bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improving chemical shift encoding‐based water–fat separation based on a detailed consideration of magnetic field contributions
Authors: Diefenbach Maximilian N. , Ruschke Stefan , Eggers Holger , Meineke Jakob , Rummeny Ernst J. , Karampinos Dimitrios C. 
Published: February 2018

PurposeTo improve the robustness of existing chemical shift encoding‐based water–fat separation methods by incorporating a priori information of the magnetic field distortions in complex‐based water–fat separation.MethodsFour major field contributions are considered: inhomogeneities of the scanner magnet, the shim field, an object‐based field map estimate, and a residual field. The former two are completely determined by spherical harmonic expansion coefficients directly available from the magnetic resonance (MR) scanner. The object‐based field map is forward simulated from air–tissue interfaces inside the field of view (FOV). The missing residual field originates from the object outside the FOV and is investigated by magnetic field simulations on a numerical whole body phantom. In vivo the spatially linear first‐order component of the residual field is estimated by measuring echo misalignments after demodulation of other field contributions resulting in a linear residual field. Gradient echo datasets of the cervical and the ankle region without and with shimming were acquired, where all four contributions were incorporated in the water–fat separation with two algorithms from the ISMRM water–fat toolbox and compared to water–fat separation with less incorporated field contributions.ResultsIncorporating all four field contributions as demodulation steps resulted in reduced temporal and spatial phase wraps leading to almost swap‐free water–fat separation results in all datasets.ConclusionDemodulating estimates of major field contributions reduces the phase evolution to be driven by only small differences in local tissue susceptibility, which supports the field smoothness assumption of existing water–fat separation techniques.
Retrospective multi‐phase non‐contrast‐enhanced magnetic resonance angiography (ROMANCE MRA) for robust angiogram separation in the presence of cardiac arrhythmia
Authors: Kim Hahnsung , Park Suhyung , Kim Eung Yeop , Park Jaeseok 
Published: February 2018

PurposeTo develop a novel, retrospective multi‐phase non‐contrast‐enhanced MRA (ROMANCE MRA) in a single acquisition for robust angiogram separation even in the presence of cardiac arrhythmia.MethodsIn the proposed ROMANCE MRA, data were continuously acquired over all cardiac phases using retrospective, multi‐phase flow‐sensitive single‐slab 3D fast spin echo (FSE) with variable refocusing flip angles, while an external pulse oximeter was in sync with pulse repetitions in FSE to record real‐time information on cardiac cycles. Data were then sorted into k‐bin space using the real‐time cardiac information. Angiograms were reconstructed directly from k‐bin space by solving a constrained optimization problem with both subtraction‐induced sparsity and low rank priors. Peripheral MRA was performed in normal volunteers with/without caffeine consumption and a volunteer with cardiac arrhythmia using conventional fresh blood imaging (FBI) and the proposed ROMANCE MRA for comparison.ResultsThe proposed ROMANCE MRA shows superior performance in accurately delineating both major and small vessel branches with robust background suppression if compared with conventional FBI. Even in the presence of irregular heartbeats, the proposed method exhibits clear depiction of angiograms over conventional methods within clinically reasonable imaging time.ConclusionWe successfully demonstrated the feasibility of the proposed ROMANCE MRA in generating robust angiograms with background suppression.
Phase‐correcting non‐local means filtering for diffusion‐weighted imaging of the spinal cord
Authors: Kafali Sevgi Gokce , Çukur Tolga , Saritas Emine Ulku 
Published: February 2018

