title: Accelerated short-TE 3D proton echo-planar spectroscopic imaging using 2D-SENSE with a 32-channel array coil.
abstract: MR spectroscopic imaging (MRSI) with whole brain coverage in clinically feasible acquisition times still remains a major challenge. A combination of MRSI with parallel imaging has shown promise to reduce the long encoding times and 2D acceleration with a large array coil is expected to provide high acceleration capability. In this work a very high-speed method for 3D-MRSI based on the combination of proton echo planar spectroscopic imaging (PEPSI) with regularized 2D-SENSE reconstruction is developed. Regularization was performed by constraining the singular value decomposition of the encoding matrix to reduce the effect of low-value and overlapped coil sensitivities. The effects of spectral heterogeneity and discontinuities in coil sensitivity across the spectroscopic voxels were minimized by unaliasing the point spread function. As a result the contamination from extracranial lipids was reduced 1.6-fold on average compared to standard SENSE. We show that the acquisition of short-TE (15 ms) 3D-PEPSI at 3 T with a 32 x 32 x 8 spatial matrix using a 32-channel array coil can be accelerated 8-fold (R = 4 x 2) along y-z to achieve a minimum acquisition time of 1 min. Maps of the concentrations of N-acetyl-aspartate, creatine, choline, and glutamate were obtained with moderate reduction in spatial-spectral quality. The short acquisition time makes the method suitable for volumetric metabolite mapping in clinical studies.
authors.affiliation: Electrical and Computer Engineering Department, University of New Mexico, Albuquerque, New Mexico 87131, USA. otazo@ece.unm.edu
authors.forename: Ricardo
authors.initials: R
authors.lastname: Otazo
authors.forename: Shang-Yueh
authors.initials: SY
authors.lastname: Tsai
authors.forename: Fa-Hsuan
authors.initials: FH
authors.lastname: Lin
authors.forename: Stefan
authors.initials: S
authors.lastname: Posse
mesh_terms: D001921:Brain / Q000033:anatomy & histology* / Q000378:metabolism*; D017352:Echo-Planar Imaging / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods; D008280:Magnetics / Q000295:instrumentation; D018377:Neurotransmitter Agents / Q000378:metabolism; D012680:Sensitivity and Specificity; D013997:Time Factors; D014018:Tissue Distribution; D014159:Transducers
chemical_list: D018377:Neurotransmitter Agents