bluuebunny/crossref_metadata_2025 huggingface dataset:
Macromol. Rapid Commun. 23/2008
Authors: Smart Thomas P. , Fernyhough Christine , Ryan Anthony J. , Battaglia Giuseppe
Published: November 2008

Cover: The cover shows a scanning electron microscopy image of one of the aggregates formed by the addition of poly(ethylene oxide) (PEO) to poly(ethylene oxide)16‐ poly(butylene oxide)22 polymersomes. In this case using a higher concentration PEO (10% w/w) 3D aggregation took place to form 1.5 µm spheres. Further details can be found in the article by T. P. Smart, C. Fernyhough, A. J. Ryan, G. Battaglia* on page 1855.
Advances in analysis of microbial metabolic fluxes via 13C isotopic labeling
Authors: Tang Yinjie J. , Martin Hector Garcia , Myers Samuel , Rodriguez Sarah , Baidoo Edward E.K. , Keasling Jay D.
Published: November 2008

Metabolic flux analysis via 13C labeling (13C MFA) quantitatively tracks metabolic pathway activity and determines overall enzymatic function in cells. Three core techniques are necessary for 13C MFA: (1) a steady state cell culture in a defined medium with labeled‐carbon substrates; (2) precise measurements of the labeling pattern of targeted metabolites; and (3) evaluation of the data sets obtained from mass spectrometry measurements with a computer model to calculate the metabolic fluxes. In this review, we summarize recent advances in the 13C‐flux analysis technologies, including mini‐bioreactor usage for tracer experiments, isotopomer analysis of metabolites via high resolution mass spectrometry (such as GC‐MS, LC‐MS, or FT‐ICR), high performance and large‐scale isotopomer modeling programs for flux analysis, and the integration of fluxomics with other functional genomics studies. It will be shown that there is a significant value for 13C‐based metabolic flux analysis in many biological research fields. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 28:362–375, 2009
Improving performance through vertical disintegration: evidence from UK manufacturing firms
Authors: Desyllas Panos
Published: November 2008

Unlike previous work on the vertical integration–performance relationship, we investigate the performance consequences of vertical disintegration. We offer a theoretical justification for the disintegration decision and we condition the disintegration effect on performance on the initial degree of firm integration, the timing and the direction of disintegration. Using a sample of UK manufacturing firms and controlling for disintegration endogeneity, we find that disintegration eventually results in improved operating performance, particularly when disintegration occurs as a reaction to poor performance and in cases of forward between‐sector disintegration. However, being highly integrated does not guarantee gains from disintegration. The implications of these findings are discussed. Copyright © 2008 John Wiley & Sons, Ltd.
Movement Disorder Society‐sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS‐UPDRS): Scale presentation and clinimetric testing results
Authors: Goetz Christopher G. , Tilley Barbara C. , Shaftman Stephanie R. , Stebbins Glenn T. , Fahn Stanley , Martinez‐Martin Pablo , Poewe Werner , Sampaio Cristina , Stern Matthew B. , Dodel Richard , Dubois Bruno , Holloway Robert , Jankovic Joseph , Kulisevsky Jaime , Lang Anthony E. , Lees Andrew , Leurgans Sue , LeWitt Peter A. , Nyenhuis David , Olanow C. Warren , Rascol Olivier , Schrag Anette , Teresi Jeanne A. , van Hilten Jacobus J. , LaPelle Nancy
Published: November 2008

We present a clinimetric assessment of the Movement Disorder Society (MDS)‐sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS‐UPDRS). The MDS‐UDPRS Task Force revised and expanded the UPDRS using recommendations from a published critique. The MDS‐UPDRS has four parts, namely, I: Non‐motor Experiences of Daily Living; II: Motor Experiences of Daily Living; III: Motor Examination; IV: Motor Complications. Twenty questions are completed by the patient/caregiver. Item‐specific instructions and an appendix of complementary additional scales are provided. Movement disorder specialists and study coordinators administered the UPDRS (55 items) and MDS‐UPDRS (65 items) to 877 English speaking (78% non‐Latino Caucasian) patients with Parkinson's disease from 39 sites. We compared the two scales using correlative techniques and factor analysis. The MDS‐UPDRS showed high internal consistency (Cronbach's alpha = 0.79–0.93 across parts) and correlated with the original UPDRS (ρ = 0.96). MDS‐UPDRS across‐part correlations ranged from 0.22 to 0.66. Reliable factor structures for each part were obtained (comparative fit index > 0.90 for each part), which support the use of sum scores for each part in preference to a total score of all parts. The combined clinimetric results of this study support the validity of the MDS‐UPDRS for rating PD. © 2008 Movement Disorder Society
Repairs of complex groin wounds with contralateral rectus abdominis myocutaneous flaps
Authors: Qi Fazhi , Zhang Yong , Gu Jianying
Published: November 2008

Management of complex groin wounds posterior to complications of vascular prosthetic surgery, malignant tumor excision, and irradiation therapy for recurrent cancers continued to pose a difficult task in reconstructive surgery. Pedicled and microsurgical myocutaneous flaps are valuable tools for wound repairs, but applications of these flaps are limited when the healthy vascular vessels are not available around the wound. In this report, we present our experience on the use of the contralateral rectus abdominis myocutaneous flaps for the coverage of the groin complex wounds in 13 patients. All the flaps were completely survived and the wounds healed uneventfully. The results suggest that the contralateral myocutaneous flap can be used for the repair of the groin wound with presence of significant comorbidities in the area, in which the ipsilateral local flaps and microsurgical flaps are not available. © 2008 Wiley‐Liss, Inc. Microsurgery, 2009.
On the global existence and small dispersion limit for a class of complex Ginzburg–Landau equations
Authors: Gao Hongjun , Wang Xueqin
Published: November 2008

