bluuebunny/crossref_metadata_2025_split huggingface dataset:
In vivo determination of body iron stores by natural‐abundance deuterium magnetic resonance spectroscopy
Authors: Irving Michael G. , Brereton Ian M. , Field James , Doddrell David M. 
Published: March 2007

AbstractInduction of iron overload in mice using 1% (w/w) dietary carbonyl iron resulted in marked decreases in 2H and 31P NMR relaxation times. Natural‐abundance deuterium (2H) NMR spectroscopy has been used to measure 2H T1 values in vivo in the presence of body paramagnetic iron. This procedure offers a method for noninvasive determination of body iron stores. © 1987 Academic Press, Inc.
Pseudo‐gating: Elimination of periodic motion artifacts in magnetic resonance imaging without gating
Authors: Haacke E. Mark , Lenz Gerald W. , Nelson A. Dennis 
Published: March 2007

AbstractThis note explains and illustrates a technique of reducing artifacts produced by periodic motion without using physiologic gating. The method is simple and can be applied on any standard MRI unit. For periodic motion, effective gating can be attained by setting the product of the number of acquisitions (at each phase‐encoding step), N, times the repeat time, TR, equal to the period of the motion, T. This pseudo‐gating can be used with any TR but, if changes in the period occur, is most robust with short TR values. The method is also applicable to multislice and volume imaging. For fast field echo methods, the above rule can be used if the period of the motion is smaller than the total scan time. Otherwise, the scan need only be repeated N times to avoid artifacts and improve signal‐to‐noise. The method has been implemented to remove both respiratory and/or cardiac motion artifacts. © 1987 Academic Press, Inc.
Oxygen‐17 compounds as potential NMR T2 contrast agents: Enrichment effects of H217O on protein solutions and living tissues
Authors: Hopkins A. L. , Barr R. G. 
Published: March 2007

AbstractThe isotopic enrichment of solutions, living tissues, and organisms with oxygen‐17 in the form of H217O shortens their proton NMR transverse relaxation times (T2) and produces changes in NMR image intensity. The transverse relaxation rate (1/T2) was found to be linearly dependent on the H217O concentration in biological solutions up to 5% enrichment. The longitudinal relaxation time (T1) is not affected by enrichment. Equal concentrations of H217O do not produce the same magnitude of T1 change in all physiological environments. The reasons for these differences are discussed. The results suggest that certain oxygen‐17 compounds should be explored as “contrast agents” in magnetic resonance imaging. © 1987 Academic Press, Inc.
The effects of a static magnetic field on DNA synthesis and survival of mammalian cells irradiated with fast neutrons
Authors: Ngo Frank Q. H. , Blue James W. , Roberts William K. 
Published: March 2007

AbstractThe effects of a static magnetic field (0.75 T) on DNA synthesis and survival were examined with Chinese hamster V79 cells in cultures with and without fast‐neutron irradiation. We found that the magnetic field applied alone for up to several hours did not cause a significant effect in either the rate of DNA synthesis or cell viability; the latter was assayed by colony formation. When cells were exposed simultaneously to the magnetic field and fast neutrons, the effects resembled those observed with neutrons alone. This was the case for both inhibition of DNA synthesis and cell killing. Cells irradiated first with neutrons followed immediately by 1 h of magnetic field exposure showed a dose‐survival response curve indistinguishable from that of neutrons alone. These data suggest that the biological effect due to the magnetic field is negligible and that the presence of the magnetic field either during or subsequent to fast‐neutron irradiation does not affect the neutron‐induced radiation damage or its repair. © 1987 Academic Press, Inc.
Natural abundance 13C NMR spectrum of glycogen in humans
Authors: Jue T. , Lohman J. A. B. , Ordidge R. J. , Shulman R. G. 
Published: March 2007

AbstractIn vivo NMR has focused on using 31P and 1H to study metabolism in humans. Comparable 31C NMR studies have not been undertaken, presumably, because of its insensitivity. We report herein that the natural abundance 13C signal from C1 glycogen is observable. The ability to observe the signal opens new opportunities to noninvasively study glycogen metabolism in man. © 1987 Academic Press, Inc.
NMR relaxation times T1 and T2 of water in plasma from patients with lung carcinoma: Correlation of T2 with blood sedimentation rate
Authors: Schuhmacher Jochen H. , Clorius John H. , Semmler Wolfhard , Hauser Harald , Matys Edmund R. , Maier‐Borst Wolfgang , Hull William E. 
Published: March 2007

