bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantitative and qualitative fat analysis in human leg muscle of neuromuscular diseases by 1H MR spectroscopy in vivo
Authors: Bárány M. , Venkatasubramanian P. N. , Mok E. , Siegel I. M. , Abraham E. , Wycliffe N. D. , Mafee M. F. 
Published: March 2007

Abstract1H MR spectra were recorded from human gastrocnemius muscle at 63.86 MHz using the body coil of the Signa scanner as transmitter and a 3‐in. surface coil as receiver. The fat content of the muscle was quantified relative to that of water in a selected volume or slice. The fat/water ratio was 0.05−0.07 for normal muscle but increased to 0.5−6.0 in primary and secondary muscular disorders such as Duchenne and myotonic dystrophy, Charcot‐Marie‐Tooth and polio muscular atrophy, cerebral palsy, and spina bifida. In Werdnig‐Hoffmann spinal atrophy the ratio was above 10. Water‐suppressed and sliceselective 1H spectroscopy was used for qualitative analysis of fat. The 1H profile of gastrocnemius muscles between healthy individuals and patients with neuromuscular diseases showed two major differences. In the normal muscle spectra, the resonance from the –(CH2)n– protons at 1.6 ppm was the most pronounced, whereas in the diseased muscle spectra resonances also appeared between 1.1 and 1.4 ppm. Some diseased muscle spectra showed multiple resonances from CHCH– in polyunsaturated fatty acids between 5.5 and 7.0 ppm. The corresponding resonances from CH‐CH2–, 1.9−2.0 ppm, and CH‐CH2‐CH, 2.7−2.9 ppm, were also seen. These peaks are usually not detected in normal muscle. © 1989 Academic Press, Inc.
Relaxometry of lens homogenates. II. temperature dependence and comparison with other proteins
Authors: Beaulieu Christopher F. , Brown Rodney D. , Clark John I. , Spiller Marga , Koenig Seymour H. 
Published: March 2007

AbstractWe have extended our earlier work (C. F. Beaulieu, J. I. Clark, R. D. Brown III, M. Spiller, and S. H. Koenig, Magn. Reson. Med. 8, 45 (1988)) on the magnetic field dependence of 1/T1 (NMRD profiles) of calf lens nuclear homogenates, at 25°C, to 5°C, and to other protein systems as well. These include concentrated solutions of myoglobin and bovine serum albumin, both globular proteins, the first compact and roughly spherical, the other extended, flexible, and with weak internal bonding; chicken lens homogenate, for which the dominant crystallins (lens proteins) are ∼ 70% α‐helical compared with calf crystallins, which are essentially all β‐sheet; and hen egg white, both native and heat‐ denatured. Our earlier conjectures regarding a reversible change in protein organization of the calf lens crystallins as a function of solute protein concentration is given added support. Our findings suggest that cytoplasmic homogenate can be characterized as a heterogeneous and polymorphic solution of crystallins. At high concentrations the NH moieties of the protein backbone become accessible to solvent with water (not NH proton) exchange rates > 104s−1. This conclusion is based on two aspects of the observed NMRD profiles. At low crystallin concentration, the profiles of calf and chicken lens homogenates are similar in form to those of myoglobin and native hen egg white, a form that has been studied previously for a range of diamagnetic globular proteins and has been demonstrated to arise from the rotational thermal motion of the solute molecules. At high crystallin concentrations, the NMRD profiles of the lens homogenates develop a monotonic background (high rates at low fields), much like that of the heat‐denatured egg‐white sample and those of most tissues. In addition, there is a set of peaks in the central part of the profiles of the concentrated crystallins, seen also in the denatured egg white and some tissues but not in the myoglobin sample, which is known to arise from cross‐relaxation interactions between the water protons and (through the intermediary of the NH proton) the 14N quadrupolar levels. The magnitude of these peaks, which is larger by an order of magnitude for native calf lens homogenates than for any tissue, requires that the majority of the NH moieties be accessible to water. Finally, going to 5°C for the native calf lens homogenate takes the sample below the temperature of reversible phase separation, and it becomes opaque. However, there is no change in the profile that can be attributed to this transition and its associated opacity. © 1989 Academic Press, Inc.
Magnetic shielding of magnetic resonance systems
Authors: Andrew E. R. , Szczesniak E. 
Published: March 2007

