bluuebunny/crossref_metadata_2025 huggingface dataset:
High‐resolution uniform MR imaging of finger joints using a dedicated RF coil at 3T
Authors: Kwok Wingchi E. , You Zhigang , Monu Johnny , Seo Gwysuk , Ritchlin Christopher
Published: October 2009

Purpose

To develop a dedicated radiofrequency (RF) coil for high‐resolution magnetic resonance imaging (MRI) of finger joints at 3T to improve diagnostic evaluation of arthritic diseases.

Materials and Methods

A dedicated cylindrical RF receive coil was developed for imaging finger joints at 3T. A planar coil, a saddle coil, and a 1.5T coil with similar design as the dedicated coil were also constructed to compare imaging performance with the dedicated coil. A phantom was used for quantitative evaluation. Three‐dimensional images were obtained on four subjects and a cadaver finger specimen using isotropic resolution of 160 μm in 9:32 minutes. The images were reviewed by two musculoskeletal radiologists.

Results

The dedicated finger coil provided higher signal‐to‐noise and greater signal uniformity than the other coils. It supported high‐resolution imaging that demonstrated anatomical details of the entire finger joint, and in the subject study revealed abnormalities not detectable by traditional clinical resolution.

Conclusion

The dedicated finger coil optimizes the potential advantages of 3T scanners compared to lower field magnets. Use of this coil should facilitate early diagnosis, improve assessment of treatment response, and provide better understanding of basic mechanisms that underlie arthritis. J. Magn. Reson. Imaging 2010. © 2009 Wiley‐Liss, Inc.
Cellular expression pattern of the protease‐activated receptor 4 in the hippocampus in naïve rats and after global ischaemia
Authors: Henrich‐Noack P. , Riek‐Burchardt M. , Reymann K.G. , Reiser G.
Published: October 2009

A pronounced hippocampal expression of the Protease‐activated Receptor 4 (PAR4) has recently been shown. In the current study the authors define the PAR4‐associated sub‐cellular structures and the influence of global ischaemia on the expression of PAR4. For that purpose the authors performed double labelling with fluorescence immunohistochemistry on tissue from naïve and post‐ischaemic rats. In naïve animals ‐ apart from the expression in granular and pyramidal neurons ‐ there was an intensive lamellar expression of PAR4 in the CA4 region. Further analysis revealed that PAR4 was localised exclusively on mossy fibre axons in CA4 as detected by double‐labelling with calbindin D‐28k, but there was no overlap with markers of the neuronal cell body, interneurons, and post‐synaptic, pre‐synaptic and dendritic structures. Three and 14 days post ischaemia, CA1 neurons were degenerated and, consequently, there was no PAR4 signal in the CA1 band. In most other hippocampal structures no change in the PAR4 expression was detectable, with the exception of the CA3 region. Here, the fibre‐associated PAR4 signal was diminished and disintegrated post ischaemia. Additionally, a redistribution from the membrane‐bound neuronal localisation of PAR4 in control animals to a diffuse localisation all over the cell soma was revealed in the CA3 area 14 days post ischaemia. In conclusion, the current study proves for the first time that PAR4 is localised in mossy fibre axons. The altered expression in CA3 neurons after ischaemia indicates that PAR4 may be involved in post‐ischaemic adaptive mechanisms. © 2009 Wiley‐Liss, Inc.
Activity‐dependent somatostatin gene expression is regulated by cAMP‐dependent protein kinase and Ca2+‐calmodulin kinase pathways
Authors: Sánchez‐Muñoz Isabel , Sánchez‐Franco Franco , Vallejo Mario , Fernández Antonio , Palacios Nuria , Fernández Miriam , Cacicedo Lucinda
Published: October 2009

Ca2+ influx through L‐type voltage‐gated Ca2+ channels (L‐VSCC) is required for K+‐induced somatostatin (SS) mRNA. Increase in intracellular Ca2+ concentration leads to the activation of cyclic AMP‐responsive element binding protein (CREB), a key regulator of SS gene transcription. Several different protein kinases possess the capability of driving CREB upon membrane depolarization. We investigated which of the signalling pathways involved in CREB activation mediates SS gene induction in response to membrane depolarization in cerebrocortical cells exposed to 56 mM K+. Activity dependent phosphorylation of CREB in Ser133 was immunodetected. Activation of CREB was biphasic showing two peaks at 5 and 60 min. The selective inhibitors of extracellular signal related protein kinase/mitogen‐activated protein kinase (ERK/MAPK) PD098059, cyclic‐AMPdependent protein kinase (cAMP/PKA) H89 and RpcAMPS, and Ca2+/calmodulin‐dependent protein kinases (CaMKs) pathways KN62 and KN93 were used to determine the signalling pathways involved in CREB activation. Here we show that the early activation of CREB was dependent on cAMP/PKA along with CaMKs pathways whereas the ERK/MAPK and CaMKs were implicated in the second peak. We observed that H89, RpcAMPS, KN62 and KN93 blocked K+‐induced SS mRNA whereas PD098059 did not. These findings indicate that K+‐induced SSmRNA is mediated by the activation of cAMP/PKA and CaMKs pathways, thus suggesting that the early activation of CREB is involved in the induction of SS by neuronal activity. We also demonstrated, using transient transfections of cerebrocortical cells, that K+ induces the transcriptional regulation of the SS gene through the cAMP‐responsive element (CRE) sequence located in the SS promoter. © 2009 Wiley‐Liss, Inc.
Axon responses of embryonic stem cell‐derived dopaminergic neurons to semaphorins 3A and 3C
Authors: Tamariz Elisa , Díaz‐Martínez N. Emmanuel , Díaz Néstor F. , García‐Peña Claudia M. , Velasco Iván , Varela‐Echavarría Alfredo
Published: October 2009

