Magnetic resonance electrical impedance tomography (MREIT) attempts to provide conductivity images of an electrically conducting object with a high spatial resolution. When we inject current into the object, it produces internal distributions of current density J and magnetic flux density B = (B x, By,Bz). By using a magnetic resonance imaging (MRI) scanner, we can measure Bz data where z is the direction of the main magnetic field of the scanner. Conductivity images are reconstructed based on the relation between the injection current and B z data. The harmonic Bz algorithm was the first constructive MREIT imaging method and it has been quite successful in previous numerical and experimental studies. Its performance is, however, degraded when the imaging object contains low-conductivity regions such as bones and lungs. To overcome this difficulty, we carefully analyzed the structure of a current density distribution near such problematic regions and proposed a new technique, called the local harmonic Bz algorithm. We first reconstruct conductivity values in local regions with a low conductivity contrast, separated from those problematic regions. Then, the method of characteristics is employed to find conductivity values in the problematic regions. One of the most interesting observations of the new algorithm is that it can provide a scaled conductivity image in a local region without knowing conductivity values outside the region. We present the performance of the new algorithm by using computer simulation methods.
Bibliographical noteFunding Information:
Manuscript received August 9, 2007; revised April 17, 2008. Current version published November 21, 2008. This work was supported by the SRC/ERC program of MOST/KOSEF (R11-2002-103). The work of J. Liu was supported by JiangSu Natural Science Foundation (BK2007101). The work of E. J. Woo was supported by Kyung Hee University during his sabbatical year. Asterisk indicates corresponding author. J. K. Seo and S. Kim are with the Department of Mathematics, Yonsei University, Seoul 120-749, Korea. S. W. Kim is with the Division of Liberal Arts, Hanbat National University, Daejeon 305-719, Korea. J. J. Liu is with the Department of Mathematics, Southeast University, Nanjing 210096, China. *E. J. Woo is with the Department of Biomedical Engineering, Kyung Hee University, Gyeonggi 446-701, Korea (e-mail: email@example.com). K. Jeon and C.-O. Lee are with the Department of Mathematical Sciences, KAIST, Daejeon 305-701, Korea. Digital Object Identifier 10.1109/TMI.2008.926055
All Science Journal Classification (ASJC) codes
- Radiological and Ultrasound Technology
- Computer Science Applications
- Electrical and Electronic Engineering