AbstractBasic theoretical concepts of static magnetic shielding are summarized. Expressions describing the magnetic field produced by a solenoidal coil confined coaxially inside a long thin ferromagnetic cylinder of constant permeability are derived. Conditions for the optimum arrangement of a magnetic screen for whole‐body NMR systems are discussed. © 1989 Academic Press, Inc.
The synthesis of pulse sequences yielding arbitrary magnetization vectors
Authors: Shinnar Meir , Eleff Scott , Subramanian Harihara , Leigh John S. 
Published: March 2007

AbstractA new procedure and algorithm are presented to allow the synthesis of a pulse sequence which will generate an arbitrary frequency‐dependent spin excitation. This procedure is a generalization of our previous paper, where this was done subject to the restriction that the spin excitation was symmetric about zero offset frequency, and pulses were restricted to being about a fixed axis. The required final z‐magnetization vector (Mz) is expressed as a function of the off‐resonance frequency as an Nth order complex Fourier series. We then form a consistent Fourier series for (Mxy). As many as 2 2N different pulse sequences may be directly generated all of which produce a different Mxy(f), but the same Mz(f). A pulse sequence is then generated which will yield the desired Mz(f) and Mxy(f). This is done by an analytic inversion of the Bloch equation, not by the classical Fourier approximation. This technique enables us to generate any Mz which is potentially realizable by a pulse sequence. © 1989 Academic Press, Inc.
Studies of the metabolism of human breast cancer spheroids by NMR
Authors: Ronen S. , Degani H. 
Published: March 2007

AbstractSpheroids present a model for tumor behavior in vivo. In NMR studies, a problem of spheroid adhesion occurs. Here, we present a method which overcomes this problem and show the variations in phosphate metabolite concentrations as well as the rate of glucose metabolism as a function of spheroid age. © 1989 Academic Press, Inc.
Inhibition of lymphocyte stimulation by shift reagents
Authors: Sze Daniel Y. , Corbelletta Nancy L. , Shochat Stephen J. , Jardetzky Oleg 
Published: March 2007

AbstractLanthanide shift reagents have opened a new avenue in the study of membrane biochemistry, but their stabilities and biological reactivities remain questionable. We present evidence that shift reagents are not biologically inert, and that they exhibit the ability to inhibit stimulation of human peripheral lymphocytes at commonly used concentrations. A survey of various mitogens yielded no shift reagent‐resistant modes of stimulation, and a survey of various shift reagents yielded no effective and nontoxic alternatives. Involvement of calcium‐regulating mechanisms was not apparent. The assumption that lanthanide shift reagents used in NMR studies are nondestructive and physiologically innocuous is thus shown to be unwarranted.
Spatial localization for motion‐rejected nmr imaging: slo‐motion
Authors: Blackband S. J. 
Published: March 2007

AbstractA new method of eliminating NMR image artifacts caused by random or sporadic motion is presented. The method uses only NMR techniques. A combination of a spatial localization method and a standard 2DFT imaging sequence is employed and consequently named SLO‐MOTION. Alternatively, the sequence may be used to aid motion artifact reduction by postprocessing methods. The feasibility of the method is demonstrated on a phantom.
Uterine cervical punch biopsy specimens can be analyzed by 1h mrs
Authors: Mountford Carolyn E. , James Delikatny E. , Dyne Marlen , Holmes Kerry T. , Mackinnon Wanda B. , Ford Robert , Christopher Hunter J. , Truskett Ian D. , Russell Peter 
Published: March 2007

AbstractBiopsy specimens of the uterine cervix, including colposcopically directed punch biopsy specimens of females with atypical Papanicolaou smear tests, are suitable for analysis by magnetic resonance (MR) spectroscopy. A narrow lined lipid MR spectrum, characteristic of malignant tissue, is obtained from a 6‐mm3 biopsy specimen of histologically confirmed squamous carcinoma of the cervix. In contrast, specimens containing inflammatory cells generate a broad component only centered at 1.3 ppm with a T2 relaxation value of less than 350 ms. Most biopsy specimens which contain dysplastic cells or evidence of human papilloma virus (HPV) infection have a discernible lipid spectrum similar to that of the malignant tissue specimen. Long T2 relaxation values found in malignant tissue specimens at 1.3 and 1.2 ppm are observed in some but not all of the biopsies which show evidence of HPV infection. The suitability of small tissue samples, such as punch biopsy specimens, for study by MR illustrates the sensitivity of this technique and its potential as an aid to histopathological discrimination between the various precursor states of cervical cancer.
High‐field localized in vivo proton spectroscopy on micro volumes
Authors: Doddrell David M. , Field James , Crozier Stuart , Brereton Ian M. , Galloway Graham J. , Rose Stephen E. 
Published: March 2007

