bluuebunny/crossref_metadata_2025_split huggingface dataset:
T2‐weighted balanced SSFP imaging (T2‐TIDE) using variable flip angles
Authors: Paul Dominik , Markl Michael , Fautz Hans‐Peter , Hennig Jürgen 
Published: June 2006

AbstractA new technique for acquiring T2‐weighted, balanced steady‐state free precession (b‐SSFP) images is presented. Based on the recently proposed transition into driven equilibrium (TIDE) method, T2‐TIDE uses a special flip angle scheme to achieve T2‐weighted signal decay during the transient phase. In combination with half‐Fourier image acquisition, T2‐weighted images can be obtained using T2‐TIDE. Numerical simulations were performed to analyze the signal behavior of T2‐TIDE in comparison with TSE and b‐SSFP. The results indicate identical signal evolution of T2‐TIDE and TSE during the transient phase. T2‐TIDE was used in phantom experiments, and quantitative ROI analysis shows a linear relationship between TSE and T2‐TIDE SNR values. T2‐TIDE was also applied to abdominal and head imaging on healthy volunteers. The resulting images were analyzed quantitatively and compared with standard T2‐weighted and standard b‐SSFP methods. T2‐TIDE images clearly revealed T2 contrast and less blurring compared to T2‐HASTE images. In combination with a magnetization preparation technique, STIR‐weighted images were obtained. T2‐TIDE is a robust technique for acquiring T2‐weighted images while exploiting the advantages of b‐SSFP imaging, such as high signal‐to‐noise ratio (SNR) and short TRs. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Toward single breath‐hold whole‐heart coverage coronary MRA using highly accelerated parallel imaging with a 32‐channel MR system
Authors: Niendorf Thoralf , Hardy Christopher J. , Giaquinto Randy O. , Gross Patrick , Cline Harvey E. , Zhu Yudong , Kenwood Gontran , Cohen Shmuel , Grant Aaron K. , Joshi Sanjay , Rofsky Neil M. , Sodickson Daniel K. 
Published: June 2006

AbstractCoronary MR angiography (CMRA) is generally confined to the acquisition of multiple targeted slabs with coverage dictated by the competing constraints of signal‐to‐noise ratio (SNR), physiological motion, and scan time. This work addresses these obstacles by demonstrating the technical feasibility of using a 32‐channel coil array and receiver system for highly accelerated volumetric breath‐hold CMRA. The use of the 32‐element array in unaccelerated CMRA studies provided a baseline SNR increase of as much as 40% over conventional cardiac‐optimized phased array coils, which resulted in substantially enhanced image quality and improved delineation of the coronary arteries. Modest accelerations were used to reduce breath‐hold durations for tailored coverage of the coronary arteries using targeted multi‐oblique slabs to as little as 10 s. Finally, high net accelerations were combined with the SNR advantages of a 3D steady‐state free precession (SSFP) technique to achieve previously unattainable comprehensive volumetric coverage of the coronary arteries in a single breath‐hold. The merits and limitations of this simplified volumetric imaging approach are discussed and its implications for coronary MRA are considered. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Q‐ball reconstruction of multimodal fiber orientations using the spherical harmonic basis
Authors: Hess Christopher P. , Mukherjee Pratik , Han Eric T. , Xu Duan , Vigneron Daniel B. 
Published: June 2006

AbstractDiffusion tensor imaging (DTI) accurately delineates white matter pathways when the Gaussian model of diffusion is valid. However, DTI yields erroneous results when diffusion takes on a more complex distribution, as is the case in the brain when fiber tracts cross. High angular resolution diffusion imaging (HARDI) overcomes this limitation of DTI by more fully characterizing the angular dependence of intravoxel diffusion. Among the various HARDI methods that have been proposed, QBI offers advantages such as linearity, model independence, and relatively easy implementation. In this work, reconstruction of the q‐ball orientation distribution function (ODF) is reformulated in terms of spherical harmonic basis functions, yielding an analytic solution with useful properties of a frequency domain representation. The harmonic basis is parsimonious for typical b‐values, which enables the ODF to be synthesized from a relatively small number of noisy measurements and thus brings the technique closer to clinical feasibility from the standpoint of total imaging time. The proposed method is assessed using Monte Carlo computer simulations and compared with conventional q‐ball reconstruction using spherical RBFs. In vivo results from 3T whole‐brain HARDI of adult volunteers are also provided to verify the underlying mathematical theory. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
History of the stiffness method
Authors: Samuelsson A. , Zienkiewicz O. C. 
Published: June 2006