Class 3 Semaphorins are a subfamily of chemotropic molecules implicated in the projection of dopaminergic neurons from the ventral mesencephalon and in the formation of the nigrostriatal pathway (NSP) during embryonic development. In humans, loss of mesencephalic dopaminergic neurons leads to Parkinson's disease (PD). Cell replacement therapy with dopaminergic neurons generated from embryonic stem cells (ES‐TH+) is being actively explored in models of PD. Among several requisites for this approach to work are adequate reconstruction of the NSP and correct innervation of normal striatal targets by dopaminergic axons. In this work, we characterized the response of ES‐TH+ neurons to semaphorins 3A, 3C, and 3F and compared it with that of tyrosine hidroxylase‐positive neurons (TH+) obtained from embryonic ventral mesencephalon (VM‐TH+). We observed that similar proportions of ES‐TH+ and VM‐TH+ neurons express semaphorin receptors neuropilins 1 and 2. Furthermore, the axons of both populations responded very similarly to semaphorin exposure: semaphorin 3A increased axon length, and semaphorin 3C attracted axons and increased their length. These effects were mediated by neuropilins, insofar as addition of blocking antibodies against these proteins reduced the effects on axonal growth and attraction, and only TH+ axons expressing neuropilins responded to the semaphorins analyzed. The observations reported here show phenotypic similarities between VM‐TH+ and ES‐TH+ neurons and suggest that semaphorins 3A and 3C could be employed to guide axons of grafted ES‐TH+ in therapeutic protocols for PD. © 2009 Wiley‐Liss, Inc.
Recurrent systemic infections with Streptococcus pneumoniae do not aggravate the course of experimental neurodegenerative diseases
Authors: Ebert Sandra , Goos Miriam , Rollwagen Lena , Baake Daniel , Zech Wolf‐Dieter , Esselmann Hermann , Wiltfang Jens , Mollenhauer Brit , Schliebs Reinhard , Gerber Joachim , Nau Roland
Published: October 2009

Neurological symptoms of patients suffering from neurodegenerative diseases such as Alzheimer's dementia (AD), Parkinson's disease (PD), or amyotrophic lateral sclerosis (ALS) often worsen during infections. We assessed the disease‐modulating effects of recurrent systemic infections with the most frequent respiratory pathogen, Streptococcus pneumoniae, on the course of AD, PD, and ALS in mouse models of these neurodegenerative diseases [transgenic Tg2576 mice, (Thy1)‐[A30P]αSYN mice, and Tg(SOD1‐G93A) mice]. Mice were repeatedly challenged intraperitoneally with live S. pneumoniae type 3 and treated with ceftriaxone for 3 days. Infection caused an increase of interleukin‐6 concentrations in brain homogenates. The clinical status of (Thy1)‐[A30P]αSYN mice and Tg(SOD1‐G93A) mice was monitored by repeated assessment with a clinical score. Motor performance was controlled by the tightrope test and the rotarod test. In Tg2576 mice, spatial memory and learning deficits were assessed in the Morris water maze. In none of the three mouse models onset or course of the disease as evaluated by the clinical tests was affected by the recurrent systemic infections performed. Levels of α‐synuclein in brains of (Thy1)‐[A30P]αSYN mice did not differ between infected animals and control animals. Plaque sizes and concentrations of Aβ 1–40 and Aβ 1–42 were not significantly different in brains of infected and uninfected Tg2576 mice. In conclusion, onset and course of disease in mouse models of three common neurodegenerative disorders were not influenced by repeated systemic infections with S. pneumoniae, indicating that the effect of moderately severe acute infections on the course of neurodegenerative diseases may be less pronounced than suspected. © 2009 Wiley‐Liss, Inc.
Laser‐Schwingungsmesstechnik in der Serienproduktion
Authors: Sauer Jörg , Holzmann Philipp
Published: October 2009

Der Flächendeckende Einsatz des Lasers in der Produktion sorgt für neue Möglichkeiten, höchste Qualität bei geringen Kosten zu erreichen. In diesem Beitrag wird anhand eines Beispiels aus der Medizintechnik ein anderer Einsatzfall der Lasertechnologie vorgestellt: die 100% Qualitätskontrolle der Eigenschaften des Herzstücks eines Inhalationssystems zur optimierten Therapie von Atemwegserkrankungen.
Zellulare Neuronale Netzwerke
Authors: Blug Andreas
Published: October 2009

