bluuebunny/crossref_metadata_2025_split huggingface dataset:
31P Transverse Relaxation Times of the ATP NMR Signals of Human Skeletal Muscle in Vivo
Authors: Jung Wulf‐Ingo , Straubinger Klaus , Bunse Michael , Schick Fritz , Küper Klaus , Dietze Günther , Lutz Otto 
Published: March 2007

Abstract31P MRS examinations of the calf muscles of 12 healthy volunteers were performed to determine T2 of the coupled ATP signals by using the 90°–TE/2–2662‐TE/2‐acq selective spin‐echo sequence for elimination of phase and intensity distortions. The T2 relaxation times obtained are much longer than those usually assumed: γ‐ATP, 93 ms; α‐ATP, 74 ms; β‐ATP, 75 ms.© 1992 Academic Press,Inc.
Phosphoarginine‐Adenosine Triphosphate Exchange Detected in Vivo in a Microscopic Nematode Parasite by Flow 31P FT‐NMR Spectroscopy
Authors: Thompson S. N. , Platzer E. G. , Lee R.W.‐K. 
Published: March 2007

AbstractIn vivo flow 31P NMR spectroscopy of a microscopic nematode, Steinernema carpocapsae, is described. Long‐term viability was maintained during analysis by continuous circulation of an oxygenated suspension of the parasite through an NMR spectrometer. Saturation transfer and inversion recovery were employed under flowing conditions to investigate the kinetics of phosphoarginine ⇌ adenosine triphosphate exchange. The kinetic constants for the forward and reverse reactions were 0.37/s and 1.45/s, respectively. This report is the first to demonstrate a functional phosphagen kinase in the metabolism of a parasitic helminth.© 1992 Academic Press,Inc.
A high‐field superferric NMR magnet
Authors: Huson F. Russell , Bryan R. Nick , Mackay William W. , Herrick Richard C. , Colvin John , Ford Joseph J. , Pissanetzky Sergio , Plishker Gordon A. , Rocha Richard , Schmidt William , Teodorescu Michael , Shotzman Gary , Zeigler John 
Published: March 2007

AbstractStrong, extensive magnetic fringe fields are a significant problem with magnetic resonance imaging magnets. This is particularly acute with 4‐T, whole‐body research magnets. To date this problem has been addressed by restricting an extensive zone around the unshielded magnet or by placing external unsaturated iron shielding around the magnet. This paper describes a solution to this problem which uses superconducting coils closely integrated with fully saturated iron elements. A 4‐T, 30‐cm‐bore prototype, based on this design principle, was built and tested. The 5 G fringe field is contained within 1 meter of the magnet bore along the z axis. Homogeneity of the raw magnetic field is 10 ppm over 30% of the magnet's diameter after passive shimming. Compared with an unshielded magnet, 20% less superconductor is required to generate the magnetic field. Images and spectra are presented to demonstrate the magnet's viability for magnetic resonance imaging and spectroscopy.
Quantitative measurement of velocity at multiple positions using comb excitation and fourier velocity encoding
Authors: Dumoulin C. L. , Doorly D. J. , Caro C. G. 
Published: March 2007

AbstractAn MR imaging technique that simultaneously acquires Fourier velocity encoded data from multiple stations is described. The technique employs a comb excitation rf pulse that excites an arbitrary number of slices. As the Fourier velocity phase encoding gradient pulse is advanced, the phase of each slice is the comb is advanced by a unique amount. This causes the signals from the spins in a particular slice to appear at a position in the phase encoding direction, which is the sum of the spin velocity and an offset arising from the phase increment given to that excitation slice. Acquisition of spin velocity information occurs simultaneously for all slices, permitting the calculation of wave velocities arising from pulsatile flow. These wave velocities can then be used to determine vessel distensibility.
A 1H‐NMR method for determining temperature in cell culture perfusion systems
Authors: Lutz N. W. , Kuesel A. C. , Hull W. E. 
Published: March 2007

AbstractThis report describes a noninvasive 1H‐NMR method for measuring absolute temperatures (±0.2°C) in biological samples and, in particular, in cell culture perfusion systems, utilizing the linear temperature dependence of the water chemical shift relative to the temperature‐independent shift of one of the components of the biological medium, e.g., pyruvate, acetate, or lactate. The effects of flow on temperature can be monitored and appropriate adjustments of the temperature controller can be made.
Molecular self‐diffusion of intracellular metabolites in rat brain in vivo Investigated by Localized Proton NMR Diffusion Spectroscopy
Authors: Merboldt Klaus‐Dietmar , Hörstermann Dirk , Hänicke Wolfgang , Bruhn Harald , Frahm Jens 
Published: March 2007

