bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pulse encoding for ZTE imaging: RF excitation without dead‐time penalty
Authors: Froidevaux Romain , Weiger Markus , Pruessmann Klaas P. 
Published: November 2021

PurposeTo overcome limitations in the duration of RF excitation in zero‐TE (ZTE) MRI by exploiting intrinsic encoding properties of RF pulses to retrieve data missed during the dead time caused by the pulse.MethodsAn enhanced ZTE signal model was developed using multiple RF pulses, which enables accessing information hidden in the pulse‐induced dead time via encoding intrinsically applied by the RF pulses. Such ZTE with pulse encoding was implemented by acquisition of two ZTE data sets using excitation with similar frequency‐swept pulses differing only by a small off‐resonance in their center frequency. In this way, the minimum scan time is doubled but each acquisition contributes equally to the SNR, as with ordinary averaging. The method was demonstrated on long‐T2 and short‐T2 phantoms as well as in in vivo experiments.ResultsZTE with pulse encoding provided good image quality at unprecedented dead‐time gaps, demonstrated here up to 6 Nyquist dwells. In head imaging, the ability to use longer excitation pulses led to approximately 2‐fold improvements in SNR efficiency as compared with conventional ZTE and allowed the creation of T1 contrast.ConclusionExploiting intrinsic encoding properties of RF pulses in a new signal model enables algebraic reconstruction of ZTE data sets with large dead‐time gaps. This permits larger flip angles, which can be used to achieve enhanced T1 contrast and significant improvements in SNR efficiency in case the Ernst angle can be better approached, thus broadening the range of application of ZTE MRI.
Optimization of pseudo‐continuous arterial spin labeling using off‐resonance compensation strategies at 7T
Authors: Saïb Gaël , Koretsky Alan P. , Talagala S. Lalith 
Published: November 2021

PurposeThe sensitivity of pseudo‐continuous arterial spin labeling (PCASL) to off‐resonance effects (ΔB0) is a major limitation at ultra‐high field (≥7T). The aim of this study was to assess the effectiveness of different PCASL ΔB0 compensation methods at 7T and measure the labeling efficiency with off‐resonance correction.Theory and MethodsPhase offset errors induced by ΔB0 at the feeding arteries can be compensated by adding an extra radiofrequency (RF) phase increment and transverse gradient blips into the PCASL RF pulse train. The effectiveness of an average field correction (AVGcor), a vessel‐specific field‐map‐based correction (FMcor) and a vessel‐specific prescan‐based correction (PScor) were compared at 7T. After correction, the PCASL labeling efficiency was directly measured in feeding arteries downstream from the labeling location.ResultsThe perfusion signal was more uniform throughout the brain after off‐resonance correction. Whole‐brain average perfusion signal increased by a factor of 2.4, 2.5, and 2.1, respectively, with AVGcor, FMcor and PScor compared to acquisitions without correction. With off‐resonance correction, the maximum labeling efficiency was ~0.68 at mean B1 (B1mean) of 0.70 µT when using a mean gradient (Gmean) of 0.25 mT/m.ConclusionEither a prescan or a field map can be used to correct for off‐resonance effects and retrieve a good brain perfusion signal at 7T. Although the three methods performed well in this study, FMcor may be better suited for patient studies because it accounted for vessel‐specific ΔB0 variations. Further improvements in image quality will be possible by optimizing the labeling efficiency with advanced hardware and software while satisfying specific absorption rate constraints.
The impeded diffusion fraction quantitative imaging assay demonstrated in multi‐exponential diffusion phantom and prostate cancer
Authors: Malyarenko Dariya I. , Swanson Scott D. , McGarry Sean D. , LaViolette Peter S. , Chenevert Thomas L. 
Published: November 2021

