bluuebunny/crossref_metadata_2025 huggingface dataset:
Selective missing pulse steady state free precession (MP‐SSFP): Inner volume and chemical shift selective imaging in a steady state sequence
Authors: Hwang Ken‐Pin , Flask Chris , Lewin Jonathan S. , Duerk Jeffrey L.
Published: December 2003

Purpose

To examine new sequences that restrict acquisition of spins to those excited by both of the RF pulses in missing pulse steady state free precession (MP‐SSFP) MRI.

Materials and Methods

New MP‐SSFP sequences were created by replacing one of the slice selective pulses (SSPs) with an orthogonal SSP for inner volume imaging, and with a chemical shift selective (CHESS) pulse for chemical shift imaging. The inner volume sequence was applied to a reduced field of view at the center of a resolution phantom; resulting images were evaluated for differences in the aliased signal. The CHESS sequence was applied to volunteers, as well as to and fat, water, and acetic acid phantoms. Results were evaluated with SNR measurements.

Results

The inner volume sequence eliminated the aliased signal, while nonselected fat and water levels were suppressed to that of noise by the CHESS sequence.

Conclusion

Results suggest a novel steady state technique for rapid inner volume or chemical shift imaging. J. Magn. Reson. Imaging 2004;19:124–132. © 2003 Wiley‐Liss, Inc.
Synovitis and soft tissue impingement of the ankle: Assessment with enhanced three‐dimensional FSPGR MR imaging
Authors: Huh Yong‐Min , Suh Jin‐Suck , Lee Jin‐Woo , Song Ho‐Taek
Published: December 2003

Purpose

To assess soft tissue impingement as well as synovitis of the ankle associated with trauma by using contrast‐enhanced (CE), fat‐suppressed, three‐dimensional, fast gradient‐recalled acquisition in the steady state with radiofrequency spoiling (FSPGR) magnetic resonance (MR) imaging.

Materials and Methods

A total of 36 patients who had had chronic ankle pain associated with a traumatic injury undertook fat‐suppressed CE three‐dimensional FSPGR MR imaging and then arthroscopy of the ankle. The ankle joint was divided into four compartments by anatomic details: the anterolateral gutter, anteromedial gutter, anterior recess, and posterior recess. Synovial enhancement was graded as follows: grade I, no enhancement; grade II, linear enhancement; grade III, focal nodular enhancement; and grade IV, irregular nodular enhancement. MR grading of the synovial enhancement (synovitis, grade III or IV; soft tissue impingement, grade III or IV with its intrusion from the capsular reflection) was compared with arthroscopic findings. A control study of twenty asymptomatic ankles was done for determining enhancement. Arthroscopy confirmed synovitis in 47 compartments of 27 patients. Of the 27 patients, 15 revealed soft tissue impingement in 17 compartments.

Results

For the assessment of synovitis, fat‐suppressed CE three‐dimensional FSPGR MR imaging had an accuracy of 72.9%, sensitivity of 91.5%, and specificity of 63.9%; whereas for that of soft tissue impingement it had an accuracy of 94.4%, sensitivity of 76.5%, and specificity of 96.9%. All of the asymptomatic subjects showed grade I (81%) or II (19%) synovial enhancement.

Conclusion

Fat‐suppressed CE three‐dimensional FSPGR MR imaging was sensitive for the evaluation of synovitis of the ankle associated with trauma, whereas it was specific for soft tissue impingement evaluation. J. Magn. Reson. Imaging 2004;19:108–116. © 2003 Wiley‐Liss, Inc.
Temperature‐frequency characteristics simulation of piezoelectric resonators and their equivalent circuits based on three‐dimensional finite element modelling
Authors: Wakatsuki N. , Kagawa Y. , Suzuki K. , Haba M.
Published: December 2003

The electromechanical resonators made of piezoelectric crystals such as a quartz crystal are widely used for electronic devices. Their frequency–temperature characteristics are of primary importance for their applications to the frequency control devices. The present paper demonstrates numerical simulation for several types of resonators using 3‐D Finite Element Modelling. The results are compared with the theoretical values whenever they are available. As they are electronic devices, the equivalent circuit representation is often favourable for describing the admittance at the electrical terminals which enables the circuit analysis including the effect of the temperature change by using commercially available circuit simulators. Copyright © 2003 John Wiley & Sons, Ltd.
A novel approach to propagation prediction in confined and diffracting rough surfaces
Authors: Ndoh Moïse , Delisle Gilles Y. , Le René
Published: December 2003