PurposeDWI suffers from low SNR when compared to anatomical MRI. To maintain reasonable SNR at relatively high spatial resolution, multiple acquisitions must be averaged. However, subject motion or involuntary physiological motion during diffusion‐sensitizing gradients cause phase offsets among acquisitions. When the motion is localized to a small region, these phase offsets become particularly problematic. Complex averaging of acquisitions lead to cancellations from these phase offsets, whereas magnitude averaging results in noise amplification. Here, we propose an improved reconstruction for multi‐acquisition DWI that effectively corrects for phase offsets while reducing noise.Theory and MethodsEach acquisition is processed with a refocusing reconstruction for global phase correction and a partial k‐space reconstruction via projection‐onto‐convex‐sets (POCS). The proposed reconstruction then embodies a new phase‐correcting non‐local means (PC‐NLM) filter. PC‐NLM is performed on the complex‐valued outputs of the POCS algorithm aggregated across acquisitions. The PC‐NLM filter leverages the shared structure among multiple acquisitions to simultaneously alleviate nuisance factors including phase offsets and noise.ResultsExtensive simulations and in vivo DWI experiments of the cervical spinal cord are presented. The results demonstrate that the proposed reconstruction improves image quality by mitigating signal loss because of phase offsets and reducing noise. Importantly, these improvements are achieved while preserving the accuracy of apparent diffusion coefficient maps.ConclusionAn improved reconstruction incorporating a PC‐NLM filter for multi‐acquisition DWI is presented. This reconstruction can be particularly beneficial for high‐resolution or high‐b‐value DWI acquisitions that suffer from low SNR and phase offsets from local motion.
Unveiling a hidden 31P signal coresonating with extracellular inorganic phosphate by outer‐volume‐suppression and localized 31P MRS in the human brain at 7T
Authors: Ren Jimin , Shang Ty , Sherry A. Dean , Malloy Craig R. 
Published: February 2018

PurposeThe study was undertaken to demonstrate that there is more than 1 component in the extracellular Pi 31P signal (
) acquired from human head using nonlocalized 31P MRS.MethodsOuter‐volume‐suppression (OVS) saturation and 1D/2D 31P CSI were utilized to reveal the presence of an additional component in the
signal.Results67% of the head extracellular Pi signal was attenuated upon OVS saturation of the peripheral meningeal tissues, likely reflecting elimination of the Pi signal in the meningeal fluids (the blood and CSF). Localized 1D/2D CSI data provided further support for this assignment. Upon correction for the meningeal contribution, the extracellular Pi concentration was 0.51 ± 0.07 mM, whereas the intracellular Pi was 0.85 ± 0.10 mM. The extracellular pH was measured as 7.32 ± 0.04 when using OVS, as compared to 7.39 ± 0.03 when measured without OVS (N = 7 subjects).ConclusionThe extracellular Pi signal acquired from the human head using nonlocalized 31P MRS contains a significant component likely contributed by peripheral blood and CSF in meninges that must be removed in order to use this signal as an endogenous probe for measuring extracellular pH and other properties in the brain.
Dynamic 2D self‐phase‐map Nyquist ghost correction for simultaneous multi‐slice echo planar imaging
Authors: Yarach Uten , Tung Yi‐Hang , Setsompop Kawin , In Myung‐Ho , Chatnuntawech Itthi , Yakupov Renat , Godenschweger Frank , Speck Oliver 
Published: February 2018

PurposeTo develop a reconstruction pipeline that intrinsically accounts for both simultaneous multislice echo planar imaging (SMS‐EPI) reconstruction and dynamic slice‐specific Nyquist ghosting correction in time‐series data.MethodsAfter 1D slice‐group average phase correction, the separate polarity (i.e., even and odd echoes) SMS‐EPI data were unaliased by slice GeneRalized Autocalibrating Partial Parallel Acquisition. Both the slice‐unaliased even and odd echoes were jointly reconstructed using a model‐based framework, extended for SMS‐EPI reconstruction that estimates a 2D self‐phase map, corrects dynamic slice‐specific phase errors, and combines data from all coils and echoes to obtain the final images.ResultsThe percentage ghost‐to‐signal ratios (%GSRs) and its temporal variations for MB3Ry2 with a field of view/4 shift in a human brain obtained by the proposed dynamic 2D and standard 1D phase corrections were 1.37 ± 0.11 and 2.66 ± 0.16, respectively. Even with a large regularization parameter λ applied in the proposed reconstruction, the smoothing effect in fMRI activation maps was comparable to a very small Gaussian kernel size 1 × 1 × 1 mm3.ConclusionThe proposed reconstruction pipeline reduced slice‐specific phase errors in SMS‐EPI, resulting in reduction of GSR. It is applicable for functional MRI studies because the smoothing effect caused by the regularization parameter selection can be minimal in a blood‐oxygen‐level–dependent activation map.
Spin‐lock imaging of 3‐o‐methyl‐D glucose (3oMG) in brain tumors
Authors: Zu Zhongliang , Jiang Xiaoyu , Xu Junzhong , Gore John C. 
Published: February 2018