Eine echte Regelung schneller industrieller Prozesse scheitert nicht selten an der Bildverarbeitung. Hier müssen über 10 000 Bilder pro Sekunde verarbeitet werden, um Messwerte in Regelsignale umzuwandeln. Mit einer neuen Kameraarchitektur gelingt es, Laserschweißprozesse in Echtzeit zu regeln. Rechen‐ und Speicherelemente, integriert in die einzelnen Pixel eines Kamerachips, ermöglichen es, Prozessschritte nicht wie üblich sequenziell, sondern parallel auf eine Vielzahl von Daten anzuwenden. Voraussetzung sind Algorithmen, welche die Eigenschaften solcher Zellularen Neuronalen Netzwerke effizient nutzen.
Den Schweißpunkt immer im Fokus
Authors: Nicolay Thomas , Bayer Volker
Published: October 2009

Direkt durch die Schweißoptik nimmt die Kamera des koaxialen Nahtverfolgungssystems LPF von Precitec die Dachnähte von Automobilen ins Visier. Im hier beschriebenen Beispiel erzeugen zwei übereinander angeordnete Liniengeneratoren jeweils drei bis fünf Millimeter vor und nach dem Schweißpunkt einen Lichtstreifen quer zur Schweißnaht. Auf Basis der kontinuierlichen Auswertung des jeweils vorlaufenden Linienprofils wird der Fokus des Laserstrahls in beiden Richtungen mit Hilfe einer hochgenauen Linearachse exakt entlang der seitlichen Dachflanschkante geführt.
CO2 Lasers and Robotics in Modern Automotive Manufacturing
Authors: Gaebler Frank , Clark Christopher
Published: October 2009

Carbon dioxide lasers have been utilized by the automotive industry for many years, originally being employed for heavy duty auto body welding applications. But over the last decade the advent of compact, sealed CO2 lasers with improved output characteristics, together with the development of more sophisticated robotic systems, have enabled lasers to move into high precision processing tasks for non‐metallic materials (e.g. for leather, plastics or carbon fiber composites) particularly components destined for automotive interiors. This article reviews some current high precision automotive manufacturing applications and the lasers and robotic technology that service them.
Permanent, Non‐Leaching Antimicrobial Polyamide Nanocomposites Based on Organoclays Modified with a Cationic Polymer
Authors: Nigmatullin Rinat , Gao Fengge , Konovalova Victoria
Published: October 2009

The intercalation of cationic copolymer into a smectic clay, montmorillonite, has been used to produce polymerically modified organoclays. The organoclays of different lamellar morphology and content of quaternary ammonium groups have been prepared by altering the clay/polymer ratio. The organoclays prepared have been explored in the design of antimicrobial materials based on clay/polymer nanotechnology. Polyamide nanocomposites containing organoclays with incorporated cationic polymer showed an antimicrobial activity and improved mechanical properties. The antimicrobial efficiency and the mechanical properties of the nanocomposites were controlled by the variation of the content of the cationic polymer incorporated into the organoclay and organoclay loading.

magnified image
Model‐based blind estimation of kinetic parameters in dynamic contrast enhanced (DCE)‐MRI
Authors: Fluckiger Jacob U. , Schabel Matthias C. , DiBella Edward V.R.
Published: October 2009

A method to simultaneously estimate the arterial input function (AIF) and pharmacokinetic model parameters from dynamic contrast‐enhanced (DCE)‐MRI data was developed. This algorithm uses a parameterized functional form to model the AIF and k‐means clustering to classify tissue time‐concentration measurements into a set of characteristic curves. An iterative blind estimation algorithm alternately estimated parameters for the input function and the pharmacokinetic model. Computer simulations were used to investigate the algorithm's sensitivity to noise and initial estimates. In 12 patients with sarcomas, pharmacokinetic parameter estimates were compared with “truth” obtained from model regression using a measured AIF. When arterial voxels were included in the blind estimation algorithm, the resulting AIF was similar to the measured input function. The “true” Ktrans values in tumor regions were not significantly different than the estimated values, 0.99 ± 0.41 and 0.86 ± 0.40 min−1, respectively, P = 0.27. “True” kep values also matched closely, 0.70 ± 0.24 and 0.65 ± 0.25 min−1, P = 0.08. When only tissue curves free of significant vascular contribution are used (vp < 0.05), the resulting AIF showed substantial delay and dispersion consistent with a more local AIF such as has been observed in dynamic susceptibility contrast imaging in the brain. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Three‐dimensional micro‐MRI analysis of cerebral artery development in mouse embryos
Authors: Berrios‐Otero Cesar A. , Wadghiri Youssef Zaim , Nieman Brian J. , Joyner Alexandra L. , Turnbull Daniel H.
Published: October 2009

Vascular system development involves a complex, three‐dimensional branching process that is critical for normal embryogenesis. In the brain, the arterial systems appear to develop in a stereotyped fashion, but no detailed quantitative analyses of the mouse embryonic cerebral arteries have been described. In this study, a gadolinium‐based contrast perfusion method was developed to selectively enhance the cerebral arteries in fixed mouse embryos. Three‐dimensional magnetic resonance micro‐imaging (micro‐MRI) data were acquired simultaneously from multiple embryos staged between 10 and 17 days of gestation, and a variety of image analysis methods was used to extract and analyze the cerebral arterial patterns. The results show that the primary arterial branches in the mouse brain are very similar between individuals, with the patterns established early and growth occurring by extension of the segments, while maintaining the underlying vascular geometry. To investigate the utility of this method for mutant mouse phenotype analysis, contrast‐enhanced micro‐MRI data were acquired from Gli2‐/‐ mutant embryos and their wild‐type littermates, showing several previously unreported vascular phenotypes in Gli2−/− embryos, including the complete absence of the basilar artery. These results demonstrate that contrast‐enhanced micro‐MRI provides a powerful tool for analyzing vascular phenotypes in a variety of genetically engineered mice. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Robust GRAPPA‐accelerated diffusion‐weighted readout‐segmented (RS)‐EPI
Authors: Holdsworth Samantha J. , Skare Stefan , Newbould Rexford D. , Bammer Roland
Published: October 2009

