Non‐uniformly under‐sampled multi‐dimensional spectroscopic imaging in vivo: maximum entropy versus compressed sensing reconstruction. (20th December 2013)

• Record Type: Journal Article
• Authors: Burns, Brian; Wilson, Neil E.; Furuyama, Jon K.; Thomas, M. Albert
• Is Part Of: NMR in biomedicine. Volume 27:Number 2(2014:Feb.)
• Page Start: 191
• Page End: 201
• Publication Date: 2013-12-20
• Subjects: Nuclear magnetic resonance -- Periodicals; Magnetic Resonance Spectroscopy -- Periodicals; 574
• DOI: 10.1002/nbm.3052
• Languages: English
• ISSNs: 0952-3480

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p>The four‐dimensional (4D) echo‐planar correlated spectroscopic imaging (EP‐COSI) sequence allows for the simultaneous acquisition of two spatial (<italic>k<sub>y</sub></italic>, <italic>k<sub>x</sub></italic>) and two spectral (<italic>t</italic><sub>2</sub>, <italic>t</italic><sub>1</sub>) dimensions <italic>in vivo</italic> in a single recording. However, its scan time is directly proportional to the number of increments in the <italic>k<sub>y</sub></italic> and <italic>t</italic><sub>1</sub> dimensions, and a single scan can take 20–40 min using typical parameters, which is too long to be used for a routine clinical protocol. The present work describes efforts to accelerate EP‐COSI data acquisition by application of non‐uniform under‐sampling (NUS) to the <italic>k<sub>y</sub>–t</italic><sub>1</sub> plane of simulated and <italic>in vivo</italic> EP‐COSI datasets then reconstructing missing samples using maximum entropy (MaxEnt) and compressed sensing (CS). Both reconstruction problems were solved using the Cambridge algorithm, which offers many workflow improvements over other <italic>l<sub>1</sub>‐norm</italic> solvers. Reconstructions of retrospectively under‐sampled simulated data demonstrate that the MaxEnt and CS reconstructions successfully restore data fidelity at signal‐to‐noise ratios (SNRs) from 4 to 20 and 5× to 1.25× NUS. Retrospectively and prospectively 4× under‐sampled 4D EP‐COSI <italic>in vivo</italic> datasets show that both reconstruction methods successfully remove NUS artifacts; however, MaxEnt provides reconstructions equal to or better than CS. Our results show that NUS combined with iterative reconstruction can reduce 4D EP‐COSI scan times by 75% to a clinically viable 5 min <italic>in vivo</italic>, with MaxEnt being the preferred method. Copyright © 2013 John Wiley & Sons, Ltd.</p> </abstract>