ISSN:0740-3194    

DOI:10.1002/mrm.1910340403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractFive patients, each with a brain abscess, were examined by means of1H MR spectroscopic imagingin vivo.The aspirated pus was analyzedin vitroby means of 1D and 2D COSY1H MRS. In addition to resonance lines from compounds (lactate, alanine and lipids) often found in the spectra from intracranial tumors, resonance lines were detected from a number of markers of infectious involvement (acetate, succinate, and various amino acids). These results suggest that1H MRSin vivomight contribute in establishingnoninvasivelya differential diagnosis between brain abscess and tumor.

ISSN:0740-3194    

DOI:10.1002/mrm.1910340404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractAs tissue oxygen tension (pO2is an important variable in cancer therapy, it would be of major clinical benefit to be able to measure pO2noninvasively. Current methods for determining pO2in clinical settings are limited to superficial tumors. The authors measured the apparent diffusion constant (ADC) in an implanted murine fibrosarcoma (RIF‐1) using magnetic resonance imaging and correlated the ADC with tissue pO2measured by electron paramagnetic resonance oximetry. The ADC correlates significantly with tissue pO2in this tumor (r= 0.89;n= 14) and so may provide a noninvasive index of pO2in tumor

ISSN:0740-3194    

DOI:10.1002/mrm.1910340405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA version of interleaved echo‐planar imaging (EPI) is presented in which only one polarity of the readout gradient is used for signal acquisition to avoid ghosting artifacts. Two possible forms of the phase encoding gradient, blipped and constant, are discussed. With the constant phase encoding, interleaving of partial trajectories in the Fourier domain (k‐space) is controlled automatically by the echo train delay. The constant phase encoding gradient introduces a shear distortion of thek‐space grid. A modification of the reconstruction procedure is given which corrects for this effect. The method provides a 128 × 128 image in 1 s on a clinical system with standard gra

ISSN:0740-3194    

DOI:10.1002/mrm.1910340406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA new ultra‐fast imaging technique that does not place extreme demands on the speed of the gradient system is described. When used with comparable MRI systems, the rotating ultra‐fast imaging sequence (RUFIS) can acquire images 4 to 5 times faster than gradient‐moment nulled EPI and more than twice as fast as DUFIS, OUFIS, or BURST techniques. Because the technique uses free induction decays instead of echoes, it can be made particularly insensitive to effects of motion, flow, and diffusion. Preliminary images of turbulent flow are presented to demonstrate this insensitivity. However, with appropriate encoding, flow effects may be i

ISSN:0740-3194    

DOI:10.1002/mrm.1910340407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA new contrast preparation based on modified driven equilibrium Fourier transfer is introduced and evaluated for generation ofT1‐weighted images for assessment of the myocardial perfusion with contrast agent first‐pass kinetics. The new preparation scheme producesT1contrast with insensitivity to arrhythmias in prospectively triggered sequential imaging thereby eliminating one of the major sources of problems in potential patient studies with previously employed contrast preparations sche

ISSN:0740-3194    

DOI:10.1002/mrm.1910340408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractAn MRI time course of 512 echo‐planar images (EPI) in resting human brain obtained every 250 ms reveals fluctuations in signal intensity in each pixel that have a physiologic origin. Regions of the sensorimotor cortex that were activated secondary to hand movement were identified using functional MRI methodology (FMRI). Time courses of low frequency (<0.1 Hz) fluctuations in resting brain were observed to have a high degree of temporal correlation (P<10−3) within these regions and also with time courses in several other regions that can be associated with motor function. It is concluded that correlation of low frequency fluctuations, which may arise from fluctuations in blood oxygenation or flow, is a manifestation of functional connectivity of the br

ISSN:0740-3194    

DOI:10.1002/mrm.1910340409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractQuantitative31P NMR was used to follow the time variation of the hypometabolic response to hypoxic partial ischemia in an animal model. The purpose of the study was to establish the value of this repeated spectroscopy operating by means of a surface coil. It aimed at determining whether a therapeutic intervention could influence the transient changes occurring during the insult or early recovery. A pharmacological substance was thus used during a reversible forebrain ischemia, induced by a combination of vascular occlusion and mild hypoxia in two groups of rats. As an available and convenient example, L‐carnitine was chosen. Statistical analysis of the experimental results revealed a significant difference of theP1and PCr levels between treated and untreated animal

ISSN:0740-3194    

DOI:10.1002/mrm.1910340410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractWe have used29Si solid‐state nuclear magnetic resonance (NMR) spectroscopy to study the chemical structure of the silicone gels in virgin and explanted breast prostheses. Despite evidences of alteration in the morphological appearance of the silicone gel inside the breast prosthesis, our results do not reveal changes in the chemical nature and structure of the silicone gels after implantation. In addition to the main29Si resonance peak at −22.26 ppm that corresponds to the resonance frequency of the D repeat unit of the polysiloxane chains, the high sensitivity of our NMR technique allows the detection of very low concentrations of silicone compounds. Within our experimental detection limit of 0.2%, no signal between −90 ppm and −150 ppm are observed. This indicates that no silica products are present inside the gel of the prostheses. Furthermore, our29Si NMR spectra indicate differences in the chemical compositions of the silicone gels from different manufa

ISSN:0740-3194    

DOI:10.1002/mrm.1910340411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA particularly powerful paradigm for functional MR imaging of microvascular hemodynamics incorporates paramagnetic materials that create significant image contrast. These include exogenous (lanthanide chelates) and endogenous (de‐oxygenated hemoglobin) agents for mapping cerebral blood volume and neuronal activity, respectively. Accurate interpretation of these maps requires an understanding of the bio‐physics of susceptibility‐based image contrast. The authors developed a novel Monte Carlo model with which the authors quantified the relationship between microscopic tissue parameters, NMR imaging parameters, and susceptibility contrastin vivo.The authors found vascular permeability to water and the flow of erythrocytes to be relatively unimportant contributors to susceptibility‐induced ΔR2. However, pulse sequence, echo time, and concentration of contrast agent have profound effects on the vessel size dependence of ΔR2. For a model vasculature containing both capillaries and venules, the authors predicted a linear volume fraction dependence for physiological volume changes based on recruitment and dilation, and a concentration dependence that is nonlinear and pulse sequence dependent. Using the model, the authors demonstrated that spin echo functional images have greater microvascular sensitivity than gradient echo images, and that the specifics of the volume fraction and concentration dependence of transverse relaxivity change should allow for robust mapping of relative blood volume. The authors also demonstrated excellent agreement between the predictions of their model and experimental data obtained from the serial injection of superparamagnetic contrast agent in a

ISSN:0740-3194    

DOI:10.1002/mrm.1910340412

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY