bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aortic ghost artifact in ultrashort te multislice gradient echo MR images is not increased by paramagnetic enhancement
Authors: Mitchell Donald G. , Ortega Hector , Mohamed Feroze , Tascyian Talin , Vinitski Simon 
Published: March 2007

AbstractPulsation artifact on gradient echo images with ultrashort TE (i.e., <3 msec) and intermediate TR is primarily from view‐to‐view amplitude modulation. Paramagnetic contrast agents increase the signal from blood during diastole without increasing the intensity of unsaturated systolic blood, decreasing signal modulation between systole and diastole. In a phantom and in humans, artifact decreased or remained the same following contrast enhancement.
In vitro high resolution 1h‐spectroscopy of the human prostate: Benign prostatic hyperplasia, normal peripheral zone and adenocarcinoma
Authors: Schiebler Mark L. , Miyamoto Kent K. , White Mark , Maygarden Susan J. , Mohler James L. 
Published: March 2007

Abstract1H‐spectra at 360 MHz from perchloric extracts of 35 human prostate specimens were obtained. First, we sought to define what peaks can be assigned in vitro, and thus, potentially seen in vivo. Second, we sought to try to discriminate between adenocarcinoma, normal peripheral zone and benign prostatic hyperplasia using spectral fingerprints. Thirteen samples of adenocarcinoma, 11 samples of benign prostatic hyperplasia, and 11 samples of normal contralateral peripheral zone were analyzed by obtaining a ratio from the maximum area of each major peak and the area of an added standard (3‐trimethyl‐silyl‐propionic acid). There was a significantly larger benign prostate hyperplasia citrate standardized peak area when compared to the adenocarcinoma citrate standardized peak area for each patient (P < 0.05). However, the citrate standardized peak areas from the normal peripheral zones were not significantly different from those found in the adenocarcino‐mas. Four out of 13 cases of stromal hyperplasia had similarly low levels of citrate as their respective gland's adenocarcinoma. We also found a sharp peak at 2.05 ppm that was seen in 4 out of 13 adenocarcinoma samples and in only 1 out of 13 of the benign prostate hypertrophy samples which has tentatively been assigned to N‐acetyl neuraminic acid. Further studies are required to assess whether low citrate levels alone can serve to exclusively diagnose adenocarcinoma of the prostate.
Assessment of changes in murine tumor oxygenation in response to nicotinamide using 19F NMR relaxometry of a perfluorocarbon emulsion
Authors: Hees Paul S. , Sotak Christopher H. 
Published: March 2007

AbstractThe oxygen dependencies of the 19F NMR spin‐lattice relaxation rates (R1 = 1/T1) of a perfluorocarbon emulsion sequestered in a murine tumor model has been used to evaluate nicotinamide, a radiosensitizer believed to act through enhanced tissue oxygenation. Fluorine‐19 NMR spectroscopic measurements from solid Radiation‐Induced Fibrosarcoma (RIF‐1) tumors in C3H mice showed a statistically significant improvement in tumor pO2 for a Nicotinamide‐treated group, with a ΔpO2 = 4.7 ± 3 torr (=mm Hg) (Mean ± SEM) at t = 60 min (P <.01), and 4.5 ± 3 at t = 70 min post intraperitoneal injection (P < 0.02) as compared with saline‐treated Controls, while several other time points for which t > 30 min were significant at the P < 0.05 level. Both groups had n = 10, and the statistics were based on Student's one‐tailed group t test. By comparison, in another study group where breathing gas was switched from air to 100% O2, a statistically insignificant increase of 2 torr was realized in tumor pO2 (n = 9). The maximal treatment effect occurs at a delay of 60 to 70 min, consistent with results obtained by other investigators using radiobiology techniques. Fluorine‐19 spectroscopic relaxometry can measure therapeutically meaningful changes in in vivo tumor pO2 and represents an improvement in expenditures of time, animal resources, and statistical power over conventional radiobiological methods.
Classification of trabecular structure in magnetic resonance images based on morphological granulometries
Authors: Chen Yidong , Dougherty Edward R. , Totterman Saara M. , Hornak Joseph P. 
Published: March 2007

