bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relative volume‐average murine tumor blood flow measurement via deuterium nuclear magnetic resonance spectroscopy
Authors: Mattiello James , Evelhoch Jeffrey L. 
Published: March 2007

AbstractA deuterium NMR spectroscopic method to determine relative tumor blood flow (TBF) by measuring the increase in tumor HOD concentration after intravenous injection of 100 μl D2O (0.9% NaCl) is presented. An integration approach analogous to that validated for positron emission tomographic measurement of cerebral blood flow was implemented. Computer simulations indicated that integration from 30 to 120 s minimizes the sensitivity of the uptake integral to the shape of the arterial input function, which cannot be assessed in each mouse, while maintaining both a nearly linear relationship between TBF and the integral and high NMR signal‐to‐noise. A strong positive linear correlation was observed between the uptake integral and TBF measured by D2O clearance in both untreated tumors (n = 19; P < 0.001) and tumors after hyperthermia (n = 16; P < 0.001). This method can measure relative TBF in tumors with heterogeneous blood flow and is ideally suited to concurrent or interleaved measurement of TBF and metabolism via multinuclear NMR spectroscopy. © 1991 Academic Press. Inc.
Coronary angiography using fast selective inversion recovery
Authors: Wang Samuel J. , Hu Bob S. , Macovski Albert , Nishimura Dwight G. 
Published: March 2007

AbstractUsing a fast version of selective inversion recovery, we have obtained coronary angiograms of normal volunteers showing the proximal portions of the left coronary artery. Blood is tagged in the aortic root at end systole using a 2D inversion pulse. After a wash‐in time of 300–600 ms, the coronary vessels are imaged with a 2‐ to 3‐cm‐thick slab in either axial or oblique projection. The scan is completed within a breathhold in 24 heartbeats. © 1991 Academic Press. Inc.
Potential degradation in image quality due to selective averaging of phase‐encoding lines in Fourier transform MRI
Authors: Mugler John P. 
Published: March 2007

AbstractThe properties of the image noise for selective averaging of phase‐encoding lines have been investigated. For a given acquisition time, selective averaging results in a signal‐to‐noise ratio penalty compared to averaging all lines equally. In addition, selective averaging yields a non uniform distribution of noise characteristics in spatial frequency space, which can result in a change in the texture of the image noise. © 1991 Academic Press, Inc.
Anisotropy in diffusion‐weighted MRI
Authors: Moseley Michael E. , Kucharczyk John , Asgari Haleh S. , Norman David 
Published: March 2007

AbstractDiffusional anisotropy of water protons, induced by nonrandom, directional barriers which hinder or retard water motion, is measurable by MRI. Faster water diffusion was observed when the diffusion‐sensitizing gradient direction paralleled the long axes of white matter tracts, indicative of fewer bamers to water motion. Diffusion perpendicular to this 3xis was as much as four times slower. Anisotropy was seen pre‐ and postmortem in all axial, sagittal, and coronal planes, with and without cardiac gating. Ordering has also been observed in feline optic nerve and in human peripheral nerves. Utilization of this technique can greatly improve understanding and assessment of demyelinating disorders, of white matter infarcts and neoplasms, and of neonatal brain and spinal cord development. © 1991 Academic Press, Inc.
Oblique NMR imaging of the uterus in macaques: Uterine resdonse to estrogen stimulation
Authors: Waterton John C. , Miller Diane , Dukes Michael , Morrell John S. W. 
Published: March 2007

AbstractWe report methods for quantitative NMR imaging of the primate uterus and the application of these methods of measuring the response of the monkey (Macaca nemestrina) uterus (endometrial volume. myometrial volume, T2 values, myometrial junction zone) to estrogen stimulation. High‐gield (2.35 T), fat‐suppressed, T2‐weighted (TE50) oblique methods were used, Slice thickeness, location, and angle were varied on each examination to obtain six contiguous slices between the cervix and fundus, regardles of size or orientation of the uterus. Basal endometrial and myometrial volumes were 0.05± 0.01 cm3 and 1.31 ± 0.23 cm3 in chronically ovariectomized animals. These increased by 15.7 ± 3.6‐fold and 3.1 ± 0.4 fold, respectively, during 7 days of estrogen stimulation (estradiol benzoate, 5 ųg/kg sc daily) while myometrial T2 increased from 52 ± 1 to 67 ± 4 ms. These changes reversed following menstrual bleeding. © 1991 Academic Press, Inc.
Safety of gadolinium‐DTPA: Extended clinical experience
Authors: Niendorf H. P. , Haustein J. , Cornelius I. , Alhassan A. , Clauß W. 
Published: March 2007

