bluuebunny/crossref_metadata_2025_split huggingface dataset:
31P nuclear magnetic resonance study of acute renal dysfunction in rat kidney transplants
Authors: Shapiro J. I. , Haug C. E. , Weil R. , Chan L. 
Published: March 2007

Abstract31NMR spectroscopy was used to study renal allografts in rats subjected to allograft rejection, cyclosporine toxicity, ischemia, and ureteral obstruction. Parameters of relative peak areas and intracellular pH were accurately distinguished among the different causes of graft dysfunction. Ureteral obstruction was clearly identified by elevations in the phosphodiester/urine phosphate peak. Ischemia and rejection were. both associated with increases in inorganic phosphates and phosphomonesters and decreases in the β‐phosphate peak of adenosine triphosphate but were distinguishable from each other by differences in intracellular pH which was normal in rejected allografts (7.33 ± 0.07, n = 3) but low in ischemic allografts (7.00 ± 0.05, n = 3, P < 0.05). Grafts insulted with cyclosporine toxicity were not distinguishable from normal allografts by any of the parameters studied. These data suggest that 31P NMR spectroscopy may have potential clinical application in differentiating among the causes of graft failure of human rend allografts. © 1987 Academic Press, Inc.
Selective fourier transform localization
Authors: Brooker H. Ralph , Mareci Thomas H. , Mao Jintong 
Published: March 2007

AbstractWe have introduced the selective Fourier transform technique for spectral localization. This technique allows the acquisition of a high‐resolution spectrum from a selectable location with control over the shape and size of the spatial response function. The shape and size of the spatial response are defined during data acquisition and the location is selectable through processing after the data acquisition is complete. The technique uses pulsed‐field‐gradient phase encoding to define the spatial coordinates. In this paper the theoretical basis of the selective Fourier transform technique is developed and experimental results are presented, including comparisons of spectral localization using either the selective Fourier transform method or conventional multidimensional Fourier transform chemical‐shift imaging. © Academic Press, Inc.
Errors in spin–lattice relaxation time measurements from restricted volumes
Authors: Morrone Terry 
Published: March 2007

AbstractIn vivo T1 measurements are usually made from images. In this paper we describe an alternative method in which data are collected from a strip instead of from an entire plane. We will compare the signal‐to‐noise ratios, the time to make a measurement, and the error in T1 as well as other aspects of the two methods. We have found that the strip method has less inherent signal‐to‐noise, but that this may be compensated for by taking measurements at more than the usual two repetition rates. The method employs a selective 180° pulse as well as a selective 90° pulse. It is shown that both pulses effectively isolate the region of interest. © Academic Press, Inc.
New reconstruction technique for echo‐planar imaging to allow combined use of odd and even numbered echoes
Authors: Sekihara Kensuke , Kohno Hideki 
Published: March 2007

AbstractAn image reconstruction technique for echo‐planar imaging is proposed. This technique combines odd and even numbered echo signals. It is thus possible to reduce the frequency of the time‐modulated gradient used in echo‐planar imaging by 5070, and to reduce its amplitude by almost 50% for sinusoidal gradient modulation. © Academic Press, Inc.
Experimental acute pancreatitis: MR relaxation time studies using gadolinium–DTPA
Authors: Paajanen Hannu , Brasch Robert C. , Dean Peter B. 
Published: March 2007

AbstractSpin–lattice (T1) and spin–spin (T2) relaxation times of normal and sodium taurocholate‐induced pancreatitis (38 rats) were determined in vitro using a 10.7‐MHz magnetic resonance (MR) spectrometer. The increase in pancreatic T1 time in acute hemorrhagic pancreatitis correlated well with the elevated water content of the organ. Gadolinium–DTPA did not affect significantly the relaxation times of normal pancreas in vitro during 1 to 20 min postinjection, but it decreased the elevated TI times of inflamed pancreas almost to baseline values. MR imaging studies of rat pancreas in vivo (8 rats, 0.35‐T resistive magnet) indicated that the swollen pancreas and associated edema were depicted using a T2‐weighted SE sequence. Fifteen minutes postinjection of gadolinium–DTPA a homogeneous enhancement of inflamed pancreas was detected. The differentiation of pancreatic necrotic foci from surrounding viable tissue and edema could not be detected on Gd–DTPA‐enhanced MR images after 15 min postinjection although microscopical workup indicated these different tissue constituents in the pancreas. © 1988 Academic Press, Inc.
Quantitation of acidosis in neonatal brain tissue using the 31P NMR resonance peak of phosphoethanolamine
Authors: Corbett Ronald J. T. , Laptook Abbot R. , Hassan A. , Nunnally R. L. 
Published: March 2007

