bluuebunny/crossref_metadata_2025_split huggingface dataset:
13C nuclear magnetic resonance spectroscopy of glucose metabolism in human red blood cells
Authors: Ghai Geetha , Gonnella Nina C. 
Published: March 2007

AbstractGlucose metabolism of human red blood cells was investigated using carbon‐13 nuclear magnetic resonance spectroscopy under both oxygenated and nonoxygenated conditions. These results show that under oxygenated conditions reversal of 3‐phospho‐glyceraldehyde to glucose is in competition with its catabolism to lactate. © 1988 Academic Press, Inc.
Evaluation of polyaza macrocyclic methylene phosphonate chelates of Gd3+ ions as MRI contrast agents
Authors: Geraldes Carlos F. G. C. , Brown Rodney D. , Cacheris William P. , Koenig Seymour H. , Sherry A. Dean , Spiller Marga 
Published: March 2007

AbstractGd(DTPA)2− (diethylenetriaminepentaacetic acid) and the polyaza macrocyclic Gd(DOTA)− (1,4,7,10‐tetraazacyclododecane‐N, N′,N″,N′″) are paradigms of general purpose paramagnetic complexes useful for enhancing contrast in magnetic resonance imaging (MRI). It is of both fundamental and practical interest to determine how one might modify the chemical structure of these chelate complexes to improve their utility for MRI in specific circumstances. In the present work, we investigated polyaza methylene phosphonate complexes of Gd3+ ions to compare their NMRD profiles with those of their carboxylate analogs and with Gd(DTPA)2−. We find that the number q of exchangeable water molecules coordinated directly to the Gd3+ ions tends to be smaller in the phosphonates, in principle reducing their utility in MRI. However, these phosphonates have a tendency to oligomerize, and the resulting decrease in rotational mobility of the paramagnetic oligomers increases their relaxivity at higher fields, offsetting the effect of decreases in q. In particular, Gd(DOTRP)3− (1,5,9‐triazacyclododecane N, N′,N″,‐tris (methylenephosphonic acid) would be an increasingly effective contrast agent above ∼ 10 MHz if the oligomerization was stable in vivo (and the Gd3+ ions were sufficiently well bound). At lower fields, the relaxivity of these small chelate complexes is dominated by τso, the relaxation time of the spin moments of the paramagnetic ions. We find this to be favorably long for complexes of Gd3+ with the macrocyclic phosphonate ligands, as was found earlier by us for Gd( DOTA)−. This situation, ostensibly related to the relatively high symmetry and rigidity of the macrocyclic complexes, can increase the low‐field relaxivity of the phosphonates almost a factor of 2 beyond that of Gd(DTPA)2−. © 1989 Academic Press, Inc.
Increased rf power absorption in MR imaging due to rf coupling between body coil and surface coil
Authors: Buchli R. , Saner M. , Meier D. , Boskamp E. B. , Boesiger P. 
Published: March 2007

AbstractFears have been voiced that excessive tissue heating could occur in the event that first, a surface coil is placed with its axis parallel to the transmitting rffield leading to a maximal coupling of the two coils and second, the decoupling circuit of the surface coil breaks down. To avoid an rf coupling of the transmitting body coil to the receive‐only surface coil, conventionally applied surface coils are equipped with an active electronic rf decoupling circuit. In extensive worst‐case experiments on phantoms we have shown that no tissue heating occurs for surface coils which are equipped with semiconductor varicap diodes for tuning and matching. These coils should be safe for patient applications even if the decoupling circuit fails. Surface coils equipped with mechanically variable capacitors are generally passively decoupled. To simulate the worst‐case situation phantom experiments were performed in which a surface coil of this type having no passive decoupling circuit was coupled to the transmitter coil by its geometric position. Theoretical calculations, in agreement with the experimental results achieved during a 15‐min measurement in a 1.5‐T MRI whole‐body imager, show that a significant rfpower deposition in the tissue underneath the coil wire occurs, leading typically to a local specific absorption rate of 24 W /kg and a local temperature rise of 52°C. © 1989 Academic Press, Inc.
Multiple short‐echo (2.5‐ms) quantitation of in vivo sodium T2 relaxation
Authors: Perman William H. , Thomasson David M. , Bernstein Matt A. , Turski Patrick A. 
Published: March 2007