Readout segmentation (RS‐EPI) has been suggested as a promising variant to echo‐planar imaging (EPI) for high‐resolution imaging, particularly when combined with parallel imaging. This work details some of the technical aspects of diffusion‐weighted (DW)‐RS‐EPI, outlining a set of reconstruction methods and imaging parameters that can both minimize the scan time and afford high‐resolution diffusion imaging with reduced distortions. These methods include an efficient generalized autocalibrating partially parallel acquisition (GRAPPA) calibration for DW‐RS‐EPI data without scan time penalty, together with a variant for the phase correction of partial Fourier RS‐EPI data. In addition, the role of pulsatile and rigid‐body brain motion in DW‐RS‐EPI was assessed. Corrupt DW‐RS‐EPI data arising from pulsatile nonlinear brain motion had a prevalence of ∼7% and were robustly identified via k‐space entropy metrics. For DW‐RS‐EPI data corrupted by rigid‐body motion, we showed that no blind overlap was required. The robustness of RS‐EPI toward phase errors and motion, together with its minimized distortions compared with EPI, enables the acquisition of exquisite 3 T DW images with matrix sizes close to 5122. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
High‐contrast in vivo visualization of microvessels using novel FeCo/GC magnetic nanocrystals
Authors: Lee Jin Hyung , Sherlock Sarah P. , Terashima Masahiro , Kosuge Hisanori , Suzuki Yoriyasu , Goodwin Andrew , Robinson Joshua , Seo Won Seok , Liu Zhuang , Luong Richard , McConnell Michael V. , Nishimura Dwight G. , Dai Hongjie
Published: October 2009

FeCo‐graphitic carbon shell nanocrystals are a novel MRI contrast agent with unprecedented high per‐metal‐atom‐basis relaxivity (r1 = 97 mM‐1 sec‐1, r2 = 400 mM‐1 sec‐1) and multifunctional capabilities. While the conventional gadolinium‐based contrast‐enhanced angiographic magnetic MRI has proven useful for diagnosis of vascular diseases, its short circulation time and relatively low sensitivity render high‐resolution MRI of morphologically small vascular structures such as those involved in collateral, arteriogenic, and angiogenic vessel formation challenging. Here, by combining FeCo‐graphitic carbon shell nanocrystals with high‐resolution MRI technique, we demonstrate that such microvessels down to ∼100 μm can be monitored in high contrast and noninvasively using a conventional 1.5‐T clinical MRI system, achieving a diagnostic imaging standard approximating that of the more invasive X‐ray angiography. Preliminary in vitro and in vivo toxicity study results also show no sign of toxicity. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Classification of brain tumor type and grade using MRI texture and shape in a machine learning scheme
Authors: Zacharaki Evangelia I. , Wang Sumei , Chawla Sanjeev , Soo Yoo Dong , Wolf Ronald , Melhem Elias R. , Davatzikos Christos
Published: October 2009

The objective of this study is to investigate the use of pattern classification methods for distinguishing different types of brain tumors, such as primary gliomas from metastases, and also for grading of gliomas. The availability of an automated computer analysis tool that is more objective than human readers can potentially lead to more reliable and reproducible brain tumor diagnostic procedures. A computer‐assisted classification method combining conventional MRI and perfusion MRI is developed and used for differential diagnosis. The proposed scheme consists of several steps including region‐of‐interest definition, feature extraction, feature selection, and classification. The extracted features include tumor shape and intensity characteristics, as well as rotation invariant texture features. Feature subset selection is performed using support vector machines with recursive feature elimination. The method was applied on a population of 102 brain tumors histologically diagnosed as metastasis (24), meningiomas (4), gliomas World Health Organization grade II (22), gliomas World Health Organization grade III (18), and glioblastomas (34). The binary support vector machine classification accuracy, sensitivity, and specificity, assessed by leave‐one‐out cross‐validation, were, respectively, 85%, 87%, and 79% for discrimination of metastases from gliomas and 88%, 85%, and 96% for discrimination of high‐grade (grades III and IV) from low‐grade (grade II) neoplasms. Multiclass classification was also performed via a one‐vs‐all voting scheme. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Sodium MRI using a density‐adapted 3D radial acquisition technique
Authors: Nagel Armin M. , Laun Frederik B. , Weber Marc‐André , Matthies Christian , Semmler Wolfhard , Schad Lothar R.
Published: October 2009