AbstractThis review reports data on the general and renal tolerance of the paramagnetic contrast agent Gd‐DTPA after intravenous administration. Gd‐DTPA was administered usually at a dose level of 0.1‐0.2 mmol/kg body wt (range: 0.005‐0.25 mmol/kg body wt) in cranial, spinal and body MR indications. In phase I‐IIIa studies a total of 2154 healthy volunteers and patients were investigated, usually at a dose of 0.1 mmol/kg body wt. From the obtained results it was concluded that adverse events (AEs) may be expected in the order of magnitude of 1%. In phase IIIb‐IV studies 13,439 patients were investigated at 0.1 or 0.2 mmol/kg body wt. Tolerance data were collected according to a standardized protocol and metaanalysis of obtained data was performed. AEs, irrespective of their drug relationship, were observed in 1.15% of the patients. The observed AEs were comparable to those after intravenous administration of iodinated nonionic X‐ray contrast media. There was no correlation between patient age and the incidence of AEs. In patients with a known history of allergy the incidence of AEs increased to 2.6%. In pediatric use no added risk was observed in a total of 826 neonates, children, and adolescents up to 18 years of age. Gd‐DTPA showed good renal tolerance in patients with and without preexisting impairment of renal function. A prospective open safety and pharmacokinetic study was conducted in patients with hemodialysis. Gd‐DTPA was shown to be eliminated completely by hemodialysis. Fast bolus injections were tolerated without added risk. Presented data from postmarketing surveillance (up to March 31, 1991) cover an estimated total of more than 2,000,000 applications. In conclusion, Gd‐DTPA showed an excellent safety profile after intravenous administration of diagnostic doses to patients of all age groups, irrespective of the injection speed and preexisting renal impairment. The overall incidence of AEs after intravenous injection of 0.1 or 0.2 mmol Gd‐DTPA/kg body wt was found to be 1–2%. © 1991 Academic Press, Inc.
Correction of chemical‐shift artifacts in multislice F‐19 imaging with perfluorooctyl bromide
Authors: Özdemirel B. , Nalcioglu O. 
Published: March 2007

AbstractChemical‐shift artifact correction methods for multislice F‐19 imaging with perfluorooctyl bromide are described and results obtained with physical phantoms presented. Utilization of the two long‐T2 spectral peaks of PFOB in multislice imaging enhances the imaging efficiency considerably. Simultaneous imaging of the adjacent slices is achieved by appropriately adjusting the slice selection gradient amplitude, the bandwidth, and the slice position offset frequency of the selective RF pulses in relation to the frequency separation between the two peaks. © 1992 Academic Press, Inc.
Q optimization of RF inductors for use in NMR probes
Authors: Kan Siew , Gonord Patrick 
Published: March 2007

AbstractRadiofrequency inductors are important components of many NMR probe circuits, and a high quality factor Q of these inductors is necessary to achieve good signal‐to‐noise ratios. We have designed high Q inductors using an optimum coil diameter to coil length ratio of the order of 2.54. The latter was calculated from Lorenz's inductance formula for a solenoid and checked experimentally using a series of inductors of various diameters and lengths. The results show good agreement between theory and practice. © 1992 Academic Press, Inc.
Rapid localization of concave volumes by conformal NMR spectroscopy
Authors: Sharp Jonathan C. , Leach Martin O. 
Published: March 2007

Abstract“Conformal” spectroscopy is a method for the acquisition of accurately localized NMR spectra from noncuboidal regions with optimum signal‐to‐noise ratio, and is based upon the localization of volumes defined by a number of oblique intersecting selected slices. We have previously demonstrated conformal localization of volumes with convex surfaces. In this paper we extend the technique to the localization of concave volumes.
A new approach to split resonator design
Authors: Harpen Michael D. 
Published: March 2007

