bluuebunny/crossref_metadata_2025_split huggingface dataset:
In vivo MRI of embryonic stem cells in a mouse model of myocardial infarction
Authors: Himes Nathan , Min Jian‐Yong , Lee Rebecca , Brown Courtney , Shea Jessica , Huang Xuling , Xiao Yong‐Fu , Morgan James P. , Burstein Deborah , Oettgen Peter 
Published: November 2004

AbstractThe therapeutic potential of administering stem cells to promote angiogenesis and myocardial tissue regeneration after infarction has recently been demonstrated. Given the advantages of using embryonic stem cells and mouse models of myocardial infarction for furthering the development of this therapeutic approach, the purpose of this study was to determine if embryonic stem cells could be loaded with superparamagnetic iron oxide (SPIO) particles and imaged in a mouse model of myocardial infarction over time using MRI. Mouse embryonic stem cells were labeled with SPIO particles. When incubated with 11.2, 22.4, and 44.8 μg Fe/ml of SPIO particles, cells took up increasing amounts of iron oxide. Embryonic stem cells loaded with SPIO compared to unlabeled cells had similar viability and proliferation profiles for up to 14 days. Free SPIO injected into infarcted myocardium was not observable within 12 hr after injection. After injection of three 10‐μl aliquots of 107 SPIO‐loaded cells/ml into infarcted myocardium, MRI demonstrated that the mouse embryonic stem cells were observable and could be seen for at least 5 weeks after injection. These findings support the ability of MRI to test the long‐term therapeutic potential of embryonic stem cells in small animals in the setting of myocardial infarction. Magn Reson Med 52:1214–1219, 2004. © 2004 Wiley‐Liss, Inc.
Estimating the arterial input function using two reference tissues in dynamic contrast‐enhanced MRI studies: Fundamental concepts and simulations
Authors: Yang Cheng , Karczmar Gregory S. , Medved Milica , Stadler Walter M. 
Published: November 2004

AbstractIn dynamic contrast‐enhanced MRI (DCE‐MRI) studies, an accurate knowledge of the arterial contrast agent concentration as a function of time is crucial for the estimation of kinetic parameters. In this work, a novel method for estimating the arterial input function (AIF) based on the contrast agent concentration‐vs.‐time curves in two different reference tissues is described. It is assumed that the AIFs of the two tissues have the same shape, and that simple models with two or more compartments, and unknown kinetic parameters, can describe their tracer concentration‐vs.‐time curves. Based on the principle of self‐consistency, one can relate the two tracer concentration‐vs.‐time curves to estimate their common underlining AIF, together with the kinetic parameters of the two tissues. In practice, the measured concentration‐vs.‐time curves have noise, and the AIFs of the two tissues are not exactly the same due to different dispersion effects. These factors will produce errors in the AIF estimate. Simulation studies show that despite the two error sources, the double‐reference‐tissue method provides reliable estimates of the AIF. Magn Reson Med 52:1110–1117, 2004. © 2004 Wiley‐Liss, Inc.
On the nature of the NAA diffusion attenuated MR signal in the central nervous system
Authors: Kroenke Christopher D. , Ackerman Joseph J.H. , Yablonskiy Dmitriy A. 
Published: November 2004

AbstractIn the brain, on a macroscopic scale, diffusion of the intraneuronal constituent N‐acetyl‐L‐aspartate (NAA) appears to be isotropic. In contrast, on a microscopic scale, NAA diffusion is likely highly anisotropic, with displacements perpendicular to neuronal fibers being markedly hindered, and parallel displacements less so. In this report we first substantiate that local anisotropy influences NAA diffusion in vivo by observing differing diffusivities parallel and perpendicular to human corpus callosum axonal fibers. We then extend our measurements to large voxels within rat brains. As expected, the macroscopic apparent diffusion coefficient (ADC) of NAA is practically isotropic due to averaging of the numerous and diverse fiber orientations. We demonstrate that the substantially non‐monoexponential diffusion‐mediated MR signal decay vs. b value can be quantitatively explained by a theoretical model of NAA confined to an ensemble of differently oriented neuronal fibers. On the microscopic scale, NAA diffusion is found to be strongly anisotropic, with displacements occurring almost exclusively parallel to the local fiber axis. This parallel diffusivity, ADC‖, is 0.36 ± 0.01 μm2/ms, and ADC⟂ is essentially zero. From ADC‖ the apparent viscosity of the neuron cytoplasm is estimated to be twice as large as that of a temperature‐matched dilute aqueous solution. Magn Reson Med 52:1052–1059, 2004. © 2004 Wiley‐Liss, Inc.
Bandwidth‐modulated adiabatic RF pulses for uniform selective saturation and inversion
Authors: Warnking Jan M. , Pike G. Bruce 
Published: November 2004