AbstractMolecular self‐diffusion coefficients of water (0.75 ± 0.05), Nacetylaspartate (0.27 ± 0.04), creatines (0.27 ± 0.04), and cholines (0.28 ± 0.08) × 10−5 cm2 s−1 were obtained from localized proton NMR spectra of rat brain in vivo using diffusion‐weighted stimulated‐echo (STEAM) sequences with a diffusion time of (Δ − δ/3) = 17 ms.
Phase velocity mapping with a real time line scan technique
Authors: Butts Kim , Hangiandreou Nicholas J. , Riederer Stephen J. 
Published: March 2007

AbstractA real‐time, 20‐Hz, one‐dimensional MR velocity imaging technique is described. A two‐dimensional RF pulse excites a 3‐cm diameter column. Velocity maps are formed from the phase difference between successive flow encoded and compensated acquisitions. A three‐point subtraction variation provides reduced sensitivity to static spins.
Gel‐entrapment of perfluorocarbons: A fluorine‐19 NMR spectroscopic method for monitoring oxygen concentration in cell perfusion systems
Authors: McGovern K. A. , Schoeniger J. S. , Wehrle J. P. , Ng C. E. , Glickson J. D. 
Published: March 2007

AbstractOxygenation is a major determinant of the physiological state of cultured cells. 19F NMR can be used to determine the oxygen concentration available to cells immobilized in a gel matrix by measuring the relaxation rate (1/T1) of perfluorocarbons (PFC) incorporated into the gel matrix. In calcium alginate gel beads without cells the relaxation rate (1/T1) of the trifluoromethyl group of perfluorotripropylamine (FTPA) varies linearly with oxygen concentration, with a slope of 1.26 ± 0.15 × 10−3 s−1μM−1 and an intercept of 0.50 ± 0.04 s−1. During perfusion with medium equilibrated with 95%/5% O2/CO2, changes in PFC T1s indicate that the average oxygen concentration was reduced from 894 ± 102 μM in the absence of cells to 476 ± 65 μM and 475 ± 50 μM in the presence of 0.7 × 108 EMT6/Ro and RIF‐1 murine tumor cells per milliliter of gel, respectively. The presence of 0.2 μl of FTPA/ml of gel had no effect on the energy status of the cells as indicated by 31P NMR spectra.To calculate oxygen gradients within the beads from the average PFC T1 of the sample, a mathematical model was used assuming that oxygen is the limiting nutrient for cell metabolism and that the cellular oxygen consumption rate is independent of oxygen concentration. Data for EMT6/RO cells were fit using experimentally determined perfusion parameters together with literature values for cell volume and oxygen consumption rate. The average PFC 1/T1s predicted using different literature values for volume and oxygen consumption− 1.10 ± 0.10 and 1.28 ± 0.36 s−1−agreed well with the experimentally measured value‐1.104 ± 0.004 s−1. Thus, the model is a suitable tool for calculation of oxygen consumption rates from PFC T1s in well‐oxygenated cell perfusion systems.
QUEST ‐ a quick echo split nmr imaging technique
Authors: Heid O. , Deimling M. , Huk W. 
Published: March 2007

AbstractA novel millisecond NMR imaging method is introduced, which generalizes the principle of stopped‐pulse experiments. It has been dubbed QUEST for QUick Echo Split imaging Technique. Repeated dephasing and excitation is used to divide a primary free induction decay into an exponentially growing number of echoes. Very few gradient lobes and RF pulses already generate large numbers of echoes, so neither gradient switching speed nor RF absorption represents any real limitation. True spin echoes are easily produced.
Multi‐turn, printed surface coil inductance, and Q optimization
Authors: Raad Ahmad , Kan Siew 
Published: March 2007

AbstractWheeler's empirical inductance formula for a multi‐turn, close‐wound flat coil shows that the maximum inductance for a given length of wire occurs when the outer to inner radius ratio is equal to 15/7. A similar expression is proposed for a flat, printed spiral for surface coil antenna design by modifying one of the coefficients in Wheeler's formula. Measured inductance is in good agreement with this new formula and the optimum radius ratio for maximum inductance or Q is now of the order of 9/5.
Nuclear magnetic resonance hahn spin‐echo decay (T2) in live rats with endotoxin lung injury
Authors: Shioya Sumie , Christman Rebecca , Ailion David C. , Cutillo Antonio G. , Goodrich K. Craig 
Published: March 2007