AbstractThe MR behavior of the sodium‐23 nucleus in vivo is a complex problem which has generated considerable interest over the last 20 years. Early studies on excised tissue samples revealed that the sodium nucleus exhibited a two‐component T2 relaxation. This biexponential T2 relaxation was characterized by a short component with a T2=0.7–4.8 ms, and a long component with a T2=7.0−26.0 ms. We have developed a 3D pulse sequence capable of performing multiple Hahn echo in vivo sodium‐23 imaging at echo times as short as 2.5 ms. This sequence obtains the shorter spin echo times by presaturating the spins outside of the desired imaging region, allowing the use of nonselective rf pulses. Using this sequence we have been able to quantify the long and short T2 components of normal brain tissue, vitreous humor of the eye, and a rabbit VX‐2 carcinoma. We found that gray matter and white matter of normal brain have a monoexponential T2 relaxation with T2=17.6 ± 2.4 ms. The vitreous humor T2 relaxation is also monoex‐ ponential with T2=56.8 ± 2.1 ms. However, we find that some of the rabbit VX2 carcinomas exhibit a biexponential T2 decay with a short component of 3.3 ± 4.6 ms and a long component of 22.0 ± 9.0 ms. © 1989 Academic Press, Inc.
A quantitative study of relaxation rate enhancement produced by iron oxide particles in polyacrylamide gels and tissue
Authors: Majumdar S. , Zoghbi S. , Pope C. F. , Gore J. C. 
Published: March 2007

AbstractThe proton relaxation rate enhancements produced by two types of iron oxide particles, M4125 and AM125 (Advanced Magnetics, Cambridge, MA) designed as potential MR contrast agents, have been measured in polyacrylamide gels and in liver and spleen. The organ uptakes, time courses, and biodistributions of these materials have been measured using radiolabeling. The relaxation rate enhancements produced by these particles have been related to the concentration of iron per gram material at different magnetic field strengths. The relaxation rates increase linearly as a function of concentration at field strengths varying from 0.15 to 7 T. The relaxation effects of these particles in tissue are significantly different from the behavior in vitro. These results suggest that several different mechanisms contribute to relaxation effects in the presence of iron oxide particles and they depend strongly on the way the particles are sequestered. Diffusion effects for a specified TE may be enhanced using gradient or single‐spin echoes rather than multiple echoes. AMI25 is significantly more effective as a relaxation agent than paramagnetic metal ions only at relatively high fields, while M4125 is less effective per unit concentration. © 1989 Academic Press, Inc.
In vivo high‐resolution volume‐selected proton spectroscopy and T1 measurements in the dog brain
Authors: Galloway Graham J. , Field James , Rose Stephen E. , Haseler Luke J. , Brooks William M. , Brereton Ian M. , Bore Peter J. , Crozier Stuart , Doddrell David M. 
Published: March 2007

AbstractSuccessful in vivo NMR spectroscopy requires a combination of techniques to address the problems of volume selection, water suppression, and resolution. All this needs to be done in the very heterogeneous environment found in living organisms. Previously published techniques are used to obtain 1H spectra from a dog brain, observing metabolites with concentrations below 1 mM. Measurements of spin‐lattice relaxation times (T1) are also presented. The 1H relaxation times are long (T1 > 1.0 s) yielding information about the fluidity of the molecular environment. Comments are made concerning the achievable linewidth in vivo and the deficiencies that phase‐encoding spectroscopic methods may have in obtaining high‐resolution 1H spectra. © 1989 Academic Press, Inc.
Comparison of the signal‐to‐noise ratio at 1.5 and 2.0 T using a whole‐body system
Authors: Beckmann N. , Müller S. , Seelig J. 
Published: March 2007

AbstractSignal‐to‐noise ratios for 1H, 31P, and 13C signals at 1.5 and 2.0 T were compared using a whole‐body system with a fast rampable magnet. Results indicate that SNR lies within the predicted values of linear and 7/4th power dependency with the applied magnetic field, for lossy and lossless samples, respectivety. © 1989 Academic Press, Inc.
A method for direct in vivo measurement of drug concentrations from a single 2H NMR spectrum
Authors: Evelhoch Jeffrey L. , McCoy Cheryl L. , Giri Brij P. 
Published: March 2007

