bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a wide‐view visual presentation system for visual retinotopic mapping during functional MRI
Authors: Yan Tianyi , Jin Fengzhe , He Jiping , Wu Jinglong
Published: January 2011

Purpose

To develop and validate the functionality of a novel wide‐view visual presentation system with a horizontal and vertical eccentricity angle of 60° for retinotopic mapping by functional MRI (fMRI).

Materials and Methods

The wide‐view presentation system consisted of a 52‐mm diameter optical fiber, an entrance apparatus and a presentation apparatus. The terminal edge of the optical fiber at the entrance is flat, while the terminal edge on the presentation apparatus is a sphere of 60 mm in diameter. The subjects wore contact lenses with +20, +22, or +25 magnification to focus on the stimulus, and the visual field eccentricity angle could reach 60°. The signal to noise ratio valuation experiment was performed to evaluate the clarity and quality of the MRI picture image. Checkerboard and random dot stimuli were used to prove that this system could be applied to retinotopic mapping by fMRI.

Results

The results of the experiment demonstrated that the system is safe in the MRI environment with minimal distortion and can be used for visual retinotopic mapping studies. Wide‐field mapping areas (V6, MST) were found in the human visual cortex. Compared with previous studies, the V1 and MT+ surface area approaches but does not fully cover the anatomical area. Nonetheless, the area achieved using the new system is larger than those achievable in previous fMRI studies.

Conclusion

We developed a versatile, low‐cost system for presenting wide‐view visual stimuli in the MRI environment. The fMRI retinotopic mapping results proved the viability of this system. J. Magn. Reson. Imaging 2011. © 2011 Wiley‐Liss, Inc.
MRI of the prostate: Clinical relevance and emerging applications
Authors: Mazaheri Yousef , Shukla‐Dave Amita , Muellner Ada , Hricak Hedvig
Published: January 2011

MRI of the prostate can aid in many aspects of prostate cancer management, from initial detection to treatment planning and follow‐up. This review describes the current strengths and limitations of conventional anatomic and molecular MR imaging techniques (including MR spectroscopic imaging and dynamic contrast‐enhanced imaging) for aiding prostate cancer management. It also describes promising emerging approaches for acquiring, analyzing, and applying MR imaging data, and the major research and educational efforts that will be required to realize the potential of prostate MR imaging in routine clinical practice. J. Magn. Reson. Imaging 2011;33:258–274. © 2011 Wiley‐Liss, Inc.
Diffusion MRI predicts transrectal ultrasound biopsy results in prostate cancer detection
Authors: Chen Yu‐Jen , Pu Yeong‐Shiau , Chueh Shih‐Chieh , Shun Chia‐Tung , Chu Woei‐Chyn , Tseng Wen‐Yih Isaac
Published: January 2011

Purpose

To evaluate the ability of diffusion tensor imaging (DTI) to predict the transrectal ultrasound (TRUS) biopsy outcomes in persons who have no history of previous TRUS biopsy and present with elevated prostate‐specific antigen (PSA) levels.

Materials and Methods

Thirty‐seven participants underwent DTI, followed by 12‐core TRUS‐guided needle biopsy within 2 weeks. DTI was performed using endorectal coils on a 1.5 Tesla scanner at 1‐mm3 spatial resolution. By comparing with the TRUS biopsy results, the optimum thresholds of the trace apparent diffusion coefficient (tADC) and of the nodular size were investigated. The diagnostic performance of both criteria, the tADC threshold (Criteria A) and the tADC threshold combined with nodular size threshold (Criteria B), were evaluated.

Results

The optimum tADC threshold was 1.0 μm2/ms. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of prostate cancer (PCA) detection for Criteria A were 98%, 89%, 73%, 99%, and 91%, respectively, and were 97%, 98%, 92%, 99% and 98% for Criteria B.

Conclusion

Owing to high negative predictive value, the tADC threshold could be used to exclude subjects with clinically undetectable PCA. Adding the nodular size threshold, the combined threshold could identify the tADC‐positive segments that are likely to yield positive biopsy results. J. Magn. Reson. Imaging 2011;33:356–363. © 2011 Wiley‐Liss, Inc.
Susceptibility‐related MR signal dephasing under nonstatic conditions: Experimental verification and consequences for qBOLD measurements
Authors: Sohlin Maja C. , Schad Lothar R.
Published: January 2011

Purpose

To experimentally verify a theoretical model describing the MR signal dephasing under nonstatic conditions in a voxel containing a vascular network, and to estimate the stability of the model for qBOLD measurements.

Materials and Methods

Measurement phantoms reflecting the properties of the theoretical model, i.e., statistically distributed and randomly oriented cylinders in a homogeneous medium were constructed by randomly coiled polyamide fibers immersed in a NiSO4 solution. The resemblance between measured and theoretical signal curves was investigated by calculation of root mean squared error maps. Simulated nonstatic dephasing data were evaluated using the static dephasing model to estimate the stability of the model and the influence of input parameters.

Results

The theoretical model describing the MR signal dephasing under nonstatic conditions was experimentally verified in phantom measurements. In simulations, it was found that, by neglecting the effect of diffusion when predicting the MR signal‐time course expected in an in vivo measurement of the tissue oxygenation, errors of 10–30% would be introduced into the parameter estimation. The simulations indicate unpredictable results for simultaneous evaluation of blood oxygenation level and blood volume fraction.

