Arpinar, V E; Hamamura, M J; Degirmenci, E; Muftuler, L T
Magnetic resonance electrical impedance tomography (MREIT) is a technique that produces images of conductivity in tissues and phantoms. In this technique, electrical currents are applied to an object and the resulting magnetic flux density is measured using magnetic resonance imaging (MRI) and the conductivity distribution is reconstructed using these MRI data. Currently, the technique is used in research environments, primarily studying phantoms and animals. In order to translate MREIT to clinical applications, strict safety standards need to be established, especially for safe current limits. However, there are currently no standards for safe current limits specific to MREIT. Until such standards are established, human MREIT applications need to conform to existing electrical safety standards in medical instrumentation, such as IEC601. This protocol limits patient auxiliary currents to 100 µA for low frequencies. However, published MREIT studies have utilized currents 10-400 times larger than this limit, bringing into question whether the clinical applications of MREIT are attainable under current standards. In this study, we investigated the feasibility of MREIT to accurately reconstruct the relative conductivity of a simple agarose phantom using 200 µA total injected current and tested the performance of two MREIT reconstruction algorithms. These reconstruction algorithms used are the iterative sensitivity matrix method (SMM) by Ider and Birgul (1998 Elektrik 6 215-25) with Tikhonov regularization and the harmonic B(Z) proposed by Oh et al (2003 Magn. Reason. Med. 50 875-8). The reconstruction techniques were tested at both 200 µA and 5 mA injected currents to investigate their noise sensitivity at low and high current conditions. It should be noted that 200 µA total injected current into a cylindrical phantom generates only 14.7 µA current in imaging slice. Similarly, 5 mA total injected current results in 367 µA in imaging slice. Total
Zulfikar, Can; Alcik, Hakan; Mert, Aydin; Tahtasizoglu, Bahar; Kafadar, Nafiz; Korkmaz, Ahmet; Ozel, Oguz; Erdik, Mustafa
designated GSM network and through a microwave system. A shake map and damage distribution map (using aggregate building inventories and fragility curves) will then be automatically generated using the algorithm developed for this purpose. Loss assessment studies are complemented by a large citywide digital database on the topography, geology, soil conditions, building, infrastructure and lifeline inventory. The shake and damage maps will be conveyed to the governor's and mayor's offices and army headquarters within 3 minutes using radio modem and GPRS communication. Self Organizing Seismic Early Warning Information Network (SOSEWIN) in Atakoy District SOSEWIN sensors were developed by GFZ and Humbold University as part of SAFER project and EDIM project, and with cooperation of KOERI, the sensors were installed in Atakoy district of Istanbul city with Early Warning purpose. The main features of the SOSEWIN system are each sensing unit is comprised of low-cost components, undertakes its own seismological data processing, analysis and archiving, and its self-organizing capability with wireless mesh network communication. Seismic Network in Important Structures Some of the critical structures located in Istanbul city such as Fatih Sultan Mehmet Suspension Bridge which is connecting Asian and European sides of the city, Hagia Sophia Museum and Suleymaniye Mosque which are historical structures with an age of over 1000 years and 450 years respectively, . Kanyon Tower&Mall, Trakya Elektrik (formerly ENRON) and Isbank Tower (ISKULE) are monitorized to observe their seismic behaviors.