title: Improving the spectral resolution and spectral fitting of (1) H MRSI data from human calf muscle by the SPREAD technique.
abstract: Proton magnetic resonance spectroscopic imaging ((1) H MRSI) has been used for the in vivo measurement of intramyocellular lipids (IMCLs) in human calf muscle for almost two decades, but the low spectral resolution between extramyocellular lipids (EMCLs) and IMCLs, partially caused by the magnetic field inhomogeneity, has hindered the accuracy of spectral fitting. The purpose of this paper was to enhance the spectral resolution of (1) H MRSI data from human calf muscle using the SPREAD (spectral resolution amelioration by deconvolution) technique and to assess the influence of improved spectral resolution on the accuracy of spectral fitting and on in vivo measurement of IMCLs. We acquired MRI and (1) H MRSI data from calf muscles of three healthy volunteers. We reconstructed spectral lineshapes of the (1) H MRSI data based on field maps and used the lineshapes to deconvolve the measured MRS spectra, thereby eliminating the line broadening caused by field inhomogeneities and improving the spectral resolution of the (1) H MRSI data. We employed Monte Carlo (MC) simulations with 200 noise realizations to measure the variations of spectral fitting parameters and used an F-test to evaluate the significance of the differences of the variations between the spectra before SPREAD and after SPREAD. We also used Cramer-Rao lower bounds (CRLBs) to assess the improvements of spectral fitting after SPREAD. The use of SPREAD enhanced the separation between EMCL and IMCL peaks in (1) H MRSI spectra from human calf muscle. MC simulations and F-tests showed that the use of SPREAD significantly reduced the standard deviations of the estimated IMCL peak areas (p < 10(-8) ), and the CRLBs were strongly reduced (by ~37%).
authors.affiliation: Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, USA; New York State Psychiatric Institute, New York, USA.
authors.forename: Zhengchao
authors.initials: Z
authors.lastname: Dong
authors.forename: Yudong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Feng
authors.initials: F
authors.lastname: Liu
authors.forename: Yunsuo
authors.initials: Y
authors.lastname: Duan
authors.forename: Alayar
authors.initials: A
authors.lastname: Kangarlu
authors.forename: Bradley S
authors.initials: BS
authors.lastname: Peterson
mesh_terms: D003198:Computer Simulation; D045604:Extracellular Fluid / Q000737:chemistry; D006801:Humans; D008055:Lipids / Q000032:analysis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008954:Models, Biological; D009010:Monte Carlo Method; D018482:Muscle, Skeletal / Q000737:chemistry*; D019047:Phantoms, Imaging; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D011522:Protons; D012016:Reference Values
chemical_list: D008055:Lipids; D011522:Protons
keywords: calf muscle; magnetic resonance spectroscopic imaging; spectral fitting; spectral resolution