  Purpose: Proton MR spectroscopic imaging (1H MRSI) without water suppression
(WS) possess some distinct advantages over the conventionally used 1H MRSI with
WS. However, the sideband artifacts in the non-water suppressed spectra hinder
the applications of the 1H MRSI without WS. Although many hardware or software
techniques to tackle the sidebands have been developed, they suffer from
various shortcomings, such as the prolonged data acquisition time, insufficient
elimination of the sidebands, or loss of some spectral information. Here, we
present a software method that allows the elimination of sideband artifacts
from 1H MRSI data acquired without WS. Methods The presented method is based on
the following observations: (1) the real part of the sidebands is
anti-symmetric, and the imaginary part of sidebands is symmetric about the
unsuppressed water signal, which is at the center of the spectrum, and (2)
there is no observable metabolite resonances in the downfield region spectrum
acquired with conventional MRSI pulse sequences. We model the complex sidebands
in the downfield region using a singular value decomposition-based method,
reconstruct from them the upfield sidebands according to the symmetry features
of the sidebands, and subtract the sidebands from the spectrum. We demonstrate
the method using phantom and in vivo data. Results The method can remarkably
reduce sideband artifacts in both the real and the imaginary parts of the
spectrum. In both phantom data and high-quality in vivo data, the residual
sidebands are smaller than those in the WS spectra. Conclusion The method
allows to remove sideband artifacts in both the real and the imaginary parts of
the spectrum. The performance of the method on phantom data and high-quality in
vivo data outperforms on poor quality in vivo data.