Conclusion

Neglecting the effects of diffusion in quantitative BOLD measurements could give rise to substantial errors in the parameter estimation. J. Magn. Reson. Imaging 2011;33:417–425. © 2011 Wiley‐Liss, Inc.
Left ventricular diastolic function assessment from three‐dimensional three‐directional velocity‐encoded MRI with retrospective valve tracking
Authors: Brandts Anne , Bertini Matteo , van Dijk Evert‐Jan , Delgado Victoria , Marsan Nina Ajmone , van der Geest Rob J. , Siebelink Hans‐Marc J. , de Roos Albert , Bax Jeroen J. , Westenberg Jos J.M.
Published: January 2011

Purpose

To compare parameters describing left ventricular (LV) diastolic function obtained with three‐dimensional (3D) three‐directional velocity‐encoded (VE) MRI with retrospective valve tracking and two‐dimensional (2D) one‐directional VE MRI in patients with ischemic heart failure. Second, to compare classification of LV diastolic function, and in particular for discriminating restrictive filling patterns, with both MRI techniques versus Doppler echocardiography.

Materials and Methods

The 3D and 2D VE MRI early (E) and atrial (A) peak flow rate indices, determined from transmitral waveform analyses, were compared. Also, net forward flow volume per cycle and transmitral regurgitation fraction were determined. Agreement in classifying diastolic filling patterns between 3D and 2D VE MRI versus Doppler echocardiography was evaluated using kappa statistics.

Results

The 3D three‐directional VE MRI with retrospective valve tracking was statistically significantly different from 2D one‐directional VE MRI for net forward flow volume and regurgitation fraction through the mitral valve and all parameters describing the diastolic waveform filling pattern, except for the E deceleration time and E/A filling ratio. Kappa‐agreement between 3D three‐directional VE MRI with retrospective valve tracking and echocardiography for classifying diastolic filling patterns was superior to 2D one‐directional VE MRI and echocardiography (i.e., κ = 0.91 versus κ = 0.79, respectively).

Conclusion

The 3D three‐directional VE MRI with retrospective valve tracking better describes LV diastolic function as compared to 2D one‐directional VE MRI in patients with ischemic heart failure. J. Magn. Reson. Imaging 2011;33:312–319. © 2011 Wiley‐Liss, Inc.
Support vector machine multiparametric MRI identification of pseudoprogression from tumor recurrence in patients with resected glioblastoma
Authors: Hu Xintao , Wong Kelvin K. , Young Geoffrey S. , Guo Lei , Wong Stephen T.
Published: January 2011

Purpose

To automatically differentiate radiation necrosis from recurrent tumor at high spatial resolution using multiparametric MRI features.

Materials and Methods

MRI data retrieved from 31 patients (15 recurrent tumor and 16 radiation necrosis) who underwent chemoradiation therapy after surgical resection included post‐gadolinium T1, T2, fluid‐attenuated inversion recovery, proton density, apparent diffusion coefficient (ADC), and perfusion‐weighted imaging (PWI) ‐derived relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF), and mean transit time maps. After alignment to post contrast T1WI, an eight‐dimensional feature vector was constructed. An one‐class‐support vector machine classifier was trained using a radiation necrosis training set. Classifier parameters were optimized based on the area under receiver operating characteristic (ROC) curve. The classifier was then tested on the full dataset.

Results

The sensitivity and specificity of optimized classifier for pseudoprogression was 89.91% and 93.72%, respectively. The area under ROC curve was 0.9439. The distribution of voxels classified as radiation necrosis was supported by the clinical interpretation of follow‐up scans for both nonprogressing and progressing test cases. The ADC map derived from diffusion‐weighted imaging and rCBV, rCBF derived from PWI were found to make a greater contribution to the discrimination than the conventional images.

Conclusion

Machine learning using multiparametric MRI features may be a promising approach to identify the distribution of radiation necrosis tissue in resected glioblastoma multiforme patients undergoing chemoradiation. J. Magn. Reson. Imaging 2011;33:296–305. © 2011 Wiley‐Liss, Inc.
Detailed assessment of the hemodynamic response to psychosocial stress using real‐time MRI
Authors: Jones Alexander , Steeden Jennifer A. , Pruessner Jens C. , Deanfield John E. , Taylor Andrew M. , Muthurangu Vivek
Published: January 2011

Purpose

To demonstrate that combining the Montreal Imaging Stress Task (MIST) with real‐time cardiac magnetic resonance imaging (MRI) allows detailed assessment of the cardiovascular mental stress response.

Materials and Methods

22 healthy volunteers (1:1 M:F, 26–64 years) underwent MRI during rest and the MIST. Real‐time spiral phase contrast MR, accelerated with sensitivity encoding (SENSE) was used to assess stroke volume (SV), and radial k‐t SENSE was used to assess ventricular volumes. Simultaneous heart rate (HR) and blood pressure (BP) measures allowed calculation of cardiac output (CO), systemic vascular resistance (SVR), and arterial compliance (TAC). Endocrine responses were assessed using salivary cortisol.

Results

In response to stress, BP increased due to increased CO and reduced TAC but not increased SVR, which fell. HR, not SV, determined CO increases. Greater BP responses occurred in men due to greater CO increases and relatively higher SVR. Older participants had greater BP responses due to greater falls in TAC. Greater cortisol response was correlated with greater falls in TAC but resting cortisol and TAC were not related.

Conclusion

This new approach allows detailed, accurate assessment of stress physiology. Preliminary findings suggest stress exposes relationships, not seen at rest, of cardiovascular function with age, sex, and endocrine function. J. Magn. Reson. Imaging 2011;33:448–454. © 2011 Wiley‐Liss, Inc.
Performance of μMRI‐Based virtual bone biopsy for structural and mechanical analysis at the distal tibia at 7T field strength
Authors: Bhagat Yusuf A. , Rajapakse Chamith S. , Magland Jeremy F. , Love James H. , Wright Alexander C. , Wald Michael J. , Song Hee Kwon , Wehrli Felix W.
Published: January 2011

Purpose

To assess the performance of a 3D fast spin echo (FSE) pulse sequence utilizing out‐of‐slab cancellation through phase alternation and micro‐magnetic resonance imaging (μMRI)‐based virtual bone biopsy processing methods to probe the serial reproducibility and sensitivity of structural and mechanical parameters of the distal tibia at 7.0T.

