A practical double-tuned H-1/P-31 quadrature birdcage headcoil optimized for P-31 operation

A double-tuned H-1/P-31 birdcage head coil for use with humans at 1.5 T is described, The coil was designed for proton decoupled P-31 excitation and r eception and incorporated a number of practical features including optimize d sensitivity for P-31, quadrature operation at H-1 and P-31 frequencies, a nd a radiofrequency (RF) mirror for improved B-1 homogeneity. The design ac hieved similar B-1 homogeneity at both P-31 and H-1 frequencies. Inductive matching was used to accommodate samples with large loading differences. A facile method for tuning and matching over a variety of sample loadings is presented, along with capacitively shortened bazookas for suppression of ca ble braid currents. The proton sensitivity, although down by approximately a factor of two compared with an optimized H-1 birdcage head coil, was stil l ample for shimming and generation of scout images. Advantages of the desi gn are discussed and proton-decoupled P-31 spectra of human brain are prese nted. Magn Reson Med 42:173-182, 1999. (C) 1999 Wiley-Liss, Inc.