SUPER-Q DETECTION OF TRANSIENT MAGNETIC-RESONANCE SIGNALS

The signal-to-noise ratio (SNR) improvements with increasing detection coil quality factor, Q, are examined for the detection of known magne tic resonance signals in noise. It is found that in the absence of amp lifier noise, SNR continues to increase with increasing Q even in the ''super-Q'' limit, when the bandwidth of the tuned detection circuit i s smaller than that of the signal to be detected. In the super-Q limit , the maximum obtainable SNR is thus limited by noise from the amplifi ers in the system. This contrasts with typical NMR measurements where the ultimate SNR is limited by thermal noise from the detection circui t. Explicit expressions are derived and are compared to experiments pe rformed using electronically simulated spin echo signals. (C) 1998 Aca demic Press.