AbstractRadiofrequency (RF) inversion and saturation pulses with extremely high spatial selectivity and uniform profiles are a requirement for numerous MR techniques, such as pulsed arterial spin labeling and outer volume suppression. Adiabatic pulses used for inversion of longitudinal magnetization are ubiquitous, but the superior selectivity of adiabatic full passages has not been widely exploited for saturation because a simple way of calibrating the amplitude of these subadiabatic pulses is lacking. An analytically derived calibration equation is presented, applicable to a large class of pulses including the hyperbolic secant (HS) pulse and allowing the determination of the precise amplitude required to achieve any effective flip angle. The properties of this calibration are examined, and a highly selective and homogeneous HS saturation pulse is demonstrated. Based on this calibration a new class of RF pulses is developed. These bandwidth‐modulated adiabatic selective saturation and inversion (BASSI) RF pulses afford optimal amplitude modulation, achieving uniform profiles at any effective flip angle. BASSI pulses are compared to existing gradient modulated adiabatic pulses in simulations and phantom experiments and shown to be superior in terms of selectivity and homogeneity, while requiring less RF energy. An application of BASSI pulses to pulsed arterial spin labeling is shown. Magn Reson Med 52:1190–1199, 2004. © 2004 Wiley‐Liss, Inc.
Parallel imaging performance as a function of field strength—An experimental investigation using electrodynamic scaling
Authors: Wiesinger Florian , Van de Moortele Pierre‐Francois , Adriany Gregor , De Zanche Nicola , Ugurbil Kamil , Pruessmann Klaas P. 
Published: November 2004

AbstractIn this work, the dependence of parallel MRI performance on main magnetic field strength is experimentally investigated. Using the general framework of electrodynamic scaling, the B0‐dependent behavior of the relevant radiofrequency fields at a single physical field strength of 7 T is studied. In the chosen implementation this is accomplished by adjusting the permittivity and conductivity of a homogeneous spherical phantom. With different mixing ratios of decane, ethanol, purified water, N‐methylformamide, and sodium chloride, field strengths in the range of 1.5 to 11.5 T are mimicked. Based on sensitivity maps of an eight‐coil receiver array, the field‐dependent performance of parallel imaging is assessed in terms of the geometry factor g, which reflects noise enhancement in parallel imaging reconstruction. At low field strengths the SNR penalty was nearly independent of B0 and favorably low for 1D reduction factors up to between 3 and 4. At higher field strengths the transition between favorable and prohibitive parallel imaging conditions was found to shift toward higher feasible reduction factors. These findings are in good agreement with previous theoretical predictions. From this agreement it is concluded that parallel MRI at high B0 benefits specifically from onsetting far‐field behavior of the involved radiofrequency fields. Magn Reson Med 52:953–964, 2004. © 2004 Wiley‐Liss, Inc.
Activity patterns of wrist extensor muscles during wrist extensions and deviations
Authors: Finsen L. , Søgaard K. , Graven‐Nielsen T. , Christensen H. 
Published: November 2004

AbstractWrist extensor muscles are prone to certain focal musculoskeletal disorders for which the activation pattern of the extensor carpi radialis (ECR) and ulnaris (ECU) muscles may be important risk factors. Surface and intramuscular EMG of these muscles were recorded during isometric low‐force wrist extension in semipronation and pronation as well as for ulnar/radial deviation, and were analyzed using root mean square (RMS) and decomposition methods. Despite shorter ECR length at semipronation, higher amplitudes of intramuscular EMG and of motor unit action potentials (MUAPs) were found in pronation than in semipronation. However, these changes were not detectable in the surface EMG. Higher ECR activity levels were also found during wrist extension compared to ulnar/radial deviation, and differences in the motor unit (MU) properties were found during ulnar deviation compared to radial deviation and extension. Remarkably, the MUAPs of ECR were almost twice as large as those of the ECU. Overall, the ECR muscle did not respond as predicted from biomechanical considerations, and in general activity level was higher than expected. This may partly explain why the tendon of the ECR often is associated with lateral epicondylitis. Muscle Nerve, 2005
The effect of crowd density on the expected number of casualties in a suicide attack
Authors: Kress Moshe 
Published: November 2004