A density‐adapted three‐dimensional radial projection reconstruction pulse sequence is presented which provides a more efficient k‐space sampling than conventional three‐dimensional projection reconstruction sequences. The gradients of the density‐adapted three‐dimensional radial projection reconstruction pulse sequence are designed such that the averaged sampling density in each spherical shell of k‐space is constant. Due to hardware restrictions, an inner sphere of k‐space is sampled without density adaption. This approach benefits from both the straightforward handling of conventional three‐dimensional projection reconstruction sequence trajectories and an enhanced signal‐to‐noise ratio (SNR) efficiency akin to the commonly used three‐dimensional twisted projection imaging trajectories. Benefits for low SNR applications, when compared to conventional three‐dimensional projection reconstruction sequences, are demonstrated with the example of sodium imaging. In simulations of the point‐spread function, the SNR of small objects is increased by a factor 1.66 for the density‐adapted three‐dimensional radial projection reconstruction pulse sequence sequence. Using analytical and experimental phantoms, it is shown that the density‐adapted three‐dimensional radial projection reconstruction pulse sequence allows higher resolutions and is more robust in the presence of field inhomogeneities. High‐quality in vivo images of the healthy human leg muscle and the healthy human brain are acquired. For equivalent scan times, the SNR is up to a factor of 1.8 higher and anatomic details are better resolved using density‐adapted three‐dimensional radial projection reconstruction pulse sequence. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Disease state prediction from resting state functional connectivity
Authors: Craddock R. Cameron , Holtzheimer Paul E. , Hu Xiaoping P. , Mayberg Helen S.
Published: October 2009

The application of multivoxel pattern analysis methods has attracted increasing attention, particularly for brain state prediction and real‐time functional MRI applications. Support vector classification is the most popular of these techniques, owing to reports that it has better prediction accuracy and is less sensitive to noise. Support vector classification was applied to learn functional connectivity patterns that distinguish patients with depression from healthy volunteers. In addition, two feature selection algorithms were implemented (one filter method, one wrapper method) that incorporate reliability information into the feature selection process. These reliability feature selections methods were compared to two previously proposed feature selection methods. A support vector classifier was trained that reliably distinguishes healthy volunteers from clinically depressed patients. The reliability feature selection methods outperformed previously utilized methods. The proposed framework for applying support vector classification to functional connectivity data is applicable to other disease states beyond major depression. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Tailored RF pulse for magnetization inversion at ultrahigh field
Authors: Hurley Aaron C. , Al‐Radaideh Ali , Bai Li , Aickelin Uwe , Coxon Ron , Glover Paul , Gowland Penny A.
Published: October 2009

The radiofrequency (RF) transmit field is severely inhomogeneous at ultrahigh field due to both RF penetration and RF coil design issues. This particularly impairs image quality for sequences that use inversion pulses such as magnetization prepared rapid acquisition gradient echo and limits the use of quantitative arterial spin labeling sequences such as flow‐attenuated inversion recovery. Here we have used a search algorithm to produce inversion pulses tailored to take into account the heterogeneity of the RF transmit field at 7 T. This created a slice selective inversion pulse that worked well (good slice profile and uniform inversion) over the range of RF amplitudes typically obtained in the head at 7 T while still maintaining an experimentally achievable pulse length and pulse amplitude in the brain at 7 T. The pulses used were based on the frequency offset correction inversion technique, as well as time dilation of functions, but the RF amplitude, frequency sweep, and gradient functions were all generated using a genetic algorithm with an evaluation function that took into account both the desired inversion profile and the transmit field inhomogeneity. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Initial results on in vivo human coronary MR angiography at 7 T
Authors: van Elderen Saska G. C. , Versluis Maarten J. , Webb Andrew G. , Westenberg Jos J. M. , Doornbos Joost , Smith Nadine B. , de Roos Albert , Stuber Matthias
Published: October 2009

Seven tesla (T) MR imaging is potentially promising for the morphologic evaluation of coronary arteries because of the increased signal‐to‐noise ratio compared to lower field strengths, in turn allowing improved spatial resolution, improved temporal resolution, or reduced scanning times. However, there are a large number of technical challenges, including the commercial 7 T systems not being equipped with homogeneous body radiofrequency coils, conservative specific absorption rate constraints, and magnified sample‐induced amplitude of radiofrequency field inhomogeneity. In the present study, an initial attempt was made to address these challenges and to implement coronary MR angiography at 7 T. A single‐element radiofrequency transmit and receive coil was designed and a 7 T specific imaging protocol was implemented, including significant changes in scout scanning, contrast generation, and navigator geometry compared to current protocols at 3 T. With this methodology, the first human coronary MR images were successfully obtained at 7 T, with both qualitative and quantitative findings being presented. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Radial k‐t FOCUSS for high‐resolution cardiac cine MRI
Authors: Jung Hong , Park Jaeseok , Yoo Jaeheung , Ye Jong Chul
Published: October 2009