Modern wireless systems operating in the millimetre waves bands are now to be used in complex confined media such as mining environment. System designs require that multipath, fading and diffraction effects be accounted for in a suitable model. This paper presents a new propagation prediction method that can be used in mine corridors, buildings, underground roads, galleries with rough surfaces and others complex sub‐surface installations. A method named cascade impedance method (CIM) is used in combination with the segmental statistic method (SSM) in mine tunnels having considerable wall roughness and bending forms. Two (2D)‐ and three (3D)‐dimensional profiles of the radio waves are simulated and compared with available measurements at 2.45 and 18 GHz. Copyright © 2003 John Wiley & Sons, Ltd.
Interpreting workplace identities: the role of office décor
Authors: Elsbach Kimberly D.
Published: December 2003

Using qualitative methods, I examine how employees in corporate office environments interpreted a variety of relatively permanent office décor (e.g., furniture, photos, personal mementos) as indicators of their colleagues' workplace identities (i.e., central and enduring categorizations regarding employees' status and distinctiveness in the workplace). Similar to the encoding of behavioral cues of identity, findings suggest that interpretation of physical identity markers begins with either (1) a top‐down process of social categorization, in which specific rules are applied to encoding a few, focal, and visually salient pieces of office decor as evidence of management prototypes, or (2) a bottom‐up process of social categorization, in which a variety of physical artifacts are examined and compared to specific managerial exemplars to develop a complex representation of workplace identity. Findings also suggest that some of the unique attributes of physical identity markers (i.e., their potential to be viewed independently from their displayer, and their relative permanence) may be associated with the focus of each profiling process (i.e., on interpreting status vs. distinctiveness, and consistency vs. change). Copyright © 2004 John Wiley & Sons, Ltd.
Evidence toward an expanded model of organizational identification
Authors: Kreiner Glen E. , Ashforth Blake E.
Published: December 2003

Recent research on organizational identification has called for the consideration of an expanded model of identification, which would include a more thorough treatment of the ways an individual could derive his or her identity from the organization. This paper begins to answer that call by testing operationalizations of the four dimensions of the expanded model: identification, disidentification, ambivalent identification, and neutral identification. Survey results from 330 employed adults support the discriminability of the four dimensions. This exploratory study also begins to establish the criterion‐related validity of the model by examining organizational, job‐related, and individual difference variables associated with the four dimensions of the model, and suggests implications for the expanded model's strong potential for applications in organizational identification research. Copyright © 2004 John Wiley & Sons, Ltd.
The overseas marketing performance of successful small UK high‐technology firms: an exploratory study comparing indigenous and subsidiary firms' competitiveness
Authors: Crick Dave , Chaudhry Shiv , Bradshaw Robert
Published: December 2003

This paper compares the overseas business performance of two groups of technologically oriented successful firms, i.e. UK based subsidiaries and indigenous firms.

Although there were no statistical differences between the two groups' measures of performance and few in terms of the sources of competitiveness, qualitative analysis indicates their strategies were markedly different.

The low rating towards government support suggests that policy advisors involved in trade assistance are recommended to consider ways of supporting technology based firms in modes of market entry outside of the exporting route.

A substantial body of knowledge exists on both the areas of export strategy and competitiveness in small firms, although empirical data has tended to involve findings derived from broad surveys. A gap exists in the literature with respect to the subsidiaries of higher performing technology oriented small firms in comparison to those that are indigenously owned. Statistical analysis of survey data drawn from a questionnaire indicates that limited differences exist between the performance and competitiveness of these firms. However, supplementary in‐depth analysis suggests that the strategies and decision‐making employed by the two groups are markedly different and the findings offer a contribution to knowledge in the international entrepreneurship literature. Copyright © 2003 John Wiley & Sons, Ltd.
Strategic challenges in the football business: a SPACE analysis
Authors: Cross John , Henderson Steven
Published: December 2003

The football business has been transformed from a tawdry pastime to a major industry that is scrutinized by city analysts and is the subject of important take‐over bids. Yet as Grundy observes in an earlier issue of this journal, there are few serious attempts to examine the industry with strategic rigour.

This paper reports on and analyses data from professional football clubs and uses SPACE analysis to generate strategic positions for individual clubs and a prognosis for the overall industry. This evidence enables Grundy's model of the industry to be contextualized and shows that in most respects, his ideas are supported. The paper also reveals that environmental factors play a significant role in the business success of a club. This identifies the paradox that success on the football field can have a deleterious effect on the strategic future of the club.

The paper also concludes that the structure of the industry would not support reasonable business expectations and suggests that we are observing a corporate hobby rather than modern business activity.