AbstractThe T1 and T2 NMR relaxation times of water protons in plasma, obtained from patients with lung carcinoma, healthy volunteers, and patients with nontumor diseases were measured at a resonance frequency of 20 MHz. Additionally hematologic parameters were determined. In tumor patients the mean plasma T2 was shortened by about 20%, and an increase in the blood sedimentation rate (BSR) was noted. Similar but less pronounced results were found for the nontumor group of patients, indicating that the shortening of T2 in plasma is a secondary host response. However, a plot of plasma 1/T2 versus BSR from tumor patients showed a significant correlation between these two parameters. No such correlation could be detected in the nontumor group of patients. The correlation of 1/T2 with BSR, found solely in the tumor patient group, increased the diagnostic sensitivity of T2 measurements and may help to differentiate between malignant and nonmalignant disease. No significant variation in the T1 spin‐lattice relaxation time was observed. © Academic Press, Inc.
Some observations of the design of rf coils for human internal use
Authors: Harman R. R. , Butson P. C. , Hall A. S. , Young I. R. , Bydder G. M. 
Published: March 2007

AbstractSome features of the design and implementation of NMR probes for insertion into peripheral orifices of the body are described. In particular, the possibilities of using parasitic coils without direct connections in conjunction with conventional whole body coils are examined. The use of windings around the NMR probe carrying gradient pulses as a means of eliminating the very high signals from tissue immediately adjacent to the coil windings is also evaluated. These approaches are, in practice, difficult to combine, and hence need to be viewed almost as alternative possibilities. Practical results of experimental investigations are presented using both phantoms and volunteers. © 1988 Academic Press, Inc.
Fast MRI data acquisition using multiple detectors
Authors: Hutchinson Michael , Raff Ulrich 
Published: March 2007

AbstractWe present a novel imaging procedure using multiple receiver coils. This circumvents the sequential acquisition of signals required by conventional imaging strategies. The advantage of this technique over existing subsecond imaging techniques is that (a) contrast can be maintained and (b) there is no magnetic field gradient switching involved. © 1988 Academic Press, Inc.
The noninvasive determination of linoleic acid content of human adipose tissue by natural abundance carbon‐13 nuclear magnetic resonance
Authors: Moonen Chrit T. W. , Dimand Robert J. , Cox Kenneth L. 
Published: March 2007

AbstractA new method to assess noninvasively the proportionate storage of poly‐ and mono‐unsaturated fatty acids in human adipose tissue is described. The method is based on in vivo natural abundance 13C NMR at 1.9 T using a TMR 32/200. Data were acquired with a concentric coil system placed below subcutaneous adipose tissue of the calf or the lower arm. Continuous single‐frequency decoupling was used to optimize the signal in the spectral region of interest and minimize potential heating effects. Only adipose triglycerides contributed significantly to the resonance intensities. Typical linewidths for the in vivo13C resonances were 10‐14 Hz resulting in excellent resolution in the region of the unsaturated carbons. Signal‐to‐noise ratios for the resonance at 128.4 ppm (due to carbon atoms of polyunsaturated fatty acids) were typically 50‐90 in 8 min using 0.25s repetition time. The relative storage of polyunsaturated fatty acids was determined by comparing the peak intensity at 128.4 ppm with the intensities of the peaks due to the carbonyl, the glycerol, or the main methyl carbons. High‐resolution in vitro NMR of adipose biopsies and various mixtures of triglycerides studied with the in vivo NMR protocols provided further evidence that the described in vivo NMR methods allowed precise information on the relative storage of linoleic acid, the main constituent of the pool of polyunsaturated fatty acids. Conventional gas chromatography was performed on adipose biopsies of two volunteers and resulted in close agreement with the in vivo NMR methods. The average polyunsaturated fatty acid concentration in adipose tissue in seven healthy volunteers was 19.83 mol% ± 1.74 (SD) as determined by in vivo NMR, consistent with conventional studies based on gas chromatography of biopsied material. Preliminary data on three cystic fibrosis patients showed a decreased polyunsaturated fatty acid concentration of 13.12 mol% ± 2.73 (SD). The high accuracy of this method and its noninvasive character should be especially valuable in clinical research and diagnosis as repetitive adipose biopsies can be avoided. © 1988 Academic Press, Inc.
Dynamic range compression in MRI by means of a nonlinear gradient pulse
Authors: Wedeen Van J. , Chao Yong‐Sheng , Ackerman Jerome L. 
Published: March 2007