PurposeTo demonstrate a method for quantification of impeded diffusion fraction (IDF) using conventional clinical DWI protocols.MethodsThe IDF formalism is introduced to quantify contribution from water coordinated by macromolecules to DWI voxel signal based on fundamentally different diffusion constants in vascular capillary, bulk free, and coordinated water compartments. IDF accuracy was studied as a function of b‐value set. The IDF scaling with restricted compartment size and polyvinylpirrolidone (PVP) macromolecule concentration was compared to conventional apparent diffusion coefficient (ADC) and isotropic kurtosis model parameters for a diffusion phantom. An in vivo application was demonstrated for six prostate cancer (PCa) cases with low and high grade lesions annotated from whole mount histopathology.ResultsIDF linearly scaled with known restricted (vesicular) compartment size and PVP concentration in phantoms and increased with histopathologic score in PCa (from median 9% for atrophy up to 60% for Gleason 7). IDF via non‐linear fit was independent of b‐value subset selected between b = 0.1 and 2 ms/µm2, including standard‐of‐care (SOC) PCa protocol. With maximum sensitivity for high grade PCa, the IDF threshold below 51% reduced false positive rate (FPR = 0/6) for low‐grade PCa compared to apparent diffusion coefficient (ADC > 0.81 µm2/ms) of PIRADS PCa scoring (FPR = 3/6).ConclusionThe proposed method may provide quantitative imaging assays of cancer grading using common SOC DWI protocols.
Acquisition and quantification pipeline for in vivo hyperpolarized 13C MR spectroscopy
Authors: Hong Donghyun , Batsios Georgios , Viswanath Pavithra , Gillespie Anne Marie , Vaidya Manushka , Larson Peder E. Z. , Ronen Sabrina M. 
Published: November 2021

PurposeThe goal of this study was to combine a specialized acquisition method with a new quantification pipeline to accurately and efficiently probe the metabolism of hyperpolarized 13C‐labeled compounds in vivo. In this study, we tested our approach on [2‐13C]pyruvate and [1‐13C]α‐ketoglutarate data in rat orthotopic brain tumor models at 3T.MethodsWe used a multiband metabolite‐specific radiofrequency (RF) excitation in combination with a variable flip angle scheme to minimize substrate polarization loss and measure fast metabolic processes. We then applied spectral‐temporal denoising using singular value decomposition to enhance spectral quality. This was combined with LCModel‐based automatic 13C spectral fitting and flip angle correction to separate overlapping signals and rapidly quantify the different metabolites.ResultsDenoising improved the metabolite signal‐to‐noise ratio (SNR) by approximately 5. It also improved the accuracy of metabolite quantification as evidenced by a significant reduction of the Cramer Rao lower bounds. Furthermore, the use of the automated and user‐independent LCModel‐based quantification approach could be performed rapidly, with the kinetic quantification of eight metabolite peaks in a 12‐spectrum array achieved in less than 1 minute.ConclusionThe specialized acquisition method combined with denoising and a new quantification pipeline using LCModel for the first time for hyperpolarized 13C data enhanced our ability to monitor the metabolism of [2‐13C]pyruvate and [1‐13C]α‐ketoglutarate in rat orthotopic brain tumor models in vivo. This approach could be broadly applicable to other hyperpolarized agents both preclinically and in the clinical setting.
Joint estimation and correction of motion and geometric distortion in segmented arterial spin labeling
Authors: Huber Jörn , Hoinkiss Daniel Christopher , Günther Matthias 
Published: November 2021

PurposeArterial spin labeling allows noninvasive measurement of cerebral blood flow by magnetically labeling inflowing blood, using it as endogenous tracer. Unfortunately, sensitivity to subject motion is high due to the subtractive nature of arterial spin labeling, which is especially problematic if Cartesian segmented 3D gradient and spin echo (GRASE) is applied. Using a 3D GRASE PROPELLER (3DGP) segmentation, retrospective correction of in‐plane rigid body motion is possible before final combination of different segments. However, the standard 3DGP reconstruction is affected by off‐resonance effects and has not yet been validated with different motion patterns and levels of background suppression.MethodsThe standard algorithm (1) and a Cartesian segmented 3D GRASE (2), as well as a new 3DGP reconstruction algorithm, which allows joint estimation of motion and geometric distortion (called 3DGP‐JET), are validated in 5 healthy volunteers. Image quality of perfusion‐weighted images was investigated for background suppression levels of 0%, 5%, and 10% in combination with no motion, as well as slow and fast intentional motion patterns during the scan.ResultsThe proposed 3DGP‐JET algorithm allowed robust estimation of field maps and motion for all scenarios, and greatly reduced motion‐related artifacts in perfusion‐weighted images when compared with Cartesian segmented 3D GRASE.ConclusionFurther improvements of the presented 3DGP‐JET routine and a combination with prospective motion correction are recommended to compensate for through‐plane motion, making the presented technique a good candidate for dealing with motion‐related artifacts in arterial spin labeling images in clinical reality.
Pure balanced steady‐state free precession imaging (pure bSSFP)
Authors: Schäper Jessica , Bauman Grzegorz , Ganter Carl , Bieri Oliver 
Published: November 2021

