Patent ID: 7180291

Claim:
A birdcage coil system for use in conjunction with a magnetic resonance apparatus, the birdcage coil system comprising: a birdcage coil tuned to degeneracy the coil including: a first conductive loop, a second conductive loop, and a plurality of first conductor rungs disposed between the first and second conductive loops and in electrical connection therewith; and a switching system which switches the birdcage coil at least between: an RF transmit mode, and an RF receive mode, the switching system including: a plurality of RF transmit feed points in electrical connection with the first conductive loop for feeding RF transmit signals to the coil; a plurality of transmit PIN diodes for coupling RF transmit feeds to the feed points; a plurality of RF receive take-off points disposed across matching capacitors; a plurality of matching PIN diodes arranged in parallel with the matching capacitors; and a plurality of cage DC bias inputs in electrical connection with the transmit and matching diodes for biasing the transmit and matching PIN diodes.