Recent progress in magnetic resonance electrical impedance tomography (MREIT) research via simulation and biological tissue phantom studies have shown that conductivity images with higher spatial resolution and accuracy are achievable. In order to apply MREIT to human subjects, one of the important remaining problems to be solved is to reduce the amount of the injection current such that it meets the electrical safety regulations. However, by limiting the amount of the injection current according to the safety regulations, the measured MR data such as the z-component of magnetic flux density Bz in MREIT tend to have low SNR and get usually degraded in their accuracy due to the nonideal data acquisition system of an MR scanner. Furthermore, numerical differentiations of the measured Bz required by the conductivity image reconstruction algorithms tend to further deteriorate the quality and accuracy of the reconstructed conductivity images. In this paper, we propose a denoising technique that incorporates a harmonic decomposition. The harmonic decomposition is especially suitable for MREIT due to the physical characteristics of Bz. It effectively removes systematic and random noises, while preserving important key features in the MR measurements, so that improved conductivity images can be obtained. The simulation and experimental results demonstrate that the proposed denoising technique is effective for MREIT, producing significantly improved quality of conductivity images. The denoising technique will be a valuable tool in MREIT to reduce the amount of the injection current when it is combined with an improved MREIT pulse sequence.
Bibliographical noteFunding Information:
Manuscript received July 21, 2004; revised April 10, 2005. This work was supported by the Korea Science and Engineering Foundation under Grant R11-2002-103. Asterisk indicates corresponding author. B. I. Lee and E. J. Woo are with the Department of Biomedical Engineering, College of Electronics and Information, Kyung Hee University, Kyungki 449-701, Korea. S.-H. Lee and J. K. Seo are with the Department of Mathematics, Yonsei University, Seoul 120-749, Korea. *T.-S. Kim is with the Department of Biomedical Engineering, College of Electronics and Information, Kyung Hee University, Kyungki 449-701, Korea (e-mail: firstname.lastname@example.org). O. Kwon is with the Department of Mathematics, Konkuk University, Seoul 143-701, Korea. Digital Object Identifier 10.1109/TBME.2005.856258
All Science Journal Classification (ASJC) codes
- Biomedical Engineering