Human in-vivo Magnetic Resonance Current Density Imaging (MRCDI) and MR Electrical Impedance Tomography (MREIT)

Cihan Göksu, Lars G. Hanson, Hartwig R. Siebner, Philipp Ehses, Klaus Scheffler, Axel Thielscher

    Research output: Contribution to journalConference abstract in journalResearchpeer-review

    Abstract

    Purpose. Information on the electrical tissue conductivity might be useful for the diagnosis and characterization of pathologies such as tumors [1]. MRCDI and MREIT are two emerging non-invasive techniques for imaging of weak currents and ohmic conductivities. In this study, we demonstrated human in vivo brain MRCDI to pave the way for its clinical use [2,3]. Methods. In short, weak alternating currents up to 1–2 mA are injected into human head in synchrony with tailored phasesensitive MRI. The currents create a magnetic field DBz;c, which shifts the precession frequency of the magnetization and modulates the acquired MR images. The acquired images are used to measure DBz;c and reconstruct the current flow and conductivity distributions. We employed a steady-state free precession free-induction-decay (SSFP-FID) sequence in five subjects, and injected currents of 1 mA by an MR-conditional current source via electrodes attached to the scalp (two current profiles: Right-left (RL), electrodes placed near the temporoparietal junctions; anterior-posterior (AP), one attached to the forehead and one above the inion). Additionally, an ultrashort-echo-time sequence was performed to track the feeding cables for correcting the stray magnetic fields induced by cable currents.
    Corrected ΔBz;c measurements were used to calculate current flow distributions and compared with Finite-Element simulations of the current flow based on individualized head models [4]. Results. The current-induced magnetic field ΔBz;c with ≤ 1 nT was reliably measured and the reconstructed current flows showed good agreement with the simulations (average coefficient of determination R2 = 71%). The injected current flow differed substantially among individuals according to the electrode placements and anatomical differences. The calculated currents are stronger in CSF-filled highly conductive regions, e.g. the longitudinal fissure.
    Conclusions. The strong correlation between the simulations and measurements validates the accuracy of the method and demonstrates the potential of the method for determining accurate brain tissue conductivities. These initial current flow recordings pave the way for human brain MREIT that might complement standard MR
    methods for tumor characterization.
    Original languageEnglish
    JournalPhysica Medica
    Volume52
    Issue numberSupplement 1
    Pages (from-to)8-8
    Number of pages1
    ISSN1120-1797
    DOIs
    Publication statusPublished - 2018
    Event2nd European Congress of Medical Physics - H.C. Ørsteds Institute, Copenhagen, Denmark
    Duration: 23 Aug 201825 Aug 2018
    Conference number: 2
    http://ecmp2018.org/

    Conference

    Conference2nd European Congress of Medical Physics
    Number2
    LocationH.C. Ørsteds Institute
    Country/TerritoryDenmark
    CityCopenhagen
    Period23/08/201825/08/2018
    Internet address

    Bibliographical note

    Part of special issue: Abstracts from the 2nd European Congress of Medical Physics

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