bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temporal physicochemical changes during in vitro relaxation time measurements: The cerebrospinal fluid
Authors: Grant R. , Condon B. , Moyns S. , Patterson J. , Hadley D. , Teasdale G. 
Published: March 2007

AbstractDocumented relaxation time measurements of body fluids such as cerebrospinal fluid (CSF) vary considerably. This may be largely due to lack of an appropriate method of maintaining the in vivo physiological and biochemical characteristics of the fluid. We have developed an in vitro technique that maintains the in vivo characteristics of body fluid samples for a sufficiently long period to establish the true relaxation times. To illustrate this we studied changes in CSF pH, pO2, and pO2, first as it equilibrated with air and then under anaerobic conditions as found in vivo. Relaxation times of CSF were then studied under aerobic and anaerobic conditions. Under the particular aerobic conditions used the pH and pO2 of CSF increased quickly and pO2 fell within the first 30 min. By 3–4 h equilibration with air was complete. The T1 and T2 relaxation times of CSF decreased by 14 and 16%, respectively, as a result of these physicochemical changes. It is important that such changes be considered when relaxation measurements of any body fluid are performed in vitro and efforts to maintain the in vivo milieu should not be neglected. © 1988 Academic Press, Inc.
Rapid local rectangular views and magnifications: Reduced phase encoding of orthogonally excited spin echoes
Authors: Conturo Thomas E. , Price Ronald R. , Beth Albert H. 
Published: March 2007

AbstractA method is described for rapid, artifact‐free imaging and magnification of small regions within a larger sample. This combines a rectangular window, reconstructed from a reduced number of phase‐encoding steps, and confinement of spin echoes to a similar rectangular strip by orthogonal π/2 and π excitations. Phase encoding is along the width of the strip (along Y). Off‐center strips are excited by offsetting the Y slice‐selecting gradient, and the reconstruction window is kept coincident with excitation by similarly offsetting the Y phase‐encoding gradient. The excited strip is centered in the reconstruction window by setting the radiofrequency transmitter on resonance. The method is shown to be useful for long narrow structures such as the spine where the acquisition time is reduced by over a factor of 5 determined by the image aspect ratio. © 1988 Academic Press, Inc.
A comparison of one‐shot and recovery methods in T1 imaging
Authors: Crawley Adrian P. , Henkelman R. Mark 
Published: March 2007

AbstractSpin–lattice (T1) relaxation times are conventionally estimated using inversion recovery or saturation recovery sequences. Such “recovery” methods are limited in magnetic resonance imaging by the long times required to collect multiple points along the T1 relaxation curve. This problem can be overcome by the use of “one‐shot” methods, which collect all points along the relaxation curve in a single excitation. We have compared the relative efficiency of these methods, on the basis of the signal‐to‐noise ratio obtained in the calculated T1 image from an exam time of fixed duration. We have found that a one‐shot method using stimulated echoes has a poor efficiency. However, a method based on a technique first proposed by Look and Locker has an efficiency that is almost equal to the inversion recovery method and therefore possesses highly favorable properties for T1 imaging. © 1988 Academic Press, Inc.
In vivo determination of T1 and T2 in the brain of patients with severe but stable multiple sclerosis
Authors: Larsson H. B. W. , Frederiksen J. , Kjær L. , Henriksen O. , Olesen J. 
Published: March 2007

AbstractIn vivo measurements of relaxation processes in multiple sclerosis (MS) lesions by magnetic resonance imaging (MRI) may be important for evaluation of the disease activity in individual MS plaques. To obtain information of presumably chronic plaques, 10 patients with severe, but stable MS were investigated, using a whole‐body superconductive MR scanner, operating at 1.5 T. By employing 12‐point (or 6‐point) partial saturation inversion recovery (PSIR) and 32‐echo multiple spin‐echo sequences we measured T1 and T2 in MS plaques, white matter, and cortical gray matter. We also focused on the issue, whether T1 and T2 relaxation processes in fact were monoexponential. T1 and T2 in plaques were found to cover a wide range, which could be explained only by inherent biophysical dis similarity of the plaques, possibly due to differences in disease activity, edema and gliosis. T1 appeared monoexponential in all the plaques, but in seven cases T2 showed biexponential behavior. This was found to be most pronounced near the cerebrospinal fluid of the ventricles, probably caused by partial volume effects or increased free water content. The T2 of apparently normal white matter was significantly longer in MS patients than in healthy subjects. © 1988 Academic Press, Inc.
Nonedited 1H NMR lactate/n‐acetyl aspartate ratios and the in vivo determination of lactate concentration in brain
Authors: Vink Robert , McIntosh Tracy K. , Faden Alan I. 
Published: March 2007