AbstractUsing a novel application of the method of images we show how a plane array of resonant elements can be substituted for the conducting plane in a semicylindrical or split resonator. In an experimental low‐pass split resonator‐plane array system used as a magnetic resonance imaging receive coil at 0.5 T sensitivity values are shown to be uniform (∼ ±3%) across the field of view. © 1992 Academic Press, Inc.
Localized 1H NMR spectra of glutamate in the human brain
Authors: Rothman D. L. , Hanstock C. C. , Petroff O. A. C. , Novotny E. J. , Prichard J. W. , Shulman R. G. 
Published: March 2007

AbstractLocalized 1H NMR spectra at TE = 12 ms were obtained from cerebralcortex of human subjects using ISIS with surface suppression. The 2.29‐ppm resonance was assigned to C4 glutamate with contributions from C4 glutamine and GABA using in vivo spectral editing and comparison of chemical shift with pure compounds. The measured intensity ratio between the 2.29 resonance and the creatine resonance at 3.03 ppm was in good agreement with the ratio predicted from previously reported measurements of glutamate. glutamine, and GABA concentrations in biopsied human brain tissue.
Selective suppression of lipid resonances by lipid‐soluble nitroxides in NMR spectroscopy
Authors: Chen Kai , Lutz Norbert W. , Wehrle Janna P. , Glickson Jerry D. , Swartz Harold M. 
Published: March 2007

AbstractThe ability of lipid‐soluble nitroxides to suppress selectively the peaks of lipid resonances in 31P, 1H, and 13C NMR spectra was investigated in serum as part ofstudies aimed at using these contrast agents for magnetic resonance imaging and magnetic resonance spectroscopy in vivo. Nitroxides are especially interesting potential contrast agents because they can reversibly be converted in cells to diamagnetic hydroxylamines, with conversion rates that are dependent on the redox potential and the intracellular concentration of oxygen; the characterization of nitroxide‐dependent changes in NMR spectra may therefore be a useful means to measureoxygen‐dependent redox metabolism in vivo. The fatty acid analogs, doxyl stearates, suppressed the methyl resonance of choline and the methyl and methylene peaks of lipids in the 1H NMR spectra of serum samples. As a consequence, lactate peaks, which were not readily detected became clearly resolved and could be evaluated quantitatively. The 31P resonance of phosphatidylcholine in the 31P NMR spectrum was suppressed by 5doxyl stearate and 4‐(N,Ndimethyl‐Nhexadecyl)ammonium‐2,2,6,6‐tetramethylpiperidine‐I‐oxyl, iodide (Cat16). In the 13C NMR spectrum, the resonances of the methyl groups of choline and the lipids also were broadened significantly by addition of 5‐doxyl stearate. Differential suppression of lipid resonances can be employed to facilitate quantitation of lactate.
Deblurring for non‐2D fourier transform magnetic resonance imaging
Authors: Noll Douglas C. , Pauly John M. , Meyer Craig H. , Nishimura Dwight G. , Macovskj Albert 
Published: March 2007

AbstractFor several non‐2D Fourier transform imaging methods, off‐resonant reconstruction does not just cause geometric distortion, but changes the shape of the point spread function and causes blurring. This effect is well known for projection reconstruction and spiral k‐space scanning sequences. We introduce here a method that automatically removes blur introduced by magnetic field inhomogeneity and susceptibility without using a resonant frequency map, making these imaging methods more useful. In this method, the raw data are modulated to several different frequencies and reconstructed to create a series of base images. Determination of degree of blur is done by calculating a focusing measure for each point in each base image and a composite image is then constructed using only the unblurred regions from each base image. This method has been successfully applied to phantom and in vivo images using projection‐reconstruction and spiral‐scan sequences. © 1992 Academic Press, Inc.
Improving resolution in MRI by interleaving data acquisition for increased digitization rates
Authors: Barker G. J. , Williams S. C. R. 
Published: March 2007

AbstractIn certain situations in magnetic resonance imaging the digital resolution in the frequency encode direction may be compromised by hardware limits on data digitization rates. We demonstrate a method of overcoming this restriction, without hardware modifications, by interleaving data from several acquisitions to produce a higher resolution composite data set. © 1992 Academic Press, Inc.
MR imaging of brain surface using steady‐state free precession
Authors: Takane Atsushi , Koizumi Hideaki 
Published: March 2007

