bluuebunny/crossref_metadata_2025_split huggingface dataset:
MR imaging during endovascular procedures: An evaluation of the potential for catheter heating
Authors: Martin Alastair J. , Baek Bryant , Acevedo‐Bolton Gabriel , Higashida Randall T. , Comstock John , Saloner David A. 
Published: December 2008

AbstractMRI in catheterized patients is considered unsafe due to the potential for focal heating. This concern arises from the continuous metallic braid that is incorporated into catheters to provide their desired physical properties. The potential for catheter heating during MR scanning was assessed in an in vitro model simulating a patient undergoing a neurovascular procedure in which MR scans of the brain will be performed. Heating adjacent to endovascular devices was assessed with fluoroptic temperature probes in a polyacrylamide gel. The effect of variable immersion lengths, lateral and longitudinal offsets, position along the endovascular device, physical MR system, and specific absorption rate (SAR) level were studied to determine their effect on catheter heating. A rapid temperature rise was evident next to endovascular devices during MR scanning and varied moderately with immersed length, position within the bore, measurement point on the device, and MR system used. Peak heating rates were less than 1°C/min with maximal SAR exposure and anatomically realistic geometries. Heating scaled linearly with SAR and SAR values below 0.2 W/kg produced negligible heating near catheters. For the evaluated application, substantial SAR restrictions, coupled with limited imaging durations, are proposed as sufficient to permit MRI without concern for thermal injury. Magn Reson Med 61:45–53, 2009. © 2008 Wiley‐Liss, Inc.
Turboprop IDEAL: A motion‐resistant fat–water separation technique
Authors: Huo Donglai , Li Zhiqiang , Aboussouan Eric , Karis John P. , Pipe James G. 
Published: December 2008

AbstractSuppression of the fat signal in MRI is very important for many clinical applications. Multi‐point water–fat separation methods, such as IDEAL (Iterative Decomposition of water and fat with Echo Asymmetry and Least‐squares estimation), can robustly separate water and fat signal, but inevitably increase scan time, making separated images more easily affected by patient motions. PROPELLER (Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction) and Turboprop techniques offer an effective approach to correct for motion artifacts. By combining these techniques together, we demonstrate that the new TP‐IDEAL method can provide reliable water–fat separation with robust motion correction. The Turboprop sequence was modified to acquire source images, and motion correction algorithms were adjusted to assure the registration between different echo images. Theoretical calculations were performed to predict the optimal shift and spacing of the gradient echoes. Phantom images were acquired, and results were compared with regular FSE‐IDEAL. Both T1‐ and T2‐weighted images of the human brain were used to demonstrate the effectiveness of motion correction. TP‐IDEAL images were also acquired for pelvis, knee, and foot, showing great potential of this technique for general clinical applications. Magn Reson Med 61:188–195, 2009. © 2008 Wiley‐Liss, Inc.
Long‐range diffusion of hyperpolarized 3He in rats
Authors: Rodríguez Ignacio , Pérez‐Sánchez José Manuel , Peces‐Barba Germán , Kaulisch Thomas , Stiller Detlef , Ruiz‐Cabello Jesús 
Published: December 2008

AbstractBased on a stimulated‐echo technique, a method to construct an apparent diffusion coefficient (ADC) map of hyperpolarized 3He in a long‐range diffusion scale is presented with a phase‐cycle alternative to remove all unwanted echoes. The approach was successfully applied to determine in vivo diffusion constants in rat lungs. The ADC values in healthy rats show a good agreement with reported values for diffusion times of ≈. These long diffusivity measurements may be sensitive to detect emphysema progression or tissue remodeling and thus have enormous potential for the diagnosis and tracking of disease progression and for drug evaluation. Magn Reson Med 61:54–58, 2009. © 2008 Wiley‐Liss, Inc.
Orientation of lipid strands in the extracellular compartment of muscle: Effect on quantitation of intramyocellular lipids
Authors: Khuu Anthony , Ren Jimin , Dimitrov Ivan , Woessner Donald , Murdoch James , Sherry A. Dean , Malloy Craig R. 
Published: December 2008

