bluuebunny/crossref_metadata_2025_split huggingface dataset:
Natural abundance 13C NMR spectra of human muscle, normal and diseased
Authors: Bárány Michael , Doyle Donald D. , Graff Gustav , Westler William M. , Markley John L. 
Published: March 2007

Abstract13C NMR spectra of human surgical muscle samples have been obtained at 50 and 118 MHz. Numerous sharp peaks in the 13C spectrum have been assigned to carbon atoms of soluble metabolites and fatty acyl chains of neutral fats and membrane‐bound phospholipids. Comparisons have been made of 13C NMR spectra of normal and diseased muscles after removal of neutral fat by extraction with isopentane. Creatine, lactic acid, and phosholipids are not removed from muscles by isopentane. The most striking difference between 13C NMR spectra of isopentane‐extracted normal and diseased muscle samples was the size of the residual 30.5 ppm methylene carbon resonance, that is, small in normal muscles and in nonspecific muscle diseases, but large in myogenic and neurogenic muscle diseases. In addition, differences were also found between normal and diseased muscles in their creatine content and their ability to produce lactic acid. By deoxycholate treatment of isopentane‐extracted diseased muscle it is estimated that about one‐fifth of the total phospholipids are highly mobile. T1 and NOE measurements indicated that the differences in peak height for the 30.5 ppm resonance between normal and diseased muscle are due only to difference in the amount of highly mobile fatty acyl chains in the muscle and not due to differences in relaxation parameters. 13C NMR of isopentane‐extracted muscle appears to permit differentiation of normal from diseased muscle and, within diseased muscle, grading of the severity of the disease.
Depth pulse sequences for surface coils: spatial localization and T1 measurements
Authors: Ng Thian C. , Glickson Jerry D. , Bendall M. Robin 
Published: March 2007

AbstractThe depth pulse sequences θ;[2θ(±x,±y)]2 and 2θ;θ(±x);[2θ(±x,±y)]2 have been implemented with a 20 mm diameter two‐turn surface coil operating at 31P resonance (89.96 MHz). In these sequences θ refers to the π/2 rf pulse at the center of the sensitive region of the coil, ±x and ±y denote the four orthogonal phases of the rf pulses, and “;” represents an optional brief delay (e.g., 4 m̈sec) between pulses to facilitate switching between different phases. Localization of the sensitive region was demonstrated with phantom samples by in vivomonitoring of rat livers and detection of necrotic regions of subcutaneously implanted tumors. The inversion‐recovery pulse sequence, 2θ−τ−θ(±x);[2θ(±x,±y)]2, where τ is a variable delay, was employed to measure the spin‐lattice relaxation time of a selected region. which could be varied by changing the pulse width and the size of the surface coil.
Driven‐equilibrium radiofrequency pulses in NMR imaging
Authors: Van Uijen C. M. J. , Den Boef J. H. 
Published: March 2007

AbstractDriven‐equilibrium pulse techniques are applied to NMR imaging to extend the possibilities of manipulating image contrasts in pulse sequences with a high repetition rate. In many cases the data acquisition time can be much shorter than in more conventional pulse techniques. Both calculations and experiments reveal that the intensity of tissue with slowly relaxing nuclear magnetizations can significantly be enhanced, thus facilitating the detection of a number of pathologies.
Characterization of normal and malignant mouse tissue by NMR lineshape‐relaxation correlations in the rotating frame
Authors: Sridharan K. R. , Schreiner L. J. , Kydon D. W. , Pintar M. M. , Inch W. R. 
Published: March 2007

AbstractWith the NMR lineshape‐relaxation correlation technique the relaxation times and the relative magnitudes of the proton spin ‐groups characterized by these respective relaxation times are obtained. In most tissues the spin‐lattice relaxation in the rotating frame is nonexponential. The magnetization evolution can be represented as the sum of three exponential decays characterized by three T1p relaxation times. The short T1p component, corresponding to the rigid network protons, gives the most interesting information on the tissue. Results at 38 MHz are given for muscle, spleen, lung, and tumor EMT6 fibrosarcoma grown in the dorsal subcutaneous tissue of BALB/c mice. The absence of the magnetization component with short T1p and short T2 in spleen tissue of tumorous mice demonstrates that the spleen is swollen to at least 5 times its original size so that the relative magnitude of the magnetization corresponding to collagen network is proportionally reduced. The NMR correlation technique is thus shown to be appropriate for such quantitative analysis.
Variations in slice shape and absorption as artifacts in the determination of tissue parameters in NMR imaging
Authors: Young I. R. , Bryant D. J. , Payne J. A. 
Published: March 2007