AbstractIn current magnetic resonance imaging (MRI), valuable information must often be discarded because the NMR signal has greater dynamic range than the analog‐to‐digital converter (ADC) hardware. Typically, a small set of high‐intensity data points near the center of the spin echo is responsible for most of the MRI data dynamic range. We predict that it is possible to reduce the dynamic range of the MRI spin echo by incorporating an identical nonlinear gradient pulse into each repetition of the imaging pulse sequence, prior to data sampling. This pulse converts the phase distribution of the subject, ordinarily a linear function of image coordinates, into a nonlinear function. A nonlinear phase distribution can have a negligible impact on image magnitude and yet a profound impact on spin‐echo magnitude. Given a nonlinear phase distribution, there will no longer be a single data point at which all of the protons have an identical phase (the echo center). Instead, the protons become phase coherent on a piecemeal basis, the echo peak is smoothed out, and its maximum amplitude and dynamic range are greatly diminished. Using gradient pulses of quadratic spatial variation, we estimate that maximum echo amplitude and dynamic range can be reduced in most cases by an order of magnitude. © 1988 Academic Press, Inc.
Localized double‐quantum filter and correlation spectroscopy experiments
Authors: McKinnon G. C. , Bosiger P. 
Published: March 2007

AbstractProblems with in vivo proton spectroscopy include strong water and lipid signals, and the very complicated structures of the spectra. Multiple‐quantum experiments can be designed to overcome these difficulties. Using a volume selective refocusing technique, one can demonstrate how multiple‐quantum experiments can be performed in a spatially localized manner. Rather than trying to integrate a localization procedure into a particular spectroscopy experiment itself, the approach here is to leave the basic experiment intact and to add a volume selective “block” to the end of the sequence. This “block” must, of course, preserve the integrity of the particular experiment. The volume selective refocusing method, presented here, does just this for a wide variety of proton NMR experiments. The advantage of this approach is that the analysis of the particular experiment is not changed. This is very important considering the complexity involved. Using this procedure, two very elementary multiple‐quantum experiments have been performed on a 1.5‐T whole‐body scanner. These experiments are a localized double‐quantum filter experiment (for water suppression) and a localized two‐dimensional correlation spectroscopy experiment. © 1988 Academic Press, Inc.
Magnetic resonance imaging of rabbit brain after intracarotid injection of large multivesicular liposomes containing paramagnetic metals and DTPA
Authors: Turski Patrick , Kalinke Tom , Strother Lars , Perman William , Scott Grayson , Kornguth Steven 
Published: March 2007

AbstractA procedure has been developed for the preparation of large (10‐ to 80‐μm‐diameter) multivesicular liposomes that contain magnetic resonance contrast agent (DTPA and either manganese or gadolinium). Blue dextran was observed to induce the formation of the large liposomes with dioleoylphosphatidylcholine and cholesterol (1:1 molar ratio) and with dipalmitoylphosphatidylcholine and cholesterol (1:1 molar ratio). The formation of the large liposomes is dependent upon mixing the blue dextran with the lipid films at temperatures above the transition point of the lipids. Tracer amounts of 153Gd were added to the aqueous phase to permit quantitation of the recovery of encapsulated materials. Liposomes that were prepared using equimolar ratios of phospholipid and cholesterol were stable in serum for more than 12 h. The ultrastructure of the large multivesicular liposomes reveals the existence of individual vesicles (12 μm diameter) bound together by a multi‐lamellar coating. When injected into the internal carotid artery of the rabbit, the large liposomes became entrapped in the vascular bed primarily in the frontal and occipital regions of brain. The resulting emboli may provide a means to deliver drugs to a specific site in brain, such as a tumor, if the vascular bed of the site can be cannulated precisely. © 1988 Academic Press, Inc.
Simultaneous monitoring of coronary blood flow and 31P NMR detected myocardial metabolites
Authors: Portman Michael A. , James Susan , Heineman F. W. , Balaban Robert S. 
Published: March 2007

