title: Calculated signal-to-noise ratio of MRI detected with SQUIDs and Faraday detectors in fields from 10 microT to 1.5 T.
abstract: We examine the calculated signal-to-noise ratio (SNR) achievable with different MRI detection modalities in precession fields ranging from 10 microT to 1.5 T. In particular, we compare traditional Faraday detectors with both tuned and untuned detectors based on superconducting quantum interference devices (SQUIDs). We derive general expressions for the magnetic field noise due to the samples and the detectors, and then calculate the SNR achievable for a specific geometry with each modality with and without prepolarization. We show that each of the three modalities is superior in one of the three field ranges. SQUID-based detection is superior to conventional Faraday detection for MRI in precession fields below 250 mT for a 65 mm diameter surface coil placed a distance of 25 mm from the voxel of interest embedded in a cylinder of tissue 50 mm tall and of radius 50 mm. This crossover field, however, is sensitive to the geometry.
authors.affiliation: Department of Physics, University of California, Berkeley, and Materials Sciences Division, Lawrence Berkeley National Laboratory, CA 94720, USA.
authors.forename: Whittier
authors.initials: W
authors.lastname: Myers
authors.forename: Daniel
authors.initials: D
authors.lastname: Slichter
authors.forename: Michael
authors.initials: M
authors.lastname: Hatridge
authors.forename: Sarah
authors.initials: S
authors.lastname: Busch
authors.forename: Michael
authors.initials: M
authors.lastname: Mössle
authors.forename: Robert
authors.initials: R
authors.lastname: McDermott
authors.forename: Andreas
authors.initials: A
authors.lastname: Trabesinger
authors.forename: John
authors.initials: J
authors.lastname: Clarke
mesh_terms: D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008280:Magnetics / Q000295:instrumentation*