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Sensitivity enhancement of remotely coupled NMR detectors using wirelessly powered parametric amplification
Author(s) -
Qian Chunqi,
MurphyBoesch Joseph,
Dodd Stephen,
Koretsky Alan
Publication year - 2012
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.23274
Subject(s) - amplifier , electromagnetic coil , sensitivity (control systems) , parametric statistics , rf power amplifier , bandwidth (computing) , linearity , materials science , detector , signal (programming language) , nuclear magnetic resonance , physics , optics , computer science , electronic engineering , telecommunications , engineering , statistics , mathematics , quantum mechanics , programming language
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. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.