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Magn Reson Imaging. 2014 Jul;32(6):766-70. doi: 10.1016/j.mri.2014.01.012. Epub 2014 Jan 28.

Current-density imaging using ultra-low-field MRI with zero-field encoding.

Author information

1
Department of Biomedical Engineering and Computational Science, Aalto University School of Science, P.O. Box 12200, FI-00076 AALTO, Finland. Electronic address: panu.t.vesanen@gmail.com.
2
Department of Biomedical Engineering and Computational Science, Aalto University School of Science, P.O. Box 12200, FI-00076 AALTO, Finland.
3
Department of Biomedical Engineering and Computational Science, Aalto University School of Science, P.O. Box 12200, FI-00076 AALTO, Finland; Department of Mathematics, National Taiwan University, Taipei, TW-10617, Taiwan.

Abstract

Electric current density can be measured noninvasively with magnetic resonance imaging (MRI). Determining all three components of the current density, however, requires physical rotation of the sample or current injection from several directions when done with conventional methods. However, the emerging technology of ultra-low-field (ULF) MRI, in which the signal encoding and acquisition is conducted at a microtesla-range magnetic field, offers new possibilities. The low applied magnetic fields can even be switched off completely within the pulse sequence, increasing the flexibility of the available sequences. In this article, we present a ULF-MRI sequence designed for obtaining all three components of a current-density pattern without the need of sample rotations. The sequence consists of three steps: prepolarization of the sample, signal encoding in the current-density-associated magnetic field without applying any MRI fields, and spatial encoding in a microtesla-range field using any standard ULF-MRI sequence. The performance of the method is evaluated by numerical simulations. The method may find applications, e.g., in noninvasive conductivity imaging of tissue.

KEYWORDS:

Current-density imaging; Rotation-free; Ultra-low-field MRI; Zero field

PMID:
24731792
DOI:
10.1016/j.mri.2014.01.012
[Indexed for MEDLINE]
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