Double tuned 23 Na  1 H nuclear magnetic resonance birdcage for application on mice in vivo

The design and the characterization of a double tuned nuclear magnetic birdcage resonator is presented. It abandons quadrature drive and uses the two orthogonal modes of the birdcage for two different frequencies. In order to tune the birdcage to frequencies that are far apart, the number of legs is reduced to only four. This limits the homogeneity of the rf field, but enables the birdcage to be tuned to very different frequencies without further B 1 field distortions. Following a brief explanation of the theory of the coil design, a 23 Na 1 H four leg birdcage for in vivo measurements on mice is presented. The performance of the coil is demonstrated in experiments on both a phantom and a mouse.