Simultaneous Acquisition of Metabolite and Water Signals in 3D Echo Planar Spectroscopic Imaging

Introduction Echo planar spectroscopic imaging (EPSI) is one of several approaches to speeding up acquisitions of metabolite spectra from multiple voxels [1, 2]. However, EPSI measurements are very sensitive to temporally and spatially dependent phase and frequency shifts that arise from eddy current caused by oscillating readout gradient of the EPSI sequence. As a result, these phase and frequency shifts can easily distort the metabolite spectrum. Although measuring the water signal to correct the phase and frequency shifts as well as water-suppressed metabolite signal is effective to reduce such spectrum distortion, it increases the scan time, especially for 3D spatial measurement. Therefore, simultaneously acquiring metabolite and water signals is preferable. We have developed a technique to simultaneously acquire both signals in 2D conventional PRESS-CSI sequence [3] and 2D EPSI sequence [4]. In this paper, we describe a technique applied to the 3D EPSI sequence and present the results of phantom measurements utilizing the proposed method.