bluuebunny/crossref_metadata_2025_split huggingface dataset:
In vivo localized ESR spectroscopy reflecting metabolism
Authors: Bacic G. , Nilges M. J. , Magin R. L. , Walczak T. , Swartz H. M. 
Published: March 2007

AbstractLocalized electron spin resonance spectroscopy in Live mice was performed using a surface coil operating at 1.1 GHz with sufficient sensitivity and stability to measure quantitatively the time course of the distribution, uptake, and reduction of nitroxides in selected organsfregions (liver, bladder, head) of mice. The ability to measure regional concentrations of nitroxides in vivo could be used for pharmacokinetic analysis of drugs labeled with nitroxides and for measurement of oxygen concentrations and redox metabolism. © 1989 Academic Press, Inc.
Self‐refocusing 270° gaussian pulses for slice selection without gradient reversal in magnetic resonance imaging
Authors: Emsley Lyndon , Bodenhausen Geoffrey 
Published: March 2007

AbstractIt is demonstrated, on the grounds of simulations, how 270° Gaussian pulses can be used for slice selection in nuclear magnetic resonance imaging experiments. It is shown that the usual gradient reversal procedure can be omitted if the selective 90° pulse normally used is replaced by a self‐refocusing 270° pulse with a Gaussian timedomain amplitude profile, and some of the properties which are specific to this type of pulse are explored. © 1989 Academic Press, Inc.
An automated iterative algorithm for the quantitative analysis of in vivo spectra based on the simplex optimization method
Authors: Lenkinski Robert E. , Allman Tim , Scheiner Jacob D. , Deming Stanley N. 
Published: March 2007

AbstractThe success in utilizing in vivo NMR to identify and/or monitor metabolic abnormalities will be determined in large part on the reliability with which the spectral parameters of the metabolites present can be measured. For these reasons it is clear that there is a need for the development of algorithms with which to obtain quantitatively reliable estimates ofthe spectral parameters ofthe peaks present. In this report we describe an adaptation of the simplex algorithm which we have found useful in fitting in vivo spectral data in the frequency domain. This simplex algorithm was implemented on an IBM‐PC AT compatible computer. We evaluated the simplex algorithm on three representative kinds of spectral data: a simulated spectrum, 31P spectrum of normal calf muscle, and the 31P spectrum of a pediatric patient with a brain tumor. In each case we generated a set of spectra by adding varying amounts of noise. On the basis of our simulations and the two examples discussed, we conclude that the simplex method generates parameters which are reliable estimates of the areas of the peaks present when the signal‐to‐noise is above 8:1 for phosphocreatine. We found that the speed of convergence of the algorithm was improved by overestimating the linewidths of the peaks present. We also found that the method converged more rapidly in the presence of a moderate amount of noise. We conclude that the algorithm described here can provide a robust method with which to analyze in vivo spectra in a quantitative manner. Because the method requires little user intervention, it lends itself to implementation in a semi‐, or fully, automated fashion. © 1989 Academic Press, Inc.
Use of ultralong echo time imaging to assist in measuring the velocity of perfused flow in vivo
Authors: Young I. R. , Coutts G. A. , Bryant D. J. , Bydders G. M. 
Published: March 2007

AbstractThe measurement of the velocity of perfused flow in tissue in vivo is complicated by the presence ofstationary as well as moving spins and by a variety ofdephasing phenomena which affect signal amplitudes. This paper describes a technique by which, using flow‐sensitized spin‐echo sequences with a set of very long TE times, the velocity of the moving component can be assessed. © 1989 Academic Press, Inc.
Myocardial creatine kinase exchange rates and 31P NMR relaxation rates in intact pigs
Authors: Martin Joel F. , Guth Brian D. , Griffey Richard H. , Hoekenga David E. 
Published: March 2007