Abstract31P NMR brain spectra were obtained from piglets over a range of mild hypocarbia to severe hypercarbia (PaCO2 25 to 198 mm Hg). The chemical shifts of the phosphoethanolamine and inorganic phosphate were used to calculate intracellular brain pH (pHet and pHpi, respectively). Both pHpi and pHet underwent parallel significant decreases during hypercarbia, corresponding to 51 and 53% pHregulation, respectively. We conclude that the chemical shift of the phosphomonoester peak in vivo can be used to measure decreases in intracellular pH in neonatal brain. © 1988 Academic Press, Inc.
Enhanced proton magnetic resonance imaging of experimental mammary tumors
Authors: Block Ronald E. , Parekh Barbara C. 
Published: March 2007

AbstractThe proton magnetic resonance imaging contrast of experimental mammary tumors in rats has been dramatically improved. The technique developed combines T2 weighting and chemical‐shift imaging in order to suppress the thoracic wall, muscle, and subcutaneous fat contributions to the image. The technique is demonstrated using the R3230AC mammary adenocarcinoma in F344 rats at 4.7 T. © 1988 Academic Press, Inc.
Dynamic imaging with lanthanide chelates in normal brain: Contrast due to magnetic susceptibility effects
Authors: Villringer Arno , Rosen Bruce R. , Belliveau John W. , Ackerman Jerome L. , Lauffer Randall B. , Buxton Richard B. , Chao Yong‐Sheng , Wedeenand Van J. , Brady Thomas J. 
Published: March 2007

AbstractUsing a one‐dimensional rapid imaging technique, we have found that injection of lanthanide chelates such as Gd(DTPA)2− leads to a significant decrease (50%) in rat brain signal intensity at 1.45 T using T2‐weighted pulse sequences; however, no effect of comparable size is observed with T1‐weighted pulse sequences. The transient effect and its kinetics were followed with a temporal resolution of between 1 and 8 s. Experiments with different lanthanide chelates show that the observed decrease in signal intensity correlates with the magnetic moment of each agent but not with their longitudinal relaxivity. Three‐dimensional chemical‐shift resolved experiments demonstrate significant line broadening in brain during infusion with Dy(DTPA)2− Our results show that the cause of this effect is the difference in susceptibility between the capillaries, containing the contrast agent, and the surrounding tissue. As a result of these susceptibility differences, field gradients are produced in the tissue and diffusion of water through these gradients leads to a loss of spin phase coherence and thus a decrease in signal intensity. We propose this as a new type of contrast agent mechanism in NMR. The effect and its kinetics are likely to be related to important physiological parameters such as cerebral blood volume and cerebral blood flow, and do not depend on a breakdown of the blood‐brain barrier as do conventional contrast agent techniques. © 1988 Academic Press, Inc.
Postnatal NMR changes in guinea pig central nervous system: Potential relevance to experimental allergic encephalomyelitis
Authors: Noseworthy J. H. , Gilbert J. J. , Vandervoort M. K. , Karlik S. J. 
Published: March 2007

AbstractThe age of sensitization determines the clinical course of experimental allergic encephalomyelitis (EAE) in the guinea pig. Adult animals immunized with central nervous system (CNS) tissue develop acute, fulminant EAE, whereas a relapsing‐remitting illness resembling multiple sclerosis occurs if sensitization occurs in the first 2 weeks of life. This study characterized the changes in the proton nuclear magnetic resonance (NMR) relaxometry and imaging of the CNS during the immediate postnatal period. T1 and T2 relaxation times in cerebral hemispheres and spinal cords of strain 13 guinea pigs were consistently prolonged at birth, progressively shortened in the first few weeks of life, and achieved adult levels by age 6 to 11 weeks. There were no age‐dependent differences in T1 and T2 relaxation times and tissue specific gravity in either strain 13 or Hartley guinea pigs following immunization with complete Freund's adjuvant, an agent previously reported to disrupt the blood‐brain barrier to IgG and albumin in strain 13 guinea pigs. The CNS of neonatal guinea pigs appeared well myelinated by light microscopy and there was no apparent difference in the extent of myelination between newborn and adult animals. Although it was possible to distinguish gray from white matter in the cervical spinal cord of newborn guinea pigs by magnetic resonance imaging (MRI) techniques, gray/white contrast was less satisfactory in the cerebral hemispheres until approximately 6 weeks of life when it was possible to differentiate gray matter, white matter, and cerebrospinal fluid. This study indicates that NMR relaxation times change during early postnatal life, at a time corresponding to the unexplained differences in susceptibility to an immune challenge. These developmental changes appear to be independent of the degree of CNS myelination. © 1988 Academic Press, Inc.
Spin‐echo 1H NMR detected response of ergothioneine to oxidative stress in the intact human erythrocyte
Authors: Reglinski J. , Smith W. E. , Sturrock R. D. 
Published: March 2007

AbstractHuman erythrocytes were subjected to oxidative stress using arsenicals. The study is a model for thiol‐related redox processes observed in the etiology of diseases such as rheumatoid arthritis. Spin‐echo NMR spectroscopy of the living cell was used to monitor the cellular biochemistry. Oxidation of glutathione and the first demonstrated response of ergothioneine to a chemical stimulus in a cell were observed. The reversible nature of the ergothioneine response is interpreted as an environmental rather than a chemical change. © 1988 Academic Press, Inc.
Simultaneous image acquisition from the Head (or body) coil and a surface coil
Authors: Hyde James S. , Froncisz W. , Jesmanowicz A. , Kneeland J. B. 
Published: March 2007

AbstractAny number of coils can in principle be used simultaneously and independently in magnetic resonance imaging if the mutual inductances are sufficiently small. Surface coils and head or body coils have equal sensitivity at some crossover depth of the order of 6 to 10 cm. Using a 7.5‐cm‐diameter surface coil that was intrinsically isolated from the head coil, images were acquired simultaneously from both coils and combined to improve the signal‐to‐noise ratio at 6 cm depth by 21/2. A similar experiment with the body coil showed 21/2 improvement at about 8 cm depth. © 1988 Academic Press, Inc.
Doubly tuned local coils for MRI and MRS at 1.5 T
Authors: Grist Thomas M. , Jesmanowicz A. , Kneeland J. Bruce , Froncisz W. , Hyde James S. 
Published: March 2007

AbstractWe describe a doubly tuned radiofrequency (RF) local coil probe designed specifically for performing in vivo image‐localized spectroscopy. The probe was designed using principles developed in connection with the counter‐rotating‐current (CRC) and planar‐pair loop gap resonators for magnetic resonance imaging (MRI). The probe design satisfies several criteria useful for in vivo 1H/31P experiments at 1.5 T. First, sensitivity on the low‐frequency mode is preserved relative to a singly tuned coil. This result was confirmed by bench‐test and in vitro MR experimental data. Second, through principles of intrinsic decoupling the probe is isolated from any externally applied uniform excitation field, which is desirable for in vivo 1H imaging and solvent suppression. Third, the regions of sensitivity of the high‐ and low‐frequency modes of the coil are similar, and therefore spectroscopic volumes of interest identified on an image will reflect the same volumes as those selected during spectroscopy. Finally, interface to the MR system is such that the high‐ or low‐frequency circuits may be selected entirely under software control, with no requirement for changing coils or cables or moving the subject. © 1988 Academic Press, Inc.
Parallel‐plate split‐conductor surface coil: Analysis and design
Authors: Gonord P. , Kan S. , Leroy‐Willig A. 
Published: March 2007

AbstractA split‐conductor circular parallel‐plate resonator with one end shorted to ground can be used to one's advantage as a surface coil for NMR imaging experiments. It can be easily constructed by a printed‐circuit method and possesses a relatively high loaded Q with negligible frequency detuning. From the proposed equivalent circuit, an equation was derived that relates the self‐resonance frequency of the resonator to the split distance measured from a reference point. An example of a 101‐mm‐diameter surface coil operating at 26 MHz for 34P in vivo spectroscopy is given to illustrate the concordance between calculated and experimental results. Complementary equations and formulas are also included to assist researchers in designing their own antennas to meet specific requirements. © 1988 Academic Press, Inc.
Quantitation of phosphate metabolites in human leg in vivo
Authors: Venkatasubramanian P. N. , Mafee M. F. , Bárány M. 
Published: March 2007