AbstractThis paper presents a brief history of the development of the stiffness method. We start by tracing the evolution of the method to solve discrete‐type problems such as trusses and frames composed of two node members. We then describe the method as it is applied to solve continuum problems modelled by finite‐difference and finite‐element methods. Copyright © 2006 John Wiley & Sons, Ltd.
Hybrid and enhanced finite element methods for problems of soil consolidation
Authors: Zhou X. X. , Chow Y. K. , Leung C. F. 
Published: June 2006

AbstractHybrid and enhanced finite element methods with bi‐linear interpolations for both the solid displacements and the pore fluid pressures are derived based on mixed variational principles for problems of elastic soil consolidation. Both plane strain and axisymmetric problems are studied. It is found that by choosing appropriate interpolation of enhanced strains in the enhanced method, and by choosing appropriate interpolations of strains, effective stresses and enhanced strains in the hybrid method, the oscillations of nodal pore pressures can be eliminated. Several numerical examples demonstrating the capability and performance of the enhanced and hybrid finite element methods are presented. It is also shown that for some situations, such as problems involving high Poisson's ratio and in other related problems where bending effects are evident, the performance of the enhanced and hybrid methods are superior to that of the conventional displacement‐based method. The results from the hybrid method are better than those from the enhanced method for some situations, such as problems in which soil permeability is variable or discontinuous within elements. Since all the element parameters except the nodal displacements and nodal pore pressures are assumed in the element level and can be eliminated by static condensation, the implementations of the enhanced method and the hybrid method are basically the same as the conventional displacement‐based finite element method. The present enhanced method and hybrid method can be easily extended to non‐linear consolidation problems. Copyright © 2006 John Wiley & Sons, Ltd.
Assessment of the cost and accuracy of the generalized FEM
Authors: Strouboulis Theofanis , Zhang Lin , Babuška Ivo 
Published: June 2006

AbstractIn this paper, we address the cost versus accuracy capabilities for the generalized FEM (GFEM) which was developed in (Comput. Methods Appl. Mech. Eng. 2003; 192:3109–3161, Int. J. Numer. Meth. Engng 2004; 60:1639–1672, Ph.D. Thesis, Texas A&M University, College Station, TX, August 2003 (Advisor: T. Strouboulis)), and also the construction of two‐sided a posteriori error estimates, which can be used to assess the achieved accuracy at all levels of the method. Copyright © 2006 John Wiley & Sons, Ltd.
Inexact FETI‐DP methods
Authors: Klawonn Axel , Rheinbach Oliver 
Published: June 2006

AbstractInexact FETI‐DP domain decomposition methods are considered. Preconditioners based on formulations of FETI‐DP as a saddle point problem are used which allow for an inexact solution of the coarse problem. A positive definite reformulation of the preconditioned saddle point problem, which also allows for approximate solvers, is considered as well. In the formulation that iterates on the original FETI‐DP saddle point system, it is also possible to solve the local Neumann subdomain problems inexactly. Given good approximate solvers for the local and coarse problems, convergence bounds of the same quality as for the standard FETI‐DP methods are obtained. Numerical experiments which compare the convergence of the inexact methods with that of standard FETI‐DP are shown for 2D and 3D elasticity using GMRES and CG as Krylov space methods. Based on parallel computations, a comparison of one variant of the inexact FETI‐DP algorithms and the standard FETI‐DP method is carried out and similar parallel performance is achieved. Parallel scalability of the inexact variant is also demonstrated. It is shown that for a very large number of subdomains and a very large coarse problem, the inexact method can be superior. Copyright © 2006 John Wiley & Sons, Ltd.
High‐order DGTD methods for dispersive Maxwell's equations and modelling of silver nanowire coupling
Authors: Ji Xia , Cai Wei , Zhang Pingwen 
Published: June 2006

