Ivan Evseev
Rio de Janeiro State University
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Featured researches published by Ivan Evseev.
Medical Physics | 2005
Reinhard W. Schulte; V. Bashkirov; Margio Cezar Loss Klock; Tianfang Li; A Wroe; Ivan Evseev; D. C. Williams; T. Satogata
Conformal proton radiation therapy requires accurate prediction of the Bragg peak position. Protons may be more suitable than conventional x-rays for this task since the relative electron density distribution can be measured directly with proton computed tomography (CT). However, proton CT has its own limitations, which need to be carefully studied before this technique can be introduced into routine clinical practice. In this work, we have used analytical relationships as well as the Monte Carlo simulation tool GEANT4 to study the principal resolution limits of proton CT. The noise level observed in proton CT images of a cylindrical water phantom with embedded tissue-equivalent density inhomogeneities, which were generated based on GEANT4 simulations, compared well with predictions based on Tschalars theory of energy loss straggling. The relationship between phantom thickness, initial energy, and the relative electron density resolution was systematically investigated to estimate the proton dose needed to obtain a given density resolution. We show that a reasonable density resolution can be achieved with a relatively small dose, which is comparable to or even lower than that of x-ray CT.
Brazilian Journal of Physics | 2004
Ivan Evseev; Margio Cezar Loss Klock; Sergei A. Paschuk; Hugo R. Schelin; J. A. P. Setti; R.T. Lopes; Reinhard W. Schulte; D. C. Williams
The use of protons instead of X-rays for computerized tomography (CT) studies has potential advantages, especially for medical applications in proton treatment planning. However, the spatial resolution of proton CT is limited by multiple Coulomb scattering (MCS). We used the Monte Carlo simulation tool GEANT4 to study the resolution achievable with different experimental arrangements of a proton CT scanner. The passage of a parallel 200MeV proton beam through a virtual cylindrical aluminum phantom with 50mm external diameter was simulated. In our study, the phantom contained a set of cylindrical holes with diameters ranging from 4mm to 0.5mm. The GEANT4 simulation consisted of a series of 180 projections at 2 degree intervals with 350 proton track histories for each one. The filtered back projection algorithm was used to reconstruct a 2D tomographic image of phantom.
Applied Radiation and Isotopes | 2010
Edney Milhoretto; H.R. Schelin; J. A. P. Setti; Valery Denyak; S.A. Paschuk; Ivan Evseev; Joaquim Teixeira de Assis; Olga Yevseyeva; R.T. Lopes; Ubirajara Maribondo Vinagre Filho
This work presents the recent results of computer simulations for the low energy proton beam tomographic scanner installed at the cyclotron CV-28 of IEN/CNEN. New computer simulations were performed in order to adjust the parameters of previous simulation within the first experimental results and to understand some specific effects that affected the form of the final proton energy spectra. To do this, the energy and angular spread of the initial proton beam were added, and the virtual phantom geometry was specified more accurately in relation to the real one. As a result, a more realistic view on the measurements was achieved.
Medical Imaging 2005: Physics of Medical Imaging | 2005
Ivan Evseev; Joaquim Teixeira de Assis; Olga Yevseyeva; Hugo R. Schelin; Margio Cezar Loss Klock; J. A. P. Setti; R.T. Lopes; Ubirajara Maribondo Vinagre Filho; Reinhard W. Schulte; D. C. Williams
In existing proton treatment centers, dose calculations are performed based on x-ray computerized tomography (CT). Alternatively, the therapeutic proton beam could be used to collect the data for treatment planning via proton CT (pCT). With the development of medical proton gantries, first at Loma Linda University Medical Center and now in several other proton treatment centers, it is of interest to continue the early pCT investigations of the 1970s and the early 1980s. From that time, the basic idea of the pCT method has advanced from average energy loss measurements to an individual proton tracking technique. This reduces the image degradation due to multiple Coulomb scattering. Thereby, the central pCT problem shifts to the fidelity of the physical information obtained about the scanned patient, which will be used for proton treatment planning. The accuracy of relative electron density distributions extracted from pCT images was investigated in this work using continuous slowing down approximation (CSDA) and water-equivalent-thickness (WET) concepts. Analytical results were checked against Monte Carlo simulations, which were obtained with SRIM2003 and GEANT4 Monte Carlo software packages. The range of applications and the sources of absolute errors are discussed.
Optical Science and Technology, the SPIE 49th Annual Meeting | 2004
Reinhard W. Schulte; Margio Cezar Loss Klock; V. Bashkirov; Ivan Evseev; Joaquim Teixeira de Assis; Olga Yevseyeva; R.T. Lopes; Tianfang Li; D. C. Williams; A Wroe; Hugo R. Schelin
Conformal proton radiation therapy requires accurate prediction of the Bragg peak position. This problem may be solved by using protons rather than conventional x-rays to determine the relative electron density distribution via proton computed tomography (proton CT). However, proton CT has its own limitations, which need to be carefully studied before this technique can be introduced into routine clinical practice. In this work, we have used analytical relationships as well as the Monte Carlo simulation tool GEANT4 to study the principal resolution limits of proton CT. The GEANT4 simulations were validated by comparing them to predictions of the Bethe Bloch theory and Tschalars theory of energy loss straggling, and were found to be in good agreement. The relationship between phantom thickness, initial energy, and the relative electron density uncertainty was systematically investigated to estimate the number of protons and dose needed to obtain a given density resolution. The predictions of this study were verified by simulating the performance of a hypothetical proton CT scanner when imaging a cylindrical water phantom with embedded density inhomogeneities. We show that a reasonable density resolution can be achieved with a relatively small number of protons, thus providing a possible dose advantage over x-ray CT.