PurposeTo evaluate the ability of spin‐lock imaging to detect the uptake of 3‐o‐methyl‐D‐glucose (3oMG) in normal brain and brain tumors in animals.MethodsMeasurements of the longitudinal relaxation rate in the rotating frame (R1ρ) were made over a range of spin‐lock powers in rat brains bearing 9L tumors. The dispersion of R1ρ values was quantified by ΔR1ρ, the difference of R1ρ values acquired with low and high locking powers. The glucose analogue 3oMG was administered intravenously and the differences of ΔR1ρ values (
) before and as a function of time after administration were calculated to isolate the contribution of 3oMG to the dispersions, which at high fields primarily reflects chemical exchange effects. In addition, the ratio of image signals from low and high locking fields (the spin‐lock ratio, SLR), which requires fewer acquisitions and varies directly with ΔR1ρ, was computed as an alternative measure of the variation with locking power, and changes in SLR (SLRdiff) after 3oMG were evaluated.ResultsBoth
and SLRdiff in tumors increased rapidly after injection, whereas intact brain showed a gradual increase up to 1 h. The
and SLRdiff were significantly different between tumors and contralateral normal tissues.ConclusionSpin‐lock methods can be used to detect 3oMG in vivo after injection, and appropriate analyses of MRI signals allow tumors to be distinguished from normal brain.
Feasibility of in vivo measurement of glucose metabolism in the mouse hypothalamus by 1H‐[13C] MRS at 14.1T
Authors: Lizarbe Blanca , Lei Hongxia , Duarte Joao M.N. , Lanz Bernard , Cherix Antoine , Gruetter Rolf 
Published: February 2018

PurposeDetermine the feasibility of 1H‐[13C] MRS in the mouse hypothalamus using a 14.1T magnet.MethodsWe optimized the design of a 1H‐[13C] surface coil to maximize the signal‐to‐noise ratio of 1H‐[13C] MRS in the mouse hypothalamus. With enhanced signal, 13C accumulation in glucose metabolites was measured in a 8.7 µL voxel in the hypothalamus of 5 healthy mice during the continuous administration of [1,6‐13C2]glucose.ResultsAccumulation of 13C label in glucose C6 and lactate C3 was visible in the hypothalamus 11 min after glucose administration. The 13C fractional enrichment (FE) curves of lactate C3, glutamate and glutamine C4, glutamate+glutamine C3 and C2, GABA C2, C3, and C4, and aspartate C3 were measured with a time resolution of 11 min over 190 min. FE time‐courses and metabolic pool sizes were averaged to fit a novel one‐compartment model of brain energy metabolism that incorporates the main features of the hypothalamus.ConclusionDynamic 1H‐[13C] MRS is able to measure in vivo brain metabolism in small and deep areas of the mouse brain such as the hypothalamus, and it can be used to calculate metabolic fluxes, including glutamatergic and GABAergic metabolism as well as the contribution of metabolic sources other than glucose.
Volumetric wireless coil based on periodically coupled split‐loop resonators for clinical wrist imaging
Authors: Shchelokova Alena V. , van den Berg Cornelis A.T. , Dobrykh Dmitry A. , Glybovski Stanislav B. , Zubkov Mikhail A. , Brui Ekaterina A. , Dmitriev Dmitry S. , Kozachenko Alexander V. , Efimtcev Alexander Y. , Sokolov Andrey V. , Fokin Vladimir A. , Melchakova Irina V. , Belov Pavel A. 
Published: February 2018

PurposeDesign and characterization of a new inductively driven wireless coil (WLC) for wrist imaging at 1.5 T with high homogeneity operating due to focusing the B1 field of a birdcage body coil.MethodsThe WLC design has been proposed based on a volumetric self‐resonant periodic structure of inductively coupled split‐loop resonators with structural capacitance. The WLC was optimized and studied regarding radiofrequency fields and interaction to the birdcage coil (BC) by electromagnetic simulations. The manufactured WLC was characterized by on‐bench measurements and in vivo and phantom study in comparison to a standard cable‐connected receive‐only coil.ResultsThe WLC placed into BC gave the measured
increase of the latter by 8.6 times for the same accepted power. The phantom and in vivo wrist imaging showed that the BC in receiving with the WLC inside reached equal or higher signal‐to‐noise ratio than the conventional clinical setup comprising the transmit‐only BC and a commercial receive‐only flex‐coil and created no artifacts. Simulations and on‐bench measurements proved safety in terms of specific absorption rate and reflected transmit power.ConclusionsThe results showed that the proposed WLC could be an alternative to standard cable‐connected receive coils in clinical magnetic resonance imaging. As an example, with no cable connection, the WLC allowed wrist imaging on a 1.5 T clinical machine using a full‐body BC for transmitting and receive with the desired signal‐to‐noise ratio, image quality, and safety.
Motor unit number index: Guidelines for recording signals and their analysis
Authors: Nandedkar Sanjeev D. , Barkhaus Paul E. , Stålberg Erik V. , Neuwirth Christoph , Weber Markus 
Published: February 2018