AbstractExisting models for the contrast between one tissue and another in NMR imaging have shown that there are regions of ambiguity particularly in spin‐echo sequences. This paper indicates that there are further problems due to variations in slice formation with tissue parameters, and that it is necessary to be very conservative in assessing the magnitude of T1 in any imaging system. The change in shape affects the appearance of images due, in essence, to adjustments in partial volume effects, with some of the contributions to the signal from lesions with long T1 coming from different regions to those for normal tissue. A simple model for a slice is used because the actual form in a real imaging situation is the result of a number of factors which are usually not accurately enough known.
Vascular Occlusions Detected by Magnetic Resonance Imaging
Authors: Choyke Peter L. , Kressel Herbert Y. , Axel Leon , Gefter Warren , Thickman David , Arger Peter H. , Meranze Steven G. 
Published: March 2007

AbstractEarly experience with magnetic resonance imaging (MRI) indicates that it is well suited as a noninvasive vascular imaging modality. Blood flow at physiologic velocities results in a low signal within the vessel lumen and this property allows the separation of flowing blood from surrounding soft tissues. While flow effects, aneurysms, and mural lesions have been emphasized in the literature, vascular occlusions have received less attention. We evaluated 21 patients with documented venous or arterial occlusions on a 0.12‐T developmental resistive unit. Venous occlusions caused by thrombus generally appeared as focal regions of increased signal. In 3 of 10 cases the venous thrombus itself could not be identified but the absence of a low‐signal lumen in a normal location confirmed the impression of thrombus. In 2 of 17 venous occlusions a rim of low signal was noted around the thrombus. Venous collaterals were commonly seen. Tumor thrombus tended to have signal characteristics similar to the main bulk of the tumor from which it arose. There were four arterial occlusions including two cases of emboli, one arteriosclerotic occlusion, and one case of tumor invasion. Vascular calcifications, clearly evident on plain radiographs, were not seen on MRI. MIR appears to be a potentially useful nonivasive means of detecting vascular occlusions.© 1985 Academic Press,Inc.
Phosphorus‐31 nuclear magnetic resonance measurements of 2, 3‐DPG degradation in human adult and cord blood erythrocytes
Authors: Zwerling Hayward K. , Diamond Joel N. , Levy George C. , Clark David A. 
Published: March 2007

AbstractWe have measured the percent change in 2, 3‐diphosphoglycerate (DPG) concentration in cord blood erythrocytes and adult erythrocytes during incubation at 37°C using 31P nuclear magnetic resonance spectroscopy. DPG concentrations remained unchanged during the first 4.0 ± 0.9 h (mean + SD) for cord blood erythrocytes and 6.0 ± 1.0 h for adult blood erythrocytes. After this plateau phase, cord blood and adult erythrocyte DPG concentrations decreased at a rate of 11.6 ± 0.4 and 11.4 ± 0.5% of the baseline DPG concentration per hour, respectively. There was no statistically significant difference in the percent rate of DPG degradation when comparing cord blood erythrocytes to adult erythrocytes during either the plateau phase or the decay phase. Starting at the onset of the decay phase, the neonate 3‐P DPG resonance shifted downfield at a rate of 0.03 ± 0.006 ppm per hour; the adult 3‐P DPG resonance shifted downfield at a rate of 0.02 ± 0.003 ppm per hour. © 1986 Academic Press, Inc.
Instrumentation for rapid MR image synthesis
Authors: Lee James N. , Riederer Stephen J. , Bobman Stuart A. , Farzaneh Farhad , Wang Henry Z. 
Published: March 2007

AbstractMR image synthesis has previously been developed as a means of retrospectively optimizing contrast of arbitrary materials in MR images. The first step of this process is to form computed N(H), T1, and T2 images from source images acquired at a variety of echo delay and repetion times. The second step is to take these computed images, along with operatorselected timing parameters, and mathematically generate a synthesized image. Computation is carried out pixel by pixel according to the equation describing the chosen pulse sequence. This paper presents a study of design considerations for a digital image processor capable of rapidly performing the second step, the actual synthesis. In this work the computations inherent to image synthesis are identified, and the feasibility of performing them in highspeed hardware examined. An analysis of the imprecision due to bit‐limited calculations shows that an error bound of 0.4% is possible with a 16‐bit processor design. A method is described which uses a commercially available image processor by which images can be synthesized according to any of the standard pulse sequences in less than 600 ms. © 1986 Academic Press, Inc.
Differentiation of parenchymal lung disorders with in vitro proton nuclear magnetic resonance
Authors: Vinitski Simon , Pearson Michael G. , Karlik Stephen J. , Morgan W. Keith C. , Carey Lewis S. , Perkins Garth , Goto Tohihiro , Befus Dean 
Published: March 2007