AbstractUtilizing elementary geometric and probability considerations, we estimate the effect of crowd blocking in suicide bombing events. It is shown that the effect is quite significant. Beyond a certain threshold, the expected number of casualties decreases with the number of people in the arena. The numerical results of our model are consistent with casualty data from suicide bombing events in Israel. Some operational insights are discussed. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2005.
The utility of superparamagnetic contrast agents in MRI: theoretical consideration and applications in the cardiovascular system
Authors: Bjørnerud Atle , Johansson Lars 
Published: November 2004

AbstractThis review will discuss the in vivo physical chemical relaxation properties of superparamagnetic iron oxide particles. Various parameters such as size, magnetization, compartmentalization and water exchange effects and how these alter the behavior of the iron oxide particles in an in vitro vs an in vivo situation with special reference to the cardiovascular system will be exemplified. Furthermore, applications using iron oxide particles for vascular, perfusion and viability imaging as well as assessment of the inflammatory status of a given tissue will be discussed. Copyright © 2004 John Wiley & Sons, Ltd.
Applications of ultrasmall superparamagnetic iron oxide contrast agents in the MR study of animal models
Authors: Wu Ed X. , Tang Haiying , Jensen Jens H. 
Published: November 2004

AbstractUltrasmall superparamagnetic iron oxide nanoparticles have been widely used during the past decade as MR intravascular contrast agents in the study of animal models. Such agents enhance both T1 and T2/T2* relaxation, although for animal studies it is the later type of enhancement that is most commonly exploited. Their strong microscopic intravascular susceptibility effect enables the local blood volume distribution to be mapped in various organs. High spatial resolution and sensitivity can be achieved, because the long half‐life of these agents in blood, combined with anesthetization, permits steady‐state measurements over extended periods. This capability has been utilized to study the cerebrovascular blood volume distributions and their changes in normal, activated, pathologic and pharmacologically or genetically modified states, particularly in rodent animal models. It has also been applied to study blood volume changes in other tissues, such as the myocardium. The relaxation rate shifts ΔR2 and ΔR2* induced by iron oxide agents may differ depending on certain morphological characteristics of the microvascular network, and sensitive ΔR2 and ΔR2* mapping can potentially provide, in addition to blood volume, measurement of other important microvascular parameters such as blood vessel density and size. This work aims to review the applications of ultrasmall superparamagnetic iron oxide contrast agents in MR animal studies, with an emphasis on the investigation of microvascular parameters. Copyright © 2004 John Wiley & Sons, Ltd.
Iron‐containing nodules of cirrhosis
Authors: Zhang Jingbo , Krinsky Glenn A. 
Published: November 2004

AbstractIn the absence of genetic hemochromatosis and systemic hemosiderosis, patients with cirrhosis can accumulate focal iron within regenerative or dysplastic hepatic nodules, commonly referred to as ‘siderotic nodules’. Siderotic dysplastic nodules are premalignant lesions while siderotic regenerative nodules are a marker for severe viral or alcoholic cirrhosis. The relationship of hepatic iron deposition to hepatic cirrhosis and neoplasia has not been fully clarified. This article will review the current literature regarding selective iron accumulation in siderotic nodules in chronic liver disease, followed by a discussion of current MR imaging techniques for detection and characterization of these nodules. Copyright © 2004 John Wiley & Sons, Ltd.
Treatment of material discontinuity in two meshless local Petrov–Galerkin (MLPG) formulations of axisymmetric transient heat conduction
Authors: Batra R. C. , Porfiri M. , Spinello D. 
Published: November 2004

AbstractWe use two meshless local Petrov–Galerkin (MLPG) formulations to analyse heat conduction in a bimetallic circular disk. The continuity of the normal component of the heat flux at the interface between two materials is satisfied either by the method of Lagrange multipliers or by using a jump function. The convergence of the H0 and H1 error norms for the four numerical solutions with an increase in the number of equally spaced nodes and in the number of quadrature points is scrutinized. With an increase in the number of uniformly spaced nodes, the two error norms decrease monotonically for the MLPG5 formulation but are essentially unchanged for the MLPG1 formulation. To our knowledge, this is the first study comparing the performance of the two methods of modelling a discontinuity in the gradient of a field variable at the interface between two different materials. Copyright © 2004 John Wiley & Sons, Ltd.
Rate‐independent behavior of ferromagnets
Authors: Kružík Martin 
Published: November 2004