In this paper we consider a class of complex Ginzburg–Landau equations. We obtain sufficient conditions for the existence and uniqueness of global solutions for the initial‐value problem in d‐dimensional torus 𝕋d, and that solutions are initially approximated by solutions of the corresponding small dispersion limit equation for a period of time that goes to infinity as dispersive coefficient goes to zero. Copyright © 2008 John Wiley & Sons, Ltd.
Complete assignment of 1H and 13C NMR data of pravastatin derivatives
Authors: Bacher Markus , Baumann Karl , Knapp Hermann , Steck Andrea , Teibl Sigrid
Published: November 2008

The complete 1H and 13C NMR data of 27 pravastatin derivatives are presented. Assignment was achieved by use of 1D and 2D NMR experiments (selective 1D NOE, COSY, NOESY, HSQC, HMBC). Copyright © 2008 John Wiley & Sons, Ltd.
Gleaning multicomponent T1 and T2 information from steady‐state imaging data
Authors: Deoni Sean C.L. , Rutt Brian K. , Arun Tarunya , Pierpaoli Carlo , Jones Derek K.
Published: November 2008

The driven‐equilibrium single‐pulse observation of T1 (DESPOT1) and T2 (DESPOT2) are rapid, accurate, and precise methods for voxelwise determination of the longitudinal and transverse relaxation times. A limitation of the methods, however, is the inherent assumption of single‐component relaxation. In a variety of biological tissues, in particular human white matter (WM) and gray matter (GM), the relaxation has been shown to be more completely characterized by a summation of two or more relaxation components, or species, each believed to be associated with unique microanatomical domains or water pools. Unfortunately, characterization of these components on a voxelwise, whole‐brain basis has traditionally been hindered by impractical acquisition times. In this work we extend the conventional DESPOT1 and DESPOT2 approaches to include multicomponent relaxation analysis. Following numerical analysis of the new technique, renamed multicomponent driven equilibrium single pulse observation of T1/T2 (mcDESPOT), whole‐brain multicomponent T1 and T2 quantification is demonstrated in vivo with clinically realistic times of between 16 and 30 min. Results obtained from four healthy individuals and two primary progressive multiple sclerosis (MS) patients demonstrate the future potential of the approach for identifying and assessing tissue changes associated with several neurodegenerative conditions, in particular those associated with WM. Magn Reson Med 60:1372–1387, 2008. © 2008 Wiley‐Liss, Inc.
A single‐scan T mapping method based on two gradient‐echo images with compensation for macroscopic field inhomogeneity
Authors: Meng Yuguang , Lei Hao
Published: November 2008

T‐weighted imaging (TWI) and quantitative T mapping with conventional gradient‐echo acquisition are often hindered by severe signal loss induced by macroscopic field inhomogeneity. Various z‐shimming approaches have been developed for TWI/T mapping in which the effects of macroscopic field inhomogeneity are suppressed while the sensitivity of T‐related signal intensity to alterations in the microscopic susceptibility is maintained. However, this is often done at the cost of significantly increased imaging time. In this work, a fast T mapping method with compensation for macroscopic field inhomogeneity was developed. A proton density‐weighted image and a composite T‐weighted image, both of which were essentially free from macroscopic field inhomogeneity‐induced signal loss, were used for the T calculation. The composite T‐weighted image was reconstructed from a number of gradient‐echo images acquired with successively incremented z‐shimming compensation. Because acquisition of the two images and z‐shimming compensation were realized in a single scan, the total acquisition time for obtaining a T map with the proposed method is the same as the time taken for a conventional multiecho gradient‐echo imaging sequence without compensation. The performance and efficiency of the proposed method were demonstrated and evaluated at 4.7 T. Magn Reson Med 60:1388–1395, 2008. © 2008 Wiley‐Liss, Inc.
High‐resolution maps of magnetization transfer with inherent correction for RF inhomogeneity and T1 relaxation obtained from 3D FLASH MRI
Authors: Helms Gunther , Dathe Henning , Kallenberg Kai , Dechent Peter
Published: November 2008

An empirical equation for the magnetization transfer (MT) FLASH signal is derived by analogy to dual‐excitation FLASH, introducing a novel semiquantitative parameter for MT, the percentage saturation imposed by one MT pulse during TR. This parameter is obtained by a linear transformation of the inverse signal, using two reference experiments of proton density and T1 weighting. The influence of sequence parameters on the MT saturation was studied. An 8.5‐min protocol for brain imaging at 3 T was based on nonselective sagittal 3D‐FLASH at 1.25 mm isotropic resolution using partial acquisition techniques (TR/TE/α = 25ms/4.9ms/5° or 11ms/4.9ms/15° for the T1 reference). A 12.8 ms Gaussian MT pulse was applied 2.2 kHz off‐resonance with 540° flip angle. The MT saturation maps showed an excellent contrast in the brain due to clearly separated distributions for white and gray matter and cerebrospinal fluid. Within the limits of the approximation (excitation <15°, TR/T1 ≪ 1) the MT term depends mainly on TR, the energy and offset of the MT pulse, but hardly on excitation and T1 relaxation. It is inherently compensated for inhomogeneities of receive and transmit RF fields. The MT saturation appeared to be a sensitive parameter to depict MS lesions and alterations of normal‐appearing white matter. Magn Reson Med 60:1396–1407, 2008. © 2008 Wiley‐Liss, Inc.
Efficient 1H to 31P polarization transfer on a clinical 3T MR system
Authors: Klomp D.W.J. , Wijnen J.P. , Scheenen T.W.J. , Heerschap A.
Published: November 2008