AbstractThe use of 2H‐labeled drugs provides a measure of drug concentration in situ directly from a single 2H NMR spectrum obtained with any antenna by correcting only for differential saturation effects. The limit of detection for a drug labeled with three equivalent deuterons is roughly 0.5 mM. © 1989 Academic Press, Inc.
Use of solvent suppression technique to enhance changes due to susceptibility variations in magnetic resonance imaging
Authors: Hall A. S. , Collins A. G. , Bryant D. J. , Young I. R. , Bydder G. M. 
Published: March 2007

AbstractThis communication describes the use of a binomial pulse sequence designed from solvent suppression in proton spectroscopy to convert the small frequency changes associated with field variations into significant amplitude changes in magnetic resonance images. This technique can be used to demonstrate tissue susceptibility change. © 1989 Academic Press, Inc.
Characterization of fluid flow using low‐spatial‐resolution velocity spectra from NMR images
Authors: Wendt Richard E. , Nitz Wolfgang , Murphy Paul H. , Bryan R. Nick 
Published: March 2007

AbstractFlow velocity distributions or spectra may be obtained by NMR imaging using an anisotropic three‐dimensional Fourier transform pulse sequence in which the low‐resolution direction encodes perpendicular velocity. Velocity spectra from regions of interest covering the entire lumens of pipes in a flow phantom containing straight sections, a jet, and a constriction suggest that velocity spectra provide useful information even when the vessels are not spatially well‐resolved. The flow in the phantom was characterized and limited measurements were made. © 1989 Academic Press, lnc.
Therapeutic response of breast carcinoma monitored by 31P MRS in situ
Authors: Ng Thian C. , Grundfest Sharon , Vijayakumar Srinivasan , Baldwin Nicholas J. , Majors Anthony W. , Karalis Ipatia , Meaney Thomas F. , Shin Kyu Ho , Thomas Frank J. , Tubbs Raymond 
Published: March 2007

AbstractIn situ phosphorous MRS was employed to study the metabolites of normal and cancerous breasts, and the alterations of tumor response to therapy. In a group of 7 normal volunteers and 12 patients, the total mobile phosphate content of breast carcinomas was found to be at least two to three times higher than that of the normal breast measured off menstruation. The metabolite profiles of normal and tumorous breasts are coarsely similar. In both cases the intracellular pH (pHi) was either neutral or slightly alkaline (pH > 7.0). Prior to treatments, the metabolite levels of phosphoryl monoester‐to‐ATP ratio of breast neoplasms were higher than those of the controls and decreased after the patients received a few treatments while the pHi fluctuated at a value greater than 7.0. The phosphoryl diester‐to‐ATP ratio also demonstrated to a lesser extent a decreasing trend in response to therapy. © 1989 Academic Press, Inc.
Single‐scan volume‐selective editing of NMR spectra with the aid of a split‐pathway technique for homonuclear applications
Authors: üttel A. Kn , Kimmich R. 
Published: March 2007

AbstractAn RF and field‐gradient pulse sequence that permits the recording of localized and edited proton spectra is presented. The editing principle is a technique of splitting and recombining the coherence pathways. While the recombination of the pathways of uncoupled spins is destructive, that of coupled spins can be adjusted to be constructive. © 1989 Academic Press, Inc.
Efficient biphasic spin‐echo magnetic resonance imaging
Authors: Parker Dennis L. , Caputo Gary R. , Frederick Philip R. 
Published: March 2007

AbstractThe concept of temporal echo multiplexing is defined and used to develop rapid bipha‐sic spin‐echo sequences for imaging the heart. Three imaging sequences, based on four‐echo and two‐echo multiplexing and rapid single echo (i.e., conventional spin‐echo imaging), are compared. Preliminary results indicate that two‐echo multiplexing yields a significantly reduced acquisition time window with image quality that is only slightly inferior to single‐echo imaging. Single‐echo biphasic imaging results in the most consistent image quality. © 1989 Academic press, Inc.
Computing material‐selective projection images in MR
Authors: Wright G. A. , Brosnan T. J. , Macovski A. , Nishimura D. G. 
Published: March 2007

AbstractWe detail a robust, general method for computing projection images of individual materials in a volume as linear combinations of MR projection images with different material‐dependent weightings. Signal per unit volume for each material in each raw image is acquired directly for accurate cancellation of undesired, overlapping materials. The weighted sum of the input images is determined to maximize the signal‐to‐noise ratio (SNR) and minimize inhomogeneity effects in the material‐selective images. We tested the implementation experimentally in both phantom and human studies, producing selective images with reasonable SNRs and material isolation. With further develop ment of sequences to rapidly acquire input images having greater material differentiability, we envision the application of the selective projection imaging format to screening studies searching over large volumes for diseased tissues. © 1989 Academic Press, Inc.
Metabolism of tumor regression from angiogenesis inhibition: 31P magnetic resonance spectroscopy
Authors: Hoffer Fredric A. , Taylor George A. , Spevak Melissa , Ingber Donald , Fenton Terry 
Published: March 2007