A compressed sensing dynamic MR technique called k‐t FOCUSS (k‐t FOCal Underdetermined System Solver) has been recently proposed. It outperforms the conventional k‐t BLAST/SENSE (Broad‐use Linear Acquisition Speed‐up Technique/SENSitivity Encoding) technique by exploiting the sparsity of x‐f signals. This paper applies this idea to radial trajectories for high‐resolution cardiac cine imaging. Radial trajectories are more suitable for high‐resolution dynamic MRI than Cartesian trajectories since there is smaller tradeoff between spatial resolution and number of views if streaking artifacts due to limited views can be resolved. As shown for Cartesian trajectories, k‐t FOCUSS algorithm efficiently removes artifacts while preserving high temporal resolution. k‐t FOCUSS algorithm applied to radial trajectories is expected to enhance dynamic MRI quality. Rather than using an explicit gridding method, which transforms radial k‐space sampling data to Cartesian grid prior to applying k‐t FOCUSS algorithms, we use implicit gridding during FOCUSS iterations to prevent k‐space sampling errors from being propagated. In addition, motion estimation and motion compensation after the first FOCUSS iteration were used to further sparsify the residual image. By applying an additional k‐t FOCUSS step to the residual image, improved resolution was achieved. In vivo experimental results show that this new method can provide high spatiotemporal resolution even from a very limited radial data set. Magn Reson Med, 2010. © 2009 Wiley‐Liss, Inc.
Quantitative T2 analysis: The effects of noise, regularization, and multivoxel approaches
Authors: Bjarnason Thorarin A. , McCreary Cheryl R. , Dunn Jeff F. , Mitchell J. Ross
Published: October 2009

Typical quantitative T2 (qT2) analysis involves creating T2 distributions using a regularized algorithm from region‐of‐interest averaged decay data. This study uses qT2 analysis of simulated and experimental decay signals to determine how (a) noise‐type, (b) regularization, and (c) region‐of‐interest versus multivoxel analyses affect T2 distributions. Our simulations indicate that regularization causes myelin water fraction and intra/extracellular water geometric mean T2 underestimation that worsens as the signal‐to‐noise ratio decreases. The underestimation was greater for intra/extracellular water geometric mean T2 measures using Rician noise. Simulations showed significant differences between myelin water fractions determined using region‐of‐interest and multivoxel approaches compared to the true value. The nonregularized voxel‐based approach gave the most accurate measure of myelin water fraction and intra/extracellular water geometric mean T2 for a given signal‐to‐noise ratio and noise type. Additionally, multivoxel analysis provides important information about the variability of the analysis. Results obtained from in vivo rat data were similar to our simulation results. In each case, a nonregularized, multivoxel analysis provided myelin water fractions significantly different from the regularized approaches and obtained the largest myelin water fraction. We conclude that quantitative T2 analysis is best performed using a nonregularized, multivoxel approach. Magn Reson Med, 2010. © 2009 Wiley‐Liss, Inc.
Robust water/fat separation in the presence of large field inhomogeneities using a graph cut algorithm
Authors: Hernando Diego , Kellman P. , Haldar J. P. , Liang Z.‐P.
Published: October 2009

Water/fat separation is a classical problem for in vivo proton MRI. Although many methods have been proposed to address this problem, robust water/fat separation remains a challenge, especially in the presence of large amplitude of static field inhomogeneities. This problem is challenging because of the nonuniqueness of the solution for an isolated voxel. This paper tackles the problem using a statistically motivated formulation that jointly estimates the complete field map and the entire water/fat images. This formulation results in a difficult optimization problem that is solved effectively using a novel graph cut algorithm, based on an iterative process where all voxels are updated simultaneously. The proposed method has good theoretical properties, as well as an efficient implementation. Simulations and in vivo results are shown to highlight the properties of the proposed method and compare it to previous approaches. Twenty‐five cardiac datasets acquired on a short, wide‐bore scanner with different slice orientations were used to test the proposed method, which produced robust water/fat separation for these challenging datasets. This paper also shows example applications of the proposed method, such as the characterization of intramyocardial fat. Magn Reson Med, 2010. © 2009 Wiley‐Liss, Inc.
T2 measurement in articular cartilage: Impact of the fitting method on accuracy and precision at low SNR
Authors: Raya José G. , Dietrich Olaf , Horng Annie , Weber Jürgen , Reiser Maximilian F. , Glaser Christian
Published: October 2009

T2 relaxation time is a promising MRI parameter for the detection of cartilage degeneration in osteoarthritis. However, the accuracy and precision of the measured T2 may be substantially impaired by the low signal‐to‐noise ratio of images available from clinical examinations. The purpose of this work was to assess the accuracy and precision of the traditional fit methods (linear least‐squares regression and nonlinear fit to an exponential) and two new noise‐corrected fit methods: fit to a noise‐corrected exponential and fit of the noise‐corrected squared signal intensity to an exponential. Accuracy and precision have been analyzed in simulations, in phantom measurements, and in seven repetitive acquisitions of the patellar cartilage in six healthy volunteers. Traditional fit methods lead to a poor accuracy for low T2, with overestimations of the exact T2 up to 500%. The noise‐corrected fit methods demonstrate a very good accuracy for all T2 values and signal‐to‐noise ratio. Even more, the fit to a noise‐corrected exponential results in precisions comparable to the best achievable precisions (Cramér‐Rao lower bound). For in vivo images, the traditional fit methods considerably overestimate T2 near the bone‐cartilage interface. Therefore, using an adequate fit method may substantially improve the sensitivity of T2 to detect pathology in cartilage and change in T2 follow‐up examinations. Magn Reson Med, 2010. © 2009 Wiley‐Liss, Inc.
Optimization ofk‐space trajectories for compressed sensing by Bayesian experimental design
Authors: Seeger Matthias , Nickisch Hannes , Pohmann Rolf , Schölkopf Bernhard
Published: October 2009