31P MR spectroscopy (MRS) in the detection of phosphocholine (PC), glycerolphosphocholine (GPC), phosphorylelthanolamine (PE), and glycerolphosphoethanolamine (GPE) compounds has shown clinical potential at 1.5T for several human diseases. The use of 1H to 31P polarization transfer can improve the sensitivity using a refocused INEPT method with a potential enhancement of 2.4 (γ1H/γ31P). However, in this method the 31P signals of PE, PC, GPE, and GPC are strongly attenuated (50% or more) due to J‐coupling between 31P and 1H that have similar magnitudes for homonuclear J‐coupling constants in those metabolites. A method to cancel the homonuclear J‐coupling effects in polarization transfer experiments is to apply frequency‐selective refocusing pulses, which becomes feasible at 3T due to the increased chemical shift dispersion as compared to 1.5T. In this study, full 1H to 31P polarization transfer was realized using chemical shift selective refocusing pulses at 3T. T1 and T2 values for 1H and 31P spins of PE, PC, GPE, and GPC were measured in the human brain. A more than 2‐fold signal‐to‐noise ratio (SNR) improvement was obtained compared to an optimized direct 31P MRS method. As shifted RF pulses were used, this method can be applied on a broadband clinical MR system with a single RF system. Magn Reson Med 60:1298–1305, 2008. © 2008 Wiley‐Liss, Inc.
Characterizing fiber directional uncertainty in diffusion tensor MRI
Authors: Jeong Ha‐Kyu , Anderson Adam W.
Published: November 2008

Image noise in diffusion tensor MRI (DT‐MRI) causes errors in the measured tensor and hence variance in the estimated fiber orientation. Uncertainty in fiber orientation has been described using a circular “cone of uncertainty” (CU) around the principal eigenvector of the DT. The CU has proved to be a useful construct for quantifying and visualizing the variability of DT‐MRI parameters and fiber tractography. The assumption of circularity of the CU has not been tested directly, however. In this work, bootstrap analysis and simple theoretical arguments were used to show that the CU is elliptical and multivariate normal in the vast majority of white matter (WM) voxels for typical measurement conditions. The dependence of the cone angle on the signal‐to‐noise ratio (SNR) and eigenvalue contrast was established. The major and minor cone axes are shown to be coincident with the second and third eigenvectors of the tensor, respectively, in the limit of many uniformly spaced diffusion‐encoding directions. The deviation between the major cone axis and the second eigenvector was quantified for typical sets of diffusion‐weighting (DW) directions. The elliptical CU provides more realistic error information for fiber‐tracking algorithms and a quantitative basis for selecting DT imaging acquisition protocols. Magn Reson Med 60:1408–1421, 2008. © 2008 Wiley‐Liss, Inc.
Slice‐selective RF pulses for in vivo B inhomogeneity mitigation at 7 tesla using parallel RF excitation with a 16‐element coil
Authors: Setsompop Kawin , Alagappan Vijayanand , Gagoski Borjan , Witzel Thomas , Polimeni Jonathan , Potthast Andreas , Hebrank Franz , Fontius Ulrich , Schmitt Franz , Wald Lawrence L. , Adalsteinsson Elfar
Published: November 2008

Slice‐selective RF waveforms that mitigate severe B inhomogeneity at 7 Tesla using parallel excitation were designed and validated in a water phantom and human studies on six subjects using a 16‐element degenerate stripline array coil driven with a butler matrix to utilize the eight most favorable birdcage modes. The parallel RF waveform design applied magnitude least‐squares (MLS) criteria with an optimized k‐space excitation trajectory to significantly improve profile uniformity compared to conventional least‐squares (LS) designs. Parallel excitation RF pulses designed to excite a uniform in‐plane flip angle (FA) with slice selection in the z‐direction were demonstrated and compared with conventional sinc‐pulse excitation and RF shimming. In all cases, the parallel RF excitation significantly mitigated the effects of inhomogeneous B on the excitation FA. The optimized parallel RF pulses for human B mitigation were only 67% longer than a conventional sinc‐based excitation, but significantly outperformed RF shimming. For example the standard deviations (SDs) of the in‐plane FA (averaged over six human studies) were 16.7% for conventional sinc excitation, 13.3% for RF shimming, and 7.6% for parallel excitation. This work demonstrates that excitations with parallel RF systems can provide slice selection with spatially uniform FAs at high field strengths with only a small pulse‐duration penalty. Magn Reson Med 60:1422–1432, 2008. © 2008 Wiley‐Liss, Inc.
Functional MRI with magnetization transfer effects: Determination of BOLD and arterial blood volume changes
Authors: Kim Tae , Hendrich Kristy , Kim Seong‐Gi
Published: November 2008

The primarily intravascular magnetization transfer (MT)‐independent changes in functional MRI (fMRI) can be separated from MT‐dependent changes. This intravascular component is dominated by an arterial blood volume change (ΔCBVa) term whenever venous contributions are minimized. Stimulation‐induced ΔCBVa can therefore be measured by a fit of signal changes to MT ratio. MT‐varied fMRI data were acquired in 13 isoflurane‐anesthetized rats during forepaw stimulation at 9.4T to simultaneously measure blood‐oxygenation‐level–dependent (BOLD) and ΔCBVa response in somatosensory cortical regions. Transverse relaxation rate change (ΔR2) without MT was –0.43 ± 0.15 s−1, and MT ratio decreased during stimulation. ΔCBVa was 0.46 ± 0.15 ml/100 g, which agrees with our previously‐presented MT‐varied arterial‐spin‐labeled data (0.42 ± 0.18 ml/100 g) in the same animals and also correlates with ΔR2 without MT. Simulations show that ΔCBVa quantification errors due to potential venous contributions are small for our conditions. Magn Reson Med 60:1518–1523, 2008. © 2008 Wiley‐Liss, Inc.
Pharmacokinetic modeling of delayed gadolinium enhancement in the myocardium
Authors: Knowles Benjamin R. , Batchelor Philip G. , Parish Victoria , Ginks Matthew , Plein Sven , Razavi Reza , Schaeffter Tobias
Published: November 2008