AbstractSlice‐selective 31P MR spectra were recorded from human legs with a pulse program which has only a 1.5‐ms delay between excitation and acquisition. The volume of the slice was calculated from its thickness and cross‐sectional area measured with the aid of a computer program. A phosphate reference standard spectrum was recorded from the Same interplanar location as that of the human leg slice. Since signal integral is proportional to the phosphate concentration and to the volume of the slice, metabolite concentrations in the selected slice could be quantitated. © 1988 Academic Press, Inc.
Comparison of intracellular pH measurements by 31P NMR and weak acid partitioning in Chinese hamster ovary fibroblasts
Authors: Gonzälez‐Méndez Ricardo , Hahn George M. , Wade‐Jardetzky Norma G. , Jardetzky Oleg 
Published: March 2007

AbstractIntracellular pH measurements obtained by 31P NMR and DMO partitioning are compared. A continuous‐flow culture system was used to measure the intracellular pH of Chinese hamster ovary fibroblasts in response to changes in the extracellular pH. These measurements were repeated with the CHO cells in suspension and under similar experimental conditions using the weak acid partitioning technique employing 14C‐DMO. It is shown that the pHi values are identical, within experimental error, for both techniques in the 6.80–7.70 pH range, with the DMO technique giving slightly more acidic intracellular pH in the 6.00–6.80 range. It is concluded that both techniques give similar values for intracellular pH in the physiological range, with the DMO partitioning giving more acidic values at pH's less than 6.80. The range of validity for pHi measurements using 31P NMR lies between 6.70 and 7.50. © 1988 Academic Press, Inc.
An experimental approach to 31P spin–lattice relaxation time measurement in biological systems
Authors: Seo Yoshiteru , Murakami Masataka , Suzuki Eiji , Maeda Munehiko , Watari Hiroshi 
Published: March 2007

AbstractThe accuracy of measurement of the spin‐lattice relaxation time (T1) in biological systems using the variable nutation angle method is discussed using computer simulations. This method could reduce the time required for measurement to 10% of that using the inversion recovery method. In the perfused salivary gland of the rat (310 K), the T1 values of sugar phosphates, creatine phosphate, γ‐phosphate, and β‐phosphate of nucleotide triphosphates determined by this method were 5.2, 4.8, 0.9, and 0.8 s, respectively. During secretion of saliva, the T1 value of sugar phosphates decreased to 3.7 s, which could be due to an increased chemical exchange of phosphate in glycolysis. © 1988 Academic Press, Inc.
Projective Fourier angiography
Authors: Norris David G. , Jones Richard A. , Hutchison James M. S. 
Published: March 2007

AbstractThe Fourier imaging of flow is discussed, and the limitations of imaging time, spatial and velocity resolution, imposed on this technique when applied in conjunction with ECG synchronization are examined. It is argued that this method is best used in projective format, and in vivo examples are presented. The relative velocity spectrum obtained is largely system independent, and quantification of velocity is implicit in the Fourier technique. © 1988 Academic Press, Inc.
A simple method for processing NMR spectra in which acquisition is delayed: Applications to in vivo localized 31P NMR spectra acquired using the DRESS technique
Authors: Allman Tim , Holland G. A. , Lenkinski R. E. , Charles H. Cecil 
Published: March 2007

AbstractIt is a requirement of many localized NMR spectroscopy experiments, such as DRESS, that collection of the free induction decay be delayed a significant time after the middle of the last pulse. This leads to distortion of the spectra and seriously impedes the retrieval of quantitative information from these spectra. A technique is described in which a correction function is derived from the convoluted spectrum and is used to produce a spectrum with much reduced distortion from which quantitative information may easily be obtained by conventional techniques. © 1988 Academic Press, Inc.
Acute volume loading studied in cat myocardium with 31P Nuclear magnetic resonance
Authors: Osbakken Mary , Young Marie , Huddell Judy , Closter Jeffery , Prammer Manfred , Chance Britton 
Published: March 2007

AbstractTo study the effects of acute volume loading on myocardial metabolic and mechanical function, seven cats were volume loaded via anastomosis of the abdominal aorta to the vena cava (A V shunt). Metabolic effects were evaluated with31 P nuclear magnetic resonance (NMR). Mechanical function was evaluated with heart rate × systolic blood pressure product (HR × SBP). Shunts were opened for 1–2 h during which time phosphocreatine (PCr), adenosine triphosphate (ATP), inorganic phosphate (Pi), and HR × SBP were monitored. High‐energy phosphate energetics as determined by Pi/PCr and PCr/ATP ratios were correlated with HR × SBP. Opening of the AV shunts was associated with an increase (four cats) or a decrease (three cats) in HR × SBP. Pi/PCr ratios increased and PCr/ATP ratios decreased in cats with an increase in HR × SBP. In cats with a decrease in HR × SBP, Pi/PCr and PCr/ATP generally did not change significantly. In summary, acute volume loading could be associated with an increase or decrease in myocardial external work as evaluated by HR × SBP, accompanied by metabolic changes suggestive of appropriate induction of state 3 metabolism (active metabolic state: ADP + Pi → ATP) in those cats with increased mechanical work, and minimal change in bioenergetics in cats with no or minimal increase in mechanical work. These induced metabolic responses to myocardial mechanical loading can be evaluated with 31P NMR techniques and may provide insight into in vivo metabolic control mechanisms. © 1988 Academic Press, Inc.
Dependence of the solvent proton 1/T1 on the iron content in normal human serum
Authors: Yilmaz Ali , Chu Simon C. , Osmanoglu Semsettin 
Published: March 2007