AbstractWe review properties of a model allowing for rate‐independent evolution ofbulk ferromagnets. The model is based on Brown's micromagnetic theory specialized to a large‐body limit by DeSimone [2] which is enriched by a rate‐independent dissipative mechanism. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Portal hypertension develops in a subset of children with standard risk acute lymphoblastic leukemia treated with oral 6‐thioguanine during maintenance therapy
Authors: Broxson Emmett H. , Dole Mukund , Wong Raymond , Laya Bernard F. , Stork Linda 
Published: November 2004

AbstractBackground6‐Thioguanine (TG) was recently studied to determine whether TG in maintenance therapy achieves better event free survival than 6‐mercaptopurine (MP) for standard risk acute lymphoblastic leukemia (ALL) on the clinical trial, CCG‐1952 (5/1996–1/2000). Veno‐occlusive disease was previously recognized as a complication of TG on CCG‐1952. We report a newly recognized pediatric complication of TG: splenomegaly and portal hypertension (PH) developing during maintenance or after completion of therapy.ProcedureTwelve patients (3–10 years) had been randomized to receive a targeted dose of 50 mg/m2/day of TG during maintenance phases. Actual TG dose ranged from 25 to 77 mg/m2/day (median 34 mg/m2/day).ResultsThe initial patient, a boy who had marked thrombocytopenia and intermittent splenomegaly during maintenance therapy, was evaluated for persistent pancytopenia and progressive splenomegaly 3 months after completion of therapy. Dilated splenic vein and collaterals consistent with PH were documented by MRI/MRA. Esophagogastroduodenoscopy found esophageal varices. Liver biopsy showed periportal fibrosis and marked dilatation of veins and venules. Of the other 12 patients, 9 patients studied had abnormal MRI/MRAs with evidence of varices in 4. Eight patients had splenomegaly on physical examination. Liver biopsies in a girl after 3.3 courses of TG and a boy after 4.6 courses of TG showed periportal fibrosis and dilatation of venules and sinusoids and minimal focal fatty changes. Subsequent MRI/MRAs have been stable or improved.ConclusionsThe evaluations of these 12 patients suggest that treatment with TG causes injury to the liver leading to PH and that thrombocytopenia and splenomegaly are clinical hallmarks of this toxicity. © 2004 Wiley‐Liss, Inc.
Prenatal diagnosis by rapid aneuploidy detection and karyotyping: a prospective study of the role of ultrasound in 1589 second‐trimester amniocenteses
Authors: Leung Wing Cheong , Waters Jonathan J. , Chitty Lyn 
Published: November 2004

AbstractBackgroundReliable methods are available for rapid aneuploidy detection (RAD) for the prenatal diagnosis of trisomies 21, 18 and 13. This study examines the potential advantages and limitations of using RAD as a replacement rather than as an adjunct to traditional karyotyping.MethodsOne thousand five hundred and eighty‐nine consecutive pregnancies referred for cytogenetic assessment were offered RAD (FISH or QF‐PCR) as an adjunct to traditional karyotyping. The results of these two processes were compared, and the effects of three policies for cytogenetic evaluation were determined: RAD alone, a combination of RAD for all and traditional karyotyping for cases with ultrasound anomalies or a policy of RAD and traditional karyotyping in all cases.ResultsRAD was uninformative because of maternal‐cell contamination in 37 (2.3%) cases compared to 4 (0.3%) cases of culture failure in traditional karyotyping. RAD and traditional karyotyping results were concordant in 1526 of 1548 (98.6%) cases. All non‐mosaic cases of trisomies 21, 18 and 13 and cases of triploidy were correctly identified by RAD, and there were no false‐positive diagnoses. The gold standard of a traditional karyotype in each case would have detected all chromosomal abnormalities. A policy of RAD alone would have identified 60 of 73 (82%) clinically important chromosomal abnormalities. The addition of a full karyotype for cases with evidence of ultrasound abnormalities would have improved detection to 95%.ConclusionA policy offering RAD to all patients, but restricting traditional karyotyping to cases with ultrasound anomalies, would reduce the number of traditional karyotypes requested by 70%, but maintain a 95% detection rate for all clinically important chromosomal abnormalities. Further studies are required to determine whether similar results could be obtained in district general hospital units and to determine whether this approach would be acceptable to health professionals and patients. Copyright © 2004 John Wiley & Sons, Ltd.
Prenatal ultrasound detection of bilateral focal polymicrogyria
Authors: Delle Urban Linei Augusta Brolini , Righini Andrea , Rustico Mariangela , Triulzi Fabio , Nicolini Umberto 
Published: November 2004