Delayed contrast‐enhanced magnetic resonance imaging (DCE‐MRI) provides prognostic information by delineating regions of myocardial scar. The mechanism of this delayed enhancement in myocardial infarctions (MIs) is hypothesized to result from altered kinetics and changes in the volumes of distribution in the myocardium. Pharmacokinetic models with two and three compartments were fitted to the concentration‐time curves of dynamic contrast‐enhanced MRI data obtained from five patients with known MI. Furthermore, the parameter stability was investigated in simulations for the two different models. The transfer constants and volumes of distribution showed a good correlation with imaging findings on early and delayed contrast‐enhanced MRI. The two compartment model showed higher parameter stability. The three compartment model allows a more in‐depth quantification of myocardial scarring. These models have the potential to improve the diagnosis of myocardial pathologies involving scar, with differing kinetics and volumes of distribution such as infarction or cardiomyopathy. Magn Reson Med 60:1524–1530, 2008. © 2008 Wiley‐Liss, Inc.
Hypercapnia‐induced effects on image contrast based on intermolecular double‐quantum coherences
Authors: Schäfer Andreas , Zysset Stefan , Heinke Wolfgang , Möller Harald E.
Published: November 2008

Intermolecular double‐quantum coherences (iDQCs) are well known to be sensitive to magnetic‐field perturbations inside tissues. However, the exact relation between iDQC contrast in magnetic resonance imaging (MRI) and the underlying physiology is less well understood. To investigate parameters that influence iDQC signal changes observed during neuronal activation, carbogen‐inhalation experiments were performed to produce a pure hemodynamic response without affecting oxidative metabolism. Eight human volunteers were studied at 2.9 T using gradient‐recalled echo (GRE) and spin‐echo (SE) variants of a single‐shot sequence selecting iDQCs. Results were compared with conventional recordings of the blood oxygen level‐dependent (BOLD) effect. Maps of voxels responding to the carbogen challenge showed similar distributions for iDQC and conventional MRI after adjustment for different sensitivities. Strong diffusion weighting of iDQC sequences and transverse relaxation effects suggested quantitative suppression of intravascular signal contributions. A particular susceptibility to local gradients during the evolution period (in which iDQCs evolve at twice the Larmor frequency) plus a strong relaxation weighting during the detection period due to the use of a long echo time (for refocusing of the dipolar signal) produced iDQC signal changes up to 21.7% ± 2.5%. These results agreed quantitatively with computations based on the balloon model of BOLD‐weighted MRI without requiring further assumptions. Magn Reson Med 60:1306–1312, 2008. © 2008 Wiley‐Liss, Inc.
Single‐shot multiecho parallel echo‐planar imaging (EPI) for diffusion tensor imaging (DTI) with improved signal‐to‐noise ratio (SNR) and reduced distortion
Authors: Nana Roger , Zhao Tiejun , Hu Xiaoping
Published: November 2008

In this work, a multiecho parallel echo‐planar imaging (EPI) acquisition strategy is introduced as a way to improve the acquisition efficiency in parallel diffusion tensor imaging (DTI). With the use of an appropriate echo combination strategy, the sequence can provide signal‐to‐noise ratio (SNR) enhancement while maintaining the advantages of parallel EPI. Simulations and in vivo experiments demonstrate that a weighted summation of multiecho images provides a significant gain in SNR over the first echo image. It is experimentally demonstrated that this SNR gain can be utilized to reduce the number of measurements often required to ensure adequate SNR for accurate DTI measures. Furthermore, the multiple echoes can be used to derive a T2 map, providing additional information that might be useful in some applications. Magn Reson Med 60:1512–1517, 2008. © 2008 Wiley‐Liss, Inc.
Quantitative bone matrix density measurement by water‐ and fat‐suppressed proton projection MRI (WASPI) with polymer calibration phantoms
Authors: Cao Haihui , Ackerman Jerome L. , Hrovat Mirko I. , Graham Lila , Glimcher Melvin J. , Wu Yaotang
Published: November 2008

The density of the organic matrix of bone substance is a critical parameter necessary to clinically evaluate and distinguish structural and metabolic pathological conditions such as osteomalacia in adults and rickets in growing children. Water‐ and fat‐suppressed proton projection MRI (WASPI) was developed as a noninvasive means to obtain this information. In this study, a density calibration phantom was developed to convert WASPI intensity to true bone matrix density. The phantom contained a specifically designed poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA) blend, whose MRI properties (T1, T2, and resonance linewidth) were similar to those of solid bone matrix (collagen, tightly bound water, and other immobile molecules), minimizing the need to correct for differences in T1 and/or T2 relaxation between the phantom and the subject. Cortical and trabecular porcine bone specimens were imaged using WASPI with the calibration phantom in the field of view (FOV) as a stable intensity reference. Gravimetric and amino acid analyses were carried out on the same specimens after WASPI, and the chemical results were found to be highly correlated (r2 = 0.98 and 0.95, respectively) to the WASPI intensity. By this procedure the WASPI intensity can be used to obtain the true bone matrix mass density in g cm–3. Magn Reson Med 60:1433–1443, 2008. © 2008 Wiley‐Liss, Inc.
Tumor imaging using P866, a high‐relaxivity gadolinium chelate designed for folate receptor targeting
Authors: Corot Claire , Robert Philippe , Lancelot Eric , Prigent Philippe , Ballet Sébastien , Guilbert Irène , Raynaud Jean‐Sébastien , Raynal Isabelle , Port Marc
Published: November 2008