AbstractThe 1H lactate/n‐acetyl aspartate ratio is commonly used for the quantitation of brain lactate under pathological conditions. We demonstrate that the intensity of the lactate methyl region in water‐suppressed, nonedited 1H spectra increases following mild brain trauma as a result of factors other than lactate accumulation. © 1988 Academic Press, Inc.
Efficient algorithms for generating interpolated (zoomed) MR images
Authors: Smith M. R. , Nichols S. T. 
Published: March 2007

AbstractThis paper discusses the two‐dimensional implementation of a number of modified fast Fourier transform (FFT) algorithms that efficiently interpolate (zoom) magnetic resonance (MR) images. If the original image was sampled at a rate satisfying the Nyquist criterion, these algorithms would effectively increase the sampling rate, permitting image details to be more easily discerned. The Skinner interpolating fast Fourier transform (SIFIT) avoids many of the computationally unnecessary complex multiplications that occur when interpolating using the normal fast Fourier transform algorithm. The novel interpolating fast Fourier transform (NIFFT) offers further savings when a subimage is required. Theoretical and experimental timings that compare the use of the normal FFT, SIFFT, and NIFFT algorithms for interpolation are given using magnetic resonance image reconstruction examples. Time savings of a factor of 2 to 4 are possible in typical experimental situations. Time savings of factors of 5 to 20 are possible when zooming images using two‐dimensional band selectable digital filtering (2D‐BSDF) in combination with decimation and the SIFFT algorithm. In 2D‐BSDF, the original MRI data set is reduced in size to retain only those frequency components corresponding to a desired subimage, thereby decreasing the computational load associated with further processing. A significant reduction in computation time is achieved when modeling is combined with 2D‐BSDF and SIFFT as fewer points require modeling. © 1988 Academic Press, Inc.
Characterization of high‐energy phosphate compounds during reperfusion of the irreversibly injured myocardium using 31P MRS
Authors: Wendland Michael F. , White Richard D. , Derugin Nikita , Finkbeiner Walter E. , McNamara Michael T. , Moseley Michael E. , Lipton Martin J. , Higgins Charles B. 
Published: March 2007

AbstractPhosphorus‐31 magnetic resonance spectroscopy (MRS) was used to monitor regional changes in high‐energy phosphorus compounds and intracellular pH during 60 min of acute regional ischemia (acute occlusion of left anterior descending artery) and reperfusion in open‐chest cats using a 1.2‐cm two‐turn coil sutured to the myocardium. During the 60‐min ischemic phase, phosphocreatine (PCr) intensity was reduced to 47 ± 4.9% (mean ± SE) of control (p < 0.01) by 15 min postocclusion while adenosine triphosphate (ATP) intensity decreased more slowly with the decrease (66 ± 5.6%) achieving significance (p < 0.05) only at 60 min postocclusion. Inorganic phosphate (Pi) increased to a maximum of 397 ± 42% of control (p < 0.01) while the pH decreased progressively from 7.36 ± 0.02 to 6.02 ± 0.14 (p < 0.01). After release of occlusion PCr intensity recovered to 86 ± 12% of the initial control value at 15 min postreperfusion but showed a subsequent downward trend to 79 ± 8.8%. The ATP did not recover but tended to decline further during reperfusion. The Pi intensity decreased to 260 ± 38% of control while the pH increased to 7.01 ± 0.23 by 15 min postreperfusion. Thus, the reperfused irreversibly injured myocardium is characterized by persistent depletion of PCr and ATP and elevation of Pi. Phosphorus‐31 MRS provides a nondestructive method for characterizing the reperfused irreversibly damaged myocardium. © 1988 Academic Press, Inc.
Adaptation of culture methods for NMR studies of anchorage‐dependent cells
Authors: Neeman M. , Rushkin E. , Kadouri A. , Degani H. 
Published: March 2007

