| 摘要 |
<p>The invention concerns an improved magnetic resonance apparatus and method for substantially reducing the dead time of the apparatus, in order to recover as much of the submicrosecond FID signals as quickly as possible. A double-channel, out-of-phase signal combination is employed. Two RF receiving coils are arranged with identical ringing characteristics, preferably mutually perpendicular to one another. The RF signal received by one coil is phase shifted by 180°, amplified, and combined with the amplified RF signal received by the other coil. The ringing components cancel, whilst the FID components in phase quadrature do not. The transmitter/receiver apparatus may be of duplex or crossed coil configuration. In the latter case, one of the receiver coils may be oriented parallel to the main field so that it receives no FID signal and operates only to reduce the dead time. The invention is particularly well suited for imagers and spectrometers using pulsed electron paramagnetic resonance (EPR), for the detection of free radicals in biological systems, or for pulsed nuclear magnetic resonance (NMR), where relaxation times are of the order of 100ns to 10νs.</p> |
