bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assignment of the T2 components of amphibian peripheral nerve to their microanatomical compartments
Authors: Wachowicz Keith , Snyder Richard E. 
Published: August 2002

AbstractThe proton transverse‐relaxation spectrum of peripheral nerve has been reported to consist of three components arising from microanatomical water compartments within the nerve. The component with the shortest decay time has been consistently seen to be a result of the myelin. In this study, experiments were performed to reveal the microanatomical sources of the two longest‐lived components. Transverse‐relaxation spectra were repeatedly obtained from samples of sciatic nerve of Xenopus laevis, the African clawed frog. These samples were maintained in vitro in a perfusion chamber, allowing for “on‐the‐fly” changes in perfusate composition. The changes in composition involved the addition of either 10‐mM Mn2+ or 30‐mM Gd‐DTPA to the perfusate, or the replacement of H2O in the perfusate by D2O. The D2O experiments revealed that >98% of the signal attributed to the nerve resulted from exchangeable water. Following the introduction of a paramagnetic agent into the perfusate, it was found that the intermediate‐lived component of the nerve T2 spectra disappeared within 10–50 min. However, the shortest‐ and longest‐lived components remained, experiencing much more gradual long‐term changes. It was thus concluded that the intermediate‐lived component corresponds to the interaxonal compartment of nerve tissue based upon its closer proximity to the outside environment of the nerve. Magn Reson Med 47:239–245, 2002. © 2002 Wiley‐Liss, Inc.
Coupled microstrip line transverse electromagnetic resonator model for high‐field magnetic resonance imaging
Authors: Bogdanov G. , Ludwig R. 
Published: August 2002

AbstractThe performance modeling of RF resonators at high magnetic fields of 4.7 T and more requires a physical approach that goes beyond conventional lumped circuit concepts. The treatment of voltages and currents as variables in time and space leads to a coupled transmission line model, whereby the electric and magnetic fields are assumed static in planes orthogonal to the length of the resonator, but wave‐like along its longitudinal axis. In this work a multiconductor transmission line (MTL) model is developed and successfully applied to analyze a 12‐element unloaded and loaded microstrip line transverse electromagnetic (TEM) resonator coil for animal studies. The loading involves a homogeneous cylindrical dielectric insert of variable radius and length. This model formulation is capable of estimating the resonance spectrum, field distributions, and certain types of losses in the coil, while requiring only modest computational resources. The boundary element method is adopted to compute all relevant transmission line parameters needed to set up the transmission line matrices. Both the theoretical basis and its engineering implementation are discussed and the resulting model predictions are placed in context with measurements. A comparison between a conventional lumped circuit model and this distributed formulation is conducted, showing significant departures in the resonance response at higher frequencies. This MTL model is applied to simulate two small‐bore animal systems: one of 7.5‐cm inner diameter, tuned to 200 MHz (4.7 T for proton imaging), and one of 13.36‐cm inner diameter, tuned to both 200 and 300 MHz (7 T). Magn Reson Med 47:579–593, 2002. © 2002 Wiley‐Liss, Inc.
Surface size, curvature analysis, and assessment of knee joint incongruity with MRI in vivo
Authors: Hohe Jan , Ateshian Gerard , Reiser Maximilian , Englmeier Karl‐Hans , Eckstein Felix 
Published: August 2002

AbstractThe purpose of this study was to develop an MR‐based technique for quantitative analysis of joint surface size, surface curvature, and joint incongruity and to assess its reproducibility under in vivo imaging conditions. The surface areas were determined after 3D reconstruction of the joint by triangulation and the incongruity by Gaussian curvature analysis. The precision was tested by analyzing four replicated MRI datasets of human knees in 14 individuals. The algorithms were shown to produce accurate data in geometric test objects. The interscan precision was <4% (CV%) for surface area, 2.9–5.7 m−1 (SD) for the mean principal curvature, and 4.1–7.4 m−1 for congruence indices. Incongruity was highest in the femoropatellar joint (79.7 m−1) and lowest in the medial femorotibial joint (28.6 m−1). This technique will permit identification of the specific role of surface size, curvature, and incongruity as potential risk factors for osteoarthritis. Magn Reson Med 47:554–561, 2002. © 2002 Wiley‐Liss, Inc.
Proton T2 relaxation study of water, N‐acetylaspartate, and creatine in human brain using Hahn and Carr‐Purcell spin echoes at 4T and 7T
Authors: Michaeli Shalom , Garwood Michael , Zhu Xiao‐Hong , DelaBarre Lance , Andersen Peter , Adriany Gregor , Merkle Hellmut , Ugurbil Kamil , Chen Wei 
Published: August 2002