AbstractIn this study, we used 31P NMR to investigate the relationship between cardiac work load and creatine kinase flux in intact pigs. NMR measurements were performed on anesthetized miniature swine in which a surface coil was surgically implanted on the surface of the left ventricle. Cardiac workload was varied by infusion of norepinephrine. Phosphate exchange between creatine phosphate and ATP was measured by a combined saturation transfer, saturation recovery pulse sequence. Exchange measurements showed that creatine kinase flux and concentrations of PCr and ATP were independent of workload for a 2.5‐fold range of cardiac rate‐pressure products. It appears that, if creatine kinase flux is coupled to work load, the pig heart operates in a regime where small changes in metabolite concentrations or creatine kinase flux are sufficient to maintain elevated workloads. Exchange and relaxation measurements, at 2.0 and 4.7 T, yielded T1 relaxation times for creatine phosphate and ATP which are longer than most reported values. Analysis of the T1 data indicates that chemical‐shift anisotropy is a plausible mechanism for a portion of the spin‐lattice relaxation rate at high field strengths. © 1989 Academic Press. Inc.
Motional phase artifacts in fourier transform MRI
Authors: Wedeen Van J. , Wendt Richard E. , Jerosch‐Herold Michael 
Published: March 2007

AbstractMost magnetic resonance imaging (MRI) techniques are subject to a “motional blurring” arising from the acquisition of data in the presence of a frequency‐encoding gradient. The Fourier transform of the signal from a spin moving along a magnetic field gradient obeys an equation analogous to the free space Schrijdinger equation. Computer simulations of the Bloch equations illustrate the implications of this motional blurring in MRI. © 1989 Academic Press, Inc.
Problems with achieving saturation using methods based on bursts of rf pulses with spoilers in magnetic resonance imaging
Authors: Young I. R. , Bydder G. M. , Bryant D. J. 
Published: March 2007

AbstractAttempts at saturation by nonselective rf pulses, followed by gradient spoiler pulses, are sometimes used as the basis of a method of measuring T1 in magnetic resonance imaging, because a method of this type is perceived as being less affected by slice shape artifact than partial saturation methods. This note suggests that, unless care is taken, this assumption can be quite erroneous.
In vivo31P nuclear magnetic resonance spectroscopy of rat 9l gliosarcoma treated with BCNU: Dose response of spectral changes
Authors: Grant Steen R. , Tamargo Rafael J. , Brem Henry , Glickson Jerry D. , Wehrle Janna P. 
Published: March 2007

AbstractThe 9L gliosarcoma, grown subcutaneously in juvenile Fischer 344 rats, was studied by in vivo 31P NMR spectroscopy following treatment with 1,3‐bis(2‐chloroethyl)‐ 1‐nitrosourea. Dose‐dependent increases in the proportion of high‐energy phosphates were observed for doses between 10 and 36 mg/kg (from 80% of the LD10 to greater than the LD50). These doses reduced clonogenic cell survival in a dose‐dependent fashion by as much as 3 log orders and resulted in up to 16 days of growth delay (to pretreatment tumor volume). Increases in high‐energy phosphates (relative to Pi) in the tumor were greater at higher doses despite the higher levels of clonogenic cell killing and the substantial host Systemic toxicity.
Conformal NMR spectroscopy: Accurate localization to noncuboidal volumes with optimum SNR
Authors: Sharp Jonathan C. , Leach Martin O. 
Published: March 2007

Abstract“Conformal Spectroscopy” is a general method for the acquisition of accurately localized NMR spectra from noncuboidal regions with optimum signal‐to‐noise ratio (SNR). The method is based upon the localization of volumes defined by a number of intersecting oblique slices and may be implemented using standard imager hardware. Conformal techniques can enhance many existing localization sequences such as ISIS (31P) and STEAM (1H) resulting in typical SNR improvements of around 1.8, equivalent to a more than threefold reduction in acquisition time. Applications include in vivo tumor Spectroscopy.
A computer simulation of T2 decay effects in echo planar imaging
Authors: Oshio Koichi , Singh Manbir 
Published: March 2007

AbstractThe effect of spatially variant T2 decay in echo planar images has been investigated. A simple, direct method to remove T2 effects, requiring no knowledge of actual T2 values, is also reported. The method is based on taking the geometric mean of two Hermitian symmetric data points before Fourier transformation.
Water referencing for spectroscopic imaging
Authors: Spielman Daniel , Webb Peter , Macovski Albert 
Published: March 2007

AbstractA water referencing algorithm for addressing the spectroscopic imaging problems of low SNR and main field inhomogeneities is proposed. Using the location of the water peak from each voxel and additional a priori information results in a parametric estimation problem. Optimum estimates of the desired metabolite concentrations can then be computed and displayed in an image format. The algorithm is shown to be very stable in the presence of noise and is insensitive to B0 inhomogeneity. A detailed error analysis as well as extensions to the basic data model are also discussed. Results from both 1H and 31P experiments are presented to verify the predicted good performance even with extremely low signal‐to‐noise ratio data. © 1989 Academic Press, Inc.
The application of spinors to pulse synthesis and analysis
Authors: Shinnar Meir , Leigh John S. 
Published: March 2007