AbstractTo determine the possibility of using nuclear magnetic resonance imaging to study experimentally induced lung injury, we measured in the lungs of spontaneously breathing living rats the time course of both the Hahn spin‐echo decay (T2) and the proton density after endotoxin injury. In order to minimize artifacts arising from motions of the nearby chest wall and heart, we used a motion‐insensitive technique (the interleaved line scan). A typical Hahn T2 measurement was obtained over a region of interest from a series of images each with a different echo time, which ranged from 16 to 110 ms. Lung water content was determined by integrating the proton density over the region of interest. The Hahn T2 and proton density were measured before and at 1, 3, 6, and 9 h after intravenous injection of endotoxin. The effects of the treatment administered before and after endotoxin injection were also evaluated. Endotoxin treatment caused lengthening of both fast (T2f) and slow (T2s) Hahn T2 components but had no significant effect on the proton density, consistent with the notion that endotoxin causes lung injury without significant lung water accumulation in rats. However, the methylprednisolone treatment prevented the lengthening of T2s but did not seem to have a significant effect on T2f. Our results suggest that NMR imaging can be used to detect and monitor experimental lung injury in intact living animals, even in the absence of variations of lung water content.
The appearance of neutral lipid signals in the 1H NMR spectra of a myeloma cell line correlates with the induced formation of cytoplasmic lipid droplets
Authors: Callies R. , Sri‐Pathmanathan R. M. , Ferguson D. Y. P. , Brindle K. M. 
Published: March 2007

AbstractThe appearance of high resolution neutral lipid signals in the 1H NMR spectra of myeloma cells grown in the presence of oleate was shown to correlate with the appearance of cytoplasmic lipid droplets observable by electron microscopy. The spin‐spin relaxation times of these lipid signals were similar to those measured previously for lipid resonances in other cell types. These data suggest that cytoplasmic lipid droplets could make a significant contribution to the neutral lipid signals observed in the 1H NMR spectra of some cells.
On the use of bayesian probability theory for analysis of exponential decay date: An example taken from intravoxel incoherent motion experiments
Authors: Neil Jeffrey J. , Bretthorst G. Larry 
Published: March 2007

AbstractTraditionally, the method of nonlinear least squares (NLLS) analysis has been used to estimate the parameters obtained from exponential decay data. In this study, we evaluated the use of Bayesian probability theory to analyze such data; specifically, that resulting from intravoxel incoherent motion NMR experiments. Analysis was done both on simulated data to which different amounts of Gaussian noise had been added and on actual data derived from rat brain. On simulated data, Bayesian analysis performed substantially better than NLLS under conditions of relatively low signal‐to‐noise ratio. Bayesian probability theory also offers the advantages of: a) not requiring initial parameter estimates and hence not being susceptible to errors due to incorrect starting values and b) providing a much better representation of the uncertainty in the parameter estimates in the form of the probability density function. Bayesian analysis of rat brain data was used to demonstrate the shape of the probability density function from data sets of different quality.
Quantification of regional blood volumes by rapid T1 mapping
Authors: Schwarzbauer C. , Syha J. , Haase A. 
Published: March 2007

AbstractA new method is presentd for the quantitative determination of regional blood volumes in vivo. It is based on rapid quantitative T1 mapping by Snapshot FLASH MRI combined with the injection of an intravascular MR contrast agent. Regional blood volumes in four different tissues of the rat (skeletal muscle, heart, liver, kidney) were determined in an In vivo experiment.
Radiative losses of a birdcage resonator
Authors: Harpen Michael D. 
Published: March 2007

AbstractWe present a derivation of the losses in a birdcage resonator due to radiation. We also present an expression for the radiation limited Q. It is shown that in head coil imaging at 63 MHz radiative losses may account for 20% of the total loss with a radiation limited Q on the order of 150. The results are shown to be consistent with those reported in the recent literature.
Allergen‐induced histamine secretion associated with lactate production in mast cells detected by 1H NMR
Authors: Yoshizaki Kazuo , Arizono Naoki , Hayano Takashi , Watari Hiroshi 
Published: March 2007

AbstractAllergen‐induced histamine secretion in mast cells, obtained from rats infected with Nippostrongylus brasiliensis, was detected by a 1H NMR semi‐selective excitation technique. Lactate production was also detected in association with histamine secretion as observed in mast cells stimulated with other nonimmunological agents, such as compound 48/80, poly‐myxin B, and melittin. The assignment of the lactate resonance was confirmed using lactate oxidase. Thus, 1H NMR spectroscopy is a useful method to study the activation of mast cells in allergic reaction.
The proton NMR spectrum in acute EAE: The significance of the change in the Cho:Cr ratio
Authors: Brenner R. E. , Munro P. M. G. , Williams S. C. R. , Bell J. D. , Barker G. J. , Hawkins C. P. , Landon D. N. , McDonald W. I. 
Published: March 2007