AbstractCarr‐Purcell and Hahn spin‐echo (SE) measurements were used to estimate the apparent transverse relaxation time constant (T) of water and metabolites in human brain at 4T and 7T. A significant reduction in the T values of proton resonances (water, N‐acetylaspartate, and creatine/phosphocreatine) was observed with increasing magnetic field strength and was attributed mainly to increased dynamic dephasing due to increased local susceptibility gradients. At high field, signal loss resulting from T decay can be substantially reduced using a Carr‐Purcell‐type SE sequence. Magn Reson Med 47:629–633, 2002. © 2002 Wiley‐Liss, Inc.
Respiration‐inducedB0fluctuations and their spatial distribution in the human brain at 7 Tesla
Authors: Van de Moortele Pierre‐François , Pfeuffer Josef , Glover Gary H. , Ugurbil Kamil , Hu Xiaoping 
Published: August 2002

AbstractIn functional magnetic resonance imaging (fMRI), it is known that physiological influences such as cardiac pulsation, respiration, and brain motion can induce fluctuations in signal intensity and phase. Some of the mechanisms potentially involved in those phenomena are expected to be amplified at higher magnetic fields. This study addresses the issue ofB0fluctuations induced by susceptibility changes during respiration attributed to movements of chest and diaphragm, and variations in the oxygen concentration. It is demonstrated that respiration‐induced resonance offsets (RIROs) are significant at 7T. Data were acquired with an RF pulse (no gradients), multislice echo‐planar imaging (EPI), and dynamic 3D fast low‐angle shot (3D‐ FLASH) imaging. Three main observations summarize the experimental findings. First, in FIDs measured after a single RF pulse, a RIRO with a large amplitude was consistently detected, although the average amplitude varied between subjects from 1.45 Hz to 4 Hz. Second, in transverse EPI images obtained in the occipital lobe, the RIRO amplitude showed a monotonic increase along thezaxis toward the lungs. Third, a more detailed spatial analysis with 3D‐FLASH phase maps revealed that a previously published analytical model can accurately describe the spatial distribution of RIRO. Consequential apparent motions in the EPI series, as well as the implications of slice orientation for correction strategies are discussed. Magn Reson Med 47:888–895, 2002. © 2002 Wiley‐Liss, Inc.
Volume correction for edema in single‐volume proton MR spectroscopy of contrast‐enhancing multiple sclerosis lesions
Authors: Helms Gunther 
Published: August 2002

AbstractThe effect of edema on metabolic changes in contrast‐enhancing multiple sclerosis lesions was studied by combining quantification of proton MR spectra with segmentation of the volume‐of‐interest, which was based on biexponential T2 relaxation. All lesions showed a second component (slong) with a longer T2 (185–450 ms), which was increased compared to healthy controls. Regression analysis indicated that slong replaces the short‐T2 component and total creatine. Since the water content was close to 100%, slong was used to correct for an increase in extracellular space. This compensated for the apparent loss of creatine and rendered cholines markedly increased, as observed in animals with experimental allergic encephalomyelitis. Total N‐acetyl aspartate (NAA) concentration was inversely correlated with slong and between 34–70% of its average reduction was assigned to edema. Thus, NAA loss exceeded cellular loss. Assessment of varying degrees of edema may be especially beneficial for quantitative longitudinal studies. Magn Reson Med 46:256–263, 2001. © 2001 Wiley‐Liss, Inc.
IMPACT: Image‐based physiological artifacts estimation and correction technique for functional MRI
Authors: Chuang Kai‐Hsiang , Chen Jyh‐Horng 
Published: August 2002

