title: Sensitivity enhancement of remotely coupled NMR detectors using wirelessly powered parametric amplification.
abstract: A completely wireless detection coil with an integrated parametric amplifier has been constructed to provide local amplification and transmission of MR signals. The sample coil is one element of a parametric amplifier using a zero-bias diode that mixes the weak MR signal with a strong pump signal that is obtained from an inductively coupled external loop. The NMR sample coil develops current gain via reduction in the effective coil resistance. Higher gain can be obtained by adjusting the level of the pumping power closer to the oscillation threshold, but the gain is ultimately constrained by the bandwidth requirement of MRI experiments. A feasibility study here shows that on a NaCl/D(2) O phantom, (23) Na signals with 20 dB of gain can be readily obtained with a concomitant bandwidth of 144 kHz. This gain is high enough that the integrated coil with parametric amplifier, which is coupled inductively to external loops, can provide sensitivity approaching that of direct wire connection.
authors.affiliation: Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorder and Stroke, National Institutes of Health, Bethesda, Maryland, USA. qianc2@ninds.nih.gov
authors.forename: Chunqi
authors.initials: C
authors.lastname: Qian
authors.forename: Joseph
authors.initials: J
authors.lastname: Murphy-Boesch
authors.forename: Stephen
authors.initials: S
authors.lastname: Dodd
authors.forename: Alan
authors.initials: A
authors.lastname: Koretsky
mesh_terms: D000669:Amplifiers, Electronic; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008280:Magnetics / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013686:Telemetry / Q000295:instrumentation*; D014159:Transducers