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The feasibility Study on Magnetic Resonance Spectroscopy (MRS) Thermometry in the Presence of Magnetic Field Inhomogeneity
, M.Sc. Thesis Sharif University of Technology ; Samadfam, Mohammad (Supervisor) ; Saligheh Rad, Hamid Reza (Supervisor)
Abstract
1H-MRS thermometry as one of MRI thermometry methods, provides useful information about the distribution of the absolute temperature of tissue that can be used in diagnostic and therapeutic applications. It seems that the magnetic field inhomogeneity and the reduction of spectra resolution also affects the accuracy of MRS thermometry. To our knowledge, effects of magnetic field inhomogeneity on MRS thermometry has never been reported. In this study, we evaluated the effect of susceptibility inhomogeneity on MRS thermometry. In the first stage, MRS thermometry equation was derived in the presence of field inhomogeneity. Then simulation used for estimate the effect of filed inhomogeneity based...
A Marx-based generator with adjustable FWHM using a controllable magnetic switch
, Article IEEE Transactions on Dielectrics and Electrical Insulation ; Volume 26, Issue 2 , 2019 , Pages 324-331 ; 10709878 (ISSN) ; Hadizade, A ; Mohsenzade, S ; Zarghany, M ; Kaboli, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
The lack of turn-off ability makes the spark gap-based Marx generator uncontrollable in terminating the output pulse. In addition, there are some limitations for rise time and voltage gain improvements in the conventional critically-damped Marx design. In this paper, an efficient over-damped design of Marx circuit is proposed, which leads to a shorter rise time as well as a larger voltage gain. A chopping magnetic switch is employed to achieve the desired values of the fall time and full width at half maximum (FWHM). Moreover, adding a DC bias circuit to the magnetic switch provides the ability to adjust the pulse FWHM parameter. Therefore, an output pulse with a shorter rise time, larger...
Effects of severe plastic deformation on pre-osteoblast cell behavior and proliferation on AISI 304 and Ti-6Al-4V metallic substrates
, Article Surface and Coatings Technology ; Volume 366 , 2019 , Pages 204-213 ; 02578972 (ISSN) ; Aydın, H. M ; Maleki, E ; Varol, R ; Unal, O ; Sharif University of Technology
Elsevier B.V
2019
Abstract
In this study, titanium alloy (Ti-6Al-4V) and austenitic stainless steel (AISI 304) biomedical alloys were subjected to surface severe plastic deformation (SSPD) via severe shot peening (SSP) with the conditions of A28-30 Almen intensity. SSP is widely accepted as much more effective than the conventional surface modification techniques since it forms a nano-grain layer with large number of dislocations and grain boundaries. The SSP treatment in this study was led to a very thin rough layer in Ti-6Al-4V titanium alloy compared to that of AISI 304. The thicker layer of AISI 304 was created by twin-twin intersections and a martensite structure transformations. SSP treatment was resulted in a...
Benchmarking of Monte Carlo model of Siemens Oncor® linear accelerator for 18MV photon beam: determination of initial electron beam parameters
, Article Journal of X-Ray Science and Technology ; Volume 27, Issue 6 , 2 January , 2020 , Pages 1047-1070 ; Hoseini Ghafarokhi, M ; Bolagh, R. S. M ; Haghparast, M ; Zarifi, S ; Nickfarjam, A ; Farhood, B ; Chow, J. C. L ; Sharif University of Technology
IOS Press
2020
Abstract
OBJECTIVE: This study aims to benchmark a Monte Carlo (MC) model of the 18 MV photon beam produced by the Siemens Oncor® linac using the BEAMnrc and DOSXYZnrc codes. METHODS: By matching the percentage depth doses and beam profiles calculated by MC simulations with measurements, the initial electron beam parameters including electron energy, full width at half maximum (spatial FWHM), and mean angular spread were derived for the 10×10 cm2 and 20×20 cm2 field sizes. The MC model of the 18 MV photon beam was then validated against the measurements for different field sizes (5×5, 30×30 and 40×40 cm2) by gamma index analysis. RESULTS: The optimum values for electron energy, spatial FWHM and mean...