Press, 2020) Dagli A.; Yurt F.; Yegin G.
    Aim: The aim of this study is to investigate the accuracy of dose distributions calculated by the BrachyDose Monte Carlo (MC) code in heterogeneous media for high-dose-rate (HDR) brachytherapy and to evaluate its usability in the clinical brachytherapy treatment planning systems.Materials and methods: For dose comparisons, three different dose calculation algorithms were used in this study. Namely, BrachyDose MC code, Eclipse TG-43 dose calculation tool and Acuros®BV model-based dose calculation algorithm (MBDCA). Dose distributions were obtained using any of the above codes in various scenarios including 'homogenous water medium scenario', an 'extreme case heterogeneous media scenario' and clinically important 'a patient with a cervical cancer scenario'. In the 'extreme case, heterogeneous media scenario', geometry is a rare combination of unusual high-density and low-density materials and it is chosen to provide a test environment for the propagation of photons in the interface of two materials with different absorption and scattering properties. GammaMed 192Ir Model 12i Source is used as the HDR brachytherapy source in this study. Dose calculations were performed for the cases where there is either a single source or five sources planted into the phantom geometry in all homogenous water phantom and extreme case heterogeneous media scenarios. For the scenario a patient with a cervical cancer, dose calculations were performed in a voxelized rectilinear phantom, which is constructed from a series of computed tomography (CT) slices of a patient, which are obtained from a CT device.Results: In homogeneous water phantom scenario, we observed no statistically significant dose differences among the dose distributions calculated by any of the three algorithms at almost every point in the geometry. In the extreme case heterogeneous media scenario, the dose calculation engines Acuros®BV and BrachyDose are agreed well within statistics in every region of the geometry and even in the points close to the interfaces of low-density and high-density materials. On the other hand, the dose values calculated by these two codes are significantly different from those calculated by the TG-43 algorithm. In the 'a patient with a cervical cancer scenario', the calculated D2cc dose difference between Acuros®BV and BrachyDose codes is within 2% in the rectum and 11% for the bladder and sigmoid. There was no meaningful difference in the mean dose values between MBDCAs in the bone structures.Conclusions: In this study, the accurate dose calculation capabilities of the BrachyDose program in HDR brachytherapy were investigated on various scenarios and, as a MC dose calculation tool, its effectiveness in HDR brachytherapy was demonstrated by comparative dose analysis. © Cambridge University Press 2019.