bluuebunny/crossref_metadata_2025_split huggingface dataset:
A general framework for experiment design in diffusion MRI and its application in measuring direct tissue‐microstructure features
Authors: Alexander Daniel C. 
Published: July 2008

AbstractThis article introduces a new and general framework for optimizing the experiment design for diffusion MRI of samples with unknown orientation. An illustration then uses the framework to study the feasibility of measuring direct features of brain‐tissue microstructure in vivo. The study investigates the accuracy and precision with which we can estimate potentially important new biomarkers such as axon density and radius in white matter. Simulation experiments use a simple model of white matter based on CHARMED (composite hindered and restricted model of diffusion). The optimization finds acquisition protocols achievable on modern human and animal systems that consist of 120 measurements with fixed maximum gradient strengths. Axon radii in brain tissue are typically in the range 0.25–10 μm. Simulations suggest that estimates of radii in the range 5–10 μm have highest precision and that a maximum gradient strength of 0.07 T m−1 is sufficient to distinguish radii of 5, 10, and 20 μm. Smaller radii are more difficult to distinguish from one another but are identifiable as small. A maximum gradient strength of 0.2 T m−1 distinguishes radii of 1 and 2 μm. The simulations also suggest that axon densities and diffusivity parameters in the normal range for white matter are recoverable. The experiment‐design optimization has applications well beyond the current work to optimize the protocol for fitting any model of the diffusion process. Magn Reson Med 60:439–448, 2008. © 2008 Wiley‐Liss, Inc.
13C MR spectroscopy measurements of glutaminase activity in human hepatocellular carcinoma cells using hyperpolarized 13C‐labeled glutamine
Authors: Gallagher Ferdia A. , Kettunen Mikko I. , Day Sam E. , Lerche Mathilde , Brindle Kevin M. 
Published: July 2008

AbstractDynamic nuclear polarization (DNP) is an emerging technique for increasing the sensitivity of 13C MR spectroscopy (MRS). [5‐13C1]Glutamine was hyperpolarized using this technique by up to 5%, representing a 6000‐fold increase in sensitivity. The conversion of hyperpolarized glutamine to glutamate by mitochondrial glutaminase was demonstrated using 13C‐MRS measurements in cultured human hepatoma cells (HepG2). These results represent the first step in developing an imaging technique for detecting glutamine metabolism in vivo. Furthermore, since glutamine utilization has been correlated with cell proliferation, the study suggests a new technique for detecting changes in tumor cell proliferation. Magn Reson Med 60:253–257, 2008. © 2008 Wiley‐Liss, Inc.
Lactate imaging with Hadamard‐encoded slice‐selective multiple quantum coherence chemical‐shift imaging
Authors: Pickup Stephen , Lee Seung‐Cheol , Mancuso Anthony , Glickson Jerry D. 
Published: July 2008

AbstractThe ability to generate in vivo maps of lactate may have significant diagnostic utility in staging and treatment planning of a wide variety of cancers. The double selective multiple quantum filter technique (SelMQC) has been shown to be effective for nonlocalized detection of lactate with little or no interference from other signals. Here the SelMQC technique has been combined with longitudinal Hadamard slice selection and chemical shift imaging (CSI) to yield slice‐selective images of lactate. The technique is shown to be effective in phantoms and in WSU‐DLCL2 xenografts implanted in flanks of SCID mice. Tumors exhibited an annulus of elevated lactate concentration surrounding a necrotic tumor core. Magn Reson Med 60:299–305, 2008. © 2008 Wiley‐Liss, Inc.
Diffusion‐weighted NMR spectroscopy allows probing of 13C labeling of glutamate inside distinct metabolic compartments in the brain
Authors: Valette Julien , Chaumeil Myriam , Guillermier Martine , Bloch Gilles , Hantraye Philippe , Lebon Vincent 
Published: July 2008

AbstractIn the present work, diffusion‐weighted (DW)‐NMR spectroscopy of glutamate was performed during a 13C‐labeled glucose infusion in monkey brain (six experiments). It is shown that glutamate 13C labeling occurs significantly faster at higher diffusion weightings—slightly for glutamate in position C4, and more markedly for glutamate in position C3. This demonstrates the existence of different diffusion compartments for glutamate, associated with different metabolic rates. Metabolic modeling of 13C enrichment time‐courses suggests that these compartments might be gray and white matter, each having a specific oxidative metabolism rate possibly paralleled by a specific glutamate diffusion coefficient. Magn Reson Med 60:306–311, 2008. © 2008 Wiley‐Liss, Inc.
High resolution localized two‐dimensional MR spectroscopy in mouse brain in vivo
Authors: Braakman Niels , Oerther Thomas , de Groot Huub J.M. , Alia A. 
Published: July 2008

