Fast data acquisition techniques in magnetic resonance spectroscopic imaging

Abstract

Magnetic resonance spectroscopic imaging (MRSI) is an important technique for assessing the spatial variation of metabolites in vivo. The long scan times in MRSI limit clinical applicability due to patient discomfort, increased costs, motion artifacts, and limited protocol flexibility. Faster acquisition strategies can address these limitations and could potentially facilitate increased adoption of MRSI into routine clinical protocols with minimal addition to the current anatomical and functional acquisition protocols in terms of imaging time. Not surprisingly, a lot of effort has been devoted to the development of faster MRSI techniques that aim to capture the same underlying metabolic information (relative metabolite peak areas and spatial distribution) as obtained by conventional MRSI, in greatly reduced time. The gain in imaging time results, in some cases, in a loss of signal‐to‐noise ratio and/or in spatial and spectral blurring. This review examines the current techniques and advances in fast MRSI in two and three spatial dimensions and their applications. This review categorizes the acceleration techniques according to their strategy for acquisition of the k‐space. Techniques such as fast/turbo‐spin echo MRSI, echo‐planar spectroscopic imaging, and non‐Cartesian MRSI effectively cover the full k‐space in a more efficient manner per TR. On the other hand, techniques such as parallel imaging and compressed sensing acquire fewer k‐space points and employ advanced reconstruction algorithms to recreate the spatial‐spectral information, which maintains statistical fidelity in test conditions (ie no statistically significant differences on voxel‐wise comparisions) with the fully sampled data. The advantages and limitations of each state‐of‐the‐art technique are reviewed in detail, concluding with a note on future directions and challenges in the field of fast spectroscopic imaging.

Advanced magnetic resonance spectroscopic neuroimaging: Experts' consensus recommendations

“…Initially implemented using echo planar readout (EPSI), 87,122 several non‐Cartesian trajectories have also been used 112,123,124 . These can also be combined with k‐space undersampling and multi‐band encoding to further increase sampling efficiency 125–130 . When implemented at higher field strengths these advanced MRSI methods can provide metabolite maps of relatively high spatial resolution within clinically acceptable acquisition times (Figure 3).…”

Whole-Brain High-Resolution Metabolite Mapping with 3D Compressed-Sensing-SENSE-LowRank1H FID-MRSI

“…Since then, 3D 1 H-MRSI methods for human brain imaging have been improved by implementation of acceleration techniques [7][8][9] or significant increase in spatial resolution [10,11]. A complete and exhaustive overview of 1 H-MRSI techniques that covers also 2D approaches can be found in review articles [12][13][14].…”

Lipid suppressed and tissue-fraction corrected metabolic distributions in human central brain structures using 2D1H Magnetic Resonance Spectroscopic Imaging at 7 tesla

“…The advantages and limitations of various fast MRSI techniques have been thoroughly reviewed by Shankar et. al [53].…”