Whole Brain Proton MRSI Using a Multiple 2D Sequence

Introduction A multi-planar MRSI sequence [1] has been used by many groups for nearly 15 years [2] because, compared to PRESS [3] and STEAM [4] sequences, it has the advantages of providing greater coverage of regions of interest, dynamic shimming, and time efficiency during data acquisition [5]. However, current implementations of the sequence have several shortcomings, including the limited number of slices and the spacing between slices. These shortcomings provide incomplete acquisition of information and pose substantial difficulties for the coregistration of MRSI with anatomical MR images. Increasing the number of slices will proportionally increase total scan time, and reducing the spacing between slices can cause “cross talk” or “cross excitation” across slices and thereby produce signal loss [6, 7]. We show that by adjusting sequence parameters, we can increase the number of slices without significantly increasing total scan time and we can eliminate spacing between slices without significant reducing the signal-to-noise ratio. Whole brain MRSI can be realized using this approach.