AbstractFunctional MRI (fMRI) signal variation induced by respiratory and cardiac motion affects the activation signal and limits the accuracy of analysis. Current physiological motion correction methods require either synchronization with external monitoring of respiration and heartbeat, specialized pulse sequence design, ork‐space data. The IMage‐based Physiological Artifacts estimation and Correction Technique (IMPACT), which is free from these constraints, is described. When images are acquired fast enough to sample physiological motion without aliasing, respiratory and cardiac signals can be directly estimated from magnitude images. Physiological artifacts are removed by reordering images according to the estimated respiratory and cardiac phases and then subtracting the Fourier‐fitted variation from magnitude images. Compared with thek‐space–based method, this method can efficiently and effectively reduce the overall signal fluctuation in the brain and increase the activated area. With this new technique, physiological artifacts can be reduced using traditional fMRI pulse sequences, and existing data can be corrected and reanalyzed without additional experiments. Magn Reson Med 46:344–353, 2001. © 2001 Wiley‐Liss, Inc.
In vivo hyperpolarized 129Xe NMR spectroscopy in tumors
Authors: Wolber Jan , McIntyre Dominick J.O. , Rodrigues Loreta M. , Carnochan Paul , Griffiths John R. , Leach Martin O. , Bifone Angelo 
Published: August 2002

AbstractThe first in vivo hyperpolarized 129Xe NMR study in experimental tumors is presented. Hyperpolarized 129Xe was dissolved in solutions, and was injected intratumorally in GH‐3 prolactinomas in rats and RIF‐1 fibrosarcomas in mice. The 129Xe NMR spectra and apparent spin‐lattice relaxation times in the two tumor types present characteristic differences. These differences are discussed in terms of xenon exchange between the carrier medium and the tissue compartments. Magn Reson Med 46:586–591, 2001. © 2001 Wiley‐Liss, Inc.
Analysis of MTR histograms in multiple sclerosis using principal components and multiple discriminant analysis
Authors: Dehmeshki J. , Ruto A.C. , Arridge S. , Silver N.C. , Miller D.H. , Tofts P.S. 
Published: August 2002

AbstractMagnetization transfer ratio (MTR) histograms have the potential to characterize subtle diffuse changes in multiple sclerosis (MS) and other white matter disease. A new method is described which gives improved correlation with the Expanded Disability Status Scale (EDSS). Classification of individual subjects into normal and MS subgroups is shown. Principal component analysis (PCA) and multiple discriminant analysis (MDA) are shown to give results superior to methods of MTR histogram analysis using traditional features such as peak height and peak location. Scatterplots confirm the improved separation between groups achieved using the MDA score. The histogram analysis provides a comparison of two classification approaches, based on PCA and MDA, to recognize differences between normal controls and the four different subgroups of MS disease (and all MS patients). Multiple linear regression of these PCs vs. EDSS established an MR‐based measure of disease. Using a central 60‐mm slab of brain tissue, the success rate of binary classification between control and MS subgroups using MDA was 75–95%, depending on which two groups were being compared. Multiple regression analysis of EDSS with the first three PCs as independent variables was significant (r = 0.83 for secondary progressive MS, and r = 0.80 for all MS patients). Magn Reson Med 46:600–609, 2001. © 2001 Wiley‐Liss, Inc.
Simultaneous antegrade/retrograde cardioplegia protects myocardium distal to a coronary occlusion: A study in isolated pig hearts
Authors: Tian Ganghong , Xiang Bo , Dai Guangping , Sun Jiankang , Lindsay William G. , Deslauriers Roxanne 
Published: August 2002

AbstractThis study was designed to assess the effects of simultaneous antegrade/retrograde cardioplegia (SARC) on myocardial perfusion and energy metabolism in the region supported by the occluded left anterior descending artery (LAD) in isolated pig hearts. It was found that injection of Gd‐DTPA into the aorta during antegrade cardioplegia (AC) did not result in signal increase in the LAD region on T1‐weighted images. During SARC, however, Gd‐DTPA was detected in the LAD region with the contrast agent injected into the aorta and the coronary sinus (CS), respectively. This suggests that SARC delivered blood cardioplegia to the jeopardized myocardium through both arterial and venous perfusion routes. Moreover, localized 31P spectra showed that occlusion of the LAD during AC resulted in severe ischemic changes in the LAD myocardium and the abnormal metabolic changes were completely abolished by use of SARC. Finally, recovery of myocardial contractile function during reperfusion in the hearts subjected to SARC was significantly better compared to those arrested with AC alone. It was concluded that the myocardium distal to a coronary occlusion can be fully protected by use of SARC. Magn Reson Med 46:773–780, 2001. Published 2001 Wiley‐Liss, Inc.
MR microscopy of multicomponent diffusion in single neurons
Authors: Grant S.C. , Buckley D.L. , Gibbs S. , Webb A.G. , Blackband S.J. 
Published: August 2002

