Improving Spatial Localization in MR Spectroscopic Imaging with PSF-Choice
The purpose of this work, a collaboration with NIH R21 CA110092, is to improve the point-spread-function (PSF) of MR spectroscopic imaging (MRSI) to avoid corruption from neighboring voxels. Due to partial volume effects and truncation (or ringing) artifact, spatial resolution in MRSI is very low and spatial localization of spectra is difficult. Poor localization is unavoidable if the voxel sizes are larger than the region-of-interest; however, it is degraded even further if the PSF extends beyond the voxel boundaries. Generally, the voxel size cannot be reduced due to SNR considerations; however, altering the PSF can improve localization by reducing or eliminating out-of-voxel contributions. Filtering can be used to achieve the desired PSF without compromising SNR, although this requires extending the acquisition in k-space at the cost of increased imaging time. Previously, a method called PSF-Choice was introduced that enables the shaping of the PSF in phase-encoding dimensions. The method uses RF manipulation to improve spatial localization without increasing scan time or adversely affecting SNR. An implementation of this method along one phase-encoding dimension is done and being evaluated for application in the prostate. Current work is focused on implementation of PSF-Choice along two phase-encoding directions.
Presentation describing PSF-Choice, February, 2008.
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