AbstractWe show how spinors may be used to solve many problems in pulse synthesis and analysis. They provide an elegant simple notation for many problems. We show how one can specify the component of a spinor and then, by exactly solving the Bloch equations, synthesize a hard pulse sequence or a soft pulse which will yield the desired spinor. This is done by generalizing our previous approach to inverting the Bloch equations. This can be applied to synthesizing refocusing pulses. Finally, some simple consequences about symmetric pulses are derived. It is shown that given a symmetric inversion pulse, one can always synthesize an asymmetric inverting pulse of the same duration, which, as an inversion, is better. © 1989 Academic Press, Inc.
Study of acute renal ischemia in the rat using magnetic resonance imaging and spectroscopy
Authors: Terrier François , Lazeyras François , Posse Stephan , Aue Walter P. , Zimmermann Arthur , Frey Brigitte M. , Frey Felix J. 
Published: March 2007

AbstractMagnetic resonance (MR) imaging and spectroscopy, chemical lactate measurements, and microscopic examinations were performed to investigate acute renal ischemia in rats. MR images (1H) and spectra (31P and 1H) were acquired on a 2.0‐T superconducting small‐bore magnet by using implanted coils. Occlusion of the renal artery induced a significant decrease in signal intensity of the renal parenchyma on T2‐weighted images, which was most obvious in the outer medulla (‐50 ± 15%, n = 8, P 0.001) and was the result of venous congestion, as verified histologically. 31P spectroscopy demonstrated a drop in pH from 7.3 ± 0.2 to 6.6 ± 0.2 (n = 18, P 0.001), characterized by a time constant (Tc) in the same range as that of the depletion of ATP (2.3 ± 1.3 min versus 1.9 ± 1.2 min, n = 10, P = ns). By means of 1H spectroscopy, a lactate peak was detected within 1.5 to 4 min of ischemia, still increasing in intensity after 1 h of ischemia. The Tc of the lactate buildup (15.9 ± 7.5 min, n = 8) was significantly longer than that of the drop in pH (P 0.005). The chemically measured intrarenal concentration of lactate was 1.3 ± 0.5 Mmol/g in control kidneys and 8.7 ± 3.2 μmol/g (P < 0.005) in kidneys made ischemic for 1 h. The present study demonstrated important features of acute renal ischemia: (a) acute ischemia induces venous congestion in the medulla; (b) accumulation of lactate is not the main cause of the intracellular acidification observed during ischemia. © 1989 Academic Press, Inc.
Improvement in 31P NMR signal‐to‐noise for ATP in vivo using homonuclear decoupling
Authors: Berkowitz Bruce A. , Balaban Robert S. 
Published: March 2007

AbstractThe efficiency of 31P homonuclear decoupling in vivo is demonstrated. In low‐field clinical situations, when Jpp is equal to or greater than Δv significant improvements in the precision of measuring the ATP resonance area can be expected upon decoupling due to the increase in signal‐to‐noise produced upon collapse of the J coupling. The sensitivity loss due to time sharing between the decoupler and receiver is discussed. © 1989 Academic Press, Inc.
A fast spectroscopic imaging method using a blipped phase encode gradient
Authors: Webb Peter , Spielman Daniel , Macovski Albert 
Published: March 2007

AbstractMany methods of chemical shift imaging have been described recently. In most cases, these methods couple resolution and imaging time. The most flexible methods use time‐varying gradients to cover a large region of k space on each excitation. We present here a new time‐varying gradient method that offers a decrease in scan time (when SNR is sufficient), simplifies the reconstruction problem by retaining an essentially rectilinear sampling grid, and makes efficient use of scan time by minimizing gradient reversals. Implementation on a standard high‐field imaging system (GE Signa) is discussed, and experimental results are shown. An application of the method to the generation of water reference data sets is described. © 1989 Academic Press, Inc.
Cortical spectroscopy: localized spectroscopy of the cerebral cortex in rats
Authors: Houkin Kiyohiro , Nakada Tsutomu , Suzuki Nobuyuki , Kwee Ingrid L. 
Published: March 2007