Materials and Methods

The distal tibia of five healthy subjects was imaged at three timepoints with a 3D FSE sequence at 137 × 137 × 410 μm3 voxel size. Follow‐up images were retrospectively 3D registered to baseline images. Coefficients of variation (CV) and intraclass correlation coefficients (ICCs) for measures of scale and topology of the whole tibial trabecular bone (TB) cross‐section as well as finite‐element‐derived Young's and shear moduli of central cuboidal TB subvolumes (8 × 8 × 5 mm3) were evaluated as measures of reproducibility and reliability. Four additional cubic TB subregions (anterior, medial, lateral, and posterior) of similar dimensions were extracted and analyzed to determine associations between whole cross‐section and subregional structural parameters.

Results

The mean signal‐to‐noise ratio (SNR) over the 15 image acquisitions was 27.5 ± 2.1. Retrospective registration yielded an average common analysis volume of 67% across the three exams per subject. Reproducibility (mean CV = 3.6%; range, 1.5%–5%) and reliability (ICCs, 0.95–0.99) of all parameters permitted parameter‐based discrimination of the five subjects in spite of the narrow age range (26–36 years) covered. Parameters characterizing topology were better able to distinguish two individuals who demonstrated similar values for scalar measurements (≈34% difference, P < 0.001). Whole‐section axial stiffness encompassing the cortex was superior at distinguishing two individuals relative to its central subregional TB counterpart (≈8% difference; P < 0.05). Interregion comparisons showed that although all parameters were correlated (mean R2 = 0.78; range 0.57–0.99), the strongest associations observed were those for the erosion index (mean R2 = 0.95, P ≤ 0.01).

Conclusion

The reproducibility and structural and mechanical parameter‐based discriminative ability achieved in five healthy subjects suggests that 7T‐derived μMRI of TB can be applied towards serial patient studies of osteoporosis and may enable earlier detection of disease or treatment‐based effects. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.
Scan–Rescan reproducibility of carotid bifurcation geometry from routine contrast‐enhanced MR angiography
Authors: Bijari Payam B. , Antiga Luca , Wasserman Bruce A. , Steinman David A.
Published: January 2011

Purpose

To demonstrate the feasibility of rapid and reliable geometric characterization of normal carotid bifurcation geometry from routine 3D contrast‐enhanced magnetic resonance (MR) angiograms.

Materials and Methods

Repeat scans of 61 participants, acquired as part of the Atherosclerosis Risk in Communities (ARIC) Carotid MRI substudy, were digitally segmented using automated 3D level set methods, relying on an operator only to select the branch endpoints and thresholds for the 3D lumen surface initialization. Geometric factors characterizing the 3D lumen geometry were then extracted automatically.

Results

Of 122 scans, 117 could be segmented within 5 minutes each, with 40% being of sufficiently high quality to require less than 2 minutes each. Irrespective of scan quality, geometric factors were found to be highly reproducible, with intraclass correlation coefficients (ICCs) typically above 0.9. The reconstructed lumen surfaces were reproducible to <0.3 mm on average, comparable to previous MRI‐based reproducibility studies. Owing to the automated nature of the analysis, operator reliability was near‐perfect (ICC >0.99), with lumen surface differences <0.1 mm.

Conclusion

The 3D geometry of the carotid bifurcation can be characterized rapidly and with a high degree of consistency, even for suboptimal image qualities. This bodes well for large‐scale retrospective or prospective studies aimed at teasing out the influence of local vs. systemic risk factors for early atherosclerosis. J. Magn. Reson. Imaging 2011;33:482–489. © 2011 Wiley‐Liss, Inc.
Fast spin‐echo triple echo dixon: Initial clinical experience with a novel pulse sequence for simultaneous fat‐suppressed and nonfat‐suppressed T2‐weighted spine magnetic resonance imaging
Authors: Low Russell N. , Austin Matthew J. , Ma Jingfei
Published: January 2011

Purpose

To evaluate a prototype fast spin‐echo (FSE) triple‐echo Dixon (FTED) technique for T2‐weighted spine imaging with and without fat suppression compared to conventional T2‐weighted fast recovery (FR) FSE and short‐tau inversion recovery (STIR) imaging.

Materials and Methods

Sixty‐one patients were referred for spine magnetic resonance imaging (MRI) including sagittal FTED (time 2:26), STIR (time 2:42), and T2 FRFSE (time 2:55). Two observers compared STIR and FTED water images and T2 FRFSE and FTED T2 images for overall image quality, fat suppression, anatomic sharpness, motion, cerebrospinal fluid (CSF) flow artifact, susceptibility, and disease depiction.

Results

On FTED images water and fat separation was perfect in 58 (.95) patients. Compared to STIR, the FTED water images demonstrated less motion in 57 (.93) of 61 patients (P < 0.05), better anatomic sharpness in 51 (.84) and patients (P < 0.05), and less CSF flow artifact in 7 (.11) P < 0.05) patients. There was no difference in fat suppression or chemical shift artifact. T2 FRFSE and FTED T2 images showed equivalent motion, CSF flow, and chemical shift artifact. Lesion depiction was equivalent on FTED water and STIR images and FTED T2 and T2 FRFSE images.

