bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ethnic identity, socialization factors, and culture‐specific consumption behavior
Authors: Xu Jing , Shim Soyeon , Lotz Sherry , Almeida David 
Published: December 2003

AbstractThis study is designed to discover the degree to which ethnic identity and socialization factors influence the culture‐specific consumption behaviors of Asian American young adults, in general as well as in specific situational settings. Findings indicated that perceived parental cultural identification tended to strengthen the ethnic identity, which in turn influenced Asian American young adults' culture‐specific consumption behaviors. However, although their perceived parental acculturation level had no effect on their ethnic identity, it directly weakened the subject group's culture‐specific consumption behaviors. The ethnic‐friendship orientation was found not only to influence ethnic identity but also to influence directly the group's culture‐specific consumption behavior. Further analysis revealed that a situational factor (i.e., the presence or absence of ethnic friends) influenced culture‐specific consumption behavior, regardless of the strength of ethnic identity. © 2004 Wiley Periodicals, Inc.
Dihydropteridine reductase deficiency in man: From biology to treatment
Authors: Ponzone Alberto , Spada Marco , Ferraris Silvio , Dianzani Irma , de Sanctis Luisa 
Published: December 2003

AbstractIn 1975, dihydropteridine reductase (DHPR) deficiency was first recognized as a cause of tetrahydrobiopterin (BH4) deficiency, leading to hyperphenylalaninemia (HPA) and impaired biogenic amine deficiency. So far, more than 150 patients scattered worldwide have been reported and major progresses have been made in the understanding of physiopathology, screening, diagnosis, treatment, and molecular genetics of this inherited disease. Present knowledge on different aspects of DHPR deficiency, largely derived from authors' personal experience, is traced in this article. © 2003 Wiley Periodicals, Inc. Med Res Rev, 24, No. 2, 127–150, 2004
New antithrombin‐based anticoagulants
Authors: Desai Umesh R. 
Published: December 2003

AbstractClinically used anticoagulants are inhibitors of enzymes involved in the coagulation pathway, primarily thrombin and factor Xa. These agents can be either direct or indirect inhibitors of clotting enzymes. Heparin‐based anticoagulants are indirect inhibitors that enhance the proteinase inhibitory activity of a natural anticoagulant, antithrombin. Despite its phenomenal success, current anticoagulation therapy suffers from the risk of serious bleeding. The need for safer and more effective antithrombotic agents clearly exists. The past decade has seen enormous effort directed toward discovering and/or designing new molecules with anticoagulant activity. These new molecules can be classified into (a) antithrombin and its mutants, (b) natural polysaccharides, (c) synthetic modified heparins and heparin‐mimics, (d) synthetic oligosaccharides, and (e) synthetic non‐sugar antithrombin activators. This review focuses on these efforts in designing or discovering new molecules that act through the antithrombin pathway of anticoagulation. © 2003 Wiley Periodicals, Inc. Med Res Rev, 24, No. 2, 151–181, 2004
Recent advances in selective opioid receptor agonists and antagonists
Authors: Eguchi Masakatsu 
Published: December 2003

AbstractOpioid analgesics provide outstanding benefits for relief of severe pain. The mechanisms of the analgesia accompanied with some side effects have been investigated by many scientists to shed light on the complex biological processes at the molecular level. New opioid drugs and therapies with more desirable properties can be developed on the bases of accurate insight of the opioid ligand–receptor interaction and clear knowledge of the pharmacological behavior of opioid receptors and the associated proteins. Toward this goal, recent advances in selective opioid receptor agonists and antagonists including opioid ligand–receptor interactions are summarized in this review article. © 2003 Wiley Periodicals, Inc. Med Res Rev, 24, No. 2, 182–212, 2004
Extracellular biodegradable macromolecular gadolinium(III) complexes for MRI
Authors: Lu Zheng‐Rong , Parker Dennis L. , Goodrich K. Craig , Wang Xinghe , Dalle John G. , Buswell Henry R. 
Published: December 2003

