Compressed sensing to accelerate magnetic resonance spectroscopic imaging: evaluation and application to 23Na-imaging of mouse heartsReport as inadecuate




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Journal of Cardiovascular Magnetic Resonance

, 17:45

First Online: 15 June 2015Received: 18 November 2014Accepted: 15 May 2015

Abstract

BackgroundMagnetic Resonance Spectroscopic Imaging MRSI has wide applicability for non-invasive biochemical assessment in clinical and pre-clinical applications but suffers from long scan times. Compressed sensing CS has been successfully applied to clinical H MRSI, however a detailed evaluation of CS for conventional chemical shift imaging is lacking. Here we evaluate the performance of CS accelerated MRSI, and specifically apply it to accelerate Na-MRSI on mouse hearts in vivo at 9.4 T.

MethodsSynthetic phantom data representing a simplified section across a mouse thorax were used to evaluate the fidelity of the CS reconstruction for varying levels of under-sampling, resolution and signal-to-noise ratios SNR. The amplitude of signals arising from within a compartment, and signal contamination arising from outside the compartment relative to noise-free Fourier-transformed FT data were determined. Simulation results were subsequently verified experimentally in phantoms and in three mouse hearts in vivo.

ResultsCS reconstructed MRSI data are scaled linearly relative to absolute signal intensities from the fully-sampled FT reconstructed case R > 0.8, p-value < 0.001. Higher acceleration factors resulted in a denoising of the reconstructed spectra, but also in an increased blurring of compartment boundaries, particularly at lower spatial resolutions. Increasing resolution and SNR decreased cross-compartment contamination and yielded signal amplitudes closer to the FT data. Proof-of-concept high-resolution, 3-fold accelerated Na-amplitude maps of murine myocardium could be obtained within ~23 mins.

ConclusionsRelative signal amplitudes i.e. metabolite ratios and absolute quantification of metabolite concentrations can be accurately determined with up to 5-fold under-sampled, CS-reconstructed MRSI. Although this work focused on murine cardiac Na-MRSI, the results are equally applicable to other nuclei and tissues e.g. H MRSI in brain. Significant reduction in MRSI scan time will reduce the burden on the subject, increase scanner throughput, and may open new avenues for pre- clinical metabolic studies.

KeywordsCompressed sensing Magnetic resonance spectroscopic imaging Chemical shift imaging Mouse Sodium AbbreviationsMRSIMagnetic resonance spectroscopic imaging

CSCompressed sensing

SNRSignal-to-noise ratio

FTFourier-transform

EPSIEcho-planar spectroscopic imaging

CSIChemical shift imaging

RAcceleration-undersampling factor

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Author: Mahon L. Maguire - Sairam Geethanath - Craig A. Lygate - Vikram D. Kodibagkar - Jürgen E. Schneider

Source: https://link.springer.com/article/10.1186/s12968-015-0149-6







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