The objective of this study was to evaluate the potential of a high‐relaxivity macromolecular gadolinium (Gd) chelate to target folate receptors (FRs). P866 is a dimeric high‐relaxivity Gd chelate coupled to a folate moiety. Binding affinity, in vivo biodistribution studies in KB tumor‐bearing mice at 1, 4, and 24 h, and dynamic contrast‐enhanced (DCE)‐MRI (2.35 T) over 4 h were assessed. Binding and internalization of P866 through the FR was demonstrated. Due to the high molecular volume of P866, the binding affinity compared to free FA was decreased (KD = 59.3 ± 1.8 nM and 5.9 ± 0.2 nM, respectively). Tumor/muscle (T/M) uptake was 5.4 ± 1.0, 4 h after injection of 15 μmol/kg. Competition with free FA was less effective when the dose was increased due to a saturation of FR. At a dose of 5 μmol/kg, a 70% difference in signal enhancement was observed between P866 and the nonspecific reference compound, thus demonstrating the specificity of FR targeting. While this high‐relaxivity folate‐Gd chelate has demonstrated its potential capacity to target in vivo FR on tumors, the sensitivity is probably limited to a certain extent by the saturation of the FR and by the decrease in the apparent relaxivity of the internalized part of P866 in the tumor cells. Magn Reson Med 60:1337–1346, 2008. © 2008 Wiley‐Liss, Inc.
Kinetics of avidin‐induced clearance of biotinylated bimodal liposomes for improved MR molecular imaging
Authors: van Tilborg Geralda A.F. , Strijkers Gustav J. , Pouget Emilie M. , Reutelingsperger Chris P.M. , Sommerdijk Nico A.J.M. , Nicolay Klaas , Mulder Willem J.M.
Published: November 2008

Dual labeled liposomes, carrying both paramagnetic and fluorescent lipids, were recently proposed as potent contrast agents for MR molecular imaging. These nanoparticles are coated with poly(ethylene glycol) (PEG) to increase their blood circulation half‐life, which should allow extensive accumulation at the targeted site. To eliminate nonspecific blood pool signal from the MR images, the circulating liposomes should ideally be cleared from the circulation when sufficient target‐specific contrast enhancement is obtained. To that aim, we designed an avidin chase that allowed controlled and rapid clearance of paramagnetic biotinylated liposomes from the blood circulation in C57BL/6 mice. Avidin‐induced alterations in blood clearance kinetics and tissue distribution were studied quantitatively by determination of the Gd content in blood and tissue samples ex vivo. Intrinsic liposomal blood clearance showed bi‐exponential behavior with half‐lives t1/2α = 2.1 ± 1.1 and t1/2β = 15.1 ± 5.4 hours, respectively. In contrast, the contrast agent was cleared from the blood by the avidin infusion to <1% of the initial dose within 4 hours. Avidin‐induced liposomal blood clearance was also demonstrated in vivo by dynamic T1‐weighted MRI. The ability to rapidly clear circulating contrast agents opens up exciting possibilities to study targeting kinetics, to increase the specificity of molecular MRI and to optimize nanoparticulate contrast agent formulations. Magn Reson Med 60:1444–1456, 2008. © 2008 Wiley‐Liss, Inc.
Magnetic resonance noise measurements and signal‐quantization effects at very low noise levels
Authors: Dietrich Olaf , Raya José G. , Reiser Maximilian F.
Published: November 2008

The well‐known noise distributions of magnetic resonance imaging (MRI) data (Rayleigh, Rician, or non‐central chi‐distribution) describe the probability density of real‐valued (i.e., floating‐point) signal intensities. MR image data, however, is typically quantized to integers before visualization or archiving. Depending on the scaling factors applied before the quantization and the signal‐to‐noise ratio (SNR), very low noise levels with substantial artifacts due to the quantization process can occur. The purpose of this study was to analyze the consequences of the signal quantization, to determine the theoretical absolute lower limit for noise measurements in discrete data, and to evaluate an improved method for noise and SNR measurements in the presence of very low noise levels. Image data were simulated with original noise levels of between 0.02 and 2.00. Noise measurements were performed based on the properties of background and foreground data using the conventional approach, which exploits the standard deviation or mean value of the signal, and a maximum‐likelihood approach based on the relative frequencies of the observed discrete signal intensities. Substantial deviations were found for the conventionally determined noise levels, while noise levels comparable to or lower than the quantization error can be accurately estimated with the proposed maximum‐likelihood approach. Magn Reson Med 60:1477–1487, 2008. © 2008 Wiley‐Liss, Inc.
FID sampling superior to spin‐echo sampling for T‐based quantification of holmium‐loaded microspheres: Theory and experiment
Authors: Seevinck Peter R. , Seppenwoolde Jan‐Henry , Zwanenburg Jaco J.M. , Nijsen Johannes F.W. , Bakker Chris J.G.
Published: November 2008

