Parametric Amplification of Magnetic Resonance Images

Parametric amplification is considered as a method for the detection of magnetic resonance imaging (MRI) signals. The theory of three-frequency amplifiers is reviewed, and aspects relevant to radio-frequency detection are highlighted. The modifications needed for MRI are described, and a parametrically amplified surface coil for 63.85 MHz operation is demonstrated. Electrical characterization is carried out, and good agreement is obtained with the theory. A linear gain of 100 (40 dB power gain) and a
Q
-factor of 18 000 are demonstrated.
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H MRI is carried out at 1.5 T and frequency-domain filtering of images is demonstrated.