AbstractA high‐order discontinuous Galerkin time‐domain (DGTD) method for Maxwell's equations for dispersive media of Drude type is derived and then used to study the coupling of 2D silver nanowires, which have potential applications in optical circuits without the restriction of diffraction limits of traditional dielectric waveguides. We have demonstrated the high accuracy of the DGTD for the electromagnetic wave scattering in dispersive media and its flexibility in modelling the plasmon resonant phenomena of coupled silver nanowires. Specifically, we study the cross sections of coupled nanowires, the dependence of the resonance on the number of nanowires with more resolved resonance information than the traditional FDTD Yee scheme, time‐domain behaviour of waves impinging on coupled silver nanowires of a funnel configuration, and the energy loss of resonant modes in a linear chain of circular and ellipse nanowires. Copyright © 2006 John Wiley & Sons, Ltd.
An interior‐point algorithm for elastoplasticity
Authors: Krabbenhoft K. , Lyamin A. V. , Sloan S. W. , Wriggers P. 
Published: June 2006

AbstractThe problem of small‐deformation, rate‐independent elastoplasticity is treated using convex programming theory and algorithms. A finite‐step variational formulation is first derived after which the relevant potential is discretized in space and subsequently viewed as the Lagrangian associated with a convex mathematical program. Next, an algorithm, based on the classical primal–dual interior point method, is developed. Several key modifications to the conventional implementation of this algorithm are made to fully exploit the nature of the common elastoplastic boundary value problem. The resulting method is compared to state‐of‐the‐art elastoplastic procedures for which both similarities and differences are found. Finally, a number of examples are solved, demonstrating the capabilities of the algorithm when applied to standard perfect plasticity, hardening multisurface plasticity, and problems involving softening. Copyright © 2006 John Wiley & Sons, Ltd.
Optimization of large‐scale truss structures using sparse SAND formulations
Authors: Wang Qian , Arora Jasbir S. 
Published: June 2006

AbstractSparsity features of simultaneous analysis and design (SAND) formulations are studied and exploited for optimization of large‐scale truss structures. Three formulations are described and implemented with an existing analysis code. SAND formulations have large number of variables; however, gradients of the functions and Hessian of the Lagrangian are quite sparsely populated. Therefore, this structure of the problem is exploited and an optimization algorithm with sparse matrix capability is used to solve large‐scale problems. An existing analysis software is integrated with an optimizer based on a sparse sequential quadratic programming (SQP) algorithm to solve sample problems. The formulations and algorithms work quite well for the sample problems, and their performances are compared and discussed. For all the cases considered, the SAND formulations out perform the conventional formulation except one case. Further research is suggested to fully study and utilize sparse features of the alternative SAND formulations and to develop more efficient sparse solvers for large‐scale and more complex applications. Copyright © 2006 John Wiley & Sons, Ltd.
Analysis of two‐grid methods for reaction‐diffusion equations by expanded mixed finite element methods
Authors: Chen Yanping , Liu Huan‐Wen , Liu Shang 
Published: June 2006

AbstractWe present two efficient methods of two‐grid scheme for the approximation of two‐dimensional semi‐linear reaction‐diffusion equations using an expanded mixed finite element method. To linearize the discretized equations, we use two Newton iterations on the fine grid in our methods. Firstly, we solve an original non‐linear problem on the coarse grid. Then we use twice Newton iterations on the fine grid in our first method, and while in second method we make a correction on the coarse grid between two Newton iterations on the fine grid. These two‐grid ideas are from Xu's work (SIAM J. Sci. Comput. 1994; 15:231–237; SIAM J. Numer. Anal. 1996; 33:1759–1777) on standard finite element method. We extend the ideas to the mixed finite element method. Moreover, we obtain the error estimates for two algorithms of two‐grid method. It is showed that coarse space can be extremely coarse and we achieve asymptotically optimal approximation as long as the mesh sizes satisfy H =𝒪(h¼) in the first algorithm and H =𝒪(h⅙) in second algorithm. Copyright © 2006 John Wiley & Sons, Ltd.
A fast and robust iterative solver for nonlinear contact problems using a primal‐dual active set strategy and algebraic multigrid
Authors: Brunssen S. , Schmid F. , Schäfer M. , Wohlmuth B. 
Published: June 2006

AbstractFor extending the usability of implicit FE codes for large‐scale forming simulations, the computation time has to be decreased dramatically. In principle this can be achieved by using iterative solvers. In order to facilitate the use of this kind of solvers, one needs a contact algorithm which does not deteriorate the condition number of the system matrix and therefore does not slow down the convergence of iterative solvers like penalty formulations do. Additionally, an algorithm is desirable which does not blow up the size of the system matrix like methods using standard Lagrange multipliers. The work detailed in this paper shows that a contact algorithm based on a primal‐dual active set strategy provides these advantages and therefore is highly efficient with respect to computation time in combination with fast iterative solvers, especially algebraic multigrid methods. Copyright © 2006 John Wiley & Sons, Ltd.
Psychological distress in long‐term survivors of solid tumors diagnosed in childhood: A report from the childhood cancer survivor study
Authors: Zebrack Brad J. , Zevon Michael A. , Turk Norman , Nagarajan Rajaram , Whitton John , Robison Leslie L. , Zeltzer Lonnie K. 
Published: June 2006