AbstractA new method of detecting structured changes in trabecular bone, such as those associated with osteoporosis, was evaluated on magnetic resonance images of the wrist. The method was based on gray‐scale morphological granulometries which classify image texture by iteratively filtering an image and measuring the rate of change of structural diminution in a filtered‐image sequence. A classification scheme capable of distinguishing structural changes in trabecular bone starting from normal trabeculae through sclerotic, cystic, and grossly porotic bone is presented. Results of the application of this technique to the evaluation of high resolution magnetic resonance images of the wrist are presented.
Simultaneous temperature and regional blood volume measurements in human muscle using an MRI fast diffusion technique
Authors: Morvan Daniel , Leroy‐Willig Anne , Malgouyres Agnès , Cuenod Charles A. , Jehenson Philippe , Syrota André 
Published: March 2007

AbstractThe thermal dependence of the translational diffusion coefficient and of the regional blood volume was investigated in vivo by using a special MR pulsed gradient technique with reduced sensitivity to bulk tissue motion. Measurements were done at 0.5 T, using a small gradient insert. The diffusion coefficient of muscle water was calibrated against thermocouple‐measured temperature in vitro, both with the muscle fibers parallel and perpendicular to the diffusion gradient.The maximum muscle temperature variation obtained by percutaneous conduction was −8.8 ± 1.6°C under cooling and +3.7 ± 1.6°C under heating, from basal state. Simultaneously the fractional regional blood volume decreased by a factor of 3.5 under cooling and increased by a factor of 2.7 under heating.Due to the interdependence of microcirculation and tissue temperature, this technique may be used to follow heat production or deposition in living tissue (muscle exercise, electromagnetic irradiation, etc.).
A highly sensitive lactate editing technique for surface coil spectroscopic imaging in vivo
Authors: Bourgeois Dominique , Kozlowski Piotr 
Published: March 2007

AbstractA lactate editing sequence based on the use of spin‐locking pulses with surface coils is described. The sequence retains more than 90% of the available lactate magnetization and suppresses at least 95% of the lipid signal in a single scan and ca. 99.5% after a simple two step cycle. The technique allows simultaneous observation of lactate and uncoupled metabolites in the range 2 to 3 ppm. The sequence was combined with two‐dimensional spectroscopic imaging to obtain a lactate map of an ischemic rat brain in vivo.
Elimination of susceptibility distortions and reduction of diffusion attenuation in NMR microscopy by line‐narrowed 2DFT
Authors: Sharp J. C. , Bowtell R. W. , Mansfield P. 
Published: March 2007

AbstractNMR imaging at high field strengths is adversely affected by magnetic susceptibility variations within the specimen. This is especially true in NMR microscopy. We present results using a line‐narrowed imaging sequence which overcomes the image distortions associated with the frequency encoded readout method. Signal attenuation due to diffusion in static magnetic field gradients is also reduced.
A technique for assessment of bone marrow composition using magnetic resonance phase interference at low field
Authors: Derby K. , Kramer D. M. , Kaufman L. 
Published: March 2007

AbstractIn disorders which involve the bone marrow, the fat/water ratio of the marrow is often an indicator of the progress of disease. A noninvasive method of monitoring this ratio in bone marrow could be clinically useful. We have investigated a method of bone marrow assessment, using magnetic resonance imaging at low field (0.064 Tesla). The method has been tested using calibrated phantoms; we also present results from normal human subjects.
Phosphonate‐modified Gd‐DTPA complexes. III: The detection of myocardial infarction by MRI
Authors: Adzamli I. Kofi , Blau Monte , Pfeffer Marc A. , Davis Michael A. 
Published: March 2007

AbstractThe potential of a phosphonate‐modified‐Gd‐DTPA for MR image enhancement of myocardial infarction has been demonstrated in imaging experiments on rats. The agent, 1‐hydroxy‐3‐aminopropane‐1, 1‐diphosphonate‐modified‐Gd‐DTPA (Gd‐DTPA‐HPDP) accumulates in two models of myocardial infarction, (i.e., drug‐induced diffusely infarcted whole hearts and in focal acute myocardial infarction from a left coronary artery ligation). The time course of the accumulation of the agent in the focal model of infarction and subsequent washout has also been followed in vitro. Results of this kinetics demonstrate that the agent first perfuses all normal fluid spaces and then slowly diffuses into the occluded zone where it is retained for a prolonged period, in sufficient quantities to be useful as an MRI contrast agent. Wash‐out of the agent from normal myocardium is fast and complete with MR signal returning to background in minutes.The specificity of Gd‐DTPA‐HPDP for soft‐tissue calcification and its retention within the infarcts permitted imaging at 1 to 2 h postinjection, (after unbound material has cleared the normal tissues). Infarcted tissue appeared as regions of increased signal intensity in T1‐weighted images (>200% enhancement), and correlated with histopathology. Unmodified Gd‐DTPA was not retained under identical conditions. Gd‐DTPA‐HPDP permits a more accurate infarct delineation than is possible with the unmodified agent.
A weighted least‐squares method for nuclear magnetic resonance velocity imaging
Authors: Caprihan A. , Icenogle M. V. 
Published: March 2007

