| Magnetic resonance imaging of oscillating electrical currents. | |
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MedLine Citation:
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PMID: 20421504 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Functional MRI has become an important tool of researchers and clinicians who seek to understand patterns of neuronal activation that accompany sensory and cognitive processes. However, the interpretation of fMRI images rests on assumptions about the relationship between neuronal firing and hemodynamic response that are not firmly grounded in rigorous theory or experimental evidence. Further, the blood-oxygen-level-dependent effect, which correlates an MRI observable to neuronal firing, evolves over a period that is 2 orders of magnitude longer than the underlying processes that are thought to cause it. Here, we instead demonstrate experiments to directly image oscillating currents by MRI. The approach rests on a resonant interaction between an applied rf field and an oscillating magnetic field in the sample and, as such, permits quantitative, frequency-selective measurements of current density without spatial or temporal cancellation. We apply this method in a current loop phantom, mapping its magnetic field and achieving a detection sensitivity near the threshold required for the detection of neuronal currents. Because the contrast mechanism is under spectroscopic control, we are able to demonstrate how ramped and phase-modulated spin-lock radiation can enhance the sensitivity and robustness of the experiment. We further demonstrate the combination of these methods with remote detection, a technique in which the encoding and detection of an MRI experiment are separated by sample flow or translation. We illustrate that remotely detected MRI permits the measurement of currents in small volumes of flowing water with high sensitivity and spatial resolution. |
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Authors:
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Nicholas W Halpern-Manners; Vikram S Bajaj; Thomas Z Teisseyre; Alexander Pines |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S. Date: 2010-04-26 |
Journal Detail:
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Title: Proceedings of the National Academy of Sciences of the United States of America Volume: 107 ISSN: 1091-6490 ISO Abbreviation: Proc. Natl. Acad. Sci. U.S.A. Publication Date: 2010 May |
Date Detail:
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Created Date: 2010-05-12 Completed Date: 2010-06-02 Revised Date: 2010-11-12 |
Medline Journal Info:
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Nlm Unique ID: 7505876 Medline TA: Proc Natl Acad Sci U S A Country: United States |
Other Details:
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Languages: eng Pagination: 8519-24 Citation Subset: IM |
Affiliation:
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Materials Sciences Division, Lawrence Berkeley National Laboratory and Department of Chemistry, University of California, Berkeley, CA 94720, USA. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Animals Electric Conductivity Electricity* Humans Magnetic Resonance Imaging* Magnetic Resonance Spectroscopy Neurons / physiology Phantoms, Imaging Spin Labels |
| Chemical | |
Reg. No./Substance:
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0/Spin Labels |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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