MRG-SPAMM tabanlı manyetik rezonans elektriksel empedans tomografisi.

Electrical conductivity of biological tissues differs among different kinds of tissues. Information about measured impedance of a tissue gives great deal of information about pathological state of the tissue and some biomedical applications requires this information. Magnetic Resonance Current Density Imaging (MRCDI) and Magnetic Resonance Electrical Impedance Tomography (MREIT) are two imaging modalities which investigates current and conductivity distribution inside objects by utilizing the magnetic flux density distribution induced by externally applied currents. Spatial Modulation of Magnetization (SPAMM) is a pre-imaging pulse sequence which is used to evaluate spatially dependent properties of an imaged object. Standard MREIT pulse sequences have long repetition times and this results in long acquisition times. Long acquisition times make imaging susceptible to artefacts. This problem can be overcomed by injecting current during a pre-imaging sequence and usage of pulse sequences with low repetition times. The aim of this study is to implement a new data acquisition sequence for MRCDI and MREIT applications. Spin Echo (SE) and Gradient Echo (GE) based SPAMM pulse sequences are implemented and tested on different experimental phantoms. Magnetic flux density data are obtained using this new technique. Current density and conductivity distributions are calculated. Noise levels and minimum measurable current level with proposed sequences are measured. SPAMM based pulse sequences are found to be applicable to MRCDI and MREIT studies and can help to reduce data acquisition times.M.S. - Master of Scienc

FEN BİLİMLERİ ENSTİTÜSÜ/LİSANSÜSTÜ TEZ PROJESİ

AKIM İNDÜKLEMELİ MANYETİ REZONANS ELEKTRİKSEL EMPEDANS TOMOGRAFİSİ İÇİN GÜÇLENDİRİCİ TASARIM

SPAMM Based Dual Current Injection to Accelerate Data Acquisition in Magnetic Resonance Electrical Impedance Tomography

Reducing acquisition time in magnetic resonance electrical impedance tomography (MREIT) improves signal to noise ratio and temporal resolution of measured conductivity data. On the other hand, the reconstruction accuracy of MREIT can be improved by acquiring multiple data using different current injection patterns, which in turn increases the total scan time. In this study, a novel pulse sequence is proposed to reduce the scan time in MREIT by injecting two current patterns in a single acquisition. This method is experimentally realized using a physical phantom, and its feasibility is evaluated

Enhancing induced current magnetic resonance electrical impedance tomography ICMREIT image reconstruction

Induced Current Magnetic Resonance Electrical Impedance Tomography (ICMREIT) is an emerging imaging methodology that utilizes Magnetic Resonance Imaging (MRI) techniques to visualize the electrical conductivity as a new contrast. In ICMREIT, by fast switching of gradient fields of Magnetic Resonance (MR) system eddy currents are induced in the imaging volume. The secondary magnetic field generated by the induced eddy currents can be extracted from the MR phase images. Image reconstruction algorithms then use this secondary field map to recover the conductivity distribution. In this paper, a novel approach is proposed to enhance the quality of the reconstructed conductivity maps, from the perspectives of edge preservation and noise sensitivity. Simulated measurements are used to demonstrate the improvements introduced by the proposed method