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Healthy Human Brain (healthy + human_brain)
Selected AbstractsSodium MRI using a density-adapted 3D radial acquisition techniqueMAGNETIC RESONANCE IN MEDICINE, Issue 6 2009Armin M. Nagel Abstract A density-adapted three-dimensional radial projection reconstruction pulse sequence is presented which provides a more efficient k -space sampling than conventional three-dimensional projection reconstruction sequences. The gradients of the density-adapted three-dimensional radial projection reconstruction pulse sequence are designed such that the averaged sampling density in each spherical shell of k -space is constant. Due to hardware restrictions, an inner sphere of k -space is sampled without density adaption. This approach benefits from both the straightforward handling of conventional three-dimensional projection reconstruction sequence trajectories and an enhanced signal-to-noise ratio (SNR) efficiency akin to the commonly used three-dimensional twisted projection imaging trajectories. Benefits for low SNR applications, when compared to conventional three-dimensional projection reconstruction sequences, are demonstrated with the example of sodium imaging. In simulations of the point-spread function, the SNR of small objects is increased by a factor 1.66 for the density-adapted three-dimensional radial projection reconstruction pulse sequence sequence. Using analytical and experimental phantoms, it is shown that the density-adapted three-dimensional radial projection reconstruction pulse sequence allows higher resolutions and is more robust in the presence of field inhomogeneities. High-quality in vivo images of the healthy human leg muscle and the healthy human brain are acquired. For equivalent scan times, the SNR is up to a factor of 1.8 higher and anatomic details are better resolved using density-adapted three-dimensional radial projection reconstruction pulse sequence. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc. [source] Diffusion time dependence of the apparent diffusion tensor in healthy human brain and white matter diseaseMAGNETIC RESONANCE IN MEDICINE, Issue 6 2001Chris A. Clark Abstract The diffusion time dependence of the brain water diffusion tensor provides information regarding diffusion restriction and hindrance but has received little attention, primarily due to limitations in gradient amplitude available on clinical MRI systems, required to achieve short diffusion times. Using new, more powerful gradient hardware, the diffusion time dependence of tensor-derived metrics were studied in human brain in the range 8,80 ms, which encompasses the shortest diffusion times studied to date. There was no evidence for a change in mean diffusivity, fractional anisotropy, or in the eigenvalues with diffusion time in healthy human brain. The findings are consistent with a model of unrestricted, but hindered water diffusion with semipermeable membranes, likely originating from the extracellular space in which the average extracellular separation is less than 7 microns. Similar findings in two multiple sclerosis plaques indicated that the size of the water diffusion space in the lesion did not exceed this dimension. Magn Reson Med 45:1126,1129, 2001. © 2001 Wiley-Liss, Inc. [source] In vivo proton MR spectroscopy findings specific for adenylosuccinate lyase deficiencyNMR IN BIOMEDICINE, Issue 5 2010M. Henneke Abstract Adenylosuccinate lyase (ADSL) deficiency is an inherited metabolic disorder affecting predominantly the central nervous system. The disease is characterized by the accumulation of succinylaminoimidazolecarboxamide riboside and succinyladenosine (S-Ado) in tissue and body fluids. Three children presented with muscular hypotonia, psychomotor delay, behavioral abnormalities, and white matter changes on brain MRI. Two of them were affected by seizures. Screening for inborn errors of metabolism including in vitro high resolution proton MRS revealed an ADSL deficiency that was confirmed genetically in all cases. All patients were studied by in vivo proton MRS. In vitro high resolution proton MRS of patient cerebrospinal fluid showed singlet resonances at 8.27 and 8.29,ppm that correspond to accumulated S-Ado. In vivo proton MRS measurements also revealed a prominent signal at 8.3,ppm in gray and white matter brain regions of all patients. The resonance was undetectable in healthy human brain. In vivo proton MRS provides a conclusive finding in ADSL deficiency and represents a reliable noninvasive diagnostic tool for this neurometabolic disorder. Copyright © 2010 John Wiley & Sons, Ltd. [source] | ||||||||||