AbstractWe have studied by nuclear magnetic resonance spectroscopy the evolution of the proton spectral changes in acute experimental allergic encephalomyelitis. We found an in vivo elevation in the ratio between the peaks assigned to “choline containing compounds” (Cho) and creatine plus phosphocreatine (Cr). This was associated with an increase in choline, betaine, and phosphorylcholine (PC) as well as a reduction in N‐acetylaspartate (NAA), aspartate, N‐acetylaspartatyl‐glutamate and inositol in vitro. Histological examination revealed inflammation with no evidence of demyelination or neuronal loss. We conclude that the increase in the ratio of Cho:Cr was due to an increase in the concentrations of PC, betaine, and choline in association with inflammation, and not as others have suggested, with demyelination. The reported reduction in NAA may be due to dysfunction of neurones rather than their loss.
Spin‐spin relaxation in experimental allergic Encephalomyelitis. Analysis of CPMG data using a non‐linear least squares method and linear inverse theory
Authors: Stewart Wendy A. , Mackay Alex L. , Whittall Kenneth P. , Moore G. R. Wayne , Paty Donald W. 
Published: March 2007

AbstractWe have used the CPMG pulse sequence to measure proton T2 values and water content in spinal cord and brain samples from Hartley guinea pigs inoculated to produce experimental allergic encephalomyelitis (EAE). Relaxation data were fitted using minuit, a non‐linear curve fitting routine. Three exponentials provided the best fit to spinal cord data (10 ms (13%), 76 ms (57%), 215 ms (30%)) and two exponentials for brain tissue (10 ms (4%), 92 ms (96%)). Least squares algorithms were also used to analyse the spinal cord data in terms of discrete and smooth distributions of relaxation times. The discrete least squares solutions consisted of three to five isolated spikes between 0.010 and 0.300 s. This type of solution was difficult to interpret in terms of water reservoirs. Smooth solutions consisted of two broad peaks, a small peak with a T2 near 0.010 s and a larger peak near 0.100 s. The integral ratio of the larger to the smaller peak was 7.092 ± 1.782 for normal tissue, and increased to a maximum of 16 with increasing parenchymal cellular infiltration and demyelination. The short T2 peak has been assigned to water in the hydration layers of the myelin sheath. The width of the longer T2 peak was sensitive to tissue heterogeneity. The least squares and smooth distribution analysis models could be used to distinguish samples with extensive parenchymal infiltration from normal tissue, even though only a maximum of 60% of the tissue was affected. The short T2 component could provide a direct method of measuring intact myelin, which would have a profound effect on the understanding of the evolution of pathology in multiple sclerosis.
Quantitative evaluation of several partial fourier reconstruction algorithms used in mri
Authors: McGibney G. , Smith M. R. , Nichols S. T. , Crawley A. 
Published: March 2007

AbstractPartial Fourier reconstruction algorithms exploit the redundancy in magnetic resonance data sets so that half of the data is calculated during image reconstruction rather than acquired. The conjugate synthesis, Margosian, homodyne detection, Cuppen and POCS algorithms are evaluated using spatial frequency domain analysis to show their characteristics and where limitations may occur. The phase correction used in partial Fourier reconstruction is equivalent to a convolution in the frequency domain and the importance of accurately implementing this convolution is demonstrated. New reconstruction approaches, based on passing the partial data through a phase correcting, finite impulse response (FIR), digital filter are suggested. These FIR and MoFIR algorithms have a speed near that of the Margosian and homodyne detection reconstructions, but with a lower error; close to that of the Cuppen/POCS iterative approaches. Quantitative analysis of the partial Fourier algorithms, tested with three phase estimation techniques, are provided by comparing artificial and clinical data reconstructed using full and partial Fourier techniques.
1H editing of 2‐deuterated exogenous and natural endogenous D‐glucose in biological samples
Authors: Biesemans Monique , Kayser François , Van Cauteren Marc , Rehrer Nancy J. , Neirinck Peter , De Meirleir Kenny , Malaise Willy J. , Willem Rudolph 
Published: March 2007

