Title :
Local Harmonic
Algorithm With Domain Decomposition in MREIT: Computer Simulation Study
Author :
Seo, Jin Keun ; Kim, Sung Wan ; Kim, Sungwhan ; Liu, Ji Jun ; Woo, Eung Je ; Jeon, Kiwan ; Lee, Chang-Ock
Author_Institution :
Dept. of Math., Yonsei Univ., Seoul
Abstract :
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=(Bx,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 Bz 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.
Keywords :
biomedical MRI; current density; digital simulation; electric impedance imaging; image resolution; magnetic flux; medical computing; MREIT; bones; computer simulation; conductivity image; current density distribution; domain decomposition; electrically conducting object; injection current; local harmonic Bz algorithm; lungs; magnetic flux density; magnetic resonance electrical impedance tomography; Conductivity; Current density; Image reconstruction; Impedance; Magnetic field measurement; Magnetic flux density; Magnetic resonance; Magnetic resonance imaging; Spatial resolution; Tomography; Conductivity image; domain decomposition; harmonic $B_z$; magnetic resonance electrical impedance tomography (MREIT); Algorithms; Computer Simulation; Electric Impedance; Image Enhancement; Image Interpretation, Computer-Assisted; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Models, Biological; Phantoms, Imaging; Plethysmography, Impedance;
Journal_Title :
Medical Imaging, IEEE Transactions on
DOI :
10.1109/TMI.2008.926055