AbstractThe clinical application of macromolecular gadolinium (Gd) complexes as MRI contrast agents is limited by the slow excretion of Gd(III) complexes and consequent long‐term tissue accumulation of toxic Gd ions. To alleviate the problem of slow excretion, biodegradable polydisulfide‐based macromolecular Gd(III) complexes were designed and prepared based on the disulfide‐thiol exchange to allow degradation of the macromolecules by endogenous thiols and to facilitate excretion of Gd(III) complexes after the MRI examination. The in vitro degradation study showed that the polydisulfide agent was readily degraded by cysteine at plasma thiol concentrations. No cross‐reaction was observed between the cysteine‐34 on human serum albumin (HSA) with the agent. Concentration‐dependent blood pool contrast enhancement was observed for the polydisulfide agents. The agents of both high molecular weight (35,000 Da) and low molecular weight (17,700 Da) produced significant contrast enhancement in the heart and aorta in rats at relatively high doses. Except for the bladder, the signal intensities gradually decreased over time. Significant blood pool contrast enhancement was also observed for the high molecular weight agent at a low dose (0.03 mmol‐Gd/kg), but not for the agent with a lower molecular weight. The contrast enhancement in the urinary bladder increased over time for the polydisulfide agents and Gd(III)‐(DTPA‐BMA). Degradation products were identified by mass spectrometry in the urine samples from the rats administered with both polydisulfide agents, which confirmed that the polydisulfide agents were degraded in vivo and excreted through renal filtration. The preliminary results demonstrated the in vitro and in vivo degradability, superior blood pool contrast enhancement, and rapid clearance through renal filtration of the novel biodegradable macromolecular agent. This agent has a great potential for further preclinical and clinical development with application in contrast‐enhanced blood pool and cancer MR imaging. Magn Reson Med 51:27–34, 2004. © 2003 Wiley‐Liss, Inc.
On the calculation and interpretation of signal intensity in echo‐shifted sequences
Authors: Denolin Vincent , Metens Thierry 
Published: December 2003

AbstractEcho‐shifted sequences have been shown to be useful in applications where strong T*2‐weighting and short repetition times are wanted, such as BOLD‐contrast fMRI, MR thermometry, and perfusion studies. However, a full understanding of signal formation with such methods, which is mandatory to optimize sequence parameters for particular applications, has still not been achieved. Here, two methods are proposed to calculate the steady‐state signal intensity in coherent TR‐periodic and TR‐shifted gradient‐echo sequences. The integration method, which consists of averaging the steady‐state magnetization over all isochromats in a voxel, is shown to be a particularly efficient way of obtaining the analytical expression of the measurable signal. The partition method, based on a physical decomposition of the steady‐state magnetization into a sum of contributions from past excitation pulses, reveals that the net transverse magnetization results from a destructive interference between the wanted component and a series of stimulated echoes. The analysis includes off‐resonance effects and is illustrated by phantom measurements. Relationships with previous publications on this subject are discussed. Magn Reson Med 51:123–134, 2004. © 2003 Wiley‐Liss, Inc.
Monitoring angiogenesis in brain using steady‐state quantification of ΔR2 with MION infusion
Authors: Dunn Jeff F. , Roche Marcie A. , Springett Roger , Abajian Michelle , Merlis Jennifer , Daghlian Charles P. , Lu Shi Y. , Makki Malek 
Published: December 2003

AbstractAn MRI method for quantification of cerebral blood volume (CBV) in time‐course studies of angiogenesis is described. Angiogenesis was stimulated by acclimation to hypoxia. The change in relaxation rate, R2, which is relatively sensitive to the microvasculature, was quantified before and after infusion of a superparamagnetic vascular contrast agent (MION). The ΔR2 was measured in serum and brain parenchyma with a multiecho sequence. In vitro and in vivo calibration curves of MION concentration vs. R2 were approximated by a linear function. CBV was 3.14 ± 0.32% (mean ± SE, n = 13) and 6.42 ± 0.54% (n = 4) before and after acclimation. A second acclimated group was hemodiluted to control for polycythemia. CBV was not significantly different between hemodiluted and nonhemodiluted groups. In animals where NMR measurements were taken before and after acclimation, there was a 120% increase in CBV. The NMR technique was validated using quantitative morphometrics, which showed an increase of 147% in CBV with acclimation. We found a linear correlation between MRI and the morphometric results for CBV, as well as demonstrating a quantitative equivalence for relative changes in CBV. This article describes a simple, repeatable method of imaging brain microvascular volume using a plasma‐based contrast agent that can be applied to longitudinal studies of angiogenesis. Magn Reson Med 51:55–61, 2004. © 2003 Wiley‐Liss, Inc.
Determination of optimal angles for variable nutation proton magnetic spin‐lattice, T1, and spin‐spin, T2, relaxation times measurement
Authors: Deoni Sean C.L. , Peters Terry M. , Rutt Brian K. 
Published: December 2003