AbstractTwo methods for growing anchorage‐dependent cells were adapted for nuclear magnetic resonance (NMR) measurements: growing cells on agarose polyacrolein microsphere beads and on “filters” made of nonwoven polyester fabric. Both were found to be convenient and most suitable for NMR studies in any conventional spectrometer without probe modification. These methods were employed in studies of human breast cancer T47D‐A11 cells, using scanning electron microscopy and 31P NMR spectroscopy. The results show that the contents per cell of phosphorylcholine, phosphorylethanolamine, and their glycerol derivatives depend on the mode of cell assembly and decrease gradually with the increase in cell‐cell interaction along the growth curve. © 1988 Academic Press, Inc.
Sodium influxes in renal epithelial LLC‐PK1/CI4 cells monitored by 23Na NMR
Authors: Jans A. W. H. , Willem R. , Kellenbach E. R. , Kinne R. K. H. 
Published: March 2007

Abstract23Na NMR experiments with a suspension of the renal epithelial cell line, LLC‐PK1/ CI4 in the presence of the shift reagent dysprosium polyphosphate showed that the intra‐cellular sodium was only NMR visible for 64 ± 4%. Intracellular sodium content was found to be 30.6 ± 1.2 mM (25oC). Examination of the sodium influx during recovery from intracellular acidification showed that sodium is transported not only by Na+/H+ exchange but also by sodium‐D‐glucose cotransport with a stoichiometry of 1:1. © 1988 Academic Press, Inc.
MRI of extremities using perforated single‐turn solenoids
Authors: Hornak Joseph P. , Marshall Eric , Szumowski Jerzy , Bryant Robert G. 
Published: March 2007

AbstractA class of single‐turn solenoids that permits magnetic imaging of the extremities in horizontal bore magnets with improved coupling between the imaged anatomy and the rf section of the imager is described and demonstrated. These devices differ from more conventional designs primarily by the placement of one or more access holes in the side of the generally cylindrical resonant structure to permit extremity insertion. The image quality is excellent, rf efficiency and homogeneity are good, and signal‐to‐noise is high, permitting rapid acquisition of magnetic images with small fields of view. © 1988 Academic Press, Inc.
MR fluoroscopy: Technical feasibility
Authors: Riederer Stephen J. , Tasciyan Talin , Farzaneh Farhad , Lee James N. , Wright Ronald C. , Herfkens Robert J. 
Published: March 2007

AbstractA method of magnetic resonance image acquisition and reconstruction is described in which high imaging rates and fast reconstruction times are allowed. The acquisition is a modification of the basic FLASH sequence but with a restricted number N of phase encodings. The encodings are applied sequentially, periodically, and continuously. Images are formed by sliding a window of width N encodings along the acquired data and reconstructing an image for each position of the window. In general the acquisition time per image exceeds the time between successive images, and the method thus has a temporal lag. Experimental studies were performed with a dynamic phantom using 48 phase encodings and a TR of 20 ms, for an image acquisition time of about 1 s. The image display rate in the reconstructed sequence was 12.5 images/s, and the image sequence portrayed the motion of the phantom. Additional studies were done with 24 encodings. It is shown how the sliding window technique lends itself to high‐speed reconstruction, with each newly acquired echo used to quickly update the image on display. The combination of the acquisition technique described and a hardware implementation of the reconstruction algorithm can result in realtime MR image acquisition and reconstruction. © 1988 Academic Press, Inc.
Integrated volume‐selective/spectral editing 1H NMR and postdetection signal processing for the sensitive determination of lactate
Authors: Knüttel A. , Rommel E. , Clausen M. , Kimmich R. 
Published: March 2007

AbstractA new volume selection/spectral editing pulse sequence (VOSING) is presented. The features specific to the technique are that the volume selection and the editing intervals coincide and that no decoupling is necessary. The pulse sequence can be applied under both homo‐ and heteronuclear conditions. Phantom experiments with lactate solutions and human serum led to water suppression factors of about 20,000. A postdetection signal processing method has been implemented. The final sensitivity for lactate determinations could thus be improved by a factor of more than 4. Ischemia‐induced lactate could easily be detected in serum. At present, the lower detection limit of lactate is 1 mmol/liter for a(1.2cm)3 voxel and 32 scans in a 4.7‐T/40‐cmmagnet. © 1988 Academic Press, Inc.
Proton relaxation times in cancer diagnosis
Authors: Mariappan S. V. Santhana , Subramanian S. , Chandrakumar N. , Rajalakshmi K. R. , Sukumaran S. S. 
Published: March 2007