AbstractA method for obtaining nuclear magnetic resonance (NMR) spectroscopic signals confined to the cerebral cortex in rat using a cortical coil constructed based on the principles of the zig‐zag coil is described. We obtained 31P NMR spectra of normal cerebral cortex and cold‐induced injured cortex using this cortical coil. The cortical coil clearly demonstrated an increase in inorganic phosphate (Pi) confined to cerebral cortex which, by contrast, the conventional planar surface coil failed to detect. There are significant metabolic differences between cortex and subcortical tissues. The technique described here, capable of assessing cortical metabolism in vivo without contamination by the underlying tissue, has substantial application to studies of cerebral metabolism. © 1989 Academic Press, Inc.
13C spectroscopic imaging. A simple approach to in vivo 13C investigations
Authors: Müller S. , Beckmann N. 
Published: March 2007

Abstract13C spectroscopic imaging (SI) is implemented and tested on a Siemens whole‐body MR instrument for in vivo localized 13C spectroscopy. The method provides spectroscopic maps of extended regions of interest. It is found that 13C SI is an ideal field of application for the spectroscopic imaging technique since most other localization methods suffer from chemical‐shift or offset artifacts for this nucleus. Applications of 13C SI with a single 13C rf channel as well as in combination with polarization transfer experiments and heteronuclear broadband decoupling are shown. © 1989 Academic Press, Inc.
Echo‐planar imaging with asymmetric gradient modulation and inner‐volume excitation
Authors: Feinberg David A. , Turner Robert , Jakab Peter D. , Kienlin Markus Von 
Published: March 2007

AbstractSingle‐shot echo‐planar imaging is notoriously vulnerable to image artifacts, arising from the necessity of alternate echo time reversal during image reconstruction and from static field inhomogeneity. A technique for overcoming these problems, which further permits imaging on systems with relatively poor gradient waveforms, when data are collected always with the same gradient polarity, is presented. Subsectional and 3D volume imaging are presented as well as a novel phase‐correction method for Hermitian symmetry in “half‐Fourier” echo‐planar imaging.
Epicardial and endocardia1 localized 31p magnetic resonance spectroscopy: evidence for metabolic heterogeneity during regional ischemia
Authors: Gober Joel R. , Schaefer Saul , Albert Camacho S. , Degroot Michael , Obregon Richard , Botvinick Elias H. , Weiner Michael , Massie Barry 
Published: March 2007

AbstractPrevious studies have noted that myocardial blood flow and high energy phosphates are heterogeneous across the myocardial wall during ischemia. In order to determine whether differences in metabolites between the subendocardium and subepicardium could be detected using 31P magnetic resonance spectroscopy, the Fourier series window (FSW) experiment was implemented on a porcine model of graded regional ischemia. FSW experiments using a planar phantom showed a 46% improvement in localization to the subendocardium compared to a one‐pulse experiment. Animal studies of graded ischemia demonstrated a gradient in the phosphocreatine to inorganic phosphate ratio in the myocardium that paralleled the gradient in blood flow. These studies demonstrate the ability of spatially localized 31P magnetic resonance spectroscopy to detect regional changes in myocardial high energy phosphates localized to the subepicardium and subendocardium.
Discriminant factor analysis of 31p nmr spectroscopic data in myopathies
Authors: Morvan D. , Jehenson P. , Duboc D. , Syrota A. 
Published: March 2007

AbstractDiscriminant factor analysis (DFA) enables one to distinguish among diagnostic groups using diagnostic variables. It provides discriminant functions that are linear combinations of the diagnostic variables and that optimally separate diagnostic groups. It was used to enhance the accuracy of 31P NMR data in the diagnosis of myopathies. DFA allowed a good separation of normal subjects, congenital neuromuscular disorders with type I fiber predominance, and McArdle's diseases. It elicited an unexpected homogeneity of idiopathic rhabdomyolyses, the metabolic origin of which is unknown, and suggested that the abnormality could involve the mitochondrial oxidative metabolism in some of them. In mitochondrial myopathies, an expected heterogeneity is shown by DFA. It may allow an automatic diagnosis of some myopathies from 31P NMR data or guide biochemists by comparing biochemical features of a new patient to those of previously established groups.
Mri quantitation of edema in focal cerebral ischemia in cats: correlation with cytochrome aa3 oxidation state
Authors: Kline R. A. , Negendank W. G. , Mccoy L. E. , Lester M. , Berguer R. 
Published: March 2007