AbstractPurposeTo evaluate and compare psychological distress in long‐term survivors of solid tumors diagnosed in childhood and their siblings, and to identify significant correlates of psychological distress.ProcedureAdult survivors (2,778) of solid tumors diagnosed in childhood and 2,925 siblings completed a long‐term follow‐up questionnaire assessing symptoms associated with depression, somatization, and anxiety, as well as demographic, health, and medical information.ResultsOverall, a large majority of siblings and survivors reported few, if any, symptoms of psychological distress. In the aggregate, solid tumor cancer survivors reported significantly higher levels of global distress as measured by the Brief Symptom Inventory (BSI‐18), as well as higher levels of somatization and anxiety, when compared to siblings. However, when compared to population norms, both survivors and siblings reported lower levels of global and dimensional distress. Female gender, lower educational and income attainment, perceived poor health status and reports of current health problems all were associated with reporting psychological distress symptoms for both survivors and siblings. Among survivors, having a limb amputation was associated with reporting fewer symptoms of global and dimensional distress.ConclusionPoor health status, low levels of income, education, and employment appear to be predictors of distress for survivors of solid tumors. Thus, interventions that promote health and facilitate educational advancement, income attainment and social interaction to minimize isolation and maximize social support may reduce psychological distress and promote quality of life for childhood cancer survivors. Pediatr Blood Cancer 2007;49:47–51. © 2006 Wiley‐Liss, Inc.
Growth impairment after ifosfamide‐induced nephrotoxicity in children
Authors: Stöhr Wolfgang , Patzer Ludwig , Paulides Marios , Kremers Anja , Beck Jörn‐Dirk , Langer Thorsten , Rossi Rainer 
Published: June 2006

AbstractBackgroundThe goal of this study was to analyze long‐term consequences of ifosfamide‐induced nephrotoxicity on growth and renal function in children treated for cancer.ProcedureIn a retrospective study, departments for pediatric oncology and nephrology in Germany, Austria, and Switzerland were asked to report patients with serious long‐term nephrotoxicity after ifosfamide‐treatment. Data at first appearance of renal dysfunction and at the last renal examination were collected using a standardized questionnaire.ResultsFifty‐nine patients with tubulopathy (35 severe, 24 moderate) following ifosfamide therapy were eligible for analysis of long‐term outcome (median follow‐up 4 years, range 1.1 to 12.9). Median height standard deviation score was significantly reduced at renal diagnosis, and at last renal examination (−1.7 and −2.1 respectively, P < 0.01 at each point in time). Patients with tubulopathy also had stunted growth in comparison with a control group of cancer patients without renal disease (mean difference at last examination: 7.3 cm (95% confidence interval: 2.5 to 12.1 cm). In patients with severe tubulopathy, glomerular filtration rate deteriorated significantly over time. End‐stage renal disease was reported in one patient only, not solely caused by ifosfamide.ConclusionDepending on the extent of tubular dysfunction, patients with ifosfamide‐induced nephrotoxicity experienced significant growth impairment and a slow decline in glomerular filtration rate. Pediatr Blood Cancer 2007;48:571–576. © 2006 Wiley‐Liss, Inc.
First trimester diagnosis of sirenomelia
Authors: Van Keirsbilck J. , Cannie M. , Robrechts C. , de Ravel T. , Dymarkowski S. , Van den Bosch T. , Van Schoubroeck D. 
Published: June 2006

AbstractWe present a case of sirenomelia diagnosed on a first trimester ultrasound at 10 weeks' gestation and confirmed on 3D‐ultrasound and MRI. The pregnancy was terminated at 15 gestational weeks and the post‐mortem examination, including RX and microscopy, is presented. The sirenomelia sequence is a rare and lethal anomaly characterized by fusion, rotation, hypotrophy or atrophy of the lower limbs and severe urogenital abnormalities leading to oligohydramnios in the second half of pregnancy. Our case illustrates that the diagnosis of sirenomelia can be reliably made in the first trimester. Copyright © 2006 John Wiley & Sons, Ltd.
Maternal serum ADAM12 levels in Down and Edwards' syndrome pregnancies at 9–12 weeks' gestation
Authors: Laigaard Jennie , Cuckle Howard , Wewer Ulla M. , Christiansen Michael 
Published: June 2006