Copyright © 2003 John Wiley & Sons, Ltd.
Advertising montage: Two theoretical perspectives
Authors: Larsen Val , Wright Newell D. , Hergert Thomas Robert
Published: December 2003

Building upon structuralist and phenomenological theories, this article explores the effects of video montage—camera cuts in particular—on the appeal and persuasiveness of television advertisements. The article proposes a structuralist method for objectively describing ad form and tests well‐known theories propounding that responses to a stimulus are a function of boredom and confusion. Camera cuts, boredom, and confusion were all found to affect subjects' attitude toward the ad. © 2004 Wiley Periodicals, Inc.
Plugs versus placements: A comparison of alternatives for within‐program brand exposure
Authors: Roehm Michelle L. , Roehm Harper A. , Boone Derrick S.
Published: December 2003

A study is presented that compares two forms of within‐program brand appearances: product placements and celebrity plugs. Evidence suggests that plugs may often have a retention advantage over placements. This advantage is hypothesized to arise from differences in the way plugs and placements are often presented. Specifically, differences in presentation contexts may create differences in how memory for plugs and placements is organized. This, in turn, may allow plugs to receive more frequent rehearsal during subsequent viewing of a show in which a brand has appeared. © 2004 Wiley Periodicals, Inc.
An investigation of the power of emotions in relationship realignment: The gift recipient's perspective
Authors: Ruth Julie A. , Brunel Frédéric F. , Otnes Cele C.
Published: December 2003

This study investigates the types of emotions that link a broad spectrum of idiosyncratic, gift‐exchange experiences with specific relationship realignment outcomes. Content analysis and analysis‐of‐variance procedures are used to assess the link between emotions and gift recipients' perceptions of relationship quality. The results demonstrate that rather than the overall amount of felt emotions, it is the balance of positive and negative emotions that is associated with specific relationship outcomes. It also appears that coping processes allow individuals to realize an overall neutral or positive outcome for the relationship, even if negative emotions are experienced. Moreover, different patterns of emotions characterize each of five different relational outcomes of the gift‐receipt experience. These results have theoretical and practical implications for gift exchange as well as other emotion‐laden marketing relationships, such as those found in services and personal selling contexts. © 2004 Wiley Periodicals, Inc.
Romantic love and sex: Their relationship and impacts on ad attitudes
Authors: Huang Ming‐Hui
Published: December 2003

The fact that romantic love in advertising is often subsumed under sexual appeal, and that not all types of romantic love are sexual, has led to an undervaluation of romantic love as an independent ad theme, despite its universality and importance in consumers' lives. This article validates spiritual companionate love and sexual passionate love as two subtypes of romantic love separable from sex. Their impacts on ad attitudes were examined in two studies assuming pleasure and arousal to be the two underlying mechanisms. The two subtypes of romantic love demonstrated ad impacts with distinct paths, with passionate love having a pattern of impact on ad attitudes that is similar to sex, rather than to companionate love. The implications of these findings are discussed. © 2004 Wiley Periodicals, Inc.
Ethnic identity, socialization factors, and culture‐specific consumption behavior
Authors: Xu Jing , Shim Soyeon , Lotz Sherry , Almeida David
Published: December 2003

This 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

In 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

Clinically 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

Opioid 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

The 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

Echo‐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

An 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

T1 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

MRI 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

Optimal 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

This 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

An 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

Patient 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

We 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

In 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

Almost 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

The 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.
Tissue‐specific differences in 2‐fluoro‐2‐deoxyglucose metabolism beyond FDG‐6‐P: a 19F NMR spectroscopy study in the rat
Authors: Southworth Richard , Parry Craig R. , Parkes Harold G. , Medina Rodolfo A. , Garlick Pamela B.
Published: December 2003