AbstractWe report a method of dynamically measuring coronary blood flow in lambs, while simultaneously monitoring cardiac phosphate metabolism with 31P NMR at 81 MHz. This method uses an ultrasonic transit time probe in conjunction with a 4.7‐T CSI spectrometer with a 33‐cm magnet bore. © 1988 Academic Press, Inc.
Fast gradient‐echo chemical‐shift imaging
Authors: Park H. W. , Kim Y. H. , Cho Z. H. 
Published: March 2007

AbstractA fast chemical‐shift imaging using the gradient‐echo technique is proposed for the separation of the water and fat in human in vivo imaging. This technique also incorporates magnetic field inhomogeneity correction in the fast chemical‐shift imaging. Experimental results of the proposed imaging technique demonstrate that the method would be useful for quick in vivo water‐fat separation imaging with a substantially shorter time than the conventional spin‐echo imaging sequence. © 1988 Academic Press, Inc.
Fast SSFP gradient echo sequence for simultaneous acquisitions of FID and echo signals
Authors: Lee S. Y. , Cho Z. H. 
Published: March 2007

AbstractRecently, the gradient echo imaging sequence in conjunction with small flip angle excitations and short repetition times has been widely used for fast NMR imaging. As the repetition time decreases to an extent comparable to the spin‐spin relaxation time T2, the residual phase coherency of the transverse spin magnetization tends to form another nuclear signal which is heavily weighted by T2 and similar to a long TR/long TE spin‐echo signal. This effect, although expected, has not been utilized in the conventional fast gradient echo imaging. When this residual phase coherency is utilized in conjunction with the fast SSFT (steady‐state free precession) technique, both the FID and the echo signals can be obtained. In this paper, we have proposed a new technique by which simultaneous acquisitions of both the H D and the echo signals are possible. Experiments on this fast SSFP mode imaging have shown that the FTD signal is TI‐weighted while the echo signal is strongly T2‐weighted. The flip angle optimal for maximizing signal and related contrast are also studied in conjunction with the proposed sequence and the experimental results are presented. © 1988 Academic Press, Inc.
Delivery of nitroxide spin label to cultured cells by liposomes
Authors: Chan H. C. , Magin R. L. , Swartz H. M. 
Published: March 2007

AbstractThe positively charged nitroxide spin label, 2,2,6,6‐tetramethyl‐piperidine‐N‐oxyl‐4‐ trimethylammonium (Cat1), was encapsulated in two types of liposomes, phosphatidylserine/phosphatidylcholine (PS/PC) and phosphatidylserine/distearoylphosphatidylcholine/dipalmitoylphosphatidylcholine (PS/DSPC/DPPC). The liposomes were incubated with mouse thymus‐bone marrow (TB) cells to study the uptake and metabolism of nitroxides entrapped in Iiposomes. The effects of temperature, metabolic inhibitors, and fixation of cells were investigated. The results indicate that different mechanisms are involved in the uptake of these two types of liposomes. PS/PC liposomes interact predominately with the plasma membrane of TB cells and release Cat1 continuously, whereas the majority of PS/DSPC/DPPC liposomes are taken into the cells intact via endocytosis. These findings suggest that it may be possible to deliver nitroxides selectively, either to the membrane of cells or to their interior by manipulating the lipid com‐ position of the liposomes. This study also found that the rate of reduction of Cat 1 delivered using liposomes was increased under hypoxic conditions. Thus, the use of liposomes for in vivo delivery of nitroxides has the potential to provide NMR contrast that reflects different metabolic conditions. © 1988 Academic Press, Inc.
A general approach to selection of multiple cubic volume elements using the ISIS technique
Authors: Ordidge R. J. , Bowley R. M. , McHale G. 
Published: March 2007

AbstractThe ISIS method is used regularly for the selection of a single cubic volume of tissue for in vivo investigation by high‐resolution NMR spectroscopy. This technique has been extended on a theoretical basis to include the simultaneous selection of a number of cubes, the signals from which can be either assessed individually or in certain circumstances coadded to produce improvement in signal‐to‐noise ratio. The modification requires additional selective RF pulses in the spatial encoding prepulse period, and spatially localized spectra are produced by addition and subtraction of NMR signals in a manner similar to the original ISIS technique. © 1988 Academic Press, Inc.
Acute and repair stage characteristics of magnetic resonance relaxation times in oxygen‐induced pulmonary edema
Authors: Shioya Sumie , Haida Munetaka , Tsuji Chizuko , Ohta Yasuyo , Yamabayashi Hajime , Fukuzaki Minoru , Kimula Yuji 
Published: March 2007

