Abstract
Magnetic resonance spectroscopic imaging (MRSI), also called spectroscopic imaging (SI) or chemical shift imaging (CSI), has become a valuable tool for mapping metabolites in human brain, prostate, breast, and other organs. However, commercially available phase-encoded MRSI methods require long acquisition times, which limit clinical applications. High-speed MRSI methods based on echo-planar and spiral encoding have become viable alternatives to conventional proton MRSI for clinical research applications that demand short scan times, large volume coverage, and high spatial resolution. This article describes the principles of proton echo-planar spectroscopic imaging (PEPSI) and spiral MRSI, with an emphasis on designing robust data acquisition and reconstruction methods for routine applications. Covered topics include: ramp sampling, gridding, off-resonance correction, even–odd echo editing of PEPSI data, sensitivity comparison with conventional phase-encoded MRSI, gradient and receiver hardware requirements, sensitivity to eddy currents and magnetic field inhomogeneity, and variable density k-space sampling. Advanced topics include: the integration of acceleration techniques, such as parallel imaging and compressed sensing that take advantage of using large-scale array coils; the selection of volume prelocalization techniques; and implementation at different field strengths. The article will conclude with selected research applications in human brain that highlight the advantages of high-speed MRSI. Keywords: MR spectroscopic imaging; chemical shift imaging; proton echo-planar spectroscopic imaging; echo-planar spectroscopic imaging; spiral spectroscopic imaging; parallel imaging; compressed sensing; human; brain; breast
Published Version
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