2‐Fluoro‐[18F]‐2‐deoxy‐glucose (FDG) is a positron‐emitting analogue of glucose used clinically in positron emission tomography (PET) to assess glucose utilization in diseased and healthy tissue. Originally developed to measure local cerebral glucose utilization rates, it has now found applications in tumour diagnosis and in the study of myocardial glucose uptake. Once taken up into the cell, FDG is phosphorylated to FDG‐6‐phosphate (FDG‐6‐P) by hexokinase and was originally believed to be trapped as a terminal metabolite. This ‘metabolic trapping’ of FDG‐6‐P forms the basis of the analysis of PET data. In this study, we have used 19F NMR spectroscopy to investigate FDG metabolism following the injection of a bolus of the glucose tracer into the rat (n=6). Ninety minutes after the 19FDG injection, the brain, heart, liver and kidneys were removed and the 19FDG metabolites in each were extracted and quantified. We report that significant metabolism of FDG occurs beyond FDG‐6‐P in all organs examined and that the extent of this metabolism varies from tissue to tissue (degree of metabolism beyond FDG‐6‐P, expressed as percentage of total organ FDG content, was brain 45 ± 3%; heart 29 ± 2%; liver 22±3% and kidney 17 ± 3%, mean ± SEM n=6). Furthermore, we demonstrate that the relative accumulation of each metabolite was tissue‐dependent and reflected the metabolic and regulatory characteristics of each organ. Such inter‐tissue differences may have implications for the mathematical modelling of glucose uptake and phosphorylation using FDG as a glucose tracer. Copyright © 2003 John Wiley & Sons, Ltd.
Proton T1 relaxation times of cerebral metabolites differ within and between regions of normal human brain
Authors: Brief E. E. , Whittall K. P. , Li D. K. B. , MacKay A.
Published: December 2003

Saturation recovery spectra (STEAM) were acquired at 1.5 T with 7 TRs ranging from 530 to 5000 ms and a constant TE of 30 ms in voxels (7.2 ml) located in occipital grey, parietal white and frontal white matter (10 subjects each location). Spectra were also acquired at 7, 21 and 37°C from separate 100 mm solutions of inositol (Ins), choline‐containing compounds (Cho), N‐acetyl‐aspartate (NAA) and creatine. Simulations of T1 fits with 2, 3 and 7 TRs demonstrated that at typical SNR there is potential for both inaccurate and biased results. In vivo, different metabolites had significantly different T1s within the same brain volume. The same order from shortest to longest T1 (Ins, Cho, NAA, creatine) was found for all three brain regions. The order (Ins, NAA, creatine, Cho) was found in the metabolite solutions and was consistent with a simple model in which T1 is inversely proportional to molecular weight. For all individual metabolites, T1 increased from occipital grey to parietal white to frontal white matter. This study demonstrates that, in spectra acquired with TR near 1 s, T1 weightings are substantially different for metabolites within a single tissue and also for the same metabolites in different tissues. Copyright © 2003 John Wiley & Sons, Ltd.
Increased statin prescribing in patients with diabetes after the introduction of the NSF for Coronary Heart Disease
Authors: Bull N , Williams J , Nicholls P , Lawrenson RA
Published: December 2003

Cardiovascular disease accounts for 70% of deaths in people with diabetes. This is partly due to their abnormal lipoprotein profiles. Several studies have shown that the prescription of statins to this group of people can greatly reduce the risk of death. The National Service Framework for Coronary Heart Disease (NSF for CHD), introduced in March 2000, set targets for treating people at high risk of death from CHD. Our study looked at 14 practices in Surrey to see whether the NSF has had an impact on statin prescribing in people with diabetes over the age of 40. There has been a 21% increase in the prevalence of diabetes between 1999 and 2002. We have also shown a 74% increase in the prescribing of statins to people with diabetes following the introduction of the NSF for CHD. The increase in the number of people receiving statins has cost implications for primary care trusts. Copyright © 2003 John Wiley & Sons, Ltd.
‘I'm amazed I've been able to come off injections’: patients' perceptions of genetic testing in diabetes
Authors: Shepherd M
Published: December 2003

Maturity onset diabetes of the young (MODY) accounts for 1% of diabetes in the UK but the young age of diagnosis, high glucose values in slim patients and lack of professionals' familiarity with the family history often lead to a misdiagnosis of type 1 diabetes. The identification of six different genes that cause MODY means that genetic testing may confirm the diagnosis and define the subtype. MODY patients with a mutation in the hepatocyte nuclear factor‐1 alpha (HNF‐1 alpha) gene are known to be particularly sensitive to the hypoglycaemic effect of sulphonylureas which has implications for their treatment. In depth interviews were conducted with 18 HNF‐1 alpha MODY patients, on insulin from diagnosis, who were offered the possibility of transferring to a sulphonylurea. A qualitative approach was used to gain an in depth understanding of their perceptions about stopping insulin. Six key themes emerged: (i) concern and anticipation about the prospect of stopping insulin; (ii) interactions with health care professionals; (iii) the impact on glycaemic control; (iv) improved lifestyle and self‐image; (v) reflections regarding the time on insulin; and (vi) difficulty in ‘letting go’ of insulin treatment. Transferring insulin treated HNF‐1 alpha MODY patients to sulphonylureas was safe in the short term. All 18 patients reported positive lifestyle changes and most showed no deterioration in glycaemic control, although the progressive nature of HNF‐1 alpha MODY means they are likely to need insulin again in the future. These findings have implications for other patients able to stop insulin after many years, such as those undergoing islet cell transplantation. Copyright © 2003 John Wiley & Sons, Ltd.
Preparation of macromonomers by copolymerization of methyl acrylate dimer involving β fragmentation
Authors: Harada Takahiro , Zetterlund Per B. , Yamada Bunichiro
Published: December 2003