AbstractLocalized two‐dimensional MR spectroscopy (2D MRS) is impacting the in vivo studies of brain metabolites due to improved spectral resolution and unambiguous assignment opportunities. Despite the large number of transgenic mouse models available for neurological disorders, localized 2D MRS has not yet been implemented in the mouse brain due to size constraints. In this study we optimized a localized 2D proton chemical shift correlated spectroscopic sequence at field strength of 9.4T to obtain highly resolved 2D spectra from localized regions in mouse brains in vivo. The combination of the optimized 2D sequence, high field strength, strong gradient system, efficient water suppression, and the use of a short echo time allowed clear detection of cross‐peaks of up to 16 brain metabolites, allowing their direct chemical shift assignments in vivo. To our knowledge this is the first in vivo 2D MRS study of the mouse brain, demonstrating its feasibility to resolve and simultaneously assign several metabolite resonances in the mouse brain in vivo. Implementation of 2D MRS will be invaluable in the identification of new biomarkers during disease progression and treatment using the various available mouse models. Magn Reson Med 60:449–456, 2008. © 2008 Wiley‐Liss, Inc.
Asymmetric quadrature split birdcage coil for hyperpolarized 3He lung MRI at 1.5T
Authors: De Zanche Nicola , Chhina Navjeet , Teh Kevin , Randell Chris , Pruessmann Klaas P. , Wild Jim M. 
Published: July 2008

AbstractAn asymmetric quadrature birdcage body coil for hyperpolarized (HP) 3He lung imaging at 1.5T is presented. The coil is designed to rest on top of the patient support and be used as a temporary insert in a clinical system. A two‐part construction facilitates patient access and the asymmetric design makes maximal use of available bore space to ensure comfort. Highly homogeneous, circularly polarized RF magnetic fields are produced at 48.5 MHz using a conformal mapping method for the geometrical design, combined with an algebraic method to calculate the individual capacitance values on the birdcage coil's ladder network. Efficiency and isolation from the system's proton body coil are ensured by an integrated RF screen. The design methodology is readily applicable to other field strengths or nuclei. Improvements over existing 3He coils were found in terms of sensitivity and transmit field homogeneity, an important feature in HP MRI. Magn Reson Med 60:431–438, 2008. © 2008 Wiley‐Liss, Inc.
Forward‐looking intravascular orthogonal‐solenoid coil for imaging and guidance in occlusive arterial disease
Authors: Anderson Kevan J.T. , Leung General , Dick Alexander J. , Wright Graham A. 
Published: July 2008

AbstractRecent intravascular imaging coil configurations have focused on side‐viewing catheters capable of imaging the vessel wall of a patent vessel. These designs suffer from the presence of signal nulls and the inability to image in front of a device when it is oriented along the main static field. This is of particular importance when a device is being navigated through an occlusive lesion. To address these limitations we propose a new intravascular coil design consisting of two independent orthogonal solenoids located at the catheter tip. The two coils are oriented in such a way that signal nulls are eliminated and imaging is possible in planes located directly in front of the catheter. Complete characterization of the spatial signal‐to‐noise ratio (SNR) distribution of the design is presented. The coil configuration was fabricated on a 6F guide catheter, and its use is demonstrated in phantoms and in vivo. Magn Reson Med 60:489–495, 2008. © 2008 Wiley‐Liss, Inc.
Sensitivity of diffusion weighted steady state free precession to anisotropic diffusion
Authors: McNab Jennifer A. , Miller Karla L. 
Published: July 2008