AbstractA water‐suppressed volume‐selected in vivo 1H spectrum of 0.2 ml of a rat brain has been obtained at 200 MHz using the SPACE localization method. Good signal‐to‐noise and spectral resolution were obtained by averaging 256 acquisitions. The spectrum shows little T2 weighting effect.
Proton NMR study of the state of water in fibrin gels, plasma, and blood clots
Authors: Blinc A. , Lahajnar G. , Blinc R. , Zidanš A. , Sepe A. 
Published: March 2007

AbstractA proton NMR relaxation and pulsed field gradient self‐diffusion study of water in fibrin gels, plasma, and blood clots has been performed with special emphasis on the effect of the sol‐gel and shrinkage transitions. Deuteron NMR in fibrin gels was also studied to supplement the proton data. It is shown that a measurement of the water proton or deuteron T1 / T2 ratio allows for a determination of the bound water fraction in all these systems. The change in the T1 / T2 ratio at the shrinkage transition further allows for a determination of the surface fractal dimension of the gel if the change in the volume of the gel is known. The self‐diffusion coefficient of water in these systems, which determines the transport properties of the gel, is found to be proportional to the free water fraction in both the nonshrunken and shrunken state. © 1990 Academic Press, Inc.
A homonuclear shift correlated and spatially localized spectroscopy using stimulated echoes
Authors: Desmoulin F. , Seelig J. 
Published: March 2007

AbstractA new method which combines localized high‐resolution proton NMR spectroscopy with two‐dimensional correlated spectroscopy using stimulated echoes is presented. Stimulated‐echo correlated spectroscopy (STECSY) is a straightforward extension of the STEAM method. Experiments with phantoms illustrate the efficacy of STECSY. An in situ application on rat adipose tissue demonstrates that STECSY is a helpful tool with which to select and assign resonances in complex 1H NMR spectra. © 1990 Academic Press, Inc.
Nuclear magnetic resonance velocity spectra of steady flow
Authors: Wendt Richard E. , Nitz Wolfgang R. , Murphy Paul H. 
Published: March 2007

AbstractNuclear magnetic resonance (NMR) velocity spectra are a compact way to represent the flow information in a velocity‐resolved image set. Fully developed steady flow in long tubes gives NMR velocity spectra with average velocities which correlate well with the values derived from the flow rate. The ratio of average velocity to peak velocity correlates well with the Reynolds number. Tubes with compressed cross sections have velocity spectra similar to those of circular tubes. Tubes with irregular walls have velocity spectra in the entrance region that are markedly different from those from smooth‐walled tubes. © 1990 Academic Press, Inc.
A simple design for a double‐tunable probe head for imaging and spectroscopy at high fields
Authors: Gruetter Rolf , Boesch Chris , Müri Marcel , Martin Ernst , Wüthrich Kurt 
Published: March 2007

AbstractA double‐tunable probe head based on the slotted tube resonator is described. Its performance at 2.35 T is comparable to that of single‐tunable designs. The main advantages are a large tuning range, a probe volume that is not reduced by the second circuit, and a simple design. © 1990 Academic Press, Inc.
31P NMR spectra of extremity sarcomas: Diversity of metabolic profiles and changes in response to chemotherapy
Authors: Koutcher Jason A. , Ballon Douglas , Graham Martin , Healey John H. , Casper Ephraim S. , Heelan Robert , Gerweck Leo E. 
Published: March 2007

AbstractWe have used 31P NMR spectroscopy to study 22 patients with suspected sarcomas prior to any treatment. The spectra are characterized by the same peaks noted in murine tumors. The mean pH was 7.14 ± 0.08 and PCr/Pi was 1.18 ± 0.83. Comparison of pH and PCr/Pi, ratios in human and a murine tumor with a low hypoxic cell fraction revealed no significant differences. Six patients subsequently received chemotherapy and three responded to therapy (based on pathologic examination and/or tumor reduction greater than 50%). The three responding patients were noted to have significantly lower PDE/ PME in their pretreatment spectra than the three nonresponding patients. The three responding patients with sarcomas also showed a rise of > 100% in PDE/PME during the first cycle of therapy. Two of the responding patients had an increase of 0.37 pH units during this interval, which was not detected in the nonresponding patients. These data suggest that 31P NMR spectroscopy may be a useful prognostic indicator in conjunction with other clinical parameters. © 1990 Academic Press, Inc.
Quantitation of blood‐brain barrier defect by magnetic resonance imaging and gadolinium‐DTPA in patients with multiple sclerosis and brain tumors
Authors: Larsson H. B. W. , Stubgaard M. , Frederiksen J. L. , Jensen M. , Henriksen O. , Paulson O. B. 
Published: March 2007