The optimization ofk‐space sampling for nonlinear sparse MRI reconstruction is phrased as a Bayesian experimental design problem. Bayesian inference is approximated by a novel relaxation to standard signal processing primitives, resulting in an efficient optimization algorithm for Cartesian and spiral trajectories. On clinical resolution brain image data from a Siemens 3T scanner, automatically optimized trajectories lead to significantly improved images, compared to standard low‐pass, equispaced, or variable density randomized designs. Insights into the nonlinear design optimization problem for MRI are given. Magn Reson Med, 2010. © 2009 Wiley‐Liss, Inc.
3D steady‐state diffusion‐weighted imaging with trajectory using radially batched internal navigator echoes (TURBINE)
Authors: McNab Jennifer A. , Gallichan Daniel , Miller Karla L.
Published: October 2009

While most diffusion‐weighted imaging (DWI) is acquired using single‐shot diffusion‐weighted spin‐echo echo‐planar imaging, steady‐state DWI is an alternative method with the potential to achieve higher‐resolution images with less distortion. Steady‐state DWI is, however, best suited to a segmented three‐dimensional acquisition and thus requires three‐dimensional navigation to fully correct for motion artifacts. In this paper, a method for three‐dimensional motion‐corrected steady‐state DWI is presented. The method uses a unique acquisition and reconstruction scheme named trajectory using radially batched internal navigator echoes (TURBINE). Steady‐state DWI with TURBINE uses slab‐selection and a short echo‐planar imaging (EPI) readout each pulse repetition time. Successive EPI readouts are rotated about the phase‐encode axis. For image reconstruction, batches of cardiac‐synchronized readouts are used to form three‐dimensional navigators from a fully sampled central k‐space cylinder. In vivo steady‐state DWI with TURBINE is demonstrated in human brain. Motion artifacts are corrected using refocusing reconstruction and TURBINE images prove less distorted compared to two‐dimensional single‐shot diffusion‐weighted‐spin‐EPI. Magn Reson Med, 2010. © 2009 Wiley‐Liss, Inc.
IIR GRAPPA for parallel MR image reconstruction
Authors: Chen Zhaolin , Zhang Jingxin , Yang Ran , Kellman Peter , Johnston Leigh A. , Egan Gary F.
Published: October 2009

Accelerated parallel MRI has advantage in imaging speed, and its image quality has been improved continuously in recent years. This paper introduces a two‐dimensional infinite impulse response model of inverse filter to replace the finite impulse response model currently used in generalized autocalibrating partially parallel acquisitions class image reconstruction methods. The infinite impulse response model better characterizes the correlation of k‐space data points and better approximates the perfect inversion of parallel imaging process, resulting in a novel generalized image reconstruction method for accelerated parallel MRI. This k‐space‐based reconstruction method includes the conventional generalized autocalibrating partially parallel acquisitions class methods as special cases and has a new infinite impulse response data estimation mechanism for effective improvement of image quality. The experiments on in vivo MRI data show that the proposed method significantly reduces reconstruction errors compared with the conventional two‐dimensional generalized autocalibrating partially parallel acquisitions method, particularly at the high acceleration rates. Magn Reson Med, 2010. © 2009 Wiley‐Liss, Inc.
A discrete thermodynamic approach for anisotropic plastic–damage modeling of cohesive‐frictional geomaterials
Authors: Zhu Q. Z. , Zhou C. B. , Shao J. F. , Kondo D.
Published: October 2009

A discrete plastic–damage model is developed for cohesive‐frictional geomaterials subjected to compression‐dominated stresses. Macroscopic plastic strains of material are physically generated by frictional sliding along weakness planes. The evolution of damage is related to the evolution of weakness planes physically in connection with the propagation of microcracks. A discrete approach is used to account for anisotropic plastic flow and damage evolution, by introducing two stress invariants and one plastic hardening variable for each family of sliding weakness planes. Plastic flow in each family is coupled with damage evolution. The proposed model is applied to typical geomaterials and comparisons between numerical predictions and experimental data are presented. Copyright © 2009 John Wiley & Sons, Ltd.
General resolution of a convergence question of L. Krukier
Authors: Johnson Charles , Krukier Lev
Published: October 2009

It was shown that there exists a matrix norm N such that N(A−1B)<1 if A, B∈Mn(𝒞), 0∉F(A), and g(A, B)<1 where g(A, B)=max|z|, z∈G(A, B),

Copyright © 2009 John Wiley & Sons, Ltd.
A fictitious energy approach for shape optimization
Authors: Scherer M. , Denzer R. , Steinmann P.
Published: October 2009

This paper deals with shape optimization of continuous structures. As in early works on shape optimization, coordinates of boundary nodes of the FE‐domain are directly chosen as design variables. Convergence problems and problems with jagged shapes are eliminated by a new regularization technique: an artificial inequality constraint added to the optimization problem limits a fictitious total strain energy that measures the shape change of the design with respect to a reference design. The energy constraint defines a feasible design space whose size can be varied by one parameter, the upper energy limit. By construction, the proposed regularization is applicable to a wide range of problems; although in this paper, the application is restricted to linear elastostatic problems. Copyright © 2009 John Wiley & Sons, Ltd.
Computational aspects in 2D SBEM analysis with domain inelastic actions
Authors: Panzeca T. , Terravecchia S. , Zito L.
Published: October 2009

The Symmetric Boundary Element Method, applied to structures subjected to temperature and inelastic actions, shows singular domain integrals.

