title: Contrast and spatial resolution in MREIT using low amplitude current.
abstract: Magnetic resonance-electrical impedance tomography employs low amplitude currents injected or induced inside an object. The additional magnetic field due to these currents results in a phase in the MR images. In this study, a modified fast spin-echo sequence was used to measure this magnetic field, which is obtained by scaling the MR phase image. A finite element method with first order triangular elements was used for the solution of the forward problem. An iterated sensitivity matrix-based algorithm was developed for the inverse problem. The resulting ill-conditioned matrix equation was regularized using the Tikhonov method and solved using a conjugate gradient solver. The spatial and contrast resolution of the technique was tested using agarose gel phantoms. A circular phantom with 7 cm diameter and 1 cm thickness is used in the phantom experiments. The amplitude of the injected current was 1 mA. 3, 5 and 8 mm diameter insulators and high conductor objects are used for the spatial resolution study and an average full-width half-maximum value of 4.7 mm is achieved for the 3 mm insulator case. For the contrast analysis, the conductivity of a 15 mm object is varied between 44% and 500% with respect to the background and results are compared to the ideal reconstruction.
authors.affiliation: Tu and Yuen Center for Functional Onco Imaging, University of California Irvine, USA. obirgul@uci.edu
authors.forename: Ozlem
authors.initials: O
authors.lastname: Birgul
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Hamamura
authors.forename: L Tugan
authors.initials: LT
authors.lastname: Muftuler
authors.forename: Orhan
authors.initials: O
authors.lastname: Nalcioglu
mesh_terms: D000465:Algorithms; D003287:Contrast Media; D017097:Electric Impedance; D005782:Gels; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015233:Models, Statistical; D019047:Phantoms, Imaging; D012685:Sepharose / Q000737:chemistry; D012965:Sodium Chloride / Q000737:chemistry; D014055:Tomography, Emission-Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D005782:Gels; D012965:Sodium Chloride; D012685:Sepharose