AbstractIn this study quantitation of the degree of deficiency of the blood‐brain barrier (BBB) in patients with multiple sclerosis or brain tumors, by using MRI, is shown to be possible. As a measure of permeability of the BBB to Gadolinium‐DTPA (Gd‐DTPA) the flux per unit of distribution volume per unit of brain mass was used. This quantity was found by introducing the longitudinal relaxation rate (R1) as a measure of concentration of Gd‐DTPA in the brain tissue in the mathematical model for the transcapillary transport over the BBB. High accordance between the observed data points and the model was found, and the results were comparable to results obtained from similar studies using positron emission tomography. The improved possibility of quantitating the defect of the BBB by MRI may give new information about pathogenesis or etiology, and leads to improved methods in monitoring the efficacy of treatments in intracranial diseases. © 1990 Academic Press, Inc.
The NMR phased array
Authors: Roemer P. B. , Edelstein W. A. , Hayes C. E. , Souza S. P. , Mueller O. M. 
Published: March 2007

AbstractWe describe methods for simultaneously acquiring and subsequently combining data from a multitude of closely positioned NMR receiving coils. The approach is conceptually similar to phased array radar and ultrasound and hence we call our techniques the “NMR phased array.” The NMR phased array offers the signal‐to‐noise ratio (SNR) and resolution of a small surface coil over fields‐of‐view (FOV) normally associated with body imaging with no increase in imaging time. The NMR phased array can be applied to both imaging and spectroscopy for all pulse sequences. The problematic interactions among nearby surface coils is eliminated (a) by overlapping adjacent coils to give zero mutual inductance, hence zero interaction, and (b) by attaching low input impedance preamplifiers to all coils, thus eliminating interference among next nearest and more distant neighbors. We derive an algorithm for combining the data from the phased array elements to yield an image with optimum SNR. Other techniques which are easier to implement at the cost of lower SNR are explored. Phased array imaging is demonstrated with high resolution (512 × 512, 48‐cm FOV, and 32‐cm FOV) spin‐echo images of the thoracic and lumbar spine. Data were acquired from four‐element linear spine arrays, the first made of 12‐cm square coils and the second made of 8‐cm square coils. When compared with images from a single 15 × 30‐cm rectangular coil and identical imaging parameters, the phased array yields a 2X and 3X higher SNR at the depth of the spine ( ∼ 7 cm). © 1990 Academic Press, Inc.
High‐speed multislice T1 mapping using inversion‐recovery echo‐planar imaging
Authors: Ordidge R. J. , Gibbs P. , Chapman B. , Stehling M. K. , Mansfield P. 
Published: March 2007

AbstractTissue contrast in MR images is a strong function of spin‐lattice (T1) and spin‐spin (T2) relaxation times. However, the T1 relaxation time is rarely quantified because of the long scan time required to produce an accurate T1 map of the subject. In a standard 2D FT technique, this procedure may take up to 30 min. Modifications of the echo‐planar imaging (EPI) technique which incorporate the principle of inversion recovery (IR) enable multislice T1 maps to be produced in total scan times varying from a few seconds up to a minute. Using IR‐EPI, rapid quantification of T1 values may thus lead to better discrimination between tissue types in an acceptable scan time. © 1990 Academic Press, Inc.
Localized Proton NMR spectroscopy using stimulated echoes: Applications to human skeletal muscle in vivo
Authors: Bruhn H. , Frahm J. , Gyngell M. L. , Merboldt K. D. , Hänicke W. , Sauter R. 
Published: March 2007

AbstractLocalized proton NMR spectroscopy using stimulated echoes (STEAM) has been used to study metabolites in different proximal skeletal muscles of normal volunteers at rest. Single scan water‐suppressed proton NMR spectra obtained at 1.5 and 2.0 T (Siemens Magnetom) from a 64‐ml volume‐of‐interest (VOI) yield resonances due to triglycerides, phosphocreatine plus a minor contribution from creatine, and betaines comprising carnitine and choline‐containing compounds. The observation of the pH‐dependent resonances of carnosine required multiple acquisitions and echo times as short as 20 ms. T1 and T2 relaxation times of muscle metabolites were obtained by varying the repetition time and echo time of the STEAM sequence, respectively. Although rather long T2 values such as 180 ms for (phospho‐) creatine correspond to natural resonance line widths of only 2 Hz, the observed line widths of typically 10‐12 Hz are entirely determined by the short T2 relaxation times (25‐30 ms) of the water protons used for shimming. The spectroscopic results from 24 muscle studies on 17 young male volunteers show remarkable intra‐ and interindividual differences in the absolute signal intensities of mobile lipids. Further metabolic variations were observed for the relative concentrations of betaines (by a factor of 2) and carnosine (by a factor of 3) when total creatine is assumed to be constant. © 1991 Academic Press, Inc.
Data extrapolation for truncation artifact removal
Authors: Constable R. T. , Henkelman R. M. 
Published: March 2007

