A low-lossy double tuned resonator for concurrent /sup 1/H and /sup 31/P nuclear magnetic resonance

Abstract

AbsrmLA new method for double tuning a single Nuclear Magnetic Resonance (Nh4R) probe is described, providing simultaneously two resonances to a single output. Both frequencies present a high sensitivity and are easily tuned with non-interacting special frequency decoupling circuits.The lH (proton) -imaging mode of the double tuned surface coil is actively decoupled from the whole body , circular polarised transmit resonator by activating a PIN diode circuit. Results are shown, taken of a phantom containing both water and phosphorus acid.

A retunable surface coil for high field31P and1H magnetic resonance evaluations of the living mouse leg

“…This retunable design is efficient because switching between frequencies is achieved easily within the average T 1 time (<10 s) of 31 P HEP species in vivo by manually adjusting variable capacitors through the use of a reflection bridge. Contrary to other double-tuned coil designs that suffer from losses in sensitivity because of the interferences from between channels or the presence of traps (Alecci et al 2006) and/or lossy transmission cables (Annaert et al 1989), the retunable double resonance coil does not introduce such losses because each channel operates in the single resonance mode when it is active. As indication of the performance of the coil, the quality factor was theoretically and experimentally found to be over 100 for both frequencies and was stable over a range of loadings, indicating the domination of the coil noise over the sample noise contribution.…”

“…However, all double resonance coil designs in the literature suffer from losses when compared to their complementary single-tuned configuration, which reduces their efficiency especially for detecting low sensitivity nuclei. For example, reductions in RF sensitivity because of trap circuits have been identified when two loops of different sizes (one for each nucleus) are utilized (Alecci et al 2006), and decreases in signal-to-noise ratios (SNR) due to lossy transmission cables are common when a quarterwave line resonator is applied to detune one channel during the operation of the other channel (Annaert et al 1989). In work done by Fitzsimmons et al (1989), three double resonance surface coil designs (a loop-gap resonator, a transformercoupled configuration and a trapped coil) were compared to single-tuned surface coils at the desired frequency of operation.…”