This work demonstrates both theoretically and experimentally that multiple gradient‐echo sampling of free induction decay (MGEFID) is superior to MGE sampling of spin echo (MGESE) for T‐based quantification of holmium‐loaded microspheres (HoMS). An interleaved sampling strategy was applied in great detail to characterize the MR signal behavior of FID and SE signals of gels and perfused rabbit livers containing HoMS in great detail. Diffusion sensitivity was demonstrated for MGESE sampling, resulting in non‐exponential signal decay on both sides of the SE peak and in an underestimation of the HoMS concentration. Other than MGESE sampling, MGEFID sampling was demonstrated to be insensitive to diffusion, to exhibit exponential signal decay, and to allow accurate T‐based quantification of HoMS. Furthermore, a fit procedure was proposed extending the upper limit of quantifiable R relaxation rates to at least 1500 sec–1. With this post‐processing step incorporated, MGEFID was shown to correctly estimate the integral amount of inhomogeneously distributed HoMS in liver tissue, up to a clinically relevant limit. All experimental findings could be explained with the theory of nuclear magnetic resonance (NMR) signal behavior in magnetically inhomogeneous tissues. HoMS were shown to satisfy the static dephasing regime when investigated with MGEFID and to violate the static dephasing conditions for MGESE at longer echo times typically used in SE. Magn Reson Med 60:1466–1476, 2008. © 2008 Wiley‐Liss, Inc.
An auto‐calibrated, angularly continuous, two‐dimensional GRAPPA kernel for propeller trajectories
Authors: Skare Stefan , Newbould Rexford D. , Nordell Anders , Holdsworth Samantha J. , Bammer Roland
Published: November 2008

The k‐space readout of propeller‐type sequences may be accelerated by the use of parallel imaging (PI). For PROPELLER, the main benefits are reduced blurring due to T2 decay and specific absorption ratio (SAR) reduction, whereas, for EPI‐based propeller acquisitions, such as Turbo‐PROP and short‐axis readout propeller EPI (SAP‐EPI), the faster k‐space traversal alleviates geometric distortions. In this work, the feasibility of calculating a two‐dimensional (2D) GRAPPA kernel on only the undersampled propeller blades themselves is explored, using the matching orthogonal undersampled blade. It is shown that the GRAPPA kernel varies slowly across blades; therefore, an angularly continuous 2D GRAPPA kernel is proposed, in which the angular variation of the weights is parameterized. This new angularly continuous kernel formulation greatly increases the numerical stability of the GRAPPA weight estimation, allowing for generation of fully sampled diagnostic quality images using only the undersampled propeller data. Magn Reson Med 60:1457–1465, 2008. © 2008 Wiley‐Liss, Inc.
New diffusion phantoms dedicated to the study and validation of high‐angular‐resolution diffusion imaging (HARDI) models
Authors: Poupon Cyril , Rieul Bernard , Kezele Irina , Perrin Muriel , Poupon Fabrice , Mangin Jean‐François
Published: November 2008

We present new diffusion phantoms dedicated to the study and validation of high‐angular‐resolution diffusion imaging (HARDI) models. The phantom design permits the application of imaging parameters that are typically employed in studies of the human brain. The phantoms were made of small‐diameter acrylic fibers, chosen for their high hydrophobicity and flexibility that ensured good control of the phantom geometry. The polyurethane medium was filled under vacuum with an aqueous solution that was previously degassed, doped with gadolinium‐tetraazacyclododecanetetraacetic acid (Gd‐DOTA), and treated by ultrasonic waves. Two versions of such phantoms were manufactured and tested. The phantom's applicability was demonstrated on an analytical Q‐ball model. Numerical simulations were performed to assess the accuracy of the phantom. The phantom data will be made accessible to the community with the objective of analyzing various HARDI models. Magn Reson Med 60:1276–1283, 2008. © 2008 Wiley‐Liss, Inc.
Field strength dependence of R1 and R relaxivities of human whole blood to prohance, vasovist, and deoxyhemoglobin
Authors: Blockley N.P. , Jiang L. , Gardener A.G. , Ludman C.N. , Francis S.T. , Gowland P.A.
Published: November 2008

This study has measured the longitudinal and transverse (T) relaxivity curves for ProHance (Gadoteridol), Vasovist (Gadofosveset) and deoxyhemoglobin at 1.5, 3.0, and 7.0 Tesla. The plots of R1 versus both contrast agent and deoxyhemoglobin concentration were linear. The plots of R versus deoxyhemoglobin concentration showed a quadratic dependence. R versus contrast agent concentration showed a parabolic dependence with a minimum occurring at contrast agent concentrations of approximately 1.5 mM, corresponding to an accessible concentration in vivo. Monte Carlo simulations were performed to support the hypothesis that the minimum results from the susceptibility of the red blood cells being matched to the susceptibility of the plasma. Relaxivity values (s−1mM−1) for R and R1 for all agents and all three field strengths are given. Magn Reson Med 60:1313–1320, 2008. © 2008 Wiley‐Liss, Inc.
In vivo single cell detection of tumor‐infiltrating lymphocytes with a clinical 1.5 Tesla MRI system
Authors: Smirnov Pierre , Poirier‐Quinot Marie , Wilhelm Claire , Lavergne Elise , Ginefri Jean‐Christophe , Combadière Béhazine , Clément Olivier , Darrasse Luc , Gazeau Florence
Published: November 2008