AbstractT1 and T2 can be rapidly determined with a combination of multiangle spoiled gradient recalled echo (SPGR) and steady‐state free precession (SSFP) imaging. Previously, we demonstrated a simple method for determining the set of SPGR and SSFP angles that provided greater T1 and T2 precision than a set of uniformly spaced angles. In this article a more rigorous approach for determining angles is described. Weighted least‐squares is also introduced for T1 and T2 estimation and a novel weighting function described. This new approach, suited for imaging applications where large T1 and T2 ranges are anticipated, provides high and uniform precision over a wide range of T1 and T2 values. Magn Reson Med 51:194–199, 2004. © 2003 Wiley‐Liss, Inc.
Momentum‐weighted conjugate gradient descent algorithm for gradient coil optimization
Authors: Lu Hanbing , Jesmanowicz Andrzej , Li Shi‐Jiang , Hyde James S. 
Published: December 2003

AbstractMRI gradient coil design is a type of nonlinear constrained optimization. A practical problem in transverse gradient coil design using the conjugate gradient descent (CGD) method is that wire elements move at different rates along orthogonal directions (r, φ, z), and tend to cross, breaking the constraints. A momentum‐weighted conjugate gradient descent (MW‐CGD) method is presented to overcome this problem. This method takes advantage of the efficiency of the CGD method combined with momentum weighting, which is also an intrinsic property of the Levenberg‐Marquardt algorithm, to adjust step sizes along the three orthogonal directions. A water‐cooled, 12.8 cm inner diameter, three axis torque‐balanced gradient coil for rat imaging was developed based on this method, with an efficiency of 2.13, 2.08, and 4.12 mT · m‐1 · A‐1 along X, Y, and Z, respectively. Experimental data demonstrate that this method can improve efficiency by 40% and field uniformity by 27%. This method has also been applied to the design of a gradient coil for the human brain, employing remote current return paths. The benefits of this design include improved gradient field uniformity and efficiency, with a shorter length than gradient coil designs using coaxial return paths. Magn Reson Med 51:158–164, 2004. © 2003 Wiley‐Liss, Inc.
TurboFLASH FAIR imaging with optimized inversion and imaging profiles
Authors: Pell Gaby S. , Lewis David P. , Ordidge Roger J. , Branch Craig A. 
Published: December 2003

AbstractOptimal implementation of pulsed arterial spin labeling (PASL) methods such as flow‐sensitive alternating inversion recovery (FAIR), require the minimization of interactions between the inversion and imaging slabs. For FAIR, the inversion : imaging slice thickness ratio (STR) is usually at least 3:1 in order to fully contain the extent of the imaging slice. The resulting gap exacerbates the transit time. So far, efforts to minimize the STR have concentrated on the inversion profile. However, the imaging profile remains a limiting factor especially for rapid sequences such as turbo fast low‐angle shot (TurboFLASH) which uses short pulses. This study reports the implementation of a TurboFLASH sequence with optimized inversion and imaging profiles. Slice‐selection is achieved with a preparation module incorporating a pair of identical adiabatic frequency offset corrected inversion (FOCI) pulses. The optimum radiofrequency (RF) and gradient scheme for this pulse combination is described, and the relaxation characteristics of the slice‐selection scheme are investigated. Phantom experiments demonstrate a reduction in the STR to approximately 1.13:1. Implementation in an animal model is described, and the benefit of the improved profile in probing the sensitivity of the flow signal to tagging geometry is demonstrated. Sensitivity to transit time effects can be minimized with this sequence, and ASL methodologies can be better explored as a result of the improved conformance with the ideal of square slice profiles. Magn Reson Med 51:46–54, 2004. © 2003 Wiley‐Liss, Inc.
Multicoil Dixon chemical species separation with an iterative least‐squares estimation method
Authors: Reeder Scott B. , Wen Zhifei , Yu Huanzhou , Pineda Angel R. , Gold Garry E. , Markl Michael , Pelc Norbert J. 
Published: December 2003