Conclusion

FTED efficiently provides both fat‐suppressed and nonfat‐suppressed T2‐weighted spine images with excellent image quality, equal disease depiction, and 56% reduction in scan time compared to conventional STIR and T2 FRFSE. J. Magn. Reson. Imaging 2011;33:390–400. © 2011 Wiley‐Liss, Inc.
Nonenhanced methods for lower‐extremity MRA: A phantom study examining the effects of stenosis and pathologic flow waveforms at 1.5T
Authors: Offerman Erik J. , Hodnett Philip A. , Edelman Robert R. , Koktzoglou Ioannis
Published: January 2011

Purpose

To evaluate the signal properties of 2D time of flight (TOF), quiescent‐interval single‐shot (QISS), ECG‐gated 3D fast spin‐echo (FBI), and ungated 3D fast spin‐echo ghost (Ghost) magnetic resonance angiography (MRA) over a range of flow velocities in a pulsatile flow phantom with a 50% diameter stenosis at 1.5T.

Materials and Methods

Blood‐mimicking fluid was pumped at eight peak flow velocities through a stenotic region in triphasic and monophasic waveforms. Vascular signal proximal, within, and distal to the stenosis was measured from the source images of the four MRA methods. Coronal maximum intensity projection images were used to compare image quality.

Results

TOF and QISS signal trends were similar, but QISS exhibited the most consistent signal across velocities. At high velocities (≥42.4 cm/s), TOF showed poststenotic signal loss that was not observed with QISS. FBI and Ghost signals peaked at low velocities (3.9–9.7 cm/s) without flow compensation and at high velocities (≥64.6 cm/s) with flow compensation.

Conclusion

FBI and Ghost demonstrated dependence on blood flow velocity and flow compensation. TOF was sensitive to flow artifacts at high velocities. QISS proved most robust for accurately depicting the normal lumen and stenosis under a wide range of flow conditions. Monophasic and triphasic flow did not appreciably affect the signal performance of any method. J. Magn. Reson. Imaging 2011;33:401–408. © 2011 Wiley‐Liss, Inc.
Evaluation of possible drug–drug interaction between gadoxetic acid and erythromycin as an inhibitor of organic anion transporting peptides (OATP)
Authors: Huppertz Alexander , Breuer Josy , Fels Lueder M. , Schultze‐Mosgau Marcus , Sutter Gabriele , Klein Stefan , Frericks Bernd , Hamm Bernd , Wagner Moritz
Published: January 2011

Purpose

To evaluate if erythromycin compromises liver‐specific enhancement of gadoxetic acid; both compounds competing in organic anion transporting peptides (OATP) ‐mediated hepatocytic uptake.

Materials and Methods

The study was approved by institutional review board. Twelve healthy subjects (nine men, three woman; mean age, 38.7 years) were examined twice by MR imaging with prior administration of NaCl solution (placebo) or 1000 mg of erythromycin following a randomized sequence. Gadoxetic acid (0.025 mmol/kg body weight) was administered 15 min after the end of infusions. Pre‐ and 20 min postcontrast two‐dimensional gradient‐recalled‐echo sequences were acquired. Relative enhancements of liver parenchyma and ratio of means were calculated from signal intensity measurements. Plasma levels of gadoxetic acid and erythromycin were determined and given in geometric means and coefficients of variation (CV).

Results

Concentration of erythromycin directly after end of infusion was 13.9 mg/L (CV 14.9%). Gadolinium plasma concentrations 5 min after gadoxetic acid administration were 138.7 μmol/L (CV 20.4%) after erythromycin infusion and 129.6 μmol/L (CV 22.8%) after placebo. Mean relative enhancements of liver parenchyma were 88.1 (SD 24.9%) after erythromycin infusion and 92.6 (SD 17.9%) after placebo. Ratio of relative enhancements was 0.951 (95% confidence interval, 0.833; 1.061; statistically not significant).

Conclusion

Coadministration of erythromycin has no effect on gadoxetic acid enhanced liver MR imaging. J. Magn. Reson. Imaging 2011;33:409–416. © 2011 Wiley‐Liss, Inc.
MR spectroscopy of normative premature newborns
Authors: Xu Duan , Bonifacio Sonia L. , Charlton Natalie N. , P. Vaughan Charles , Lu Ying , Ferriero Donna M. , Vigneron Daniel B. , Barkovich A. James
Published: January 2011

Purpose

To establish normative metabolite ratios throughout the newborn brain using three‐dimensional (3D) MR spectroscopic imaging (MRSI).

Materials and Methods

MRI and MRSI have been valuable tools for assessing normal and abnormal neuronal maturation for newborns. In this study, we performed whole brain 3D MRSI in addition to comprehensive anatomic and other functional imaging methods to examine maturation. Fifty‐five newborn subjects (28.4 ± 2.6 weeks postconception age at birth, 34.1 ± 3.1 weeks postconception age at scan, 32 males and 23 females) had high quality MRSI studies (104 exams) and normal neurodevelopmental outcome (neuromotor score = 0, mental development index score > 85) at age 12 months.

Results

The NAA to Cho ratio increased significantly with age for all regions. Lac to NAA ratio decreased significantly with age in the regions of thalamus, basal ganglia, cortical spinal tract, and parietal white matter, and showed a decreasing trend in the other regions.

Conclusion

Brain metabolites can be obtained through in vivo 3D MRSI and used to monitor newborn brain maturation. J. Magn. Reson. Imaging 2011;33:306–311. © 2011 Wiley‐Liss, Inc.
Pacemaker lead tip heating in abandoned and pacemaker‐attached leads at 1.5 tesla MRI
Authors: Langman Deborah A. , Goldberg Ira B. , Finn J. Paul , Ennis Daniel B.
Published: January 2011

Purpose

To assess the risk of RF‐induced heating in pacemaker‐attached and abandoned leads using in vitro temperature measurements at 1.5 Tesla as a function of lead length.

Materials and Methods

Five custom lead lengths, 20–60 cm, were exposed to a uniform magnitude and phase radiofrequency electric field to examine the effect of lead length on pacemaker lead tip heating for pacemaker‐attached and abandoned pacemaker leads.

