Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine
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Early detection of cartilage degeneration in the hip may help prevent onset and progression of osteoarthritis in young patients with femoroacetabular impingement. Delayed gadolinium-enhanced MRI of cartilage is sensitive to cartilage glycosaminoglycan loss and could serve as a diagnostic tool for early cartilage degeneration. ⋯ T1 measurements by the two pulse sequences were strongly correlated (R2>0.95) and in excellent agreement (mean difference=-8.7 ms; upper and lower 95% limits of agreement=64.5 and -81.9 ms, respectively). T1 measurements were insensitive to B1+ variation as large as 20%, making the proposed T1 mapping technique suitable for 3 T.
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A weighted averaging scheme with flip angle adaptation is presented for segmented 2D-selective RF excitations and applied to single-line segments of a blipped-planar trajectory. Segments covering the central k-space, i.e. those with significant signal contributions, are averaged more often than the (outer) segments with low RF amplitudes and minor signal contributions. ⋯ Its application to single-voxel MR spectroscopy of a corpus-callosum-shaped region-of-interest yielded, due to an optimum coverage of the target volume, higher signal amplitudes than conventional localization based on cross-sectional RF excitations. Thus, the approach could improve the reliability of single-voxel MR spectroscopy.
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This article introduces regularized lineshape deconvolution in conjunction with TE-averaged PRESS spectroscopy to measure N-acetyl-aspartyl-glutamate (NAAG). Averaging different echo times suppressed the signals of multiplets from strongly coupled spin systems near 2 ppm; thus, minimizing the interfering signals to detect the acetyl proton signal of NAAG. ⋯ This new approach was used to measure NAAG in the two regions of interest of healthy volunteers, dominated by gray matter and white matter, respectively. The acetyl proton signal of NAAG was directly quantified by fitting the deconvoluted spectra to a Voigt-lineshape spectral model function, yielding the NAAG-N-acetyl-aspartate (NAA) ratios of 0.11±0.02 for the gray matter voxels (n=8) and 0.18±0.02 for the white matter voxels (n=12).
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Diffusion-weighted imaging (DWI) has shown great benefits in clinical MR exams. However, current DWI techniques have shortcomings of sensitivity to distortion or long scan times or combinations of the two. Diffusion-weighted echo-planar imaging (EPI) is fast but suffers from severe geometric distortion. ⋯ By separating the gradient and spin echoes into individual blades and removing the off-resonance phase, the off-resonance artifacts in X-PROP are minimized. Special reconstruction processes are applied on these blades to correct for the motion artifacts. In vivo results show its advantages over EPI, PROPELLER DWI, and TurboPROP techniques.