AbstractThis work describes a new approach to multipoint Dixon fat–water separation that is amenable to pulse sequences that require short echo time (TE) increments, such as steady‐state free precession (SSFP) and fast spin‐echo (FSE) imaging. Using an iterative linear least‐squares method that decomposes water and fat images from source images acquired at short TE increments, images with a high signal‐to‐noise ratio (SNR) and uniform separation of water and fat are obtained. This algorithm extends to multicoil reconstruction with minimal additional complexity. Examples of single‐ and multicoil fat–water decompositions are shown from source images acquired at both 1.5T and 3.0T. Examples in the knee, ankle, pelvis, abdomen, and heart are shown, using FSE, SSFP, and spoiled gradient‐echo (SPGR) pulse sequences. The algorithm was applied to systems with multiple chemical species, and an example of water–fat–silicone separation is shown. An analysis of the noise performance of this method is described, and methods to improve noise performance through multicoil acquisition and field map smoothing are discussed. Magn Reson Med 51:35–45, 2004. © 2003 Wiley‐Liss, Inc.
High‐resolution myocardial perfusion mapping in small animals in vivo by spin‐labeling gradient‐echo imaging
Authors: Kober Frank , Iltis Isabelle , Izquierdo Marguerite , Desrois Martine , Ibarrola Danielle , Cozzone Patrick J. , Bernard Monique 
Published: December 2003

AbstractAn ECG and respiration‐gated spin‐labeling gradient‐echo imaging technique is proposed for the quantitative and completely noninvasive measurement and mapping of myocardial perfusion in small animals in vivo. In contrast to snapshot FLASH imaging, the spatial resolution of the perfusion maps is not limited by the heart rate. A significant improvement in image quality is achieved by synchronizing the inversion pulse to the respiration movements of the animals, thereby allowing for spontaneous respiration. High‐resolution myocardial perfusion maps (in‐plane resolution = 234 × 468 μm2) demonstrating the quality of the perfusion measurement were obtained at 4.7 T in a group of seven freely breathing Wistar‐Kyoto rats under isoflurane anesthesia. The mean perfusion value (group average ± SD) was 5.5 ± 0.7 ml g–1min–1. In four animals, myocardial perfusion was mapped and measured under cardiac dobutamine stress. Perfusion increased to 11.1 ± 1.9 ml g–1min–1. The proposed method is particularly useful for the study of small rodents at high fields. Magn Reson Med 51:62–67, 2004. © 2003 Wiley‐Liss, Inc.
Comprehensive approach for correction of motion and distortion in diffusion‐weighted MRI
Authors: Rohde G.K. , Barnett A.S. , Basser P.J. , Marenco S. , Pierpaoli C. 
Published: December 2003

AbstractPatient motion and image distortion induced by eddy currents cause artifacts in maps of diffusion parameters computed from diffusion‐weighted (DW) images. A novel and comprehensive approach to correct for spatial misalignment of DW imaging (DWI) volumes acquired with different strengths and orientations of the diffusion sensitizing gradients is presented. This approach uses a mutual information‐based registration technique and a spatial transformation model containing parameters that correct for eddy current‐induced image distortion and rigid body motion in three dimensions. All parameters are optimized simultaneously for an accurate and fast solution to the registration problem. The images can also be registered to a normalized template with a single interpolation step without additional computational cost. Following registration, the signal amplitude of each DWI volume is corrected to account for size variations of the object produced by the distortion correction, and theb‐matrices are properly recalculated to account for any rotation applied during registration. Both qualitative and quantitative results show that this approach produces a significant improvement of diffusion tensor imaging (DTI) data acquired in the human brain. Magn Reson Med 51:103–114, 2004. Published 2003 Wiley‐Liss, Inc.
Effects of end‐ring/shield configuration on homogeneity and signal‐to‐noise ratio in a birdcage‐type coil loaded with a human head
Authors: Liu Wanzhan , Collins Christopher M. , Delp Pamela J. , Smith Michael B. 
Published: December 2003