PurposeTo show that for tissues the conspicuous asymmetries in the frequency response function of bSSFP can be mitigated by using a short enough TR.Theory and MethodsConfiguration theory indicates that bSSFP becomes apparently “pure” (i.e., exhibiting a symmetric profile) in the limit of TR . To this end, the frequency profile of bSSFP was measured as a function of the TR using a manganese‐doped aqueous probe, as well as brain tissue that was shown to exhibit a pronounced asymmetry due to its microstructure. The frequency response function was sampled using (phantom) and (in vivo) equally distributed linear RF phase increments in the interval . Imaging was performed with 2.0 mm isotropic resolution over a TR range of 1.5–8 ms at 3 and 1.5 T.ResultsAs expected, pure substances showed a symmetric TR‐independent frequency profile, whereas brain tissue revealed a pronounced asymmetry. The observed asymmetry for the tissue, however, decreases with decreasing TR and gives strong evidence that the frequency response function of bSSFP becomes symmetric in the limit of TR , in agreement with theory. The limit of apparently pure bSSFP imaging can thus be achieved for a TR 1.5 ms at 1.5 T, whereas at 3 T, tissues still show some residual asymmetry.ConclusionIn the limit of short enough TR, tissues become apparently pure for bSSFP. This limit can be reached for brain tissue at 1.5 T with TR 1–2 ms at clinically relevant resolutions.
Unified elasto‐plastic analysis of rock mass supported with fully grouted bolts for deep tunnels
Authors: Cui Lan , Sheng Qian , Dong You‐kou , Xie Ming‐xing 
Published: November 2021

AbstractThis paper presents a unified elasto‐plastic analysis of rock mass supported with fully ground bolts for deep tunnels. In the analysis, depending on whether the relative movement at the grout–bolt interface is considered, two finite‐difference algorithms are discussed. For each algorithm, two conditions, one when the rock bolt is inserted into the elastic area and one when it is included within the plastic area, are comprehensively investigated. In the algorithms, the initial and final states for the rock–bolt interaction are presented, and for each state, the surrounding rock mass consisting of the bolt or the plastic area is divided into a finite number of annuli through a constant radius increment. Based on this, the stress and displacement for the rock mass and the rock bolt are obtained step by step. The results of the two algorithms are verified by the analytical method and the field test data, respectively. Parametric studies were conducted to compare bolt force, rock displacement and stress components that are solved by the algorithms with and without considering relative movement. The proposed algorithms can be written into the software for guiding the rock bolt design in practical engineering.
Think big, see small—A review of nanomaterials for neural interfaces
Authors: Zeng Qi , Li Xiaojian , Zhang Shiyun , Deng Chunshan , Wu Tianzhun 
Published: November 2021

AbstractDuring the past decades, neural interfaces have been widely applied in various fields, such as neural‐degeneration disease diagnosis and therapy, remote control, and mind‐based interaction with the outside world. The neural interfaces, as the foundation technologies for the bi‐directional communication between the brain and machines, are critical for the development of next generation implanted neural interfaces. Recently, plenty of micro‐ and nanostructured coating materials, together with various devices based on micro/nano fabrication, provide improved performances and novel functions to achieve more precise, chronic and better‐efficiency neural interfaces. In this paper, we review the development of different kinds of neural interfaces from the material and device perspectives. Some innovative functionalized techniques utilizing nanomaterials such as metallic nanostructures, carbon materials, conductive polymers (CPs) are reviewed. Additionally, novel implanted devices for neural signal recording and stimulation with improved or novel performances enabled by nanotechnologies are also presented. Finally, the potential challenges that hinder the development of neural interfaces and the opportunities for future research directions are discussed in brief.
The fractal version of the bond‐based peridynamics method
Authors: Armandei Mojtaba , Burgos Diego F. S. , Savioli Rafael 
Published: November 2021