Abstract1H MRI permits detection of edema in the brain. In a middle cerebral artery stroke model in the cat, we found a significant correlation between an edema index based on MRI and a sensitive metabolic index of ischemia, the in vivo oxidation status of mito‐chondrial cytochrome aa3 determined by near‐infrared reflectance spectrophotometry (r= −0.70, α = 0.001). This result suggests that a simple, noninvasive study using MRI can provide an index of the extent of ischemic damage in an experimental acute stroke model.
In vivo19f spin relaxation in index finger bones
Authors: Code R. F. , Harrison J. E. , Mcneill K. G. , Szyjkowski M. 
Published: March 2007

Abstract19F free induction decay (FID) signals have been observed from the index fingers of four male and two female adult volunteers using a 27‐MHz pulsed nuclear magnetic resonance spectrometer equipped with a split ring resonator probe. The value of the in vivo spin‐lattice relaxation time T1 of the fluoride ions naturally accumulated in bone mineral has been determined to be 2.0 ± 0.3 s. The shape of the observed FID signals in the inhomogeneous external magnetic field indicates that the F distribution is not uniform along the length of the finger. The fluoride ion content of the index finger (within a 65‐mm length from its distal end) was measured with a sensitivity of ±0.5 mg F within a 30‐min observation time
Assessment of a superparamagnetic iron oxide (ami‐25) as a brain contrast agent
Authors: Kent Thomas A. , Quast Michael J. , Kaplan Barry J. , Lifsey Robert S. , Eisenberg Howard M. 
Published: March 2007

AbstractWe have applied a superparamagnetic iron oxide formulation (AMI‐25, Advanced Magnetics, Inc., Cambridge, MA) to image the cerebral vasculature. Contrast‐enhanced images of normal anesthetized rats demonstrated excellent gray/white matter differentiation, consistent with known differences in blood perfusion, and cerebrospinal fluid spaces were clearly seen. Alterations in normal perfusion patterns due to barbiturate anesthesia and ischemia were clearly visible. We propose the use of this agent as an adjunct to MRI for the imaging of conditions with perfusion abnormalities. © 1990 Academic Press, Inc.
Nmr spectral analysis of kinetic data using natural lineshapes
Authors: Heineman F. W. , Eng J. , Berkowitz B. A. , Balaban R. S. 
Published: March 2007

AbstractAn automated rapid data analysis scheme for NMR spectroscopy time course studies is presented. This method uses a high signal‐to‐noise reference spectrum collected at the beginning of a time course as a lineshape model to analyze subsequent low signal‐to‐noise data collected with higher time resolution. The method is fast (approximately 1 s to evaluate two peaks in a 2K spectrum) and easily implemented on NMR spectrometer computers. An application of this method to spectroscopic studies on the heart is provided.
Assessment of intracellular magnesium depletion in rat striated muscle by in vivo31p nmr
Authors: Le Rumeur E. , Le Moyec L. , Yvin J. C. , Percehais S. , De Certaines J. D. 
Published: March 2007

AbstractPrevious in vivo studies have demonstrated that α, β. and γ ATP chemical shifts measured by 31P NMR spectroscopy can be used to determine intracellular magnesium in erythrocytes, but up to now such results have not been confirmed in striated muscle in vivo. We report BATP chemical‐shift in vivo measurements revealing the depletion of free intracellular magnesium in striated muscle of rats fed a magnesium deficient diet.
In vivo proton spectroscopy in presence of eddy currents
Authors: Klose Uwe 
Published: March 2007

AbstractSpatially localized methods in spectroscopy often operate with magnetic field gradients for volume selection. The eddy currents induced by these gradients produce time‐dependent shifts of the resonance frequency in the selected volume, which results in a distortion of the spectrum after Fourier transformation. In whole‐body systems the complete compensation of eddy currents is a difficult procedure. To avoid this, a correction method is proposed for proton spectroscopy, which uses the signal of prominent water protons as a reference for the water‐suppressed signal. The correction is performed in the time domain, dividing the water‐suppressed signal by the phase factor of the water signal for each data point. The corrected spectra have a good resolution as shown by phantom measurements and brain and muscle spectra of volunteers. © 1990 Academic Press, Inc.