AbstractSingle‐voxel 1H NMR spectra from gastrocnemius and soleus muscle were acquired in healthy volunteers at 7T with the objective of measuring the concentration of intramyocellular lipid [IMCL] (note: throughout this article, square brackets indicate concentration). However, significant asymmetry in the resonance assigned to the methylene protons (‐CH2‐)n in extramyocellular lipids (EMCL) interfered with fitting the spectra. Since muscle fibers in these tissues are generally not parallel to B0, the influence of variable orientation in strands of extracellular fat was examined using a mathematical model. Modest variation in orientation produced asymmetric lineshapes that were qualitatively similar to typical observations at 7T. Analysis of simulated spectra by fitting with a Voigt function overestimated [IMCL]/[EMCL] except when EMCL fibers were nearly parallel to B0. Estimates of [IMCL]/[EMCL] were improved by including variations in fiber orientation in the lineshape analysis (fiber orientation modeling, or FOM). Calculated [IMCL] using FOM, 4.8 ± 2.2 mmol/kg wet weight, was lower compared to most previous reports in soleus. Magn Reson Med 61:16–21, 2009. © 2008 Wiley‐Liss, Inc.
Design of cosine modulated very selective suppression pulses for MR spectroscopic imaging at 3T
Authors: Osorio Joseph A. , Xu Duan , Cunningham Charles H. , Chen Albert , Kerr Adam B. , Pauly John M. , Vigneron Daniel B. , Nelson Sarah J. 
Published: December 2008

AbstractThe advantages of using a 3 Tesla (T) scanner for MR spectroscopic imaging (MRSI) of brain tissue include improved spectral resolution and increased sensitivity. Very selective saturation (VSS) pulses are important for maximizing selectivity for PRESS MRSI and minimizing chemical shift misregistration by saturating signals from outside the selected region. Although three‐dimensional (3D) PRESS MRSI is able to provide excellent quality metabolic data for patients with brain tumors and has been shown to be important for defining tumor burden, the method is currently limited by how much of the anatomic lesion can be covered within a single examination. In this study we designed and implemented cosine modulated VSS pulses that were optimized for 3T MRSI acquisitions. This provided improved coverage and suppression of unwanted lipid signals with a smaller number of pulses. The use of the improved pulse sequence was validated in volunteer studies, and in clinical 3D MRSI exams of brain tumors. Magn Reson Med, 2009. © 2008 Wiley‐Liss, Inc.
Transverse relaxation and magnetization transfer in skeletal muscle: Effect of pH
Authors: Louie Elizabeth A. , Gochberg Daniel F. , Does Mark D. , Damon Bruce M. 
Published: December 2008

AbstractExercise increases the intracellular T2 (T2,i) of contracting muscles. The mechanism(s) for the T2,i increase have not been fully described, and may include increased intracellular free water and acidification. These changes may alter chemical exchange processes between intracellular free water and proteins. In this study, the hypotheses were tested that (a) pH changes T2,i by affecting the rate of magnetization transfer (MT) between free intracellular water and intracellular proteins, and (b) the magnitude of the T2,i effect depends on acquisition mode (localized or nonlocalized) and echo spacing. Frog gastrocnemius muscles were excised and their intracellular pH was either kept at physiological pH (7.0) or modified to model exercising muscle (pH 6.5). The intracellular transverse relaxation rate (R2,i = 1/T2,i) always decreased in the acidic muscles, but the changes were greater when measured using more rapid refocusing rates. The MT rate from the macromolecular proton pool to the free water proton pool, its reverse rate, and the spin‐lattice relaxation rate of water decreased in acidic muscles. It is concluded that intracellular acidification alters the R2,i of muscle water in a refocusing rate‐dependent manner, and that the R2,i changes are correlated with changes in the MT rate between macromolecules and free intracellular water. Magn Reson Med, 2009. © 2008 Wiley‐Liss, Inc.
Fat/water separation using a concentric rings trajectory
Authors: Wu Hochong H. , Lee Jin Hyung , Nishimura Dwight G. 
Published: December 2008

