Noninvasive Quantification (noninvasive + quantification)

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Selected Abstracts

Noninvasive quantification of human brain ascorbate concentration using 1H NMR spectroscopy at 7,T

Melissa Terpstra
Abstract Ascorbate (Asc, vitamin C) was quantified in the human brain noninvasively using two different 1H NMR spectroscopy methods: short-echo time STEAM and MEGA-PRESS homonuclear editing. Taking advantage of increased sensitivity and chemical shift dispersion at 7,T, Asc was quantified with increased reliability relative to our previous study accomplished at 4,T. Asc concentration quantified from short-echo time spectra measured from the occipital lobe of eight healthy subjects ([Asc],=,1.1,±,0.3,µmol/g, mean,±,SD) was in excellent agreement with Asc concentration quantified from the same volume of interest using homonuclear editing ([Asc],=,1.2,±,0.2,µmol/g). This agreement indicates that at 7,T, Asc can be reliably quantified in the human brain simultaneously with 15 other metabolites. Additional advantages of the short-echo time approach were: shorter measurement time than homonuclear editing and minimal effect of T2 relaxation on Asc quantification. High magnetic field was also beneficial for Asc quantification with MEGA-PRESS because increased chemical shift dispersion enabled editing with full efficiency, which resulted in a supra-linear gain in signal-to-noise ratio relative to 4,T. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Fast and optimized T1 mapping technique for the noninvasive quantification of gastric secretion

Reto Treier MSc
Abstract Purpose To evaluate the noninvasive quantification of gastric secretion volume after administration of a labeled viscous glucose solution by fast T1 mapping. Materials and Methods T1 values of a series of labeled and diluted glucose solutions were measured in vitro to characterize the interrelationship between T1 and contrast agent concentration (CGd) as well as the dependency of relaxivity and reference T1 (T10) on the macromolecular concentration. Abdominal T1 mapping in five healthy volunteers of different body mass index was performed after filling an intragastric balloon with a labeled and diluted glucose solution. In additional ex vivo experiments, T1 values of gastric (GJ) and duodenal juice (DJ) and 0.1 N HCl solution were determined. Results A linear relationship between relaxivity and macromolecular concentration and between T10 and macromolecular concentration was found. The in vitro T1,CGd calibration curve was successfully validated in all volunteers. T1 values of GJ, DJ, and HCl (2939 msec vs. 2858 msec vs. 2760 msec) were close to the T1 of water (,3000 msec). Conclusion The presented method allows one to noninvasively quantify the spatial distribution of gastric secretory products in the human stomach and provides a valuable tool for evaluating the efficacy of drugs to stimulate/inhibit gastric secretion. J. Magn. Reson. Imaging 2008;28:96,102. © 2008 Wiley-Liss, Inc. [source]

Noninvasive Imaging of Angiogenesis Inhibition Following Nitric Oxide Synthase Blockade in the Ischemic Rat Heart in Vivo

ABSTRACT Objective: Nitric oxide synthase inhibition has anti-angiogenic properties. Magnetic resonance (MR) imaging was used to image the functional significance of these microvascular changes in a rat model of chronic ischemic myocardium in vivo. Methods: The authors quantitatively determined myocardial perfusion and regional blood volume, left ventricular geometry, and function using MR imaging. Animals received either L-NAME + hydralazine or no treatment and were investigated 1 and 2 weeks after induction of coronary artery stenosis or sham operation at rest and during vasodilatation. Double-labeling immunohistochemistry was used to visualize angiogenesis and to compare with data obtained by MR imaging. Results: Left ventricular mass and end-diastolic volumes were comparable in both groups 2 weeks after treatment. However, basal and maximum perfusion in animals with L -NAME + hydralazine treatment were reduced compared to animals not treated (p < .05). Basal regional blood volume remained constant in all groups, whereas maximum regional blood volume was reduced by L -NAME + hydralazine (p < .05). Endothelial cell proliferation, a direct marker for angiogenesis, was reduced by L -NAME + hydralazine (p < .01). Conclusions: MR imaging allows noninvasive quantification of functional microcirculation and angiogenesis in the rat heart in vivo. Nitric oxide synthase blockade results in changes in functional microcirculation and in an inhibition of angiogenesis in both ischemic and nonischemic myocardial tissue. [source]