We demonstrate the feasibility of detecting individual tumor‐infiltrating cells in vivo, by means of cellular magnetic labeling and a 1.5 Tesla clinical MRI device equipped with a high‐resolution surface coil. Using a recently developed high‐temperature superconducting (HTS) surface coil, single cells were detected in vitro in voxels of (60 μm)3 at magnetic loads as low as 0.2 pg of iron per cell. The same imaging protocol was used in vivo to monitor infiltration of ovalbumin‐expressing tumors by transferred OVA antigen‐specific cytotoxic lymphocytes with low iron load. Magn Reson Med 60:1292–1297, 2008. © 2008 Wiley‐Liss, Inc.
In vivo serial evaluation of superparamagnetic iron‐oxide labeled stem cells by off‐resonance positive contrast
Authors: Suzuki Yoriyasu , Cunningham Charle H. , Noguchi Ken‐ichiro , Chen Ian Y. , Weissman Irving L. , Yeung Alan C. , Robbins Robert C. , Yang Phillip C.
Published: November 2008

MRI is emerging as a diagnostic modality to track iron‐oxide‐labeled stem cells. This study investigates whether an off‐resonance (OR) pulse sequence designed to generate positive contrast at 1.5T can assess the location, quantity, and viability of delivered stem cells in vivo. Using mouse embryonic stem cell transfected with luciferase reporter gene (luc‐mESC), multimodality validation of OR signal was conducted to determine whether engraftment parameters of superparamagnetic iron‐oxide labeled luc‐mESC (SPIO‐luc‐mESC) could be determined after cell transplantation into the mouse hindlimb. A significant increase in signal‐ and contrast‐to‐noise of the SPIO‐luc‐mESC was achieved with the OR technique when compared to a gradient recalled echo (GRE) sequence. A significant correlation between the quantity of SPIO‐luc‐mESC and OR signal was observed immediately after transplantation (R2 = 0.74, P < 0.05). The assessment of transplanted cell viability by bioluminescence imaging (BLI) showed a significant increase of luciferase activities by day 16, while the MRI signal showed no difference. No significant correlation between BLI and MRI signals of cell viability was observed. In conclusion, using an OR sequence the precise localization and quantitation of SPIO‐labeled stem cells in both space and time were possible. However, the OR sequence did not allow evaluation of cell viability. Magn Reson Med 60:1269–1275, 2008. © 2008 Wiley‐Liss, Inc.
Challenges of conducting multi‐center, multi‐disciplinary urinary incontinence clinical trials: Experience of the urinary incontinence Treatment Network
Authors: Steers William , Richter Holly , Nyberg Leroy , Kusek John , Kraus Stephen , Dandreo Kimberly , Chai Toby , Brubaker Linda
Published: November 2008

Aims

The Urinary Incontinence Treatment Network (UITN) was established in 2000 as a multi‐disciplinary, multi‐institutional network by the National Institute for Diabetes, Digestive, and Kidney Diseases (NIDDK) to investigate treatments for urinary incontinence in women.

Methods

Over 8 years this network composed of urologists, urogynecologists, geriatricians, behavioral psychologists, physical therapists, nurses, epidemiologists, social scientists and statisticians from nine academic sites and a Data Coordinating Center has been effective in designing and completing prospective randomized clinical trials for treatments of urinary incontinence in women.

Results

Two major clinical trials have been completed and a third has completed recruitment. The focus of the completed trials was a comparison of surgical methods to treat stress urinary incontinence whereas the third examined the potential benefit of combined behavioral intervention and antimuscarinic drug therapy to eliminate the need for long‐term use of drug therapy alone to manage urge urinary incontinence. The scientific output of the network measured by abstracts, original papers and presentations demonstrates the productivity of the network.

Conclusions

Many unique challenges are posed by a multi‐disciplinary team located at sites across the United States undertaking several clinical trials. This review presents some of the logistics, barriers, tactics, and strategies used to create this successful clinical trials network focused on urinary incontinence. Neurourol. Urodynam. 28:170–176, 2009. © 2008 Wiley‐Liss, Inc.
Psychometric validation of the overactive bladder satisfaction with treatment questionnaire (OAB‐SAT‐q)
Authors: Margolis Mary Kay , Fox Kathleen M. , Cerulli Annamaria , Ariely Rinat , Kahler Kristijan H. , Coyne Karin S.
Published: November 2008

Aims

Valid and reliable questionnaires must be used to accurately assess patients' satisfaction with overactive bladder (OAB) treatment. This study evaluated the reliability and validity of the OAB Satisfaction with Treatment Questionnaire (OAB‐SAT‐q).

Methods

This was a secondary analysis of clinical study data of patients randomized to darifenacin or darifenacin plus Behavioral Modification Program. Patients completed the Overactive Bladder Questionnaire (OAB‐q) and a 3‐day bladder diary at Baseline and Week 12 and the OAB‐SAT‐q at Week 12. Internal consistency reliability was assessed by Cronbach's alpha. Concurrent validity was assessed through correlations with OAB‐q change scores and adverse events (AEs). Discriminant validity was assessed among subgroups using general linear models.

Results

Analyses utilized a per‐protocol population (completion of OAB‐q at Baseline and OAB‐q and OAB‐SAT‐q at Week 12) (n = 375). Exploratory factor analysis of the OAB‐SAT‐q revealed three 3‐item subscales (Satisfaction, Side Effects, Endorsement) and two single items (Convenience, Preference). Cronbach's alphas = 0.84–0.95. Subscale‐to‐subscale correlations = 0.10–0.67 (all P < 0.01 except Side Effects and Convenience). The Side Effects subscale significantly correlated with number of treatment‐related AEs (r = 0.27; P < 0.01) and discriminated between patients with/without dry mouth and patients with/without constipation. The Satisfaction and Endorsement subscales discriminated between patients who worsened or had no change in micturition frequency and urinary urgency and patients who had a reduction of >3 episodes (all P < 0.001). The OAB‐SAT‐q does not appear to discriminate by incontinence episodes.