AbstractThis study examines multicomponent diffusion in isolated single neurons and discusses the implications of the results for macroscopic water diffusion in tissues. L7 Aplysia neurons were isolated and analyzed using a 600 MHz Bruker wide‐bore instrument with a magnetic susceptibility‐matched radiofrequency microcoil. Using a biexponential fit, the apparent diffusion coefficients (ADCs) from the cytoplasm (with relative fraction) were 0.48 ± 0.14 × 10−3 mm2s−1 (61 ± 11%) for the fast component, and 0.034 ± 0.017 × 10−3 mm2s−1 (32 ± 11%) for the slow component (N = 10). Diffusion in the nucleus appears to be primarily monoexponential, but with biexponential analysis it yields 1.31 ± 0.32 × 10−3 mm2s−1 (89 ± 6%) for the fast component and 0.057 ± 0.073 × 10−3 mm2s−1 (11 ± 6%) for the slow (N = 5). The slow component in the nucleus may be explained by cytoplasmic volume averaging. These data demonstrate that water diffusion in the cytoplasm of isolated single Aplysia neurons supports a multiexponential model. The ADCs are consistent with previous measurements in the cytoplasm of single neurons and with the slow ADC measurement in perfused brain slices. These distributions may explain the multiple compartments observed in tissues, greatly aiding the development of quantitative models of MRI in whole tissues. Magn Reson Med 46:1107–1112, 2001. © 2001 Wiley‐Liss, Inc.
The utility of magnetic resonance imaging in evaluating peripheral nerve disorders
Authors: Grant Gerald A. , Britz Gavin W. , Goodkin Robert , Jarvik Jeffrey G. , Maravilla Kenneth , Kliot Michel 
Published: August 2002

AbstractThe evaluation of peripheral nerve injuries has traditionally relied primarily on information gained from the clinical history, physical examination, and electrodiagnostic testing. Taken together, all of this clinical and diagnostic information often allows one to determine the location and severity of the underlying peripheral nerve problem. However, it may not be sufficient in diagnosing a focal entrapment neuropathy superimposed upon a more generalized peripheral neuropathy; localizing a focal lesion along a long segment of nerve which may be difficult to assess accurately with electrodiagnostic sutdies; distinguishing early between an axonotmetic grade of injury, which can recover through axonal regeneration, and a neurotmetic grade which cannot and therefore may benefit from a surgical exploration and repair procedure; and noninvasively diagnosing and determining the surgical resectability of peripheral nerve mass lesions such as tumors. The goal of this review is to illustrate how standard and evolving magnetic resonance imaging techniques can provide additional information in dealing with some of these problems. © 2002 Wiley Periodicals, Inc. Muscle Nerve 25: 000–000, 2002 DOI 10.1002/mus.10013
Severe infantile axonal neuropathy with respiratory failure
Authors: Wilmshurst Jo M. , Bye Ann , Rittey Chris , Adams Coleen , Hahn Angelika F. , Ramsay David , Pamphlett Roger , Pollard John D. , Ouvrier Robert 
Published: August 2002

AbstractWe describe 5 infants (4 male, 1 female) with a severe intractable form of motor‐sensory axonal neuropathy. All became ventilator‐dependent, 4 have since died and 1 remains static. Diaphragmatic paralysis was an early feature with generalized neuropathy evolving rapidly. Nerve conduction studies and biopsies were consistent with axonal disease. This disorder could be a new condition or part of the spectrum of inherited neuropathies of the axonal degenerative type. It may be that there is a “switching‐off” in the infant's Schwann cell–axonal interactions in utero or in the early postnatal period, resulting in severe progressive deterioration and then a static period without recovery. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 760–768, 2001
Phrenic nerve conduction study in patients with traumatic brachial plexus palsy
Authors: Chen Zheng Yong , Xu Jian Guang , Shen Li Ying , Gu Yu Dong 
Published: August 2002

