Akademik Veri Yönetim Sistemi
Tezin Türü: Yüksek Lisans
Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Elektrik ve Elektronik Mühendisliği Bölümü, Türkiye
Tezin Onay Tarihi: 2010
Tezin Dili: İngilizce
Öğrenci: Tankut Topal
Danışman: BEHÇET MURAT EYÜBOĞLU
Özet:Magnetic resonance imaging (MRI) is a high resolution medical imaging technique based on distinguishing tissues according to their nuclear magnetic properties. Magnetic resonance electrical impedance tomography (MREIT) is a conductivity imaging technique which reconstructs images of electrical properties, based on their effect on induced magnetic flux density due to externally applied current flow. Both of these techniques are of interest for novel research and development. Simulators help researchers observe the accuracy and the results of the study. In this study a user friendly complete MRI/MREIT simulator is designed. This simulator is the combination of improved version of MRI simulator (implemented by V. E. Arpinar, H. Yigitler), a forward solver, to observe the current injection effect, the improved version of user interface that is designed on LabVIEW graphical programming environment (designed by M. Ozsut), and equi-potential projection (EPP) reconstruction algorithm (proposed by M. S. Ozdemir, M. Eyuboglu, O. Ozbek). All of these individual parts are improved and gathered in LabVIEW environment in order to work in synchrony. In addition to that, regional image reconstruction technique (proposed by H. Altunel, M. Eyuboglu) is also included in the simulator. The simulator is run for various inputs and system specifications. It is observed that the simulation results are consistent with the expected results for MRI, MREIT and conventional/regional MREIT reconstruction. Four different models are designed and results are obtained using these models. The accuracy of the results usually differs with the input parameters and model geometry. Validating numerically the accuracy of the forward solution part using Biot-Savart and Ampere's laws, the consistency of the forward problem solution part is obtained at a percentage of 95%. In the MREIT part, magnetic flux density distribution taken from forward solver part is added to the main magnetic flux density used in the MRI part. Consistency of the magnetic flux density distribution given to the simulator as input and the output taken from the MREIT part of the simulator is found as 99%. In addition to conventional EPP algorithm, regional MREIT reconstruction algorithm is applied for various noise levels. It is observed that, as the noise level increases, regional MREIT reconstruction algorithm gives relatively much better results compared to conventional MREIT reconstruction algorithm. Errors obtained by applying conventional reconstruction and regional reconstruction are compared for each inhomogeneity individually. Therefore, accuracies of the different current patterns depending on the inhomogeneities are observed as well.