AbstractBackgroundMaternal serum ADAM12 is reduced, on average, in early first‐trimester Down and Edwards' syndrome pregnancies but the extent of reduction declines with gestation. Here we study levels at 9–12 weeks when the marker might be used concurrently with other established markers.MethodsSamples from 16 Down and 2 Edwards' syndrome cases were retrieved from storage and tested together with 313 unaffected singleton pregnancies using a semi‐automated time‐resolved immuno‐fluorometric assay. Results were expressed in multiples of the gestation‐specific median (MoM) based on regression.ResultsThe median in Down syndrome was 0.94 MoM with a 10th–90th centile range of 0.22–1.63 MoM compared with 1.00 and 0.33–2.24 MoM in unaffected controls (P = 0.21, one‐side Wilcoxon Rank Sum Test). The two Edwards' syndrome cases had values 0.31 and 2.17 MoM.ConclusionsADAM12 cannot be used concurrently with other markers in the late first trimester. However, it does have the potential to be used earlier in pregnancy either concurrently with other early markers or in a sequential or contingent protocol. More data will be required to reliably predict the performance of either approach. Copyright © 2006 John Wiley & Sons, Ltd.
Prenatal Marfan syndrome: report of one case and review of the literature
Authors: Lopes K. R. M. , Delezoide A. L. , Baumann C. , Vuillard E. , Luton D. , Chitrit Y. , Azancot A. 
Published: June 2006

AbstractObjectivesOur objective was to describe the features of prenatal Marfan syndrome.MethodsDoppler fetal echocardiograms were performed. The morphology and rhythm of the fetal heart were examined sequentially.ResultsThe case was referred because of cardiomegaly and dilated great vessels. Sequential Doppler echocardiographic evaluation led to the diagnosis of prenatal Marfan syndrome. The main features are cardiomegaly, dysplastic atrioventricular valves with tricuspid regurgitation and dilated great vessels, which can be aneurysmal at their origin. The fetus died in utero at 39 weeks of gestation because of cardiac failure. Pathological study confirmed the Marfan habitus and complications. Molecular genetic study showed a de novo point mutation in exon 26 of the FBN1 gene.ConclusionWe report a case of prenatal Marfan syndrome diagnosed by sequential evaluation of the cardiac signs, which are essential for prenatal diagnosis. The prognosis seems as poor as the neonatal one. The prenatal diagnosis is essential for adequate counselling. Copyright © 2006 John Wiley & Sons, Ltd.
Multi‐centre first‐trimester screening for Down syndrome in the Netherlands in routine clinical practice
Authors: Schielen P. C. J. I. , van Leeuwen‐Spruijt M. , Belmouden I. , Elvers L. H. , Jonker M. , Loeber J. G. 
Published: June 2006

AbstractObjectivesThis is the first report on the results of a first‐trimester combined‐test screening programme in the Netherlands in a multi‐centre routine clinical setting.MethodsBetween July 2002 and May 2004, blood samples were taken from subjects in 44 centres in the Netherlands and sent to our laboratory to assay for maternal serum concentrations of fβ‐hCG and PAPP‐A. Fetal nuchal translucency (NT) was measured in the participating centres at a gestational age (GA) of 10–14 weeks. Results of those pregnancies for which a combined biochemical and NT risk was calculated were included in the epidemiological analysis of this study.ResultsA total of 4033 singleton pregnancies were included in the analysis. The median maternal age of the analysed group was 36.5 years. The distribution of GA was biphasic, with median GA of 10.3 and 12.1 weeks, respectively. The detection rate using the combined ultrasound and serum screening at a cut‐off level of 1 in 250 was 71% (15/21), with a screen‐positive rate of 4.7%.ConclusionThe results of this study show that the first‐trimester combined test is suitable as a prenatal screening test in a multi‐centre routine clinical setting in the Netherlands. Strict performance evaluation should identify weaknesses in the organisation that impair the performance of the test. Here, the performance of NT was especially identified as a candidate for improvement. Copyright © 2006 John Wiley & Sons, Ltd.