AbstractWe investigated in vitro NMR properties of bleomycin‐induced alveolitis and pulmonary fibrosis in 18 Lewis rats (6 controls). When alveolitis or fibrosis had developed, animal lungs were excised and examined histologically and gravimetrically and their T1 and T2 were determined by a NMR spectrometre at 10.7 MHz and 37°C. Clinical diagnosis was confirmed histologically in each case. The NMR signal intensities were siginificantly elevaed in both disease states (P < 0.001). Both T1 and T2 values of alveolitic lungs were about the same as in controls, but were significantly decreased in fibrotic lungs (P < 0.01). Changes in T1 and T2 correlated well (P < 0.001) with changes in water content of discased lungs. © 1986 Academic Press, Inc.
NMR studies of combined lanthanide shift and relaxation agents for differential characterization of 23Na in a two‐compartment model system
Authors: Brown M. A. , Stenzel T. T. , Ribeiro A. A. , Drayer B. P. , Spicer L. D. 
Published: March 2007

AbstractSpin relaxation and chemical shifts by lanthanide chelate complexes are used to distinguish 23Na singnals in a simulated two‐compartment model. Both effects are significant in EDTA, DTPA, and TPP complexes of Gd and in the TPP complex of Dy. The simultaneous measurement of these properties is illustrated and represents a promising method for monitoring sodium concentrations and fluxes including fast transport components. © 1986 Academic Press, Inc.
A new method for flow velocity measurement: Frequency encoded NMR
Authors: Caprihan A. , Davis J. G. , Altobelli S. A. , Fukushima Eiichi 
Published: March 2007

AbstractWe demonstrate a new rapid NMR method to measure the average velocity and the velocity distribution of a flowing fluid. We use a truncated Carr‐Purcel‐Meiboom‐Gill pulse sequence, π/2‐T‐π‐2T‐π‐T‐echo, in the presence of a static magnetic field gradient. The π/2 pulse is selective and tags a narrow slice of nuclei. The second echo from the tagged nuclei is Fourier transformed after the nuclei have evolved for a time 4T to give the velocity distribution modified by the initial slice selection profile. In this way, average velocities up to 54 cm/s were measured for water flowing in a plastic tube with either a plug or a developed velocity distribution. Each measurement required about 20 ms but this could be reduced with larger field gradients. Thus, this method is fast enough to apply to such problems as measuring pulsatile flow in arteries. © 1986 Academic Press, Inc.
Contrast‐enhanced MRI of periarticular soft‐tissue changes in experimental arthritis of the rat
Authors: Terrier François , Revel Didier , Reinhold Charles E. , Levine Jon , Grodd Wolfgang , Genant Harry K. , Brasch Robert C. 
Published: March 2007

AbstractThis study was to determine if manipulation of magnetic resonance signal intensity by means of an intravenously injected paramagnetic contrast agent is useful for the detection and characterization of periarticular inflammation. Arthritis was induced in 20 rats by means of intradermal injection of Freund's complete adjuvant. MR imaging was performed with a resistive magnet operating at 0.35 T. A double spin‐echo technique with TE's of 28 and 56 ms and TR's of 0.5 and 2.0 s was used. The hindpaws of the adjuvant‐injected rats were imaged on Day 8, Day 11, or Day 15 following injection of the adjuvant. The images were obtained in the transverse plane before and after intravenous injection of gadolinium‐DTPA (0.2 mmol/kg). Because of their long T2 relaxation time, inflammatory lesions were characterized by high MR signal intensity on precontrast images obtained with long TR and long TE (T2‐weighted images). On the other hand, because of their long T1 relaxation time, the inflammatory lesions were of relatively low intensity and not easily recognized on precontrast images obtained with short TR and short TE (T1‐weighted images). Postcontrast T1‐weighted images were also sensitive in detecting periarticular inflammation as a result of T1 shortening by the gadolinium‐DTPA. However, in our particular model, the data did not indicate any greater MR sensitivity for detecting arthritis by means of gadolinium‐DTPA enhancement. © 1986 Academic Press, Inc.
Effect of induced field inhomogeneity on transverse proton NMR relaxation in tissue water and model systems
Authors: Kurland Robert J. , Ngo Frank Q. H. 
Published: March 2007