AbstractWe modeled four different end‐ring/shield configurations of a birdcage coil to examine their effects on field homogeneity and signal‐to‐noise ratio (SNR) at 64 MHz and 125 MHz. The configurations are defined as: 1) conventional: a conventional cylindrical shield; 2) surrounding shield: a shield with annular extensions to closely shield the end rings; 3) solid connection: a shield with annular extensions connected to the rungs; and 4) thin wire connection: a shield with thin wires connected to the rungs. At both frequencies, the coil with conventional end‐ring/shield configuration produces the most homogeneous RF magnetic (B1) field when the coil is empty, but produces the least homogeneous B1 field when the coil is loaded with a human head. The surrounding shield configuration results in the most homogeneous B1 and highest SNR in the coil loaded with the human head at both frequencies, followed closely by the solid connection configuration. Magn Reson Med 51:217–221, 2004. © 2003 Wiley‐Liss, Inc.
Eddy current correction in diffusion‐weighted imaging using pairs of images acquired with opposite diffusion gradient polarity
Authors: Bodammer Nils , Kaufmann Jörn , Kanowski Martin , Tempelmann Claus 
Published: December 2003

AbstractIn echo‐planar‐based diffusion‐weighted imaging (DWI) and diffusion tensor imaging (DTI), the evaluation of diffusion parameters such as apparent diffusion coefficients and anisotropy indices is affected by image distortions that arise from residual eddy currents produced by the diffusion‐sensitizing gradients. Correction methods that coregister diffusion‐weighted and non‐diffusion‐weighted images suffer from the different contrast properties inherent in these image types. Here, a postprocessing correction scheme is introduced that makes use of the inverse characteristics of distortions generated by gradients with reversed polarity. In this approach, only diffusion‐weighted images with identical contrast are included for correction. That is, non‐diffusion‐weighted images are not needed as a reference for registration. Furthermore, the acquisition of an additional dataset with moderate diffusion‐weighting as suggested by Haselgrove and Moore (Magn Reson Med 1996;36:960–964) is not required. With phantom data it is shown that the theoretically expected symmetry of distortions is preserved in the images to a very high degree, demonstrating the practicality of the new method. Results from human brain images are also presented. Magn Reson Med 51:188–193, 2004. © 2003 Wiley‐Liss, Inc.
Animal anaesthesia for in vivo magnetic resonance
Authors: Lukasik Victoria M. , Gillies Robert J. 
Published: December 2003

AbstractAlmost all animal patients, including research subjects, presented for MRI/MRS studies are anesthetized. As MR moves rapidly beyond simple anatomic studies, becoming a powerful tool for defining physiologic processes, it is imperative that investigators become familiar with the physiologic effects of the anaesthetic drugs. This decreases confounding variables, making data interpretation more accurate and more applicable to future uses. This article is intended to be a basic resource for investigators wishing to increase their understanding of the anesthetic drugs. The following is a general discussion describing the mechanism of action and physiologic effects of the more common anaesthetic drugs used in laboratory animals. A dosing table of common anaesthetics and analgesics used in mice and rats is included because these two species comprise a great majority of MRI/MRS research subjects. Copyright © 2003 John Wiley & Sons, Ltd.
Order parameters of the orientation distribution of collagen fibers in Achilles tendon by 1H NMR of multipolar spin states
Authors: Fechete R. , Demco D. E. , Blümich B. 
Published: December 2003

AbstractThe angular distribution function of collagen fibrils in a sheep Achilles tendon was investigated by 1H NMR of multipolar spin states represented by dipolar‐encoded longitudinal magnetization and double‐quantum filtered signals. For the first time the angular distribution function based on the Legendre moment expansion is used. Order parameters were obtained from the anisotropy of 1H residual dipolar couplings of bond water, which were determined model‐free from the excitation efficiency of the multipolar spin states and from double‐quantum filtered line splitting. The orientation distribution function of collagen fibrils in Achilles tendon measured from the anisotropy of the residual dipolar couplings is characterized by the average values of center $\tilde{\beta}_0 = 1.8 \pm 0.2^\circ$ and order parameters $\langle {P_2} \rangle = 0.93 \pm 0.04$, $\langle {P_4} \rangle = 0.78 \pm 0.04$ and $\langle {P_6} \rangle = 0.58 \pm 0.04$. The order of many biological tissues in the presence of ageing, injuries or regeneration can be quantified by the order parameters of the angular distribution function. Copyright © 2003 John Wiley & Sons, Ltd.