Conclusion

The OAB‐SAT‐q demonstrated good psychometric properties in this initial evaluation—including internal consistency reliability and concurrent and discriminant validity—and appears to be a useful assessment of OAB treatment satisfaction. Neurourol. Urodynam. 28:416–422, 2009. © 2008 Wiley‐Liss, Inc.
A finite element formulation for thermoelastic damping analysis
Authors: Serra Enrico , Bonaldi Michele
Published: November 2008

We present a finite element formulation based on a weak form of the boundary value problem for fully coupled thermoelasticity. The thermoelastic damping is calculated from the irreversible flow of entropy due to the thermal fluxes that have originated from the volumetric strain variations. Within our weak formulation we define a dissipation function that can be integrated over an oscillation period to evaluate the thermoelastic damping. We show the physical meaning of this dissipation function in the framework of the well‐known Biot's variational principle of thermoelasticity. The coupled finite element equations are derived by considering harmonic small variations of displacement and temperature with respect to the thermodynamic equilibrium state. In the finite element formulation two elements are considered: the first is a new 8‐node thermoelastic element based on the Reissner–Mindlin plate theory, which can be used for modeling thin or moderately thick structures, while the second is a standard three‐dimensional 20‐node iso‐parametric thermoelastic element, which is suitable to model massive structures. For the 8‐node element the dissipation along the plate thickness has been taken into account by introducing a through‐the‐thickness dependence of the temperature shape function. With this assumption the unknowns and the computational effort are minimized. Comparisons with analytical results for thin beams are shown to illustrate the performances of those coupled‐field elements. Copyright © 2008 John Wiley & Sons, Ltd.
Preparation of porous ultrafine polyacrylonitrile (PAN) fibers by electrospinning
Authors: Ma Guiping , Yang Dongzhi , Nie Jun
Published: November 2008

A facile method for the preparation of porous ultrafine nanofibers was demonstrated. The PAN/NaHCO3 composite nanofibers were electrospun, and then NaHCO3 was removed by a selective dissolution and reaction with the solution of hydrochloric acid (10 wt%). The obtained PAN fibers showed highly porous surfaces after the extraction of NaHCO3. The structure and properties of ultrafine PAN nanofibers were characterized by Fourier transform infrared (FT‐IR), X‐ray diffraction (XRD), and thermogravimetry (TG). The results indicated that NaHCO3 could be introduced into the PAN solution and successfully electrospun. CO2 is released and pores are formed on the fibers. The morphology image of the fibers was detected by scanning electron microscope (SEM) and showed that many pores aligned the nanofibers. Copyright © 2008 John Wiley & Sons, Ltd.
Clinical practice guideline improves the treatment of sickle cell disease vasoocclusive pain
Authors: Morrissey Lisa K. , Shea Joan O'Brien , Kalish Leslie A. , Weiner Debra L. , Branowicki Patricia , Heeney Matthew M.
Published: November 2008

Background

Pain is the most common complication of sickle cell disease requiring emergency department (ED) visits and hospitalization. A Clinical Practice Guideline (CPG) to manage acute sickle cell pain offers clinicians a standardized approach for the provision of evidence‐based, cost‐effective care. After CPG implementation, monitoring of pre‐established indicators is a strategy to evaluate progress toward meeting the goal of providing rapid, effective pain relief for patients with acute sickle cell pain.

Methods

A retrospective chart review of patients with sickle cell disease admitted through the ED at Children's Hospital Boston with the primary diagnosis of vaso‐occlusive pain was performed for a period before and after implementation of the CPG. Endpoints measured were: use of a validated pain scale, time from ED triage to first dose of analgesic, use of adequate weight‐based analgesic dosing, frequency and location of PCA initiation, and time from ED triage to patient controlled analgesia (PCA) initiation.

Results

Two hundred sixty three sickle cell pain admissions in 93 unique subjects were analyzed, 51 pre‐CPG and 212 post‐CPG. Statistically significant improvements in use of pain scale, appropriate weight‐based analgesic dosing, utilization of PCA, and time to initiation of PCA were observed. There was not a statistically significant improvement in the percentage of subjects who received their 1st dose of analgesic within 1 hr; however the median time to first analgesic was reduced significantly from 80 to 65 min (P = 0.003).

Conclusions

Implementation of a CPG to manage acute sickle cell pain in the ED improves the ability to deliver timely, effective analgesia to this patient population. Establishing and monitoring internal benchmarks provides a means for ongoing evaluation of the pre‐established goals for patient care. Pediatr Blood Cancer 2009;52:369–372. © 2008 Wiley‐Liss, Inc.
Copolymers of N‐alkyl‐ and N‐arylalkylacrylamides with acrylamide: influence of hydrophobic structure on associative properties. Part I: viscometric behaviour in dilute solution and drag reduction performance
Authors: Camail Michel , Margaillan André , Martin Isabelle
Published: November 2008

BACKGROUND: Drag reduction properties from dilute aqueous polymer solution are obtained with very high molecular weight water‐soluble polymers. The aim of this work was to examine the potential of acrylamide polymers modified with small amounts of N‐alkyl‐ and N‐arylalkylacrylamides (0.5 and 1 mol%).

RESULTS: The associative properties improve with the length of the graft alkyl chain, and with its proportion in the copolymer and with the presence of aromatic groups. The drag reduction efficiency of these copolymers in very dilute solution was measured to relate the activity to the molecular parameters.

CONCLUSION: The results obtained indicate that the persistent drag reduction activity can be linked to the presence of strong intramolecular associations. Copyright © 2008 Society of Chemical Industry