AbstractThe iron content dependence of the spin‐lattice relaxation rates (I / T1) of solvent protons in healthy human serum has been studied by FT NMR at 60 MHz. A linear relationship has been established between 1/T1 and the iron content (with a correlation of 0.89). Our data suggest that Fe(III)–transferrin can contribute to the relaxation rate in healthy human Serum. © 1988 Academic Press, Inc.
Nodal inhomogeneity mapping by localized excitation—the “NIMBLE” shimming technique for high‐resolution in Vivo NMR spectroscopy
Authors: Doddrell David M. , Galloway Graham J. , Brewton Ian M. , Brooks William M. 
Published: March 2007

AbstractA method (NIMBLE) for obtaining optimum Bo field homogeneity at voxels located away from the magnet isocenter for use in volume‐selected NMR spectroscopy is described. Voxels may be shimmed using only first‐order X, Y, and Z shims to produce three‐dimensional shim current maps, thus avoiding shim coupling problems. NIMBLE shimming prior to volume selection ensures optimum spectral resolution and improves the efficiency and accuracy of the volume‐selection experiment. The benefits of the technique are illustrated by a high‐resolution volume‐selected spectrum of human tibia marrow. © 1988 Academic Press, Inc.
Water proton NMR relaxation mechanisms in lung tissue
Authors: Kveder M. , Zupančič I. , Lahajnar G. , Blinc R. , Šuput D. , Ailion D. C. , Ganesan K. , Goodrich C. 
Published: March 2007

AbstractThe NMR relaxation times T2, T2, and T1 were measured in isolated rat lungs as functions of external magnetic field B0, temperature, and lung inflation. The observed linear dependence on B0 of the tissue‐induced free induction decay rate (T2)−1 provides independent confirmation of the air/water interface model of the lung. Furthermore, measurements of the Larmor frequency dependence of T1, are consistent with a spin‐lattice relaxation rate of the form 1/Tl = Aω−1/2+ B as expected for the case in which the relaxation arises from water‐biopolymer cross‐relaxation, which should be proportional to the surface area of the lung. This prediction was verified by observations of an approximately linear dependence of 1/T1, on transpulmonary pressure and thus on the lung surface area. © 1988 Academic Press, Inc.
Considerations of magnetic resonance angiography by selective inversion recovery
Authors: Nishimura Dwight G , Macovski Albert , Pauly John M. 
Published: March 2007

AbstractIn the selective inversion recovery method for projection angiography, upstream blood is tagged by an inversion excitation and then allowed to flow into the imaged region. The subtraction of this first image from a second image acquired without the tagging leaves a signal from only the selectively tagged blood. Pulse sequence design involves consideration of the duration of the blood transit interval, excitation timing and cardiac gating, static material suppression, inversion excitation pulses, and flow compensation. Each of these considerations must be viewed with respect to the particular application. The method has demonstrated potential application to areas such as the carotid arteries, aortic arch, and peripheral Vessels. © 1988 Academic Press, Inc.
Pulse sequence and parameter choice in NMR imaging as a problem of constrained multidimensional nonlinear optimization
Authors: Dreher Wolfgang , Börnert Peter 
Published: March 2007

AbstractThe advantage of the multiparametric nature of NMR imaging is connected with the problem of finding optimum pulse sequences and sequence parameters, which ensure a high contrast‐to‐noise ratio. For a given imaging task with m (m ≥ 2) regions characterized by sets of NMR parameters (e.g., p, T1, T2) two functions are proposed, which can be used to transform the search for an optimum pulse sequence into a problem of constrained multidimensional nonlinear optimization. The numerical algorithm is described and the results of two examples are presented and discussed. A short description of useful extensions of the proposed optimization approach, which are currently implemented, is given. © 1988 Academic Press, Inc.