Results

Abandoned and pacemaker‐attached leads show resonant heating behavior and maximum heating occurs at different lead lengths due to the differences in termination conditions. For clinical lead lengths (40–60 cm) abandoned leads exhibited greater lead tip heating compared with pacemaker‐attached leads.

Conclusion

Current recommendations for MRI pacemaker safety should highlight the possible increased risk for patients with abandoned leads as compared to pacemaker‐attached leads. J. Magn. Reson. Imaging 2011;33:426–431. © 2011 Wiley‐Liss, Inc.
Aliasing artifacts with the BLADE technique: Causes and effective suppression
Authors: Kojima Shinya , Morita Satoru , Ueno Eiko , Hirata Masami , Shinohara Hiroyuki , Komori Akiyoshi
Published: January 2011

Purpose:

To elucidate the causes of aliasing artifacts with the BLADE technique and clarify the effective suppression methods.

Materials and Methods:

We separately observed the aliasing artifacts of BLADE from features inside and then outside the defined field‐of‐view (FOV) using phantom studies. The effectiveness of suppressing them with phase oversampling (POS) and presaturation pulses (SAT) was evaluated. Finally, our observations were confirmed for a healthy volunteer.

Results:

Characteristic aliasing artifacts were observed from both inside and outside the FOV. Those from inside the FOV were sufficiently suppressed by using a POS of 25%, considering the acquisition time prolongation. Those from outside the FOV were nearly suppressed using SAT outside the FOV without selecting needless receiver coils. Aliasing artifacts on the coronal images of the head and neck with a healthy volunteer were completely suppressed by a combination of using a POS of 25% and using SAT on all four sides outside the FOV.

Conclusion:

The characteristic aliasing artifacts of BLADE are caused from both inside and outside the defined FOV. They can be effectively suppressed by a combination of using a POS of 25% and using SAT on all four sides outside the FOV. J. Magn. Reson. Imaging 2011;33:432–440. © 2011 Wiley‐Liss, Inc.
Prospective motion correction for magnetic resonance spectroscopy using single camera retro‐grate reflector optical tracking
Authors: Andrews‐Shigaki Brian C. , Armstrong Brian S.R. , Zaitsev Maxim , Ernst Thomas
Published: January 2011

Purpose:

To introduce and evaluate a method of prospective motion correction for localized proton magnetic resonance spectroscopy (1H‐MRS) using a single‐camera optical tracking system.

Materials and Methods:

Five healthy participants were scanned at 3T using a point‐resolved spectroscopic sequence (PRESS) with a motion‐tracking module and phase navigator. Head motion in six degrees was tracked with a Retro‐Grate Reflector (RGR) tracking system and target via a mirror mounted inside the bore. Participants performed a series of three predetermined motion patterns during scanning.

Results:

Left–right rotation (Rz) (average 12°) resulted in an increase in the total choline to total creatine ratio (Cho/Cr) of +14.6 ± 1.5% (P= 0.0009) for scans without correction, but no change for scans with correction (+1.1 ± 1.5%;P= 0.76). Spectra with uncorrected Z‐translations showed large lipid peaks (skull) with changes in Cho/Cr of −13.2 ± 1.6% (P= 0.02, no motion correction) and −2.2 ± 2.4% (P= 0.51) with correction enabled. There were no significant changes in the ratios of N‐acetylaspartate, glutamate+glutamine, or myo‐inositol to creatine compared to baseline scans for all experiments.

Conclusion:

Prospective motion correction for 1H‐MRS, using single‐camera RGR tracking, can reduce spectral artifacts and quantitation errors in Cho/Cr ratios due to head motion and promises improved spectral quality and reproducibility. J. Magn. Reson. Imaging 2011. © 2011 Wiley‐Liss, Inc.
Rubbers Based on Conjugated Soybean Oil: Synthesis and Characterization
Authors: Valverde Marlen , Yoon Sungho , Bhuyan Satyam , Larock Richard C. , Kessler Michael R. , Sundararajan Sriram
Published: January 2011

A range of bio‐based rubbery thermosets have been synthesized by the cationic copolymerization of conjugated soybean oil, styrene, and 1,5‐hexadiene or isoprene as flexible crosslinkers. The thermal, and mechanical properties, as well as the wear behavior, of these new bio‐rubbers are reported. The amount of styrene and the type of diene incorporated have the greatest influence on the properties of the final materials. The largest variations are found in glass transition temperature, storage modulus, tan δ values, crosslink density, and abrasive wear depth, while thermal degradation and extraction analyses showed minimal variations with changes in composition.

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Amphiphilic Peptide–Polymer Conjugates with Side‐Conjugation
Authors: Dube Nikhil , Presley Andrew D. , Shu Jessica Y. , Xu Ting
Published: January 2011

Polymers conjugated to the exterior of a protein mediate its interactions with surroundings, enhance its processability and can be used to direct its macroscopic assemblies. Most studies to date have focused on peptide–polymer conjugates based on hydrophilic polymers. Engineering amphiphilicity into protein motifs by covalently linking hydrophobic polymers has the potential to interface peptides and proteins with synthetic polymers, organic solvents, and lipids to fabricate functional hybrid materials. Here, we synthesized amphiphilic peptide–polymer conjugates in which a hydrophobic polymer is conjugated to the exterior of a heme‐binding four‐helix bundle and systematically investigated the effects of the hydrophobicity of the conjugated polymer on the peptide structure and the integrity of the heme‐binding pocket. In aqueous solution with surfactants present, the side‐conjugated hydrophobic polymers unfold peptides and may induce an α‐helix to β‐sheet conformational transition. These effects decrease as the polymer becomes less hydrophobic and directly correlate with the polymer hydrophobicity. Upon adding organic solvent to solubilize the hydrophobic polymers, however, the deleterious effects of hydrophobic polymers on the peptide structures can be eliminated. Present studies demonstrate that protein structure is sensitive to the local environment. It is feasible to dissolve amphiphilic peptide–polymer conjugates in organic solvents to enhance their solution processability while maintaining the protein structures.