AbstractThe concentric rings two‐dimensional (2D) k‐space trajectory enables flexible trade‐offs between image contrast, signal‐to‐noise ratio (SNR), spatial resolution, and scan time. However, to realize these benefits for in vivo imaging applications, a robust method is desired to deal with fat signal in the acquired data. Multipoint Dixon techniques have been shown to achieve uniform fat suppression with high SNR‐efficiency for Cartesian imaging, but application of these methods for non‐Cartesian imaging is complicated by the fact that fat off‐resonance creates significant blurring artifacts in the reconstruction. In this work, two fat–water separation algorithms are developed for the concentric rings. A retracing design is used to sample rings near the center of k‐space through multiple revolutions to characterize the fat–water phase evolution difference at multiple time points. This acquisition design is first used for multipoint Dixon reconstruction, and then extended to a spectroscopic approach to account for the trajectory's full evolution through 3D k‐t space. As the trajectory is resolved in time, off‐resonance effects cause shifts in frequency instead of spatial blurring in 2D k‐space. The spectral information can be used to assess field variation and perform robust fat–water separation. In vivo experimental results demonstrate the effectiveness of both algorithms. Magn Reson Med, 2009. © 2008 Wiley‐Liss, Inc.
Magnetic resonance imaging quantification of left ventricular dysfunction following coronary microembolization
Authors: Carlsson Marcus , Martin Alastair J , Ursell Philip C , Saloner David , Saeed Maythem 
Published: December 2008

AbstractMicroembolization is common after coronary interventions, and therefore this MRI study aimed to quantify the effect of coronary microembolization on left ventricular (LV) function. The left anterior descending artery (LAD) was selectively catheterized in an XMR suite (Philips Medical Systems, Best, The Netherlands) in eight pigs to deliver MR contrast media to measure the LAD territory using first‐pass perfusion and for intracoronary delivery of the embolic agent. Cine, tagged, and delayed contrast‐enhanced MRI (DCE‐MRI) was performed to assess LV volumes, ejection fraction, radial and circumferential strain, and viability at baseline, 1 h, and 1 week after microembolization. Histopathology and histochemical staining were used to characterize and measure the extent of microinfarction. The LAD territory was 35% ± 2% LV mass. Patchy microinfarction on DCE‐MRI at 1 week was 22.0% ± 3.6% LAD territory (7.5% LV mass). Microembolization caused persistent decline in ejection fraction (baseline = 49% ± 1%, 1 h = 29% ± 1%, P = 0.02 and 1 week = 36% ± 1%, P = 0.03) and increased end‐diastolic (79.6 ± 3.9 ml, 85.5 ± 4.5 ml, P = 0.03 and 92.4 ± 6.2 ml, P = 0.06, respectively) and end‐systolic (40.8 ± 2.1 ml, 60.2 ± 3.4 ml, P = 0.02 and 59.3 ± 4.8 ml, P = 0.03, respectively) volumes. The microembolized territory was manifested as dysfunctional regions for 1 week on cine and tagged MRI. Histopathology revealed occlusive microemboli surrounded by necrotic tissue undergoing repair. Microinfarction was visualized after coronary microembolization and caused LV dysfunction disproportionate to the size of myocardial damage. It also changed LV geometry and decreased radial and circumferential strain over the course of 1 week. Magn Reson Med, 2009. © 2008 Wiley‐Liss, Inc.
On using T2 to assess extrinsic magnetic field inhomogeneity effects on T2* measurements in myocardial siderosis in thalassemia
Authors: He Taigang , Smith Gillian C. , Gatehouse Peter D. , Mohiaddin Raad H. , Firmin David N. , Pennell Dudley J. 
Published: December 2008

AbstractMagnetic resonance T2* has been validated as a noninvasive means of assessing myocardial iron overload. However, the effect on myocardial T2* of factors such as shimming, variations in capillary geometry, and susceptibility in relation to the effects of iron has not been fully clarified. Since T2 is not affected by extrinsic magnetic field inhomogeneity and has different sensitivity to capillary geometry, investigation into the in vivo relationship between myocardial T2* and T2 measurements can shed light on this important issue. This study was performed in 136 thalassemia patients. The myocardial T2 and T2* thresholds for normality created identical no‐iron‐overload and iron‐overloaded patient groups. In the no‐iron group, there was no correlation between myocardial T2 and T2*. In the iron‐overloaded patients, there was a linear correlation (R2 = 0.89) between myocardial T2* and T2 measurements, which indicates that the iron deposition is the dominant factor in determining these two relaxation values in this scenario. Magn Reson Med, 2009. © 2008 Wiley‐Liss, Inc.
k‐TE generalized autocalibrating partially parallel acquisition (GRAPPA) for accelerated multiple gradient‐recalled echo (MGRE) R2* mapping in the abdomen
Authors: Yin Xiaoming , Larson Andrew C. 
Published: December 2008