The unsaturated dimer of methyl acrylate [CH2C(CO2CH3)CH2CH2CO2CH3, or MAD] was copolymerized with various monomers to prepare copolymers bearing the ω‐unsaturated end group [CH2C(CO2CH3)CH2] arising from β fragmentation of the MAD propagating radical. Copolymerizations of MAD with cyclohexyl and n‐butyl acrylate resulted in copolymers with ω‐unsaturated end groups, and increasing the temperature up to 180 °C resulted in an increase in the rate of β fragmentation of MAD radicals relative to propagation. Only a small amount of unsaturated end groups was introduced by copolymerization with ethyl methacrylate (EMA), and the EMA content in the copolymer increased with temperature. These findings could be explained by the reversible addition of the poly(EMA) radical to MAD. The copolymerization with ethyl α‐ethyl acrylate (EEA) did yield a copolymer containing unsaturated end groups with MAD units as part of the main chain, although the steric hindrance of the ethyl group suppressed homopropagation and crosspropagation of EEA, resulting in low polymerization rates. Therefore, the copolymerization of MAD with acrylic esters at high temperatures was noted as a convenient route for obtaining acrylate–MAD copolymers bearing unsaturated end groups at the ω end (macromonomer). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 597–607, 2004
New functionalized polyesters to achieve controlled architectures
Authors: Finne Anna , Albertsson Ann‐Christine
Published: December 2003

Following our continued interest in the production of bioerodible and biodegradable functional polymers for biomedical applications, we synthesized and characterized new unsaturated polyesters. The presence of functional groups in the polymer backbone provided sites for chemical modification, and through a variation in the structure, the physical properties, such as the hydrophilicity and solubility, could be affected. With 1,1‐di‐n‐butyl‐stanna‐2,7‐dioxacyclo‐4‐heptene as the initiator in the ring‐opening polymerization of polyesters, a new set of functionalized polyesters was created. The polymerization of ϵ‐caprolactone resulted in poly(ϵ‐caprolactone) with a double bond incorporated into the structure. The polymers were obtained in a controlled manner with low molecular dispersities. The double bond was previously incorporated into L‐lactide polymers, and the two reactions were compared in this study. The conversion of ϵ‐caprolactone, with a degree of polymerization of 50, was completed within 140 min, whereas for L‐lactide, only a 45% conversion took place in the same period of time. The dispersities were somewhat higher with ϵ‐caprolactone because of the higher reaction rate and, therefore, lower selectivity. The incorporated CC double bond in the polyesters provided a variety of opportunities for further modifications. In this case, the double bond of the L‐lactide macromonomers was oxidized into epoxides. Epoxidation was carried out with m‐chloroperoxybenzoic acid as a chemical reagent. The conversion of the double bonds into epoxides was completed, and the obtained yields were good (>95%). As a result of the mild reaction conditions, the epoxidation of the double bond was carried out quantitatively without any side reactions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 444–452, 2004
Biofunctional rapid prototyping for tissue‐engineering applications: 3D bioplotting versus 3D printing
Authors: Pfister Andreas , Landers Rüdiger , Laib Andres , Hübner Ute , Schmelzeisen Rainer , Mülhaupt Rolf
Published: December 2003

Two important rapid‐prototyping technologies (3D Printing and 3D Bioplotting) were compared with respect to the computer‐aided design and free‐form fabrication of biodegradable polyurethane scaffolds meeting the demands of tissue‐engineering applications. Aliphatic polyurethanes were based on lysine ethyl ester diisocyanate and isophorone diisocyanate. Layer‐by‐layer construction of the scaffolds was performed by 3D Printing, that is, bonding together starch particles followed by infiltration and partial crosslinking of starch with lysine ethyl ester diisocyanate. Alternatively, the 3D Bioplotting process permitted three‐dimensional dispensing and reactive processing of oligoetherurethanes derived from isophorone diisocyanate, oligoethylene oxide, and glycerol. The scaffolds were characterized with X‐ray microtomography, scanning electron microscopy, and mechanical testing. Osteoblast‐like cells were seeded on such scaffolds to demonstrate their potential in tissue engineering. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 624–638, 2004