AbstractClinicians typically obtain high‐resolution clinical MR images in an effort to avoid the truncation artifacts that often arise in Fourier transform reconstruction of limited data. A method for reducing these artifacts in MR images, at the reconstruction stage, would allow for reduced imaging times, through the collection of fewer phase encode steps and increased signal‐to‐noise ratios, through increased pixel size. The approach to reducing truncation artifacts in MR images is developed and a simple algorithm is presented which significantly reduces truncation artifacts in images with as few as 96 phase encode steps. The algorithm is compared with a more sophisticated method of reconstructing truncation‐free images and is shown to be equivalently effective. Three clinical examples are shown illustrating the Success of the method. © 1991 Academic Press, Inc.
Analysis of eddy currents in nuclear magnetic resonance imaging
Authors: Ahn C. B. , Cho Z. H. 
Published: March 2007

AbstractThe eddy currents in nuclear magnetic resonance (NMR) imaging are analyzed from the solutions of Maxwell's equations and their effects are examined over various experimental conditions from whole‐body diagnostic imaging to recently developed NMR microscopy. The analysis is focused mainly on the frequency characteristics and intensity variations of the eddy‐current‐induced field which depends on the overall system size, ratio of the gradient coil size to the magnet bore diameter, and the pulse‐sequence‐dependent parameters such as input current waveform and repetition time. From the analysis, the frequency response of the eddy‐current‐induced field is that of a high‐pass filter whose cutoff frequency is inversely proportional to the square of the overall system size. The intensity ratio of the generated field to the induced field is not affected by the overall system size, but is sensitively related to the ratio of the gradient coil size to the magnet bore diameter. © 1991 Academic Press, Inc.
Tissue oxygenation: A novel determination using 19F surface coil NMR spectroscopy of sequestered perfluorocarbon emulsion
Authors: Mason Ralph P. , Nunnally Ray L. , Antich Peter P. 
Published: March 2007

AbstractThis work examines the variation with oxygen tension (pO2) of the individual spin‐lattice relaxation times (TI) of the 19F resonances of the perfluorocarbon emulsion Oxy‐pherol‐ET (FC‐43). A linear relationship between 1/T1 and pO2 has been confirmed for all four resonances at any specific temperature. Using a saturation recovery sequence, T1 has been successfully measured using surface coil NMR spectroscopy. This has facilitated measurement of TI in vivo in a subcutaneous murine tumor. Mice were predosed with Oxypherol‐ET emulsion; following complete vascular clearance of the pertluorocarbon, 19F signal was observed specifically from material sequestered in tissue, thus avoiding flow artifacts. Comparison of the pO2 estimated from each of the 19F resonances provided an internal consistency check. A pO2 = 0.1 ± 2.2% was determined in a Meth‐A murine tumor. When the mouse breathed carbogen (95% O2, 5% CO2) no significant change in tumor pO2 was detected, whereas the pO2 in the liver showed a distinct increase. © 1991 Academic Press. Inc.
Effect of L‐thyroxine (LT4) and D‐thyroxine (DT4) on cardiac function and high‐energy phosphate metabolism: A 31P NMR study
Authors: Sandhu G. S. , Steele R. , Gonnella N. C. 
Published: March 2007

Abstract31P NMR spectroscopy was used to monitor the cardiac energy metabolism in hypothyroid rat hearts. Differential alterations in phosphocreatine and inorganic phosphate levels were observed upon treatment of hypothyroid animals with DT4 and LT4, while both agents were equipotent in reducing cholesterol. These results show potential for NMR spectroscopy as a technique to determine therapeutic selectivity. © 1991 Academic Press. Inc.
Magnetic susceptibility measurement using a double‐DANTE tagging (DDT) sequence
Authors: Mosher Timothy J. , Smith Michael B. 
Published: March 2007

AbstractPreliminary results are presented for the nuclear magnetic resonance (NMR) measurement of field gradients generated by differences in magnetic susceptibility. The DDT technique maps the resonant frequency throughout the sample in a single image. Regions of paramagnetic and diamagnetic susceptibility are differentiated with a single magnitude‐calculated image. © 1991 Academic Press. Inc.