In the present paper the strong singularity involved in the domain integrals of the stresses and tractions is removed, and by means of a limiting operation, this traction is evaluated on the boundary. First the weakly singular domain integral in the Somigliana Identity (S.I.) of the displacements is regularized and the singular integral is transformed into a boundary one using the Radial Integration Method; subsequently, using the differential operator applied to the displacement field, the S.I. of the tractions inside the body is obtained and through a limit operation its expression is evaluated on the boundary. The latter operation makes it possible to substitute the strongly singular domain integral in a strongly singular boundary one, defined as a Cauchy Principal Value, with which the related free term is associated. The expressions thus obtained for the displacements and the tractions, in which domain integrals are substituted by boundary integrals, were utilized in the Galerkin approach, for the evaluation in closed form of the load coefficients connected to domain inelastic actions.

This strategy makes it possible to evaluate the load coefficients avoiding considerable difficulties due to the geometry of the solid analyzed; the obtained coefficients were implemented in the Karnak.sGbem calculus code. Copyright © 2009 John Wiley & Sons, Ltd.
Strategic drift in international non‐governmental development organizations—putting strategy in the background of organizational change
Authors: Harris Matthew , Dopson Sue , Fitzpatrick Ray
Published: October 2009

Although the use of strategic planning has become widespread in INGDOs they have often been accused of strategic drift—continuous change in their strategic directions with plans only loosely coupled to their activities. However, the way that they prioritize their activities, and the reasons why strategic drift occurs has generally escaped in‐depth research. This article draws on detailed, qualitative research of strategic planning meetings at the executive levels in a major INGDO, carried out between July 2006 and December 2007 to identify the reasons why strategic drift occurs and the role of strategic planning. It was found that by deliberately crafting multiple, ambiguous, and ambitious strategies, managers were able to effect organizational change, not by literal strategy implementation, but by using these strategies as metaphors to harness consensus and legitimacy in key stakeholder groups. Senior managers utilize the symbols, language and deliberative arenas of formal strategic planning to effect organizational change; however, strategy, in rational terms, needs to be located in the background for its role to be properly understood. The research unpacks complex decision‐making processes in an INGDO and, contrary to normative literature, recommends that, in order to avoid inflationary planning, managers should not take their strategy literally. Copyright © 2009 John Wiley & Sons, Ltd.
Novel properties of PES fabrics modified by corona discharge and colloidal TiO2 nanoparticles
Authors: Mihailović Darka , Šaponjić Zoran , Radoičić Marija , Molina Ricardo , Radetić Tamara , Jovančić Petar , Nedeljković Jovan , Radetić Maja
Published: October 2009

The objective of this study was to highlight the potential application of the corona discharge at atmospheric pressure for the surface activation of polyester (PES) fabrics in order to improve the binding efficiency of colloidal TiO2 nanoparticles. The obtained nanocomposite textile materials provide desirable level of UV protection, self‐cleaning properties, and photodegradation activity. The measured UV protection factor (UPF) of fabrics corresponds to UPF rating of 50+, designating the maximum UV protection. Additionally, the total photodegradation of methylene blue in aqueous solution was achieved after 24 hr of UV illumination and this capability was preserved and even improved after four repeated cycles. The results showed that the corona treated PES fabrics loaded with TiO2 nanoparticles had considerably enhanced the overall efficiency compared to PES fabrics loaded only with TiO2 nanoparticles. Copyright © 2009 John Wiley & Sons, Ltd.
A validated spectrophotometric method for quantification of prenylated flavanones in pacific propolis from Taiwan
Authors: Popova Milena , Chen Chia‐Nan , Chen Pen‐Yuan , Huang Chung‐Yang , Bankova Vassya
Published: October 2009

Introduction – Because of its chemical diversity, the only way to standardise propolis is to specify multiple standards for different propolis types according to the corresponding chemical profile. So far, this has been done only for European propolis.

Objective – To develop a rapid low‐cost spectrophotometric procedure for quantification of bioactive prenylated flavanones in Taiwanese propolis.

Methodology – The proposed method quantifies the total flavanones on the basis of their absorption as coloured phenylhydrazones formed by interaction with 2,4‐dinitrophenylhydrazine. The procedure was validated through model mixture of compounds representing the composition of Taiwanese propolis according to previous studies. The major flavanones of the propolis samples (propolins C, D, F and G) were quantified by HPLC. Antiradical activity against DPPH was also measured. The DNP (dinitrophenylhydrazine) spectrophotometric method is applied for the first time for quantification of prenylated flavanones.

Results – Spectophotometric procedure applicable to new type propolis (Macaranga type) was developed with recovery between 105 and 110% at the concentration range of 0.573–1.791 mg/mL. Six propolis samples were analysed by spectrophotometry using the procedure developed and validated, and by HPLC as the results demonstrated satisfactory agreement. Neither the spectrophotometric data nor the values measured by HPLC showed significant correlation with the antiradical activity against DPPH.

Conclusion – The proposed spectrophotometric procedure is useful for routine analyses of Macaranga‐type propolis, because of its simplicity, repeatability and acceptable accuracy. Its application to a number of commercial samples could be used as a basis for standardisation and quality control of Pacific propolis. Copyright © 2009 John Wiley & Sons, Ltd.