AbstractObjectivesPrenatal diagnosis by ultrasound of fetal polymicrogyria has been reported only once.MethodsWe describe an additional case of polymicrogyria in a fetus from a monozygotic twin pair, probably the consequence of twin‐to‐twin transfusion syndrome.ResultsOn ultrasound, there were bilateral cortical hyperechogenic spots, and prenatal magnetic resonance imaging demonstrated the typical features of bilateral focal polymicrogyria.ConclusionPolymicrogyria can be considered in the differential diagnosis of hyperechogenic brain lesions on fetal ultrasound. We also confirm the risk of brain damage in monochorionic twins pregnancies and the likely hypoxic–ischemic etiology of polymicrogyria. Copyright © 2004 John Wiley & Sons, Ltd.
Demonstration of cranial sutures and fontanelles at 15 to 16 weeks of gestation: a comparison between two‐dimensional and three‐dimensional ultrasonography
Authors: Ginath S. , Debby A. , Malinger G. 
Published: November 2004

AbstractObjectiveThe purpose of this study was to evaluate the feasibility of obtaining good quality three‐dimensional ultrasound pictures of the cranial sutures and fontanelles and to compare between two‐dimensional and three‐dimensional ultrasound in identifying the normal appearance of cranial sutures and fontanelles by the transvaginal approach at 15 to 16 weeks of gestation.MethodsFifty fetuses were prospectively evaluated by two‐dimensional and three‐dimensional transvaginal sonography between 15 and 16 weeks of gestation. The sagittal, coronal, lambdoidal, and metopic sutures, as well as anterior and posterior fontanelles, were inspected.ResultsThree‐dimensional ultrasound enabled visualization of all sutures in 37 (74%) fetuses compared to 28 (56%) fetuses examined by two‐dimensional ultrasonography (p = NS). The visualization of the sagittal suture was significantly superior by three‐dimensional ultrasonography compared to two‐dimensional ultrasonography (50 (100%) vs 35 (70%), p < 0.001). No significant difference between the two modalities was found in visualization of the fontanelles.ConclusionSutures and fontanelles are usually satisfactorily demonstrated by two‐dimensional and three‐dimensional ultrasound at 15 to 16 weeks of gestation. The sagittal suture is difficult to visualize using two‐dimensional ultrasound, and three‐dimensional ultrasound appears to be the best method for its demonstration. Copyright © 2004 John Wiley & Sons, Ltd.
A rare case of de novo distal 19q trisomy prenatally diagnosed
Authors: Rombout Sonia , Sartenaer Daniel , Parmentier Benoît , Dugauquier Christian , Gillerot Yves 
Published: November 2004

AbstractWe present a case of de novo trisomy of distal 19q diagnosed prenatally by cytogenetics and FISH analysis. The autopsy performed after termination of the pregnancy showed major internal and external malformations that are associated with this chromosome abnormality. Copyright © 2004 John Wiley & Sons, Ltd.
SHORT COMMUNICATION: ACCELERATED PUBLICATION: Multicrystalline silicon solar cells exceeding 20% efficiency
Authors: Schultz O. , Glunz S. W. , Willeke G. P. 
Published: November 2004

AbstractThis paper presents the first conversion efficiency above 20% for a multicrystalline silicon solar cell. The application of wet oxidation for rear surface passivation significantly reduces the process temperature and therefore prevents the degradation of minority‐carrier lifetime. The excellent optical properties of the dielectrically passivated rear surface in combination with a plasma textured front surface result in a superior light trapping and allow the use of substrates below 100 μm thickness. A simplified process scheme with laser‐fired rear contacts leads to conversion efficiencies of 20·3% for multicrystalline and 21·2% for monocrystalline silicon solar cells on small device areas (1 cm2). Copyright © 2004 John Wiley & Sons, Ltd.