Brazilian Journal of Physics | 2003
V.V. Denyak; Ivan Evseev; V. M. Khvastunov; V.P. Likhachev; S.A. Paschuk; H.R. Schelin
We present the results of the polarization and intensity measurements versus photon energy MeV for the photon beam produced by the electron plane channeling with the energies 1.2 and 1.5 GeV in silicon crystals 500 m and 290 m thick along the (110) plane. The comparison with results of another research group and theoretical calculations indicate a qualitative agreement. The correlation between the shape of the radiation intensity spectrum and its polarization energy dependence is observed.
InterScience Place | 2014
Francisco Roberto Cassetta Junior; João Antônio Palma; Setti Edney Milhoretto; Hugo R. Schelin; Ivan Evseev
The modality of radiotherapy with protons shows promising results compared to conventional treatment with photons. There are softwares, such as GEANT4 and SRIM, which allow simulations of passages of heavy particles through matter, thus making it possible to obtain useful results for specific studies in this area. Its importance comes from its relative simplicity of use mainly due to the high cost of hadron accelerators. The analysis of the parameters calculated by simulations and their levels of uncertainty in the region of the Bragg peak will be essential to future development stages of treatment plans with proton beam. This work presents some simulations about the trend of increase in mean lateral deviation (in the Bragg peek region) with increasing energy of the incident beam.
XXXV BRAZILIAN WORKSHOP ON NUCLEAR PHYSICS | 2013
Ivan Evseev; Francielle Ahmann; Hamilton P. da Silva; Hugo R. Schelin; Olga Yevseyeva; Margio Cezar Loss Klock
Computerized tomography (CT) plays an important role in medical imaging for diagnosis and therapy. However, CT imaging is connected with ionization radiation exposure of patients. Therefore, the dose reduction is an essential issue in CT. In 2011, the Expectation Maximization and Total Variation Based Model for CT Reconstruction (EM+TV) was proposed. This method can reconstruct a better image using less CT projections in comparison with the usual filtered back projection (FBP) technique. Thus, it could significantly reduce the overall dose of radiation in CT. This work reports the results of an independent numerical simulation for cone beam CT geometry with alternative virtual phantoms. As in the original report, the 3D CT images of 128×128×128 virtual phantoms were reconstructed. It was not possible to implement phantoms with lager dimensions because of the slowness of code execution even by the CORE i7 CPU.
nuclear science symposium and medical imaging conference | 2012
Edney Milhoretto; Hugo R. Schelin; Ivan Evseev; Sergei A. Paschuk; J. A. P. Setti; Sebastião R. Junior; Fabrício L. Silva; José C. Lourenso; Valeriy Denyak; Joaquim Teixeira de Assis; Olga Yevseyeva; R.T. Lopes; F. Hurley; Reinhard W. Schulte
Charged particle interactions with matter have been continuously studied by simulations based on the Monte Carlo method. In particular, the Geant4 toolkit allows to develop and test new technologies by computer simulations. A proton computed tomography (pCT) prototype has been developed at the Lorna Linda University Medical Center (LLUMC), California, in collaboration with Northern Illinois University and the UC Santa Cruz. In order to evaluate the performance of the Geant4 version 9.3 configured to simulate this prototype, two polyethylene phantoms (PEA D) with 150 mm diameter and acrylic core were constructed. Each phantom was imaged with 10 projections by rotating the phantom in steps of 36, using a 200 MeV proton cone beam. The characteristics of the prototype and phantoms were modeled in Geant4. A comparison of the experimental data and simulated projections were performed and will be presented.
XXXIII BRAZILIAN WORKSHOP ON NUCLEAR PHYSICS | 2011
Olga Yevseyeva; Joaquim Teixeira de Assis; Ivan Evseev; Hugo R. Schelin; Sergei A. Paschuk; Edney Milhoretto; João Antônio Palma Setti; Katherin S. Diaz; Joel Mesa Hormaza; R.T. Lopes
Proton beams in medical applications deal with relatively thick targets like the human head or trunk. Thus, the fidelity of proton computed tomography (pCT) simulations as a tool for proton therapy planning depends in the general case on the accuracy of results obtained for the proton interaction with thick absorbers. GEANT4 simulations of proton energy spectra after passing thick absorbers do not agree well with existing experimental data, as showed previously. Moreover, the spectra simulated for the Bethe‐Bloch domain showed an unexpected sensitivity to the choice of low‐energy electromagnetic models during the code execution. These observations were done with the GEANT4 version 8.2 during our simulations for pCT. This work describes in more details the simulations of the proton passage through aluminum absorbers with varied thickness. The simulations were done by modifying only the geometry in the Hadrontherapy Example, and for all available choices of the Electromagnetic Physics Models. As the most pr...