AbstractDiffusion‐weighted steady‐state free precession (DW‐SSFP) accumulates signal from multiple echoes over several TRs yielding a strong sensitivity to diffusion with short gradient durations and imaging times. Although the DW‐SSFP signal is well characterized for isotropic, Gaussian diffusion, it is unclear how the DW‐SSFP signal propagates in inhomogeneous media such as brain tissue. This article presents a more general analytical expression for the DW‐SSFP signal which accommodates Gaussian and non‐Gaussian spin displacement probability density functions. This new framework for calculating the DW‐SSFP signal is used to investigate signal behavior for a single fiber, crossing fibers, and reflective barriers. DW‐SSFP measurements in the corpus callosum of a fixed brain are shown to be in good agreement with theoretical predictions. Further measurements in fixed brain tissue also demonstrate that 3D DW‐SSFP out‐performs 3D diffusion weighted spin echo in both SNR and CNR efficiency providing a compelling example of its potential to be used for high resolution diffusion tensor imaging. Magn Reson Med 60:405–413, 2008. © 2008 Wiley‐Liss, Inc.
Linear least‐squares method for unbiased estimation of T1 from SPGR signals
Authors: Chang Lin‐Ching , Koay Cheng Guan , Basser Peter J. , Pierpaoli Carlo 
Published: July 2008

AbstractThe longitudinal relaxation time, T1, can be estimated from two or more spoiled gradient recalled echo images (SPGR) acquired with different flip angles and/or repetition times (TRs). The function relating signal intensity to flip angle and TR is nonlinear; however, a linear form proposed 30 years ago is currently widely used. Here we show that this linear method provides T1 estimates that have similar precision but lower accuracy than those obtained with a nonlinear method. We also show that T1 estimated by the linear method is biased due to improper accounting for noise in the fitting. This bias can be significant for clinical SPGR images; for example, T1 estimated in brain tissue (800 ms < T1 < 1600 ms) can be overestimated by 10% to 20%. We propose a weighting scheme that correctly accounts for the noise contribution in the fitting procedure. Monte Carlo simulations of SPGR experiments are used to evaluate the accuracy of the estimated T1 from the widely‐used linear, the proposed weighted‐uncertainty linear, and the nonlinear methods. We show that the linear method with weighted uncertainties reduces the bias of the linear method, providing T1 estimates comparable in precision and accuracy to those of the nonlinear method while reducing computation time significantly. Magn Reson Med 60:496–501, 2008. © 2008 Wiley‐Liss, Inc.
Baseline blood oxygenation modulates response amplitude: Physiologic basis for intersubject variations in functional MRI signals
Authors: Lu Hanzhang , Zhao Chenguang , Ge Yulin , Lewis‐Amezcua Kelly 
Published: July 2008

AbstractAlthough BOLD functional MRI (fMRI) provides a useful tool for probing neuronal activities, large intersubject variations in signal amplitude are commonly observed. Understanding the physiologic basis for these variations will have a significant impact on many fMRI studies. First, the physiologic modulator can be used as a regressor to reduce variations across subjects, thereby improving statistical power for detecting group differences. Second, if a pathologic condition or a drug treatment is shown to change fMRI responses, monitoring this modulatory parameter is useful in correctly interpreting the fMRI changes to neuronal deficits/recruitments. Here we present evidence that the task‐evoked fMRI signals are modulated by baseline blood oxygenation. To measure global blood oxygenation, we used a recently developed technique, T2 relaxation under spin‐tagging (TRUST) MRI, which yielded baseline oxygenation of 63.7% ± 7.2% in the sagittal sinus with an estimation error of 1.3%. It was found that individuals with higher baseline oxygenation tend to have a smaller fMRI signal, and vice versa. For every 10% difference in baseline oxygenation across subjects, BOLD and cerebral blood flow (CBF) signals differ by –0.4% and –30.0%, respectively, when using visual stimulation. TRUST MRI is a useful measurement for fMRI studies to control for the modulatory effects of baseline oxygenation that are unique to each subject. Magn Reson Med 60:364–372, 2008. © 2008 Wiley‐Liss, Inc.
Spherical harmonic inductive detection coils for dynamic pre‐emphasis
Authors: Edler Karl , Hoult David 
Published: July 2008

AbstractThe issue of eddy currents induced by the rapid switching of magnetic field gradients is a long‐standing problem. A new method for dealing with this problem is presented whereby spatial harmonic components of the magnetic field are continuously sensed, through their temporal rates of change, and corrected. In this way, the effects of the eddy currents on the magnetic field can be detected and correction currents applied to the appropriate gradient or shim coils in a time much less than the rise time of the gradients. This new methodology has the potential to dynamically shape eddy current corrections for multiple spatial harmonic components of the field. Magn Reson Med 60:277–287, 2008. © 2008 Wiley‐Liss, Inc.
Relaxation time measurements of bone marrow protons in the calcaneus using a compact MRI system at 0.2 Tesla field strength
Authors: Tomiha Sadanori , Iita Nachiko , Okada Fumi , Handa Shinya , Kose Katsumi 
Published: July 2008

