Analysis of magnetic resonance imaging in inhomogenous main magnetic field

Arpınar, Volkan Emre
In this study, analysis of Magnetic Resonance Imaging (MRI) in inhomogeneous main magnetic field is conducted. A numerical model based on Bloch equation is implemented for MRI, to understand effect of inhomogeneous magnetic field to Magnetic Resonance (MR) signal. Using the model, relations between inhomogeneity levels in main magnetic field with energy, decay time, bandwidth of the FID signal is investigated. Also relation between the magnetic field inhomogeneity and field of view is determined. To simulate measurement noise in the FID signal under inhomogeneous main magnetic field, noise model for MRI with homogeneous main field is altered. Following the numerical model development an image reconstruction algorithm for inhomogeneous main magnetic field is developed to remove undesirable effect of field inhomogeneity in image reconstruction. To evaluate capability of the reconstruction algorithm, the algorithm is tested for several input parameters which results in different noise levels in the FID signal. Then reconstruction errors are analysed to gain information about feasibility of MRI in inhomogeneous main magnetic field.


RF coil system design for MRI applications inhomogeneous main magnetic field
Yılmaz, Ayhan Ozan; Aşkar, Murat; Department of Electrical and Electronics Engineering (2007)
In this study, RF coil geometries are designed for MRI applications using inhomogeneous main magnetic fields. The current density distributions that can produce the desired RF magnetic field characteristics are obtained on predefined cubic, cylindrical and planar surfaces and Tikhonov, CGLS, TSVD and Rutisbauer regularization methods are applied to match the desired and generated magnetic fields. The conductor paths, which can produce the current density distribution calculated for each surface selection an...
RF Coil Design for MRI Applications in Inhomogeneous Main Magnetic Fields
Yılmaz, Ayşen; Eyueboglu, B. M. (2006-09-01)
Conventional Magnetic Resonance Imaging (MRI) techniques require homogeneous main magnetic fields. However, MRI applications that are executed in inhomogenous main magnetic fields have been developed in recent years. In this study, RF coil geometries are designed for MRI applications in inhomogeneous magnetic fields. Method of moments is used to obtain the current density distribution on a predefined surface that can produce a desired magnetic field, which is perpendicular to the given inhomogenous main mag...
Magnetohydrodynamic Flow Imaging Using Spin-Echo Pulse Sequence
Eroğlu, Hasan Hüseyin; SADIGHI, MEHDI; Eyüboğlu, Behçet Murat (2019-04-24)
In this study, magnetohydrodynamic (MHD) flow of conductive liquids due to injection of electrical current during magnetic resonance imaging (MRI) is investigated. A spin-echo based MRI pulse sequence is proposed to image the MHD flow. Magnetic resonance (MR) phase effects of the MHD flow is related to the MRI pulse parameters and injected current. Average velocity distributions of the MHD flow are reconstructed using the MR phase images. The method is validated by numerical simulations. The reconstruction ...
Investigation of photovoltaic properties of amorphous InSe thin film based Schottky devices
Yilmaz, K.; Parlak, Mehmet; Ercelebi, C. (IOP Publishing, 2007-12-01)
In this study, device behavior of amorphous InSe thin films was investigated through I-V, C-V and spectral response measurements onto SnO2/p-InSe/metal Schottky diode structures. Various metal contacts such as Ag, Au, Al, In and C were deposited onto amorphous p-InSe films by the thermal evaporation technique. The best rectifying contact was obtained in a SnO2/p-InSe/Ag Schottky structure from I-V measurements, while the Au contact had poor rectification. Other metal contacts (Al, In and C) showed almost oh...
Realization of magnetic resonance current density imaging at 3 Tesla,
Göksu, Cihan; SADIGHI, MEHDI; Eyüboğlu, Behçet Murat (2014-08-26)
Magnetic Resonance Current Density Imaging (MRCDI) is an imaging modality, which reconstructs electrical current density distribution inside a material by using Magnetic Resonance Imaging (MRI) techniques. In this study, a current source with maximum current injection capability of 224.7mA, under 1k Omega resistive load is used. Experiments are performed with a 2D uniform phantom, in which a current steering insulator is inserted. Magnetic flux density distributions are measured, and current density images ...
Citation Formats
V. E. Arpınar, “Analysis of magnetic resonance imaging in inhomogenous main magnetic field,” Ph.D. - Doctoral Program, Middle East Technical University, 2009.