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A Nanotechnology Pathway to Arresting Phase Separation in Soft Nanocomposites
Authors: Pomposo José A. , de Luzuriaga Alaitz Ruiz , García Iñaki , Etxeberria Agustín , Colmenero Juan
Published: January 2011

Direct observation of the miscibility improving effect of ultra‐small polymeric nanoparticles (radius ≈4 nm) in model systems of soft nanocomposites is reported. We have found thermodynamically arrested phase separation in classical poly(styrene) (PS)/poly(vinyl methyl ether) blends when PS linear chains were totally replaced by ultra‐small, single chain PS nanoparticles, as determined by thermo‐optical microscopy measurements. Partial arrested phase splitting on heating was observed when only some of the PS chains were replaced by unimolecular PS nanoparticles, leading to a significant increase of the lower critical solution temperature (LCST) of the system (up to 40 °C at 15 vol.‐% nanoparticle content). Atomic force microscopy and rheological experiments supported these findings. Thermodynamic arrest of the phase separation process induced by replacement of linear polymer chains by unimolecular polymer nanoparticles could have significant implications for industrial applications requiring soft nanocomposite materials with excellent nanoparticle dispersion in a broad temperature range.

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BIBuilder: Exhaustive Searching for De Novo Ligands
Authors: Teodoro Miguel , Muegge Ingo
Published: January 2011

The de novo design program BIBuilder has been developed for structure‐based as well as ligand‐based design. Incremental growth allows for the de novo design of novel molecules with putative bioactivity. In addition, linking between existing fragments enables scaffold hopping tasks. A RECAP‐based retrosynthetic fragment connection protocol yields ligands that are synthesizable. An exhaustive fragment search protocol assures that known ligands are always found if all necessary fragments exist in the database of building blocks. To make an exhaustive search possible, a strategy of connecting tens of thousands of unique fragments with only three growth or linking steps is adopted resulting in the generation of up to 1016 possible compounds with up to 1021 conformations. Ligands are scored by shape and pharmacophore matches that can be individually weighted. Final hits are evaluated through customizable scoring functions. Estrogen receptor, COX‐2, renin, and NNRTI examples illustrate the performance of BIBuilder in different tasks such as structure‐based or ligand‐based growing and linking. Not only are known ligands reproduced in all test cases but a number of interesting alternative scaffolds and ligands have been found.
Role of Metallic NiCr Dots on the Adhesion, Electrical, Optical and Mechanical Properties of Diamond‐like Carbon Thin Films
Authors: Dwivedi Neeraj , Kumar Sushil , Rauthan Chandra Mohan Singh , Panwar Omvir Singh
Published: January 2011

The effect of thermally evaporated metallic NiCr dots on the adhesion, electrical, optical and the mechanical properties of RF‐PECVD grown diamond‐like carbon (DLC) thin films was investigated. The DLC films deposited over NiCr dots containing substrates exhibited a strong adhesion to the substrate. The observed drastic increase in magnitude of the current and the decrease of optical band gap due to presence of NiCr dots revealed a considerable improvement in their electrical and optical properties, respectively. Further, load versus displacement curves were employed to estimate the hardness (H), elastic modulus (E), plastic resistance parameter (H/E) and elastic recovery (ER). The values of H and E in NiCr dots containing DLC films were found to be comparatively less than that of DLC films. Overall, NiCr metal dots improved adhesion, optical and electrical properties of DLC films with a little deterioration in their mechanical properties (e.g. H, E, ER and H/E).

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Plasma‐Assisted Synthesis of Chlorinated Polyvinyl Chloride (CPVC) Using a Gas–Solid Contacting Process
Authors: Lu Wei , Cao Tengfei , Wang Qi , Cheng Yi
Published: January 2011

Plasma‐assisted synthesis of CPVC, using a gas–solid contactor, is presented as a novel process of PVC chlorination. The basic principle is to use cold plasma to generate free radical chlorine and activate the surfaces of PVC particles at the same time. Accordingly, the chlorination process can be decoupled into two steps: plasma‐enhanced chlorination on the particle surface and chlorine transfer from the surface to the core of the particle. Experiments were carried out in a DBD plasma fixed‐bed reactor. The results demonstrated the high efficiency of this process, i.e., a total of 3 h operation with plasma can achieve up to 67% of the chlorine content in PVC particles. The characterization results by SEM/EDS, TGA, and Raman spectra showed that CPVC made by this process had the desired microstructure and the thermal stability similar to that of the commercial CPVC products.

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SuperHydrophobic and SuperHydrophilic Polycarbonate by Tailoring Chemistry and Nano‐texture with Plasma Processing
Authors: Palumbo Fabio , Di Mundo Rosa , Cappelluti Davide , d'Agostino Riccardo
Published: January 2011

Versatility of plasma processing is demonstrated for the preparation of nanotextured polycarbonate surfaces with superior wettability properties. Tens of nanometers wide pillar structures are produced on the polymer by means of oxygen plasma etching, inducing on the surface a pronounced hydrophilic behavior. As well known from literature, however, treated surfaces undergo a fast hydrophobic recovery, but a post‐deposition process can ensure the formation of transparent and stable superhydrophylic or superhydrophobic surfaces.

