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Accelerated radial echo‐planar spectroscopic imaging using golden angle view‐ordering and compressed‐sensing reconstruction with total variation regularization
Author(s) -
Saucedo Andres,
Macey Paul M.,
Thomas M. Albert
Publication year - 2021
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.28728
Subject(s) - compressed sensing , imaging phantom , undersampling , iterative reconstruction , cartesian coordinate system , image quality , total variation denoising , planar , acceleration , mathematics , algorithm , computer science , physics , artificial intelligence , optics , geometry , image (mathematics) , computer graphics (images) , classical mechanics
Purpose To implement a novel, accelerated, 2D radial echo‐planar spectroscopic imaging (REPSI) sequence using undersampled radial k‐space trajectories and compressed‐sensing reconstruction, and to compare results with those from an undersampled Cartesian spectroscopic sequence. Methods The REPSI sequence was implemented using golden‐angle view‐ordering on a 3T MRI scanner. Radial and Cartesian echo‐planar spectroscopic imaging (EPSI) data were acquired at six acceleration factors, each with time‐equivalent scan durations, and reconstructed using compressed sensing with total variation regularization. Results from prospectively and retrospectively undersampled phantom and in vivo brain data were compared over estimated concentrations and Cramer‐Rao lower‐bound values, normalized RMS errors of reconstructed metabolite maps, and percent absolute differences between fully sampled and reconstructed spectroscopic images. Results The REPSI method with compressed sensing is able to tolerate greater reductions in scan time compared with EPSI. The reconstruction and quantitation metrics (i.e., spectral normalized RMS error maps, metabolite map normalized RMS error values [e.g., for total N‐acetyl asparate, REPSI = 9.4% vs EPSI = 16.3%; acceleration factor = 2.5], percent absolute difference maps, and concentration and Cramer‐Rao lower‐bound estimates) showed that accelerated REPSI can reduce the scan time by a factor of 2.5 while retaining image and quantitation quality. Conclusion Accelerated MRSI using undersampled radial echo‐planar acquisitions provides greater reconstruction accuracy and more reliable quantitation for a range of acceleration factors compared with time‐equivalent compressed‐sensing reconstructions of undersampled Cartesian EPSI. Compared to the Cartesian approach, radial undersampling with compressed sensing could help reduce 2D spectroscopic imaging acquisition time, and offers a better trade‐off between imaging speed and quality.