AbstractA spin‐echo based 1H homonuclear pulse sequence, enabling the selective editing of homonuclear first‐order J‐multiplet types, is presented and analyzed. Its effectiveness in quantification applications is assessed. Its potential usefulness in the quantitative distinction between 2‐deuterated and natural D‐,glucose in biological samples is briefly discussed, with emphasis on studies of hexose metabolism conducted in vitro.
Incorporating lactate/lipid discrimination into a spectroscopic imaging sequence
Authors: Adalsteinsson Elfar , Spielman Daniel M. , Wright Graham A. , Pauly John M. , Meyer Craig H. , Macovski Albert 
Published: March 2007

AbstractA spectroscopic imaging sequence incorporating a two‐shot lactate editing method was used in two human brain studies to image lactate and NAA. The subtractive editing method allows separate images of lactate, NAA, and lipids to be collected during a single study with no SNR penalty. The sequence uses a spectral‐spatial excitation for slice selection and water suppression, and employs inversion recovery and an echo time of 136 ms for additional lipid suppression.
Effect of sample numbers on the kinetic data analysis of MR contrast agents
Authors: Lu Dongfeng , Gordon Monahan W. 
Published: March 2007

AbstractThe Monte Carlo simulation method is used to determine the uncertainties of the estimated area and mean transit time (MTT) of a regional cerebral concentration‐time curve of a bolus injected paramagnetic contrast agent. Many factors contribute to these uncertainties. This study concentrates on the error propagation from the sample noise at different sample time points along the concentration‐time curve. The uncertainties of area and MTT were determined as a function of the sample noise and the number of sample time points. For example, the percentage standard deviations (uncertainties) of both area and MTT are less than 12% with five samples whose signal‐to‐noise ratios are greater than 50.
Improved sensitivity to magnetic susceptibility contrast
Authors: De Crespigny A. J. , Roberts T. P. L. , Kucharcyzk J. , Moseley M. E. 
Published: March 2007

AbstractChanges in the local magnetic susceptibility of brain tissue due to injected paramagnetic contrast agent are manifest as both a linebroadening and frequency shift of the water resonance. By combining these two effects, the sensitivity of gradient recalled echo images to such changes can be increased.
Fast imaging using subencoding data sets from multiple detectors
Authors: Ra J. B. , Rim C. Y. 
Published: March 2007

AbstractA new fast imaging method using a subencoding data acquisition scheme and a multiple coil receiver system is proposed and demonstrated. In this method, a set of aliased images are produced from receiver coils by using the subencoded data without sacrificing the desired resolution, and resolved to an aliasing‐free image by using the distance‐dependent sensitivity information of each coil. The reduction rate of data acquisition time is proportional to the number of receiver coils. This method can be easily adapted to conventional imaging methods including fast imaging to further reduce the scan time.
Diffusion‐weighted MR microscopy with fast spin‐echo
Authors: Beaulieu Chris F. , Zhou Xiaohong , Cofer Gary P. , Johnson G. Allan 
Published: March 2007

AbstractA diffusion‐weighted fast spin‐echo (FSE) imaging sequence for high‐field MR microscopy was developed and experimentally validated in a phantom and in a live rat. Pulsed diffusion gradients were executed before and after the initial 180° pulse in the FSE pulse train. This produced diffusion‐related reductions in image signal intensity corresponding to gradient (“b”) factors between 1.80 and 1352 s/mm2. The degree of diffusion weighting was demonstrated to be independent of echo train length for experiments using trains up to 16 echoes long. Quantitative measurements on a phantom and on a live rat produced diffusion coefficients consistent with literature values. Importantly, the eight‐ to 16‐fold increase in imaging efficiency with FSE was not accompanied by a significant loss of spatial resolution or contrast. This permits acquisition of in vivo three‐dimensional data in time periods that are appropriate for evolving biological processes. The combination of accurate diffusion weighting and high spatial resolution provided by FSE makes the technique particularly useful for MR microscopy.
Lactate imaging of the human brain at 1.5 T using a double‐quantum filter
Authors: De Graaf A. A. , Luyten P. R. , Den Hollander J. A. , Heindel W. , Bovée W. M. M. J. 
Published: March 2007

AbstractThe use of a double‐quantum filtered 1H NMR spectroscopic imaging technique is described to detect the spatial distribution of lactate in the human brain. In two patients the feasibility of this technique is shown and compared with existing single‐quantum spectroscopic imaging and single voxel techniques. Singles lice double‐quantum fitered lactate images were obtained showing the lactate distribution over the entire slice in the brain. The lipid signal suppression was sufficient for the unambiguous detection of lactate. The signal loss of the lactate signal due to the incorporation of the double‐quantum filter was 50–70% relative to the single‐quantum signal.