Distortion-free magnetic resonance imaging in the zero-field limit |
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Authors: | Nathan Kelso, Seung-Kyun Lee, Louis-S. Bouchard, Vasiliki Demas, Michael Mü ck, Alexander Pines,John Clarke, |
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Affiliation: | aDepartment of Physics, University of California, Berkeley, CA 94720, USA;bDepartment of Chemistry, University of California, Berkeley, CA 94720, USA;cMaterials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA;dInstitut für Angewandte Physik, Justus-Leibig-Universität Gießen, D-35392 Gießen, Germany |
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Abstract: | MRI is a powerful technique for clinical diagnosis and materials characterization. Images are acquired in a homogeneous static magnetic field much higher than the fields generated across the field of view by the spatially encoding field gradients. Without such a high field, the concomitant components of the field gradient dictated by Maxwell’s equations lead to severe distortions that make imaging impossible with conventional MRI encoding. In this paper, we present a distortion-free image of a phantom acquired with a fundamentally different methodology in which the applied static field approaches zero. Our technique involves encoding with pulses of uniform and gradient field, and acquiring the magnetic field signals with a SQUID. The method can be extended to weak ambient fields, potentially enabling imaging in the Earth’s field without cancellation coils or shielding. Other potential applications include quantum information processing and fundamental studies of long-range ferromagnetic interactions. |
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Keywords: | Low-field MRI Concomitant gradients Image distortion Mobile NMR SQUID-detected NMR Coherent averaging |
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