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Physico‐Chemical Characterization of Methyl Isobutyrate‐based Plasma Polymer Films
Authors: Denis Laurent , Renaux Fabian , Cossement Damien , Bittencourt Carla , Tuccitto Nunzio , Licciardello Antonino , Hecq Michel , Snyders Rony
Published: January 2011

Methyl isobutyrate is plasma‐polymerized varying the precursor flow rate (Φp), the working pressure (p) and the radiofrequency power injected in the discharge (PRF). Through the use of an experimental design, PRF reveals to be the key parameter regarding the incorporation of oxygen‐based functionalities in the plasma polymer films (PPFs). Combining the use of X‐ray photoelectron spectroscopy (XPS), time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and principal component analysis (PCA), our results demonstrate that an increase of PRF (i) lowers the incorporation of the precursor ester groups within the PPFs and (ii) amplifies the PPF crosslinking density (χ). A correlation between the PPF physico‐chemistry and the plasma composition is established using residual gas analysis mass spectrometry. It is shown that an increase of PRF increases both the extent of the precursor fragmentation and the production of non‐reactive oxygen‐based species in the plasma that do not contribute to the PPF growth. Incidentally, in the PRF range studied, the total amount of oxygen‐based functionalities incorporated in the PPFs (at.%O) varies from 23.9 to 10.1 at.%.

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A Novel Technique Toward Bipolar Films Containing Alternating Nano–Layers of Allylamine and Acrylic Acid Plasma Polymers for Biomedical Application
Authors: Yang Zhilu , Lei Xingjiang , Wang Jin , Luo Rifang , He Tingting , Sun Hong , Huang Nan
Published: January 2011

An intentional and defined grafting of the material surface with multiple positive/negative charges produced by functional groups is desired for biomedical applications. In this work, multistacked organic bipolar films containing alternating nano‐layers of plasma polymerized acrylic acid (PPAac) and plasma polymerized allylamine (PPAam) are investigated in order to prepare highly polarized surfaces with positive/negative charges. Two kinds of composite films fabricated according to different depositing sequences and with –COOH or –NH2functional groups onto their outermost surfaces are prepared. The results of ATR‐FTIR and XPS demonstrate that a significant number of COO–and –NHpolar entities, generated from the interaction of PPAac and PPAam films, are present in these multistacked organic bipolar films. Furthermore, the remarkably increased polar surface energy of these composite films, compared with pure PPAac and PPAam films, reveals that the presence of the COO–and NHpolar entities induces strong dipole orientation polarizability, and results in the redistribution of charges. The results suggest that the surface with highly polarized –COOH and –NH2groups have high surface charges and chemical reactivity. These surfaces show promising applications for biomolecules binding and cell growth.

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Local oscillations in different models of the coherent bcc–hcp boundary in 4He and metals
Authors: Lykah Victor A. , Syrkin Eugene S.
Published: January 2011

Small local vibrations of the order parameter (the relative displacement of atomic planes) on the coherent phase boundary (PB) in the bcc–hcp 4He crystal are investigated theoretically. Dynamical differential equations for small values of the perturbations of the order parameter are obtained. On the coherent PB bcc–hcp for double‐ and triple‐well models the shape and the spectrum are found for small local vibrations of the order parameter. Characteristic frequencies are found and estimated. It is shown that the bcc–hcp boundary in the 4He crystal is a very soft system. This fact may explain the high degree of damping of 3He excitations in nuclear magnetic resonance (NMR) experiments.
High‐pressure lattice dynamics and thermodynamics in BaO
Authors: Lukačević I.
Published: January 2011

Using density functional theory and density functional perturbation theory we have studied lattice dynamics, dielectric and thermodynamic properties of the rocksalt (NaCl) phase of BaO under hydrostatic pressure, a material which has lately aroused many interests. Studying the lattice dynamics of the rocksalt phase at various pressures, in the range of the phase stability, we have found a lattice dynamical instability which governs the phase transition to NiAs phase. Monitoring the behaviour of the found soft mode, we have calculated the transition pressure of 10 GPa in an excellent agreement with experimental data. Lattice dynamics calculations reveal that the rocksalt structure is unstable with respect to soft transversal acoustic mode at a single point on the Brillouin zone boundary, which points to the fact that the transition is of displacive type. The observed pressure of the phase transition in structural measurements is reproduced more accurately than in previous calculations, which used enthalpy comparison method. Calculating the volume change during the phase transition from rocksalt to NiAs phase, we conclude that the phase transition might be of the second or weakly first order. Dielectric and thermodynamic properties at high pressures are also given. An anomalous thermal expansion coefficient is found up to about 10 K.
Elastic and electronic properties of hexagonal rhenium sub‐nitrides Re3N and Re2N in comparison withhcp‐Re and wurtzite‐like rhenium mononitride ReN
Authors: Bannikov Vyacheslav V. , Shein Igor R. , Ivanovskii Alexander L.
Published: January 2011

Very recently, two hexagonal rhenium sub‐nitrides Re3N and Re2N, which belong to a rather rare group of known metal‐rich (M/N > 1) nitrides of heavy 4d, 5d metals, have been successfully synthesized, and their potential technological applications as ultra‐incompressible materials have been proposed. In this work, we present a detailedab initiostudy of recently synthesized rhenium sub‐nitrides in comparison withhcp‐Re and wurtzite‐like rhenium mono‐nitride ReN, with the purpose to evaluate the trends of the elastic, electronic properties, and chemical bonding in the series of these hexagonal systems as a function of the Re/N stoichiometry: Re → Re3N → Re2N → ReN.
Fabrication of 6,13‐bis(triisopropyl‐silylethynyl)–pentacene thin‐film transistors with the silver ink transfer method using a polymer stamp
Authors: Oh Tae‐Yeon , Kang Nam‐Su , Dong Ki‐Young , Chang Seongpil , Park Jung‐Ho , Jung Shin‐Woo , Lee Seung‐Jun , Ju Byeong‐Kwon
Published: January 2011