AbstractProton magnetic relaxation times, T1, and T2, were determined for rat lungs exposed to 80% oxygen for a duration of 2 weeks. The transverse magnetization decay curve of the lung tissue was multiexponential. A linear combination of two decay curves with different T2 values fits the multiexponential decay suggesting that there are at least two different components of tissue water in the lung. Remarkable prolongation of T1 and T2 was demonstrated as lung injuries progressed in the acute stage of pulmonary edema. Both 1/T1, and 1/T2 were significantly correlated with 1/water content of the lung tissue. In the repair stage, T1, and T2 were significantly shortened. Shortening coincided with the spontaneous resolution of pulmonary edema. Relaxation rates showed no significant correlation with 1/water content in this stage. These results indicate that the physical state ofwater in the tissue is affected not only by the water content but also by the derange‐ ment of macromolecules in pulmonary edema. T2, was more sensitive than T1 for detecting pulmonary damage. © 1988 Academic Press, Inc.
Spectroscopic imaging and spatial localization using adiabatic pulses and applications to detect transmural metabolite distribution in the canine heart
Authors: Robitaille Pierre‐Marie , Merkle Hellmut , Hendrich Kristy , Sublett Eugene , Lew Brian , Path Gregory , From Arthur H. L. , Bache Robert J. , Garwood Michael , Uǧubil Kâmil 
Published: March 2007

AbstractAdiabatic pulses have been employed in spectroscopic imaging and relaxation rate measurements at 4.7 T to demonstrate the feasibility of obtaining spectroscopic data from the complete sensitive volume of a surface coil using the surface coil as a transmitter and receiver. With conventional B1 sensitive pulses, spectroscopic localization or imaging techniques, such as chemical‐shift imaging, yield resonance intensities that are distorted severely as a function of space, and maximal signal is detected from a small region within the complete sensitive volume of the coil. With adiabatic pulses, however, this problem is eliminated completely. In addition, a new method of spatial localization is introduced. This method, referred to as FLAX‐ISIS, is a derivative of longitudinally modulated Fourier series window and ISIS approaches and utilizes adiabatic inversion and excitation pulses. The method allows construction of localized spectra for multiple regions along the surface coil axis by postacquisition data manipulation of a single set of free induction decays. These techniques were applied to the study of the myocardium using an implanted surface coil in an instrumented closed‐chest canine model and in an open‐chest preparation. The results demonstrate that one‐dimensional techniques are adequate for transmural detection of metabolites provided signal origin is restricted to a column perpendicular to the left ventricle wall. © 1989 Academic Press, Inc.
Transmural metabolite distribution in regional myocardial ischemia as studied with 31p NMR
Authors: Robitaille Pierre‐Marie , Lew Brian , Merkle Hellmut , Sublett Eugene , Lindstrom Paul , From Arthur H. L. , Garwood Michael , Bache Robert J. , Uǧubil Kâmil 
Published: March 2007

AbstractPhosphorus‐31 nuclear magnetic resonance (31P NMR) has been applied to study the canine heart prior to and during regional myocardial ischemia induced by partial flow reduction in the left anterior descending coronary artery (LAD). NMR data were acquired in a transmural fashion by restricting the signal to a column perpendicular to the heart wall using B0 gradients and obtaining spectroscopic spatial resolution along the third dimension using the B1 gradient and adiabatic excitation. With this approach, transmural spectra were accumulated in five separate voxels spanning the wall of the left ventricle from the epicardium to the endocardium. In the normal canine myocardium the levels of high‐energy phosphates CP and ATP were relatively constant throughout the left ventricular wall, with only minor evidence of free inorganic phosphate in any of the transmural voxels. However, during sustained partial occlusion of the LAD, significant regional differences between the epi‐ and the endocardium were noted. The data demonstrate the importance of studying cardiac bioenergetics with transmural differentiation. © 1989 Academic Press, Inc.