AbstractRelaxation times (T1 and T2) of the bone marrow protons and trabecular bone volume fraction (TBVF) in the calcaneus were measured for 100 female volunteers using a compact MRI system at 0.2 T field strength. The speed of sound (SOS) through the calcaneus was measured also for the same subjects using a quantitative ultrasound system. Both relaxation times were found to have positive correlations with age (R = 0.40; P < 0.0001 and R = 0.31; P < 0.002, respectively) and negative correlations with SOS (R = −0.38; P < 0.0001 and R = −0.38; P < 0.0001, respectively). Although TBVF had a fairly high positive correlation with the SOS (R = 0.67), neither T1 nor T2 were correlated with TBVF (R = −0.062 and −0.024, respectively). These results suggest that the age dependence of both T1 and T2 is caused by the microdynamic properties of the lipid molecules in bone marrow observed using acoustic or elastic modalities. Magn Reson Med 60:485–488, 2008. © 2008 Wiley‐Liss, Inc.
Combination of standard Galerkin and subspace methods for the time‐dependent Navier‐Stokes equations with nonsmooth initial data
Authors: He Yinnian 
Published: July 2008

AbstractWe consider a combination of the standard Galerkin method and the subspace decomposition methods for the numerical solution of the two‐dimensional time‐dependent incompressible Navier‐Stokes equations with nonsmooth initial data. Because of the poor smoothness of the solution near t = 0, we use the standard Galerkin method for time interval [0, 1] and the subspace decomposition method time interval [1, ∞). The subspace decomposition method is based on the solution into the sum of a low frequency component integrated using a small time step Δt and a high frequency integrated using a larger time step pΔt with p > 1. From the H1‐stability and L2‐error analysis, we show that the subspace decomposition method can yield a significant gain in computing time. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2009
The use of Chebyshev cardinal functions for solution of the second‐order one‐dimensional telegraph equation
Authors: Dehghan Mehdi , Lakestani Mehrdad 
Published: July 2008

AbstractA numerical technique is presented for the solution of the second order one‐dimensional linear hyperbolic equation. This method uses the Chebyshev cardinal functions. The method consists of expanding the required approximate solution as the elements of Chebyshev cardinal functions. Using the operational matrix of derivative, the problem is reduced to a set of algebraic equations. Some numerical examples are included to demonstrate the validity and applicability of the technique. The method is easy to implement and produces very accurate results. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009
The development and regulation of lobbying in the new member states of the European Union
Authors: McGrath Conor 
Published: July 2008

Abstract

This paper focuses on lobbying as a political activity and the emergence of lobbying regulation in 10 new member states of the European Union (EU). The analysis begins with general observations about lobbying in post‐communist states and on the development of lobbying in three of the larger new member states: Hungary, Poland and the Czech Republic. Key to how lobbying will continue to develop in the future in these 10 countries is how it will be regulated and controlled. Therefore, the paper examines this in some detail. The analysis concludes with some recommendations on the role that could be played by professional bodies, which represent lobbyists in gaining more acceptance for interest groups in these new member states.

Copyright © 2008 John Wiley & Sons, Ltd.
Understanding interest groups, lobbying and lobbyists in developing democracies
Authors: Thomas Clive S. , Hrebenar Ronald J. 
Published: July 2008

AbstractThis introductory article sets the scene for understanding the seven articles that follow in this Special Issue of the Journal. It lays the groundwork in five areas. First, it explains key terms and concepts important for understanding interests, interest groups and lobbying in developing democracies and goes into some detail about the concept of democracy. Second, it offers insights into the characteristics of interest group systems in developing democracies. Third, it briefly reviews the form and extent of the existing work written on interest groups in these political systems. Fourth, it argues that viewing developing democracies through the role of interest groups is a valuable analytical tool but must be adapted from the study of interest groups in developed and well‐established democracies to be of use in understanding these developing systems. And fifth, it points out how the seven articles that follow help illustrate the definitions and explanations presented in the previous four sections and the promise and challenges faced by interests and interest groups in these political systems.Copyright © 2008 John Wiley & Sons, Ltd.
Nutritional status at admission of children with cancer in Malawi
Authors: Israëls Trijn , Chirambo Chawanangwa , Caron Huib N. , Molyneux Elizabeth M. 
Published: July 2008