AbstractMultiple gradient‐recalled echo (MGRE) methods are commonly used for abdominal R2* mapping. Accelerated MGRE acquisitions would offer the potential to shorten requisite breathhold times and/or increase spatial resolution and coverage. In both phantom and normal volunteer studies, view‐sharing (VS) methods, generalized autocalibrating partially parallel acquisition (GRAPPA) methods, and newly proposed k–echo time (k‐TE) GRAPPA methods were compared for the purpose of accelerating MGRE acquisitions. Utilization of water‐selective spatial spectral excitation pulses reduced artifact levels for both VS and k‐TE GRAPPA approaches. VS approaches were found to be highly sensitive to off‐resonance effects, particularly at increasing acceleration rates. k‐TE GRAPPA significantly reduced residual artifact levels compared to GRAPPA approaches while improving the accuracy of accelerated abdominal R2* measurements. These initial feasibility studies demonstrate that k‐TE GRAPPA is an effective method to reduce scan times during abdominal R2*‐mapping procedures. Magn Reson Med, 2009. © 2008 Wiley‐Liss, Inc.
A stable Lagrange multiplier space for stiff interface conditions within the extended finite element method
Authors: Béchet Éric , Moës Nicolas , Wohlmuth Barbara 
Published: December 2008

AbstractThis paper introduces a new algorithm to define a stable Lagrange multiplier space to impose stiff interface conditions within the context of the extended finite element method. In contrast to earlier approaches, we do not work with an interior penalty formulation as, e.g. for Nitsche techniques, but impose the constraints weakly in terms of Lagrange multipliers. Roughly speaking a stable and optimal discrete Lagrange multiplier space has to satisfy two criteria: a best approximation property and a uniform inf–sup condition. Owing to the fact that the interface does not match the edges of the mesh, the choice of a good discrete Lagrange multiplier space is not trivial. Here we propose a new algorithm for the local construction of the Lagrange multiplier space and show that a uniform inf–sup condition is satisfied. A counterexample is also presented, i.e. the inf–sup constant depends on the mesh‐size and degenerates as it tends to zero. Numerical results in two‐dimensional confirm the theoretical ones. Copyright © 2008 John Wiley & Sons, Ltd.
C‐terminal Tensin‐like (CTEN) is an oncogene which alters cell motility possibly through repression of E‐cadherin in colorectal cancer
Authors: Albasri Abdulkader , Seth Rashmi , Jackson Darryl , Benhasouna Ahmed , Crook Simon , Nateri Abdolrahman S. , Chapman Roger , Ilyas Mohammad 
Published: December 2008

AbstractThe Tensin gene family encodes proteins thought to modulate integrin function. C‐terminal Tensin‐like (CTEN) is a member of the Tensin gene family which lacks the N‐terminus actin‐binding domain. Cten is reported to have both oncogenic and tumour‐suppressor functions. We investigated the role that Cten may play in colorectal cancer (CRC). By quantitative RT–PCR CTEN is up‐regulated (i.e. > two‐fold increase) in 62% of cell lines and 69% of tumours compared with normal mucosa, consistent with CTEN being a possible oncogene. Stable transfection of HCT116 and SW480 (CRC cell lines with low endogenous Cten expression) with a Cten expression vector gave identical results in both cell lines. Forced Cten expression did not cause change in cell numbers, although it did confer resistance to staurosporine‐induced apoptosis (p < 0.005). Cten also induced epithelial–mesenchymal transition (EMT) in tumour cells accompanied by a significant increase in both cell migration (transwell migration and cell wounding assays, p < 0.001 and p < 0.05, respectively) and cell invasion (invasion through Matrigel, p < 0.001). Given the observed EMT, we investigated the levels of E‐cadherin. Cten induction was associated with a reduction in E‐cadherin protein expression but not levels of E‐cadherin mRNA. These data suggest that CTEN is an oncogene in CRC which stimulates EMT, cell migration and invasion and may therefore have a role in tumour invasion/spread. Furthermore, Cten induction is associated with post‐transcriptional repression of E‐cadherin. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
PGD for monogenic disorders: aspects of molecular biology
Authors: Spits Claudia , Sermon Karen 
Published: December 2008