AbstractPhrenic nerve conduction studies were performed to assess the ipsilateral nerve in 100 patients with traumatic brachial plexus palsy. Open exploration and intraoperative recordings of somatosensory evoked potentials and nerve action potentials were used to confirm the level of root lesions. The relationship between C‐5 preganglionic root lesion and the functional integrity of the ipsilateral phrenic nerve was examined. The phrenic nerves were normal in 80 cases, partially injured in 7, and severely injured in 13. We found C‐5 preganglionic root lesions in 13 (100%) patients with severely injured, 5 (71.4%) with partially injured, and 24 (30%) with normal phrenic nerves. This correlation suggests phrenic nerve conduction study is a useful tool in the diagnosis of C‐5 preganglionic root lesions in patients with traumatic brachial plexopathy. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1388–1390, 2001
Tactile directional sensibility and diabetic neuropathy
Authors: Norrsell Ulf , Eliasson Björn , Frizell Martin , Wallin B. Gunnar , Wesslau Christian , Olausson Håkan 
Published: August 2002

AbstractFive different procedures used to diagnose neuropathy were compared in a “blind” study with diabetic patients. The aim was to evaluate tests of tactile directional sensibility. Three matched groups were examined, two groups with type I diabetes, either with or without suspected neuropathy, and one of healthy controls. Testing consisted of: (1) examination by a specialist in neurology, (2) electrophysiologic measurement of nerve conduction velocity and determination of cool sensitivity, and (3) determination of directional sensibility in two stages, with categorical and quantitative techniques. Abnormal test results were obtained for both groups of diabetic patients. Quantitatively measured directional sensibility had the highest sensitivity (89%) and specificity (85%) when calculated for patients who had received a diagnosis of neuropathy from the neurologist, despite one case of abnormal directional sensibility among the healthy controls. Conduction velocity testing was almost comparably sensitive (80%) and cool sensitivity, comparably specific (85%) when calculated in the same manner. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1496–1502, 2001
Drained cavity expansion in sands exhibiting particle crushing
Authors: Russell A. R. , Khalili N. 
Published: August 2002

AbstractThe expansion of cylindrical and spherical cavities in sands is modelled using similarity solutions. The conventional Mohr–Coulomb failure criterion and the state parameter sand behaviour model, which enables hardening–softening, are used in the analysis. The sand state is defined in terms of a new critical state line, designed to account for the three different modes of compressive deformation observed in sands across a wide range of stresses including particle rearrangement, particle crushing and pseudoelastic deformation. Solutions are generated for cavities expanded from zero and finite radii and are compared to those solutions where a conventional critical state line has been used. It is shown that for initial states typical of real quartz sand deposits, pseudoelastic deformation does not occur around an expanding cavity. Particle crushing does occur at these states and causes a reduction in the stress surrounding the cavity. This has major implications when using cavity expansion theory to interpret the cone penetration test and pressuremeter test. Copyright © 2002 John Wiley & Sons, Ltd.
Estimating the probability that a simulated system will be the best
Authors: Miller J.O. , Nelson Barry L. , Reilly Charles H. 
Published: August 2002

AbstractConsider a stochastic simulation experiment consisting ofvindependent vector replications consisting of an observation from each ofkindependent systems. Typical system comparisons are based on mean (long‐run) performance. However, theprobabilitythat a system will actually be the best is sometimes more relevant, and can provide a very different perspective than the systems' means. Empirically, we select one system as the best performer (i.e., it wins) on each replication. Each system has an unknown constant probability of winning on any replication and the numbers of wins for the individual systems follow a multinomial distribution. Procedures exist for selecting the system with the largest probability of being the best. This paper addresses the companion problem of estimating the probability that each system will be the best. The maximum likelihood estimators (MLEs) of the multinomial cell probabilities for a set ofvvector replications acrossksystems are well known. We use these samevvector replications to formvkunique vectors (termed pseudo‐replications) that contain one observation from each system and develop estimators based on AVC (AllVectorComparisons). In other words, we compare every observation from each system with every combination of observations from the remaining systems and note the best performer in each pseudo‐replication. AVC provides lower variance estimators of the probability that each system will be the best than the MLEs. We also derive confidence intervals for the AVC point estimators, present a portion of an extensive empirical evaluation and provide a realistic example. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 341–358, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10019
A secure multicast protocol for the internet's multicast backbone
Authors: Yang Wen‐Her , Fan Kai‐Wei , Shieh Shiuh‐Pyng 
Published: August 2002

AbstractIn this paper we propose a secure and efficient multicast protocol where the key management is distributed to local groups. The proposed protocol takes advantage of MBone topology to maintain scalability and efficiency at the same time. Copyright © 2001 John Wiley & Sons, Ltd.