AbstractThe phase method for velocity measurements in NMR imaging with more than two velocity encoding steps is discussed. The weighted least‐squares method takes into account the variation in the accuracy of phase calculations at a voxel with the size of the velocity encoding gradients. We choose the weights so that the method is equivalent to the method of maximum‐likelihood for high signal‐to‐noise ratios. We propose a method of implementation to minimize the problem of phase wrapping. We also discuss the number of velocity encoding steps, the choice of step size, and signal averaging, to improve the reproducibility of velocity measurements. Standard deviation images for the velocity have been calculated and used to reduce velocity noise by thresholding the velocity image.
Solvate structures in water‐methanol solutions of MRI contrast agents: Electron spin echo envelope modulation in gadolinium chelates
Authors: Clarkson R. B. , Hwang J.‐H. , Belford R. L. 
Published: March 2007

AbstractElectron Spin Echo Envelope Modulation (ESEEM) data are reported for three gadolinium (III) chelates, Gd‐EDTA, Gd‐DTPA, and Gd‐TTHA, in frozen D2O/CH3OD glasses. This series includes Gd‐DTPA, an MRI contrast agent that is in clinical use. Three‐pulse electron spin echo modulation patterns can be modeled to yield geometrical information; e.g., distances and numbers of Gd+3‐OD interactions. Interpreted by a spherical shell model, the data for Gd‐TTHA are accounted for by Gd+3 surrounded by seven deuterons at an effective distance of 3.9 Å. We attribute these deuterons to second‐coordination sphere solvent molecules, since it is likely that Gd+3 is fully coordinated by a TTHA ligand. For analysis of ESEEM from Gd‐EDTA and Gd‐DTPA, the second‐sphere structures of Gd‐EDTA, Gd‐DTPA, and Gd‐TTHA are assumed equivalent. 2H‐ESEEM from inner‐sphere solvent molecules gives the effective distance between deuterons and Gd+3 to be ≈ 2.7 Å for the inner‐sphere water in both EDTA and DTPA complexes. The results of simulations also give the isotropic hyperfine and quadrupole coupling constants for solvent deuterium in these systems. Possible sources of error in the determination of r and q by this method are discussed.
A multispectral analysis of brain tissues
Authors: Fletcher Lynn M. , Barsotti John B. , Hornak Joseph P. 
Published: March 2007

AbstractWith the increasing use of three‐dimensional MRI techniques it is becoming necessary to explore automated techniques for locating pathology in the volume images. The suitability of a specific technique to locate and identify healthy tissues of the brain was examined as a first step toward eventually identifying pathology in images. This technique, called multispectral image segmentation, is based on the classification of tissue types in an image according to their characteristics in various spectral regions. The spectral regions chosen for this study were the hydrogen spin‐lattice relaxation time T1 spin‐spin relaxation time T2, and spin density, ϱ. Single‐echo, spin‐echo magnetic resonance images of axial slices through the brain at the level of the lateral ventricles were recorded on a 1.5 Tesla imager from 20 volunteers ranging in age from 17 to 72 years. These images were used to calculate the T1, T2, and ϱ images used for the classification. Tissue classification was performed by locating clusters of pixels in a threedimensional T1‐1‐T2‐1‐ρ histogram. Gray matter, white matter, cerebrospinal fluid, meninges, muscle, and adipose tissues were readily classified in magnetic resonance images of the volunteers with a single set of T1, T2, and ρ values. Cluster characteristics, such as size, shape, and location, provided information on the imaging procedure and tissue characteristics.
High‐precision MR velocity mapping by 3D‐fourier phase encoding with a small number of encoding steps
Authors: Bittoun Jacques , Bourroul Eric , Jolivet Odile , Idy‐Peretti Ilana , Mousseaux Elie , Tardivon Anne , Peronneau Pierre 
Published: March 2007

