title: Fiber orientation measurements by diffusion tensor imaging improve hydrogen-1 magnetic resonance spectroscopy of intramyocellular lipids in human leg muscles.
abstract: Twelve healthy subjects underwent hydrogen-1 magnetic resonance spectroscopy ([Formula: see text]) acquisition ([Formula: see text]), diffusion tensor imaging (DTI) with a [Formula: see text]-value of [Formula: see text], and fat-water magnetic resonance imaging (MRI) using the Dixon method. Subject-specific muscle fiber orientation, derived from DTI, was used to estimate the lipid proton spectral chemical shift. Pennation angles were measured as 23.78 deg in vastus lateralis (VL), 17.06 deg in soleus (SO), and 8.49 deg in tibialis anterior (TA) resulting in a chemical shift between extramyocellular lipids (EMCL) and intramyocellular lipids (IMCL) of 0.15, 0.17, and 0.19 ppm, respectively. IMCL concentrations were [Formula: see text], [Formula: see text], and [Formula: see text] in SO, VL, and TA, respectively. Significant differences were observed in IMCL and EMCL pairwise comparisons in SO, VL, and TA ([Formula: see text]). Strong correlations were observed between total fat fractions from [Formula: see text] and Dixon MRI for VL ([Formula: see text]), SO ([Formula: see text]), and TA ([Formula: see text]). Bland-Altman analysis between fat fractions (FFMRS and FFMRI) showed good agreement with small limits of agreement (LoA): [Formula: see text] (LoA: [Formula: see text] to 0.69%) in VL, [Formula: see text] (LoA: [Formula: see text] to 1.33%) in SO, and [Formula: see text] (LoA: [Formula: see text] to 0.47%) in TA. The results of this study demonstrate the variation in muscle fiber orientation and lipid concentrations in these three skeletal muscle types.
authors.affiliation: University of Texas Health Science Center , Research Imaging Institute, 7703 Floyd Curl Drive, San Antonio, Texas 78229-3900, United States ; University of Texas Health Science Center , Department of Radiology, 7703 Floyd Curl Drive, San Antonio, Texas 78229-3900, United States.
authors.forename: Sunil K
authors.initials: SK
authors.lastname: Valaparla
authors.affiliation: University of Texas Health Science Center , Research Imaging Institute, 7703 Floyd Curl Drive, San Antonio, Texas 78229-3900, United States.
authors.forename: Feng
authors.initials: F
authors.lastname: Gao
authors.affiliation: University of Texas Health Science Center , Department of Medicine, Diabetes Division, 7703 Floyd Curl Drive, San Antonio, Texas 78229-3900, United States ; University of Pisa , Department of Endocrinology, Via Paradisa 2, Pisa 56124, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Daniele
authors.affiliation: University of Texas Health Science Center , Department of Medicine, Diabetes Division, 7703 Floyd Curl Drive, San Antonio, Texas 78229-3900, United States.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Abdul-Ghani
authors.affiliation: University of Texas Health Science Center , Research Imaging Institute, 7703 Floyd Curl Drive, San Antonio, Texas 78229-3900, United States ; University of Texas Health Science Center , Department of Radiology, 7703 Floyd Curl Drive, San Antonio, Texas 78229-3900, United States.
authors.forename: Geoffrey D
authors.initials: GD
authors.lastname: Clarke
keywords: chemical shift; diffusion tensor imaging; intramyocellular lipids; pennation angle; proton magnetic resonance spectroscopy; soleus; tibialis anterior; two-point Dixon magnetic resonance imaging; vastus lateralis