title: Micron-scale magnetic resonance imaging of both liquids and solids.
abstract: We describe and demonstrate a novel apparatus for magnetic resonance imaging (MRI), suitable for imaging of both liquid and solid samples with micron-scale isotropic resolution. The apparatus includes a solenoidal radio-frequency microcoil with 170 μm inner diameter and a set of planar gradient coils, all wound by hand and supported on a series of stacked sapphire plates. The design ensures efficient heat dissipation during gradient pulses and also facilitates disassembly, sample changes, and reassembly. To demonstrate liquid state (1)H MRI, we present an image of polystyrene beads within CuSO4-doped water, contained within a capillary tube with 100 μm inner diameter, with 5.0 μm isotropic resolution. To demonstrate solid state (1)H MRI, we present an image of NH4Cl particles within the capillary tube, with 8.0 μm isotropic resolution. High-resolution solid state MRI is enabled by frequency-switched Lee-Goldburg decoupling, with an effective rotating frame field amplitude of 289 kHz. At room temperature, pulsed gradients of 4 T/m (i.e., 170 Hz/μm for (1)H MRI) are achievable in all three directions with currents of 10 A or less. The apparatus is contained within a variable-temperature liquid helium cryostat, which will allow future efforts to obtain MRI images at low temperatures with signal enhancement by dynamic nuclear polarization.
authors.affiliation: Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0520, USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Moore
authors.affiliation: Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0520, USA. Electronic address: robertty@mail.nih.gov.
authors.forename: Robert
authors.initials: R
authors.lastname: Tycko
mesh_terms: D000643:Ammonium Chloride / Q000737:chemistry; D019327:Copper Sulfate / Q000737:chemistry; D004058:Diffusion; D004867:Equipment Design; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008863:Microspheres; D011137:Polystyrenes; D013696:Temperature
chemical_list: D011137:Polystyrenes; D000643:Ammonium Chloride; D019327:Copper Sulfate
keywords: Constant-time imaging; Lee–Goldburg decoupling; MRI; Microcoil; Solid state NMR