AbstractThe final result of Fourier velocity mapping is a set of images, each representing the spatial distribution of spins at a given velocity. To acquire data in a short time, the number of encoding gradient steps must be as small as possible, but this can mean sacrificing velocity resolution. We used interpolation methods to obtain high velocity resolution with a small number of encoding steps involving linear interpolation from 16 encoding steps or more and zero‐filling interpolation from two to eight encoding steps. Velocity measured by interpolated Fourier‐flow encoding agreed well with values obtained using a calibrated phantom. A simulation of noise on the images of the phantom showed that, for a given acquisition time, increasing number of encoding steps in the Fourier flow encoding gave better precision for velocity measurement than did averaging identical signals in phase‐mapping methods.
Gadolinium‐DTPA enhanced MRI demonstrates uterine vascular changes associated with artificially induced decidualization and ovoimplantation in rats
Authors: Hamilton G. S. , Kennedy T. G. , Norley C. J. D. , Karlik S. J. 
Published: March 2007

AbstractGadolinium‐DTPA enhanced magnetic resonance (MR) imaging has been used to demonstrate uterine vascular changes during ovoimplantation and artificially induced decidualization in rats. Evans blue dye and Gd‐DTPA were injected i.v. into rats 10 h after unilateral decidualization was induced by injection of sesame oil into the lumen of one uterine horn. Animals were killed various times later and uteri were removed, T1‐weighted proton imaging was performed, and mean image intensities for stimulated and control uterine horns were calculated by computer‐assisted image analysis. Macroscopic bluing confined to stimulated horns was apparent 5 min after tracer injection and increased in intensity until the experiment was terminated at 320 min. Analysis of MR images showed that mean image intensity of control horns did not change significantly at any time after injection of the Gd‐DTPA and Evans blue whereas mean image intensity of stimulated horns increased significantly by 5 min after injection, peaked at 20 min, and returned to values not different from controls by 320 min. T1‐weighted images of day 6 pregnant rats injected with Gd‐DTPA and Evans blue revealed patterns of image enhancement that matched those of macroscopic bluing. Uterine concentrations of radioactivity after injection of 153Gd‐DTPA indicated that increased extracellular fluid volume (ECFV) produces the image enhancement of stimulated horns since the tracer permeates the extracellular fluid of both horns. Gd‐DTPA‐enhanced MR imaging of uteri after deciduogenic stimulation revealed significant image enhancement for stimulated horns at both 9 and 27 h after stimulation. We conclude that Gd‐DTPA enhanced MR imaging allows the identification of uterine vascular changes during ovoimplantation and decidualization and that this methodology may be useful in both experimental and clinical settings.
Localized detection of glioma glycolysis using edited 1H MRS
Authors: Schupp Daniel G. , Merkle Hellmut , Ellermann Jutta M. , Ke Yong , Garwood Michael 
Published: March 2007

AbstractIn vivo 1H MRS can be used to detect and quantify the lactate resonance at 1.3 ppm provided that overlapping lipid resonances are eliminated. A homonuclear spectral editing method was developed to acquire uncontaminated 1H spectra of lactate with adiabatic pulses. An advantage of the adiabatic pulse sequence is the ability to induce uniform flip angles and to maximize sensitivity in applications employing surface coil transmitters which produce highly inhomogeneous B1. Glycolytic activity in an intracerebral C6 glioma in rats was monitored by using adiabatic editing sequences to observe [3‐13C]lactate produced from infused [1‐13C]glucose. Acute hyperglycemia (serum glucose >22 mM, n = 10) had no significant effect (P = 0.08) on the total ([12C]+ [13C]) tumor lactate signal intensity.
Novel approaches to low‐cost MRI
Authors: Macovski Albert , Conolly Steven 
Published: March 2007

AbstractThis paper presents a combination of speculative approaches, some related to earlier work and some apparently novel, which show great promise in providing a new class of MRI machines that would be considerably less expensive. This class would have advantages and disadvantages as compared to existing MRI, over and above that of low cost. The disadvantages include the apparent inability to perform classic spectroscopy, and limited flexibility in the area of selective excitation. The advantages include a fundamental immunity to inhoinogenelty and susceptibility problems, the ability to create a wide class of machines that are designed for specific anatomy‐related applications, the ability to design open machines for physician access, and improved capability for high speed imaging. Generic to all of the methods presented are a pulsed polarizing field and an oscillatory readout bias field. The pulsed field initially polarizes the magnetic moments. Sinat it is not on during the readout operation it has negligible homogeneity requirements since changes in the field amplitude will merely shade the image intensity. During readout a relatively low bias field is used. To enable the use of a relatively inhomogeneous bias field, an osciliatory field is used that has a zero average value. This prevents any long‐term buildup of phase errors due to a frequency error associated with inhomogeneity. Thus the average bias frequency will be determined solely by the frequency rather than the amplitude of the bias field. Three methods are described, all including the above features. The first two involve imaging in the laboratory frame, while the third involves imaging in the rotating frame. The second approach requires no RF excitation and the third approach uses RF bias and gradient signals. Some approaches to slice selection are described.
Development of the human brain: In vivo quantification of metabolite and water content with proton magnetic resonance spectroscopy
Authors: Kreis Roland , Ernst Thomas , Ross Brian D. 
Published: March 2007

