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
CountryDenmark
CityCopenhagen
Period23/08/201825/08/2018
Internet address

Bibliographical note

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

Fingerprint Dive into the research topics of 'Human in-vivo Magnetic Resonance Current Density Imaging (MRCDI) and MR Electrical Impedance Tomography (MREIT)'. Together they form a unique fingerprint.

Cite this