AbstractThe effect of induced field inhomogeneity (IFI) on transverse NMR relaxation of water protons in tissue has been investigated by examining the field dependence of the effective transverse relaxation rates (1/T2 eff) for in vitro canine brain tissue samples. At fields of 0.47, 2.35, 7.05 T (corresponding to 20, 100, and 300 MHz, respectively) the transverse relaxation rates for both white and gray matter samples follow a field dependence of the form 1/T2 eff = C0 + C1 B0, where B0 is the applied field. The linearly dependent term, C1 B0, which reflects the IFI contribution, does not contribute much (i. e., less than 20%) at fields less than 2.0 T. However, at greater field strengths the contribution is appreciable, e. g., greater than 60% at 7.0 T. Results from model systems of glass beads are also reported to illustrate IFI effects. For both the model systems and canine brain tissue samples, the effects of restricted diffusion are qualitatively evident in Hahn spin‐echo experiments. © 1986 Academic Press, Inc.
31P NMR detection of mobile dog brain phospholipids
Authors: Cerdan S. , Subramanian V. Harihara , Hilberman M. , Cone J. , Egan J. , Chance B. , Williamson J. R. 
Published: March 2007

AbstractThe in vivo dog brain 31P NMR spectrum has a large peak in the phosphodiester region accounting for more than 35% of the total observable phosphorus metabolites. It is possible to reduce the intensity of this peak by off‐resonance saturation. To characterize the nature of this peak, extracts of dog brain frozen in situ were analyzed by high resolution 31P NMR. ATP, phosphocreatine, inorganic phosphate, and phosphomonoesters were recovered in appropriate amounts in the methanol: HCI extract. However, acid soluble phosphodiesters accounted for only 8% of the observable phosphorus. More NMR observable phosphodiesters were selectively recovered following CHCI3:methanol extraction of phospholipids. These results suggest that the in vivo phosphodiester resonance has substantial contributions from a fraction of mobile brain phospholipids. © 1986 Academic Press, Inc.
Optimum acquisition times of two spin echoes for MR image synthesis
Authors: Lee James N. , Riederer Stephen J. 
Published: March 2007

AbstractSpin‐echo images can be synthesized at arbitrary values of echo time TEs if two images are acquired at the same repetition time and two different echo times TEI and TE2. Depending on the value of TEs, the noise in the synthetic images can either be greater or less than the acquisition noise. This note shows that if the time between the acquired echoes TE2‐TE1 is equal to T2, the noise level in the synthetic images is no larger than the acquisition noise for TEs ⩾ TE1. This is the lowest possible noise bound for two‐echo acquisition. Also, the noise bound for images synthesized with O ⩽ TEs ⩽ TE1 is minimized by making TE1 as short as possible. © 1986 Academic Press, Inc.
Reproducibility of relaxation and spin‐density parameters in phantoms and the human brain measured by MR imaging at 1.5T
Authors: Breger Robert K. , Wehrli Felix W. , Charles H. Cecil , MacFall James R. , Haughton Victor M. 
Published: March 2007

AbstractThe reproducibility of T1, T2, and proton density, measured in phantoms and the human brain was evaluted by proton imaging techniques. The sequence used to derive T1 and density values was a multiple‐saturation recovery which consists of four pairs of 90° pules, followed by a 180° phase reversal pulse, generting four T2‐weighted images. The data were analyzed by fitting the pixel intensities to the respective equations by means of nonlinear multi‐parameter least‐squares analysis. Short‐term reproductibility between four consecutive scans was evaluted to b 1–40% depending on location with a covering the entire span of physiological T1 and T2 values. A second phantom containing a series of identiical samples served to study the depeendence of the apparment T1 and T2 on position, both radially and axially, with respect to magnet isocneter. Reproducibility across the field of view was found to be better than 7% (T1 and T2). This phantom was further used to evaluate effects of long‐term reproductibility, which at each location varied from 5–14% (T1) and 2–10% (T2). Finally, interinstrument reprducibilty, tested by means of the same protcol on three different insturments, all operating at the same magnetic field and using largely indentical hardware for each location, was found to be 1–14% (T1) and 2–10% (T2). The positional dependence of the apparent relaxation times appears to be systematic and may be due to variations in the effective field, caused by magnet and rf inhomogeneity. Finally, brain tissue relaxation and spin‐density data were determined using the same protocol in 37 scans performed on 27 normal volunteers. The tissues analyzed were putamen, thalamus, caudate nucleus, centrum semiovale, internal capsule, and corpus callosum. Excellent accordance was further obtained between left and right hemispheres. © 1986 Academic Press, Inc.
Currents and fields of thin conductors in rf saddle coils
Authors: Carlson J. W. 
Published: March 2007