AbstractCerebral metabolite concentrations and water content were measured by means of localized proton magnetic resonance spectroscopy in 50 children, while metabolite peak ratios in short echo time spectra were evaluated in 173 examinations. Normative curves for normal development were established for two cerebral locations. The current report presents the first study of absolute metabolite concentrations and T1‐and T2‐relaxation as a function of age. Myo‐inositol was found dominating the spectra at birth (12 mmoles/kg), while choline is responsible for the strongest peak in older infants (2.5 mmoles/kg). Creatine and N‐acetyl groups are at significantly lower concentrations in the neonate than in the adult (Cr: 6, NA: 5 mmoles/kg). NA and Cr are determined by gestational age, whereas the concentration of ml correlates best with postnatal age. Quantitative lH MRS is expected to be of particular value in diagnosis and monitoring of pathology in infants, since metabolite ratios are often misleading.
Metabolic assessment of a neuron‐enriched fraction of rat cerebrum using high‐resolution1H and13C NMR spectroscopy
Authors: Petroff Ognen A. C. , Pleban Lisa , Prichard James W. 
Published: March 2007

AbstractThis study explored the utility of1H and13C magnetic resonance spectroscopy to study a neuron‐enriched preparation made from rat cerebrum. The preparation contained high concentrations ofN‐acetylaspartate and γ‐aminobutyric acid and low concentrations of glutamine, indicating that it was in fact rich in neuronal cytosol. This was confirmed by immunohistochemical studies with antibodies to neuronal and glial markers. A method of metabolite quantification based on the creatine signal yielded metabolite concentrations similar to those of rat cerebrum, whereas concentrations based on the metabolite/protein ratio were five times lower, suggesting that much protein in the preparation was not associated with functioning cytoplasm. The metabolic competence of the preparation was assessed by quantitative measurements of its ability to convert 1−13C‐glucose into lactate, glutamate, aspartate, and other metabolites under well oxygenated conditions for 30 min. Calculated from the creatine standard, the mean glycolytic rate was the same as in a synaptosomal preparation studied under similar conditions and the same as rat cerebrumin vivo. Tricarboxylic acid cycle flux occurred at half the rate observed in the synaptosomal preparation and 16% of the basal cerebral metabolic ratein vivo.
Generalized matched filtering for time‐resolved MR angiography of pulsatile flow
Authors: Wang Yi , Weber David M. , Korosec Frank R. , Mistretta Charles A. , Grist Thomas M. , Shannon Swan J. , Turski Patrick A. 
Published: March 2007

AbstractGenerating flow‐specific images (arteriograms, venograms) with optimal signal‐to‐noise ratios for time‐resolved MR angiography is a conditional maximum problem, and its solutions are generalized matched filters. We have investigated six matched filters, corresponding to all possible combinations of three flow suppression conditions and two signal‐to‐noise ratio maximization procedures. Four of these matched filters correspond to previously described methods: the subtractive matched filter, the standard deviation, the global venous eigenirnage and the global arterial eigenimage. The two others are referred to here as the local venous eigenimage and the local arterial eigenimage. These six matched filters have been applied to 2D time‐resolved phase contrast angiographic data. The local arterial eigenimage is found to be the most effective in suppressing undesired venous flow and preserving desired arterial flow.
A potentially artifact‐free oral contrast agent for gastrointestinal MRI
Authors: Liebig Thomas , Stoupis Christophoros , Ros Pablo R. , Ballinger J. Ray , Briggs Richard W. 
Published: March 2007

AbstractThe combination of diamagnetic barium sulfate and superparamagnetic iron oxide (SPIO) in one suspension produces a macroscopic cancellation of positive and negative magnetic susceptibility components that can potentially eliminate susceptilbllity artifacts even with gradient echo pulse sequences. The relaxation properties that make the SPIO suspension a useful negative contrast agent are retained.