AbstractProton nuclear magnetic resonance relaxation parameters ( T1,T2) were measured for over 100 malignant and normal tissue samples of various organs of the human body. The purpose ofthis study was to estimate the reliability ofthe NMR technique in discriminating normal from malignant tissues. Breast and cervix samples were analyzed by using the malignancy index concept and we were able to distinguish malignant and normal tissue in 17 out of 18 breast samples and 5 out of 7 cervix samples. Since the relaxation data of a normal control population ofthe other organs were not available, the data for these are reported without any further analysis. The distinction between carcinomas and sarcomas was also made by using the estimated relaxation parameters. Malignancy indices of breast tissue samples for linear least‐squares and nonlinear two‐parameter and three‐parameter least‐squares procedures were calculated and used to evaluate the relative efficiencies in discriminating malignant from normal tissues. © 1988 Academic Press, Inc.
Elimination of transverse coherences in FLASH MRI
Authors: Crawley Adrian P. , Wood Michael L. , Henkelman R. Mark 
Published: March 2007

AbstractFast low‐angle shot (FLASH) imaging enables TI‐weighted scans to be acquired in a few seconds. However, the diagnostic image quality is severely compromised by the appearance of artifactual bands parallel to the frequency encode direction. We show that the band structure arises from differences in the ability of the phase encode gradient to spoil transverse coherences that build up between successive repetition intervals. A theoretical understanding of the mechanisms involved leads to a comparison between various methods of spoiling the unwanted echoes throughout the whole field of view. Spoiler gradients whose amplitudes change linearly with phase encode step number are treated in detail. The theory predicts that the spoilers will rotate and rescale the band structure and these results are confirmed experimentally. The effect of the spoilers at a given location along the gradient is equivalent to the effect on the entire field of view of an incremented phase shift applied to the radiofrequency pulse. An appropriate rf phase shift scheme should therefore provide ideal spoiling characteristics for FLASH imaging. © 1988 Academic Press, Inc.
Longitudinal proton relaxation rates in rabbit tissues after intravenous injection of free and chelated Mn2+
Authors: Spiller Marga , Brown Rodney D. , Koenig Seymour H. , Wolf Gerald L. 
Published: March 2007

AbstractThe factors that determine the field‐dependent increase in 1/T1 of tissue water protons were investigated for MnCl2, and Mn2+ (PDTA) (1, 3‐propylenediamine‐N,N′,N″,N‴‐tet‐ raacetic acid) introduced intravenously into rabbits. Mn2+ was used in preference to other paramagnetic ions in part because of the distinct NMRD profiles (magnetic field dependence of 1/T1) of free Mn2+ ions, their small chelate complexes, and their macromolecular conjugates, and in part because the relatively low toxicity of Mn2+ is favorable for animal studies. Tissue content of Mn2+ was determined in all samples by inductively coupled plasma analyses; the state of Mn2+ in excised tissues was determined from the form of the 1/T1 NMRD profile of water protons; and distribution of contrast agent within tissue and access of water on a T1 time scale were determined by double‐exponential analyses of proton relaxation behavior in intact doped tissue, as well as by the change of single‐exponential relaxation rates and proton signal intensity upon gentle disruption ofthe tissue. MnCl2 is found in all tissues, except fat and skeletal muscle, but liver is most avid at low dose, and Mn2+ accumulates in spleen after high doses. Chelation targets Mn2+ to liver and kidney, saturating the liver chemically at relatively low dose. We suggest that pronounced increase in tissue relaxivity results from irrotationally bound Mn2+, ostensibly associated with the polar head groups of cell membranes. Compartmentalization of contrast agent and restricted diffusion of tissue water influences the maximum relaxation rates attainable, so that there is an optimal dose of these contrast agents which is rather low. © 1988 Academic Press, Inc.
Dextran‐magnetite: A contrast agent for sodium‐23 MRI
Authors: Summers Ronald M. , Joseph Peter M. , Renshaw Perry F. , Kundel Harold L. 
Published: March 2007