ABSTRACTIntroduction: This study proposes guidelines for motor unit number index (MUNIX) recording and analysis. Methods: MUNIX was measured in control participants and in patients with amyotrophic lateral sclerosis. Changes in MUNIX values due to E1 electrode position, number of surface electromyography interference pattern (SIP) epochs, SIP epoch duration, force of contraction, and outlier data points were investigated. Results: MUNIX depends on optimized compound muscle action potential (CMAP) amplitude. Individual muscles showed variations when the number of epochs was low or when the SIP duration was short. Longer SIP duration allowed better recognition of artifacts. MUNIX results were affected by SIP values at all force levels but was more affected when SIP area was low. Discussion: We recommend changing the E1 electrode position to maximize CMAP amplitude. Twenty or more SIP signals of 500‐ms duration should be recorded by using force levels ranging from slight to maximum. Traces should be reviewed to identify and exclude signals with tremor or solitary spikes. Muscle Nerve 58: 374–380, 2018
The effect of tramadol on sneeze‐induced urethral continence reflex through μ‐opioid receptors in the spinal cord in rats
Authors: Ashikari Asuka , Miyazato Minoru , Kimura Ryu , Oshiro Takuma , Saito Seiichi 
Published: February 2018

AimsWe examined the efficacy of tramadol on the urethral reflex during sneezing, as well as the role of µ‐opioid receptors in the spinal cord, in rats.MethodsForty‐one female Sprague‐Dawley rats were used. The rats were divided into normal female rats and rats with vaginal distension (VD), which mimics stress urinary incontinence (SUI) in humans. Under urethane anesthesia, the sneeze‐induced amplitude of urethral responses (AUR) and baseline pressure (BP) were examined after intravenous injection of tramadol using a microtransducer‐tipped catheter in both rat groups. The effect of intrathecal cyprodime, a selective µ‐opioid receptor antagonist, following intravenous tramadol injection was examined in normal rats. The tilt leak point pressure (tilt LPP) after intravenous tramadol injection was also evaluated in both groups.ResultsIn normal rats, tramadol enhanced the AUR and BP by 33.2% and 19.5%, respectively. Tramadol also increased BP by 13.9% in rats with VD, but it did not change AUR. Intrathecal cyprodime alone did not change AUR, but it decreased BP. However, tramadol‐provoked increments in AUR were blocked by intrathecal cyprodime, while BP was recovered to the level that it was before administration of cyprodime. Tramadol was associated with a significant elevation in tilt LPP: 24.8% and 19.5% in normal and VD rats, respectively.ConclusionsThese findings suggest that tramadol effectively enhances the AUR at the spinal level and BP peripherally. Therefore, stimulation of the spinal µ‐opioid receptors may be useful for the treatment of SUI.
Enteral Nutrition: Options for Short‐Term Access
Authors: Pash Elizabeth 
Published: February 2018

AbstractThe preferred method of nutrition support in the presence of a functional gastrointestinal tract is enteral nutrition (EN). Many factors contribute to the selection process for the type of enteral access device to be used. Short‐term enteral access tubes are placed into the nares or, sometimes, orally, usually at bedside. The short‐term access provides a means to meet patient nutrient needs and can provide a chance to assess tolerance of the tube feedings if more permanent long‐term placement is determined to be required. Access for nutrition support does not come without a risk; it can be challenging, requiring an individualized approach for each patient. The selection type and access location can greatly impact the success of EN. The most advantageous tube choice must be determined carefully, taking into account the multiple considerations reviewed in this paper.
The Largest Eye That Humankind Has Cast into the Heavens
Authors: Knauer Doris , Dietzel Oliver 
Published: February 2018