AbstractWe present an imaging technique that affords direct and noninvasive visualization of brain surface structure. This technique utilizes the signal before the rf pulse in steady‐state free precession. This signal highly reflects the spin‐spin relaxation time T2, as was studied in our laboratory (Matsui et al. J. Magn. Reson. 62 12, 1985). Therefore the cerebrospinal fluid (CSf), having a long T2, is depicted as high intensity. The CSF permeates cerebral sulci and fissures. The imaging time with this technique is less than 1 min. © 1992 Academic Press, Inc.
Magnetization transfer contrast in fat‐suppressed steady‐state three‐dimensional MR images
Authors: Flame Duane P. , Pierce W. Brad , Harms Steven E. , Griffey Richard H. 
Published: March 2007

AbstractWe demonstrate that magnetization transfer contrast can be used to improve the diagnostic utility of fat‐suppressed steady‐state three‐dimensional gradient‐recalled images. Fat suppression is achieved using a “jump‐return” pair of contiguous shaped pulses. No time interval exists between the pulses, and no RF echo is generated. The sequence normally produces images with “density” weighting. Preparation of the spin magnetization with off‐resonance frequency‐selective excitation creates magnetization transfer contrast which attenuates signal intensity in proportion to the exchange rate of magnetization from free water with magnetization from water bound to macromolecules or protons that have restricted mobility. The resulting images have excellent fat suppression with low sensitivity to motion since no subtraction is used. In addition, the mechanism of signal attenuation is independent of paramagnetic effects, and addition of Gd‐DTPA produces signal enhancement from vascularized regions of tissue. Examples are presented for the knee and breast, where the observation of pathology with signal enhancement from Gd‐DTPA is improved over conventional 3D fat‐suppressed images.
Analysis of the evolution of focal cerebral ischemia in the rat using the eigenimage filter
Authors: Peck Donald J. , Spickler Eric M. , Knight Robert A. , Hearshen David O. , Windham Joe P. 
Published: March 2007

AbstractThe eigenimage filter was used to evaluate the results of a MRI study of cerebral ischemia in a rat model. This linear filter segments a desired feature in an image sequence from other features which may interfere with its observation. The animals were imaged temporally, after occlusion of the middle cerebral artery, to investigate the evolution of the ischemic process. The temporal evolution of ischemia was evaluated by analysis of the “eigenimages” calculated T2 and T1 map images, and images for the angles between signature vectors defined in the eigenimage technique. The eigenimages and angle map images demonstrated an improved visibility of the lesion at all time points, as compared to the original images and T2 and T1 map images. The eigenimages also demonstrated signal intensity changes within the area of ischemia. These changes are speculated to be related to variations in local cerebral blood flow resulting in varying degrees of tissue damage. The eigenimage intensities and the angles between signature vectors demonstrated time‐related changes similar to the T2 and T1 values. Since the eigenimage filter and angle calculations are not dependent upon physical models (like T2 and T1), and the errors associated with these models, they may be preferable as methods for tissue characterization.
Validation of 13c nmr measurement of human skeletal muscle glycogen by direct biochemical assay of needle biopsy samples
Authors: Taylor Roy , Price Thomas B. , Rothman Douglas L. , Shulman Robert G. , Shulman Gerald I. 
Published: March 2007

AbstractRecent developments in 13C nuclear magnetic resonance (NMR) spectroscopy have permitted noninvasive assessment of glycogen concentration in human skeletal muscle. Before these indirect measurements could be accepted as accurate, it was essential that validation should be carried out by comparing the widely used method of muscle biopsy and direct biochemical assay for glycogen concentration with measurement by NMR. Eight normal subjects underwent six NMR scans of gastrocnemius and three biopsies of the same muscle on the same day. The overall mean for muscle glycogen concentration was 87.4 mM by NMR and 88.3 mM by biopsy. There was a close correlation between the pairs of observations on each subject (R = 0.95; P 0.0001). The mean coefficient f variation for NMR measurement was 4.3 ± 2.1% and that for biopsy was 9.3 ± 5.9%. The performance of the muscle biopsies was accompanied by a small but significant rise in plasma‐free fatty acids (529 ± 157 to 667 ± 250; P < 0.01), epinephrine (17 ± 6 to 25 ± 8 pg/ml; P < 0.02), and norepinephrine (318 ± 119 to 400 ± 140 pg/ml; P < 0.02) but no change in plasma glucose, plasma insulin, nor muscle glycogen concentration assessed by NMR. The study demonstrates that in vivo 13C NMR measurement of human muscle glycogen can be regarded as accurate, and the technique is associated with a higher precision than biopsy with direct biochemical assessment.
Relationship between the degree of unsaturation of dietary fatty acids and adipose tissue fatty acids assessed by natural‐ abundance 13c magnetic resonance spectroscopy in man
Authors: Beckmann N. , Brocard J.‐J. , Keller U. , Seelig J. 
Published: March 2007