Abstract31P NMR spectroscopy was used to analyze the in vivo metabolism of reticulum cell sarcoma of mice. The ratio of high‐ to low‐energy phosphates ATPB/(Pi + PME) was measured to reflect the relative metabolic state in the tumor. Of the 34 mice studied, 26 were treated with an antiangiogenesis regimen of heparin and cortisone. Eighty‐two percent of the tumors treated eventually decreased in volume (P < 0.01 ). Volumes and spectroscopic information of 20 tumors were analyzed. Although the average untreated volume was similar to the volume after 3 days of treatment, the average ATPB/(Pi + PME) ratio rose from 0.34 ± 0.10 to 0.47 + 0.07 (P = 0.02). However, after 6 days of treatment, the volume significantly decreased (P < 0.0001) but the ratio did not significantly rise further (P = 0.06). The rise in the high‐energy phosphate preceded a significant decrease in volume of the tumors. In addition, the replenishment of the high‐energy stores with tumor regression coincided with the histologic findings of a decrease in the number of tumor cells, a decrease of the mitotic index, and a decrease of the number of necrotic cells present with ongoing treatment. Our data suggest that noninvasive methods of assessing early biochemical response of tumor regression may be possible.
Study of proton spin‐lattice relaxation variation induced by paramagnetic antibodies
Authors: Macr M. A. , De Luca F. , Maraviglia B. , Polizio F. , Garreffa G. , Cavallo S. , Natali P. G. 
Published: March 2007

AbstractA murine anti‐human melanoma monoclonal antibody fragment was labeled with gadolinium and its proton relaxation efficiency compared to controls at frequencies ranging from 2 to 300 MHz. Relaxation time variations were about 30–40% in 10–15 μM solutions. The labeled fragment showed proton relaxation enhancement relative to free gadolinium, while preserving its immunoreactivity. A tentative labeling of a melanoma pellet by means of the fragment, just at the borderline of a minimum expected T1 variation, gave no detectable diffemm.
1H COSY spectra of superfused brain slices of rat: Ex vivo direct assignment of resonances
Authors: Gillet B. , Mergui S. , Beloeil J‐C. , Champagnat J. , Fortin G. , Jacquin T. 
Published: March 2007

AbstractRealization of 1 D 1H spectra of superfused brain slices of rats is described. Two‐dimensional 1H− 1H COSY spectra have been used for the direct assignment of resonances on living tissue (lactate, GABA, N‐acetyl aspartate, aspartate, glutamine/glutamate, creatine/phosphocreatine, taurine, inositol, choline/ethanolamine). Utilization of the SUPERCOSY sequence permits simultaneously the enhancement of off‐diagonal signals for small metabolites and the reduction of the signals for water and macromolecules.
Continuous‐flow 13C‐filtered 1H NMR spectroscopy of ethanol metabolism in rat liver perfusate
Authors: Albert Klaus , Sudmeier James L. , Sawkat Anwer M. , Bachovchin William W. 
Published: March 2007

AbstractUsing a 188.5‐μl continuous‐flow dual probe 1H{13C} spin‐echo difference spectra of rat liver perfusate were acquired. The conversion of [1−13C]ethanol to [1−13C]‐ acetaldehyde was readily monitored as a function of time. In combination with 1‐1 water nonexcitation and WALTZ 13C decoupling, this method proved to be superior in sensitivity and selectivity to direct 1H or 13C detection.
Two‐dimensional correlated spectroscopy (COSY) of intact frog muscle: Spectral pattern characterization and lactate quantitation
Authors: Alonso Julio , Arús Carlos , Westler William M. , Markley John L. 
Published: March 2007