AbstractDextran‐magnetite, a superparamagnetic compound, is a powerful relaxation reagent for sodium. Administered intravenously, it is confined mainly to the vasculature and eliminates the signal from plasma sodium, a significant component of the tissue sodium signal. Applications ofdextran‐magnetite for in vivo sodium imaging ofa normal rat and rats with a tumor and experimentally induced peripheral edema are shown. Our results indicate that dextran‐magnetite may be useful for improving tumor detection and for imaging of edema. To our knowledge, this is the first report of a contrast agent suitable for sodium magnetic resonance imaging. © 1988 Academic Press, Inc.
High‐resolution 1H NMR spectroscopy in the diagnosis of breast cancer
Authors: Bradamante Silvia , Barchiesi Emma , Pilotti Silvana , Borasi Giovanni 
Published: March 2007

AbstractSurgical specimens from 22 patients with infiltrating ductal carcinoma of the breast were analyzed by high‐resolution 1H NMR spectroscopy at 80 and 300 MHz. Results were compared with those obtained from 9 benign (proliferative dysplasia without atypia) breast samples. NMR spectra at 80 MHz showed well‐resolved water and lipid peaks so it was possible to calculate specific T1 and T2 relaxation times. The longitudinal T1, relaxation process of the water was found to be properly represented by a monoexponential function, whereas the transverse T2 decay was well accounted for by a biexponential model. Relaxation time measurements of the water were found to be a valuable tool in breast tissue characterization, in particular (a) mean T1, values from malignant and control populations are well distinguished (P < 0.0008): (b) mean T2, values of both fast and slow components from the two populations are statistically different (P < 0.0001) and no overlap exists in the distributions of the second component. Three‐hundred‐meg‐ ahertz spectra allowed a detailed analysis of the lipidic component of the sample: malignant tumors were found to present in the region 1.3–1.2 ppm a species characterized by a very slow transverse relaxation time ( T2 = 200–1000 ms). © 1988 Academic Press, Inc.
1HNMR studies on human plasma lipids from newborn infants, healthy adults, and adults with tumors
Authors: Eskelinen S. , Hiltunen Y. , Jokisaari J. , Virtanen S. , Kiviniittys K. 
Published: March 2007

AbstractThe 1HNMR spectra of the lipid region of human plasma from healthy adults, neonates, and patients with malignant and nonmalignant tumors have been recorded on a JNM‐GX400 FT spectrometer operating at 399.6 MHz for protons. The chemical shifts of methylene and methyl groups of plasma lipids were measured with respect to the higher field component of the methyl proton resonance of the lactate molecule. The results show that there are changes in the chemical shifts of the methylene proton resonances among the plasma from healthy adults, adults with tumors, and neonates. The shifts observed in the case of cancer patients and neonates are in the direction opposite to the shift measured from the plasma of healthy adults. Thus, the observed changes cannot be explained by the activity in the cell proliferation of tissues which is high in the cases of both healthy neonates and patients with malignant tumors, but they most probably reflect the different lipoprotein compositions of neonates, healthy adults, and adults with tumors. © 1989 Academic Press, Inc.
The unequivocal determination of lactic acid using a one‐ dimensional zero‐quantum coherence‐transfer technique
Authors: Doddrell David M. , Brereton Ian M. , Moxon Leith N. , Galloway Graham J. 
Published: March 2007

AbstractA method based on zero‐quantum coherence transfer for spectral editing of metabolites in aqueous solution in a one‐dimensional experiment is described. Water suppression factors of approximately 8000 were achieved by the use of pulsed B0 field gradients and excellent editing was obtained in a single acquisition. The methyl resonances of both lactate and acetaldehyde were readily observed in a mouse brain homogenate by generat‐ ing zero‐quantum coherence using Gaussian pulses for selective excitation of the respective CH resonances. © 1989 Academic Press, Inc.
In vivo proton nuclear magnetic resonance imaging and spectroscopy studies of halocarbon‐induced liver damage
Authors: Brauer Manfred , Towner Rheal A. , Renaud Ian , Janzen Edward G. , Foxall David L. 
Published: March 2007

AbstractProton magnetic resonance imaging and localized NMR spectroscopy were used to study the rat liver in situ. Respiratory gating was used in both the imaging and the localized spectroscopy studies to control for the movement of the upper abdomen of the rat during breathing. After administration of carbon tetrachloride, bromotrichloromethane, or halothane, localized regions of high proton signal intensity were observed in the NMR images of the liver. Localized (VOSY) proton NMR spectra from within these regions indicated that the increase in a signal intensity was due to a longer T2 relaxation time for the water resonance, indicating acute edema in the region of tissue damage. © 1989 Academic Press, Inc.