AbstractBackgroundMalnutrition at diagnosis is found in 10–50% of children with cancer in industrialized countries. In developing countries a large proportion of the normal paediatric population is undernourished and children with cancer often present late with advanced disease. Therefore it would be expected that many children with cancer are malnourished at admission. Malnutrition is associated with more severe chemotherapy toxicity and infectious complications.MethodsAll new paediatric oncology patients admitted in the Queen Elizabeth Central Hospital, Blantyre, Malawi between 1, January 2007 and 1, January 2008 were included. We documented age, clinical diagnosis, HIV status, weight, height, mid‐upper‐arm‐circumference (MUAC) and triceps skinfold (TSF), and calculated arm muscle area (AMA). Nutritional data were compared with the 1978 NCHS growth curves.ResultsOf 128 children, 70 (55.1%) had an AMA for age <5th percentile and 76 (59.3%) had a TSF and MUAC below the 5th percentile, both parameters indicating acute malnutrition. Fifty seven patients (44.5%) had a height for age <−2 SD (indicative of stunting), and 22 patients (17.2%) had a weight for height (WFH) <−2 SD.ConclusionArm anthropometry shows that more than half of Malawian children with cancer are severely acutely malnourished at diagnosis. WFH, in children with large tumour masses, is less sensitive than arm anthropometry in detecting acute malnutrition. Forty‐five percent of paediatric oncology patients in Malawi are stunted, making interpretation of weight for age (WFA) very difficult. Pediatr Blood Cancer 2008;51:626–628. © 2008 Wiley‐Liss, Inc.
Complete second look operation and radiotherapy in locally advanced non‐alveolar rhabdomyosarcoma in children: A report from the AIEOP soft tissue sarcoma committee
Authors: Cecchetto Giovanni , Carretto Elena , Bisogno Gianni , Dall'Igna Patrizia , Ferrari Andrea , Scarzello Giovanni , Donfrancesco Alberto , Alaggio Rita , Indolfi Paolo , Carli Modesto 
Published: July 2008

AbstractBackgroundTo evaluate the effect of radiotherapy (RT) in association with complete second look operation, histologically confirmed, on outcome of patients with IRS Gr.III non‐alveolar RMS.ProcedureWe analyzed data from 39 patients (age: 0.5–194 months, median 52) who were enrolled between 1988 and 2005 in 2 consecutive Italian Studies, RMS 88 and RMS 96. All achieved a complete resection of the residual tumor after neoadjuvant chemotherapy; 27 did not receive any other local treatment: pelvic 8, extremities 6, head‐neck‐non‐parameningeal 5, orbit 1, genito‐urinary‐bladder‐prostate 3, trunk 2, abdomen 1, vagina 1; 12 were given RT (32–45 Gy), 5 before and 7 after the operation: genito‐urinary‐bladder‐prostate 3, pelvic 3, abdominal 1, extremities 1, head‐neck‐parameningeal 1, head‐neck‐non‐parameningeal 1, vagina 1, orbit 1. All received postoperative chemotherapy.ResultsMedian follow‐up was 81 months (range 17–219 months). With RT: 10/12 patients are in first complete remission; 2/12 had a metastatic relapse (1 also local relapse), and both of them died of disease. Without RT: 16/27 maintained the first complete remission, however 1/16 died due to a second tumor; 8 suffered from local relapse (4 pelvic, 1 orbit, 1 vagina, 1 head‐neck‐non‐parameningeal, 1 abdomen) and 3 of them died, 3 showed a metastatic recurrence (2 extremities, 1 pelvic) and 1 died.ConclusionsLocal relapses were more frequent for patients without RT, especially in pelvic sites. The two relapses after RT occurred in huge bladder‐prostate RMS. Although the limited number of patients does not allow statistically significant conclusions, our experience suggests that RT may have a positive influence on local control for completely resected non‐alveolar RMS. Pediatr Blood Cancer 2008;51:593–597. © 2008 Wiley‐Liss, Inc.