AbstractTwo‐dimensional scalar‐correlated 1H spectra (COSY) were recorded from a model solution containing varying amounts of lactate and a fixed concentration of carnosine as the reference compound. The integrated volume of the lactate methyl to methine cross peak in the magnitude‐calculated spectra showed a linear increase with respect to lactate concentration. Accordingly, the COSY cross‐peak integral volume should be a useful parameter for the quantitative study of metabolism in intact tissue. We have tested this assumption in excised gastrocnemius frog muscle. Lactate, carnosine, and creatine/ phosphocreatine cross peaks have been assigned in the spectrum of summer frog muscle. The change in concentration of lactate and phosphorylated compounds upon anaerobic storage of excised frog muscle has been followed by interleaving one‐dimensional ( 1 D) 1H and 31P spectra with 2D homonuclear 1H COSY spectra. The lactate concentration in the excised muscle derived from COSY agreed well with that determined from muscle extracts. Qualitative changes in the COSY pattern of the excised muscles under caffeineinduced contracture were detected. Furthermore, seasonal variations were observed in the COSY spectral pattern: winter frog muscle was found to differ from summer frog muscle by the appearance of cross peaks from phosphodiesters and mobile fatty acids.
in vitro NMR characterization of mammalian myocardium: Effect of specimen integrity on relaxation times
Authors: Scholz Thomas D. , Fleagle Steven R. , Skorton David J. 
Published: March 2007

AbstractWe systematically evaluated three different methods of preparing canine myocardium for NMR relaxometry: using whole specimens, specimens sliced into approximately 2‐mm3 pieces, and specimens minced into pieces <2 mm3. NMR relaxation times were determined at 20 MHz. TI relaxation time and water content were not different among the three methods. However, T2 values differed significantly between whole and sliced samples (mean ± SEM = 51.2 ± 2.2 ms (whole) vs 54.3 ± 2.7 ms (sliced); P < 0.05). Minced myocardium showed a similar increase that was not statistically significant. We conclude that tissue preparation methods must be controlled when performing NMR relaxometry studies.
Differential flow imaging by NMR
Authors: Xiang Q. S. , Nalcioglu O. 
Published: March 2007

AbstractA new method for spatially resolved NMR flow measurements, named differential flow imaging (DFI), is introduced and experimentally verified. The DFI technique is based on the fact that flow velocity in any direction may cause a pixel position shift in the phase‐encoding direction of a 2DFT NMR image. In this method two flow‐influenced magnitude images are obtained by properly encoding and/or compensating the flow velocity. A spatial map of the desired component of the flow velocity can consequently be calculated from these two images. Since the DFI technique uses only the magnitude information of the complex images, it is not sensitive to systematic phase errors in contrast to other methods which are based on the phase measurements. On the other hand, the DFI technique can be combined with the phase measurement methods to perform multidimensional flow measurements in a shorter data acquisition time when the phase errors are small or corrected. © 1989 Academic Press, Inc.
Piezoelectric‐controlled tuning capacitor for surface coils
Authors: Hyde James S. , Rilling Robert J. , Jesmanowicz A. , Kneeland J. Bruce 
Published: March 2007

AbstractThe design of a piezoelectric‐controlled trimmer capacitor and its use as a tuning element of an MRI surface coil at 63.8 MHz are described. It is found that image quality does not depend strongly on match of the coil to the transmission line but that tuning can be a significant factor. The work is intended to lead eventually to an automatic frequency control circuit in which the capacitor serves as the active element in holding the resonant frequency of the nuclei and the resonant frequency of the coil in coincidence. © 1989 Academic Press, Inc.
Phosphodiesters in the Liver: The Effect of Field Strength on the 31P Signal
Authors: Bates Timothy E. , Williams Stephen R. , Gadian David G. 
Published: March 2007

Abstract31P NMR spectra of the rat liver were recorded in vivo at 2.35 and 8.5 T. There was a large peak in the phosphodiester region of spectra obtained at 2.35 T which was much reduced at 8.5 T. The peak at 2.35 T is unlikely to be primarily from free cytosolic phosphodiesters, which would not be expected to display such a marked field dependence. © 1989 Academic Press, Inc.
Baseline deconvolution, phase correction, and signal quantification in fourier localized spectroscopic imaging
Authors: Derby K. , Hawryszko C. , Tropp J. 
Published: March 2007

AbstractLineshapes of spectra obtained through chemical‐shift imaging are often distorted due to the delay in sampling necessary for application of phase‐encoding gradients. We have developed an automated fitting procedure which simultaneously performs signal quantification, phase correction, and baseline deconvolution of such spectra. The fit is based on the maximum likelihood method and can be implemented in either the time or the frequency domain. © 1989 Academic Press, Inc.