AbstractPreimplantation genetic diagnosis (PGD) for monogenic diseases has known a considerable evolution since its first application in the early 1990s. Especially the technical aspects of the genetic diagnosis itself, the single‐cell genetic analysis, has constantly evolved to reach levels of accuracy and efficiency nearing those of genetic diagnosis on regular DNA samples. In this review, we will focus on the molecular biological techniques that are currently in use in the most advanced centers for PGD for monogenic disorders, including multiplex polymerase chain reaction (PCR) and post‐PCR diagnostic methods, whole genome amplification (WGA) and multiple displacement amplification (MDA). As it becomes more and more clear that when it comes to ethically difficult indications, PGD goes further than prenatal diagnosis (PND), we will also briefly discuss ethical issues. Copyright © 2008 John Wiley & Sons, Ltd.
Mössbauer119Sn and XPS spectroscopy of Sn2P2S6and SnP2S6crystals
Authors: Vysochanskii Yu. M. , Baltrunas D. , Grabar A. A. , Mazeika K. , Fedyo K. , Sudavicius A. 
Published: December 2008

AbstractThe monoclinic Sn2P2S6and rombohedral layered SnP2S6crystals have been investigated by119Sn Mössbauer and X‐ray photoelectron spectroscopies. By comparing the isomer shift, quadrupole splitting and binding energies for Sn 3d and 4d core levels in these crystals with such parameters for the metal tin and for different tin compounds it was found that in the Sn2P2S6crystals Sn existed in the Sn2+oxidation state and in the SnP2S6crystals – in the Sn4+state. Temperature dependences of the isomer shift and Debye–Waller factor satisfied the Debye model in the temperature interval of 6 – 300 K for the SnP2S6crystals but deviated from such behavior atT> 250 K for Sn2P2S6crystals. This peculiarity together with specific character of the temperature dependence of the quadrupole splitting were related to the role of the stereoactive Sn 5s2lone pair electrons in the determined by three‐well potential mechanism of the second order ferroelectric phase transition at 337 K in Sn2P2S6crystals. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Half‐metallic ferrimagnet formed by substituting Fe for Mn in semiconductor MnTe
Authors: Zhu Li‐Fang , Liu Bang‐Gui 
Published: December 2008

AbstractA ternary ferrimagnetic half‐metal, constructed through substituting 25% Fe for Mn in zincblende semiconductor MnTe, is predicted in terms of accurate first‐principles calculations. It has a large half‐metallic (HM) gap of 0.54 eV and its ferrimagnetic order is very stable against other magnetic fluctuations. The HM ferrimagnetism is formed because the complete moment compensation in the antiferromagnetic MnTe is replaced by an incomplete one in the Fe‐substituted MnTe. This should make a novel approach to new HM materials. The half‐metal could be fabricated because Fe has good affinity with Mn, and is useful for spintronics. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Band anti‐crossing and carrier recombination in dilute nitride phosphide based lasers and light emitting diodes
Authors: Chamings James , Ahmed Sucheta , Adams Alfred R. , Sweeney Stephen J. , Odnoblyudov Vladimir A. , Tu Charles W. , Kunert Bernardette , Stolz Wolfgang 
Published: December 2008

AbstractWe use high pressure techniques to investigate the properties of two classes of “dilute‐nitride‐phosphide”‐based devices; GaNP/GaP light emitting diodes for yellow–amber–red display applications and GaNAsP/GaP lasers, a potential route to producing lasers monolithically on silicon. Based upon high pressure electroluminescence measurements we find that the band anti‐crossing (BAC) model reasonably describes the GaN(As)P system based on an average of the nitrogen states. In terms of device characteristics, we find that carrier leakage into the X‐minima of GaP reduces the efficiency of GaNP/ GaP LEDs with increasing pressure. Lasing has been observed in GaNAsP/GaP devices with a pulsed threshold current density of 2.5 kA/cm2 at 80 K (λ = 890 nm). A weak increase in threshold current with hydrostatic pressure indicates that a carrier leakage path that does not involve the GaP X ‐minima is the dominant carrier recombination mechanism in these devices, in contrast to the LEDs. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Novel multi‐photon microscopy based on resonant nonlinear optics of colloidal quantum dots
Authors: Masia Francesco , Langbein Wolfgang , Borri Paola 
Published: December 2008

AbstractWe demonstrate a novel imaging modality based on the detection of resonant four‐wave mixing emitted by colloidal quantum dots. This third‐order signal is excited and detected at a visible wavelength in resonance with an electronic transition, and results in a significant improvement of the spatial resolution with respect to a twophoton fluorescence microscope.In particular, we have investigated the dependence of the transient reduced absorption of the sample induced by the illumination (photobleaching) on the exposure time and excitation intensity, and its influence to the fourwave mixing signal (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)