AbstractNatural‐abundance 13C magnetic resonance spectroscopy was used for determining noninvasively the relative concentration of mono‐ and polyunsaturated fatty acids of adipose tissue in two groups of volunteers. The first consisted of subjects who had followed a fat‐reduced diet for at least half a year before the 13C measurements. The second were control subjects who were on a usual high‐fat diet. The ratio of unsaturated to total fatty acids in adipose tissue determined by 13C MRS correlated significantly with the same ratio in fat of the diet composition estimated by a dietician according to food records. The results indicate that 13C MRS is capable of assessing the degree of unsaturation of dietary fatty acids consumed during the preceding months.
Improved cardiac gating and ventilation timing in animal experiments
Authors: Pruski Jan C. , Abduljalil Amir , Robitaille Pierre‐Marie 
Published: March 2007

AbstractIn this work we present an improved solution for cardiac gating and ventilation timing in in vivo spectroscopic and imaging experiments. This approach makes use of a pulse conditioner to extract primary timing signals from noisy and fluctuating input signals. A timing controller is then used to set all additional timing outputs. Full feedback control is utilized in this timing controller to optimize both magnetic resonance and respiratory timing. Feedback control also helps ensure that timing errors will not occur during acquisition.
13C and 1H NMR Study of the Metabolic Degradation of 4‐Pentenoate in Different Dog Nephron Segments
Authors: Boulanger Yvan , Wong Hong , Fleser Angelica , Commodari Fernando , Vinay Patrick 
Published: March 2007

AbstractThe metabolism of 4‐pentenoate in isolated kidney tubules has been investigated by 1H and 13C NMR. The 4‐pentenoate metabolite, 3‐keto‐4‐pentenoyl‐CoA, accumulated in proximal tubules only and its formation could be competitively inhibited by octanoate. 4‐Pentenoate was metabolized in thick ascending limbs but not in papillary collecting ducts.© 1992 Academic Press,Inc.
Phase‐Scrambled RF Excitation for 3D Volume‐Selective Multislice NMR Imaging
Authors: Oh C. H. , Hilal S. K. , Wu E. X. , Cho Z. H. 
Published: March 2007

AbstractAn RF excitation technique with which one can improve the effective dynamic range of the receiver and reduce the interference between slices for 3D volume‐selective multislice MRI is described. The basic idea of the technique is to use phase scrambling in conjunction with slice encoding through the use of RF pulses. The spins in each slice are encoded by RF pulses which have the scrambled as well as slice‐encoded phase components along the slice‐selection direction. The scrambled, or randomly distributed, phase reduces the peak signal intensity, thereby reducing the dynamic range of the signal. Since the proposed technique utilizes RF slice encoding together with phase scrambling, interslice image interference is greatly reduced and the dynamic range is improved. In addition, the method has several advantages such as a reduction in the power requirement for the RF pulses and the elimination of the necessity for hardware such as nonlinear gradient coils.© 1992 Academic Press,Inc.
NMR measurement of 39K detectability and relaxation constants in rat tissue
Authors: Wellard R. Mark , Shehan B. Philip , Adam William R. , Craik David J. 
Published: March 2007

AbstractDifferences in the NMR detectability of 39K in various excised rat tissues (liver, brain, kidney, muscle, and testes) have been observed. The lowest NMR detectability occurs for liver (61 ± 3% of potassium as measured by flame photometry) and highest for erythrocytes (100 ± 7%). These differences in detectability correlate with differences in the measured 39K NMR relaxation constants in the same tissues. 39K detectabilities were also found to correlate inversely with the mitochondrial content of the tissues. Mitochondria prepared from liver showed greatly reduced 39K NMR detectability when compared with the tissue from which it was derived, 31.6 ± 9% of potassium measured by flame photometry compared to 61 ± 3%. The detectability of potassium in mitochondria was too low to enable the measurement of relaxation constants. This study indicates that differences in tissue structure, particularly mitochondrial content are important in determining 39K detectability and measured relaxation rates.