title: Measurement of weak electric currents in copper wire phantoms using MRI: influence of susceptibility enhancement.
abstract: The use of magnetic resonance imaging (MRI)-based methods for the direct detection of neuronal currents is a topic of intense investigation. Much experimental work has been carried out with the express aim of establishing detection thresholds and sensitivity to flowing currents. However, in most of these experiments, magnetic susceptibility enhancement was ignored. In this work, we present results that show the influence of a susceptibility artefact on the detection threshold and sensitivity. For this purpose, a novel phantom, consisting of a water-filled cylinder with two wires of different materials connected in series, was constructed. Magnitude MR images were acquired from a single slice using a gradient-echo echo planar imaging (EPI) sequence. The data show that the time course of the detected MR signal magnitude correlates very well with the waveform of the input current. The effect of the susceptibility artefacts arising from the two different wires was examined by comparing the magnitudes of the MR signals at different voxel locations. Our results indicate the following: (1) MR signal enhancement arising from the magnetic susceptibility effect influences the detection sensitivity of weak current; (2) the detection threshold and sensitivity are phantom-wire dependent; (3) sub-mu A electric current detection in a phantom is possible on a 1.5-T MR scanner in the presence of susceptibility enhancement.
authors.affiliation: Institute of Medicine, Research Centre Juelich, 52425 Juelich, Germany.
authors.forename: Ruiwang
authors.initials: R
authors.lastname: Huang
authors.forename: Oleg
authors.initials: O
authors.lastname: Posnansky
authors.forename: Abdullah
authors.initials: A
authors.lastname: Celik
authors.forename: Ana-Maria
authors.initials: AM
authors.lastname: Oros-Peusquens
authors.forename: Veronika
authors.initials: V
authors.lastname: Ermer
authors.forename: Marco
authors.initials: M
authors.lastname: Irkens
authors.forename: H-Peter
authors.initials: HP
authors.lastname: Wegener
authors.forename: N Jon
authors.initials: NJ
authors.lastname: Shah
mesh_terms: D016477:Artifacts; D003300:Copper; D017097:Electric Impedance; D004574:Electromagnetic Fields; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D003300:Copper