Hadamard encoding with surface coils for high SNR MR spectroscopy.

Abstract

The advantages of Hadamard over phase encoding in magnetic resonance spectroscopy (MRS) applied with surface coils in the direction perpendicular to the coil are demonstrated experimentally. With the recently introduced, time-shifted adiabatic pulses, the application of Hadamard encoding with surface coils results with almost ideal point spread function for pixels up to a distance of a radius from the coil. Comparison to phase encoding with equal region of interest size shows the significant advantage of Hadamard encoding in slice sharpness, overlapping, and spatial contamination. In addition, since there is no aliasing in Hadamard space, the total experimental time for the same region of interest is much shorter. We conclude that the hybrid of Hadamard encoding in the direction perpendicular to the coil and phase encoding in other directions is the method of choice to obtain reliable high signal to noise ratio MRS in vivo.