AbstractThe current distribution on thin conductors and rf field homogeneity for rf coils is described theoretically. After a pedagogical introduction to the techniques and an exact solution for the current or an isolated strip conductor, this article describes current distribution and field uniformity for a variety of conventional and quadrature rf coil designs. © 1986 Academic Press, Inc.
Relaxation of water protons in the intra‐ and extracellular regions of blood containing Gd(DTPA)
Authors: Koenig Seymour H. , Spiller Marga , Brown Rodney D. , Wolf Gerald L. 
Published: March 2007

AbstractThe magnetic field dependence of the longitudinal relaxation rates 1/T1 (NMRD profiles) of blood and plasma from rabbits before and after injection of Gd(DTPA) are reported as a function of magnetic field strength from 0.01 to 50 MHz. Over 100 values along the time‐dependent magnetization were recorded for each 1/T1 and analyzed for multiple exponentials. From these data, which indicate a single exponential, from the measured Gd content of each sample, and the NMRD profiles, we show that Gd is in the extracellular space only and is present as rotationally mobile Gd(DTPA), uncomplexed with protein or blood cells; and that the water protons exchange rapidly between the intra‐ and extracellular regions. © 1986 Academic Press, Inc.
Surface‐coil T1 images
Authors: Hardy C. J. , Edelstein W. A. , Mueller O. M. 
Published: March 2007

AbstractA method for producing calculated T1 images with high signal‐to‐noise ratio and good spatial resolution using surface coils is presented. Separate transmit and receive rf coils with electronic decoupling are employed to insure uniform B1 excitation. The sensitivity profile of the receiver coil is normalized out of the image by the T1 calculation. T1 values determined by this method show close agreement with previously reported values. © 1986 Academic Press, Inc.
An evaluation of the effect of fasting on the exercise‐induced changes in pH and Pi/PCr from skeletal muscle
Authors: Lunt J. A. , Allen P. S. , Brauer M. , Swinamer D. , Treiber E. O. , Belcastro A. , Eccles R. , King E. G. 
Published: March 2007

AbstractThe changes in the response of skeletal muscle to maximal dynamic exercise were investigated in going from a fasted state to a refed state by means of 31P NMR spectroscopy. It was found that in the fasted state, exercise‐induced changes in Pi/PCr and in pH were both inhibited, in comparison with those in the refed state. © 1986 Academic Press, Inc.
Effects of calcium antagonists on high‐energy phosphates in ischemic rat brain measured by 31P NMR spectroscopy
Authors: Sauter André , Rudin Markus 
Published: March 2007

AbstractThe effects of various calcium antagonists on the ATP, PCr, and Pi levels as well as intracellular pH in normal and ischemic rat brain were examined by 31P NMR spectroscopy using a surface coil. None of the calcium antagonists tested showed any effect in the nonischemic rat brain. However, when global ischemia was induced by cardiac arrest, the ensuring rapid decrease of ATP and PCr and concomitant increase of pi were significantly retarded by dihydropyridine calcium antagonists, but not by verapamil. The fall in pH caused by ischemia was not affected by either drug. Barbiturates showed effects similar to calcium antagonists, whereas calcium agonists showed the opposite. These results suggest that dihydropyridine calcium antagonists, similar to barbiturates, decrease the high‐energy phosphate consumption of the brain, which might be beneficial in instances where their production is severely hampered, e.g., during ischemia. © 1987 Academic Press, Inc.
Localized magnetic resonance imaging with oscillating gradients
Authors: Feig Ephraim 
Published: March 2007

AbstractHinshaw's sensitive‐point method and Macovski's post‐filtering localization techniques are analyzed under very general imaging conditions. It is shown that one can obtain an expression for the FID signal induced by all resonating particles at any particular point in the imaged object. Contributors to the signal may have different relaxation behaviors, spin rates, and velocity components. In fact, in the case of flows, different nuclei contribute to the signal at different times during the observation. Localization enables us to impose local assumptions on our model rather than global ones, as is usually done in MRI. Applications to imaging slow and fast flows and in vivo spectroscopy are discussed. © 1987 Academic Press, Inc.