We fabricated 6,13‐bis(triisopropylsilylethynyl)–pentacene (TIPS–pentacene) thin film transistors using a direct metal transfer method. Using different metals, such as Au and Ag ink, electrode patterns are formed from the relief region of the polymer mold. TIPS–pentacene TFTs using the Ag ink transfer method show a similar performance to those using the Au metal transfer method. This method has advantages over the Au metal transfer method because it does not require vacuum equipment and a dry etching process. The self‐assembled monolayer (SAM) treated device exhibits a carrier mobility of 9.5 × 10–2 cm2/V · s, and an on/off ratio of 4.6 × 104. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An assistance tool employing a systematic methodology for GCC retargeting
Authors: Lin Kai‐Wei , Chen Peng‐Sheng
Published: January 2011

GCC (GNU Compiler Collection) is a popular compiler because it is open source, generates high‐quality code, and is portable. The emergence of various embedded systems has led to considerable interest in the portability of GCC. For GCC, a source programming language is parsed and internally transferred to the corresponding intermediate representation, RTL (Register Transfer Language). A machine description (MD)file, which describes the mapping relationships between RTL and the corresponding target assembly instructions, is provided at the stage of code generation. Therefore, GCC retargeting requires the construction of a target MD file. However, it is difficult for developers to understand and construct the MD because this requires considerable time spent studying the GCC intermediate representation and the strategy of code generation. In this paper, we propose a systematic methodology to help developers in retargeting GCC. The entire process is divided into seven levels according to the features of the supported source programming language. Based on this systematic methodology, a Web‐based assistance tool is also developed to guide developers through the retargeting. The assistance tool operates like a wizard to provide developers with the necessary procedures at each level and then generates the corresponding GCC files. Finally, we demonstrate the utility and practicality of the assistance tool based on the proposed methodology by applying it to the retargeting of GCC to a 32‐bit embedded processor—the helper function unit of the UniCore VisoMT processor, as developed by the System‐on‐Chips (SoC) Research Center of National Chung Cheng University, Taiwan. Copyright © 2011 John Wiley & Sons, Ltd.
A Novel Chromium 18‐Azametallacrown‐6 Complex with Antiferromagnetic Interactions
Authors: Chen Gong‐Jun , Gao Chun‐Yan , Gu Wen , Liu Xin , Yan Shi‐Ping , Tian Jin‐Lei , Liao Dai‐Zheng
Published: January 2011

A new nanometer‐sized hexanuclear chromium azametallacrown complex, [Cr6(ashz)6(H2O)6]·11H2O (1), was isolated from the reaction of Cr(ClO4)3·6H2O and N‐acetylsalicylhydrazide (H3ashz). Six triply‐deprotonated ligands (ashz3–) link six chromium ions by hydrazide N–N groups, thus generating a hexanuclear chromium aggregate with a 18‐membered ring system. The binding mode of the ligand enforces that the six ring metal ions are not located in a plane, but with a chair conformation. Interestingly, the resulting chiralities of the hexacoordinate chromium atoms alternate between Λ and Δ forms. Magnetic susceptibility data of the complex indicate intramolecular antiferromagnetic coupling of the CrIII atoms.
Synthesis, Cytotoxicity and Antibacterial Studies of Novel Symmetrically and Non‐Symmetrically p‐Nitrobenzyl‐Substituted N‐Heterocyclic Carbene–Silver(I) Acetate Complexes
Authors: Patil Siddappa , Deally Anthony , Gleeson Brendan , Hackenberg Frauke , Müller‐Bunz Helge , Paradisi Francesca , Tacke Matthias
Published: January 2011

From the reaction of 1H‐imidazole (1a), 4,5‐dichloro‐1H‐imidazole (1b), 1H‐benzimidazole (1c), 1‐methylimidazole (1d), 4,5‐dichloro‐1‐methylimidazole (1e) and 1‐methylbenzimidazole (1f) with p‐nitrobenzyl bromide (2), symmetrically and non‐symmetrically p‐nitrobenzyl‐substituted N‐heterocyclic carbene (NHC) [(3a–f)] precursors were synthesised. These NHC‐precursors were then reacted with silver(I) acetate to yield the NHC‐silver acetate complexes [1,3‐bis(4‐nitrobenzyl)imidazol‐2‐ylidene]silver(I) acetate (4a), [4,5‐dichloro‐1,3‐bis(4‐nitrobenzyl)imidazol‐2‐ylidene]silver(I) acetate (4b), [1,3‐bis(4‐nitrobenzyl)benzimidazol‐2‐ylidene]silver(I) acetate (4c), [1‐methyl‐3‐(4‐nitrobenzyl)imidazole‐2‐ylidene] silver(I) acetate (4d), [4,5‐dichloro‐1‐methyl‐3‐(4‐nitrobenzyl)imidazole‐2‐ylidene] silver(I) acetate (4e) and [1‐methyl‐3‐(4‐nitrobenzyl)benzimidazole‐2‐ylidene] silver(I) acetate (4f), respectively. The two NHC–silver(I) acetate complexes 4a and 4e were characterised by single‐crystal X‐ray diffraction. All compounds studied in this work were preliminary screened for their antimicrobial activities in vitro against Gram‐positive bacteria Staphylococcus aureus, and Gram‐negative bacteria Escherichia coli using the qualitative Kirby–Bauer disk‐diffusion method. All NHC–silver(I) acetate complexes exhibited medium to high antibacterial activity with areas of clearance ranging from 3 to 7 mm at the highest amount used, whereas the NHC‐precursors showed significantly lower activity. In addition, NHC–silver(I) acetate complexes 4a–f had their preliminary cytotoxicity tests on the human renal‐cancer cell line Caki‐1 and showed medium to high cytotoxicity with IC50 values ranging from 15 (+/–1) to 27 (+/–2) μM.