AbstractThe resolution of earthbound telescopes can be improved by large primary mirrors, which can only be realized as segmented mirrors. In order for these giant mirrors to maintain their form despite the wind load and the effect of gravity, their individual segments require stiff drives that work with a large travel on the one hand and allow nanometer‐precise positioning on the other. So‐called hybrid drives that combine a spindle‐motor drive with a piezoelectric actuator are the optimum choice for meeting these requirements.
Transparent and organosoluble cardo polyimides with different trans/cis ratios of 1,4‐diaminocyclohexane via aromatic nucleophilic substitution polymerization
Authors: Tang Yongmei , Li Lan , Ma Kai , Chen Guofei , Wang Wei , Fang Xingzhong 
Published: February 2018

AbstractTwo series of cardo polyimides were prepared from 1,4‐bis(4‐fluorophthalimide)cyclohexane with different trans/cis ratios and phenolphthalein/o‐cresolphthalein via aromatic nucleophilic substitution reaction. The inherent viscosities of the synthesized polymers were found to be 0.55–0.66 dL g−1 in N,N′‐dimethylacetamide. The cardo polyimides showed excellent solubility in organic solvents, high glass transition temperatures (Tg) of 275–312 °C and moderate thermal stability with 5% weight loss temperatures (Td5%) of 415–441 °C in nitrogen and 370–436 °C in air. The polyimide films exhibited high optical transparency with cut‐off wavelengths of 350–355 nm and moderate mechanical properties. The different properties of the polymers caused by trans and cis configurations of 1,4‐diaminocyclohexane were also investigated. It was found that with an increasing content of trans configuration of 1,4‐diaminocyclohexane in the polyimide backbone, Tg of the polyimides increased as well as Td5%, while the solubility gradually decreased. The polyimide films had good optical transparency regardless of trans/cis configuration. © 2018 Society of Chemical Industry
Diffusion of low‐molecular‐weight permeants through semi‐crystalline polymers: combining molecular dynamics with semi‐empirical models
Authors: Prasad Krishnamurthy , Nikzad Mostafa , Doherty Cara M , Sbarski Igor 
Published: February 2018

AbstractA molecular dynamics‐based computational approach was used to study the diffusion of oxygen through a model semi‐crystalline polymer, namely linear low‐density polyethylene. The simulated molecules were validated by comparing the predicted properties with experimental values of available free volumes, on atomic scale, using positron annihilation lifetime spectroscopy and measured values of density. The semi‐crystalline polymer was considered as a composite network of a continuous amorphous phase and a dispersed crystalline phase. Based on this observation, the overall diffusion was simulated, including the diffusion through the crystalline phase, which has not been previously reported. A tight correlation was then achieved between experimental and simulated data by utilising several semi‐empirical and analytical models developed for composite materials. The proposed methodology in this work can be effectively used as a basis for designing polymer networks with controlled diffusion characteristics in a bottom‐up approach. © 2018 Society of Chemical Industry
Resistance development, stability, cross‐resistance potential, biological fitness and biochemical mechanisms of spinetoram resistance in Thrips hawaiiensis (Thysanoptera: Thripidae)
Authors: Fu Buli , Li Qiang , Qiu Haiyan , Tang Liangde , Zeng Dongqiang , Liu Kui , Gao Yulin 
Published: February 2018

AbstractBACKGROUNDSpinetoram, a new type of spinosyn with novel modes of action, has been used in effective thrips control programs, but resistance remains a threat. In the present study, a laboratory Thrips hawaiiensis population was subjected to spinetoram for resistance selection to investigate resistance development, stability, cross‐resistance potential, biological fitness and underlying biochemical mechanisms.RESULTSResistance to spinetoram in T. hawaiiensis rapidly increased 103.56‐fold (for 20 generations of selection with spinetoram) compared with a laboratory susceptible population, and the average realized heritability (h2) of resistance was calculated as 0.1317. Maintaining the resistant population for five generations without any further selection pressure resulted in a decline in the resistance ratio from 19.42‐ to 9.50‐fold, suggesting that spinetoram resistance in T. hawaiiensis is unstable. Moreover, the spinetoram‐resistant population exhibited a lack of cross‐resistance to other classes of insecticides, and showed biological fitness costs. The results of synergism experiments using enzyme inhibitors and biochemical analyses revealed that metabolic mechanisms might not be responsible for the development of spinetoram resistance in T. hawaiiensis.CONCLUSIONThe current study expands understanding of spinosyn resistance in thrips species, providing a basis for proposing better integrated pest management strageties for thrips control programs and defining the most appropriate tools for such resistance management. © 2018 Society of Chemical Industry