AbstractThis article presents a new formulation of bond‐based peridynamic theory (PD) encompassing material texture heterogeneity through fractal geometry concepts and transforming all relevant variables from Euclidean space to fractal space. The heterogeneity incorporation is realized through the introduction of a linear transformation fractal coefficient (LTFC). By considering a mean value for all LTFCs of all spatial coordinates. For example, x, y, z, and using the relationship between fractal dimension and the Hurst exponent . We present a fractal version of the bond‐based PD method that the equation of motion is conformed to fractal space. Validation of the formulation is accomplished in two steps: first, the effect of irregular mass distribution is characterized by the fractal dimension of the fracture surface roughness through experimental results of a series of single‐edge notched tensile tests of a ductile material. In the next step, the proposed formulation is calibrated with the fractal dimension obtained experimentally. The results are compared with the classical bond‐based PD formulation and the finite element analysis results. The obtained results in this article indicate that the irregular mass distribution of material can be introduced into particle‐based numerical methods using an adequate fractal exponent. The fractal version provides a good approximation of the fracture behavior of materials.
A descriptive study on the treatment of pediatric CRPS in the Nordic countries and Germany
Authors: Broman Johanna , Weigel Cathrin , Hellmundt Ludwig , Persson Anna 
Published: November 2021

AbstractPediatric complex regional pain syndrome (pCRPS) is a rare, painful state that often occurs as a complication following physical trauma. Diagnosis and treatment require specialist expertise in a multidisciplinary setting. Treatment is focused on pain reduction and improvement in function, which differs from the treatment of adult CRPS. We performed a cross‐sectional survey with the aim of identifying pain centers in the Nordic countries and Germany that specialized in treating children with pain, especially pCRPS, and sought to describe their treatment strategies. Centers and health‐care professionals working with children experiencing chronic pain were identified using internet search engines, phones, or e‐mail. A standardized set of questions and an electronic questionnaire were answered by the participants. A total of 28 participants were identified in 24 centers, which were involved with patients having pCRPS (Germany: 7, Norway: 7, Sweden: 5, Finland: 5, Denmark: 3, and Island: 1). One center in Germany treated more than 20 patients per year. Half of the identified centers (n = 12) treated between 1 and 5 children with pCRPS per year. Guidelines for treating pCRPS were reportedly followed by 9/28 responders (32%), and physiotherapy was reported to be part of the treatment routine in most centers (74%). Interventional anesthesia was rarely used. Psychological therapy: 57% answered that it was always offered, 30% replied that it was proffered in most cases, and 13% responded that it was recommended in only a few patients. Pharmacological treatments were not commonly used. Treatment resources for pCRPS are scarce in the Nordic countries and Germany. Most centers treated very few children with pCRPS and did not have established guidelines. A multidisciplinary approach was used by many centers, most often combining physiotherapy and psychotherapy, and less commonly pharmacological treatment. The difficulties in diagnosing pCRPS and finding official referral units are unfortunate, considering the potentially favorable outcome with adequate treatment.
Cryo‐spun encapsulation of polyaniline‐based conducting hydrogels with high sensitivity, wide‐range linearity, and environmental stability for fibrous strain sensors
Authors: Feng Qichun , Wan Kening , Zhang Chao , Liu Tianxi 
Published: November 2021

AbstractWearable strain sensors are widely engaged in the fields of soft robotics, health monitoring, and human‐machine interfaces. However, low sensitivity, poor environmental resistance, and low‐air permeability of wearable strain sensors severely limit their practical applications. Herein, a coaxial fiber consisting of a polyvinyl alcohol/polyaniline hydrogel (PPH) core and a thermoplastic elastomer (styrene‐isoprene‐styrene block copolymer, SIS) sheath was fabricated by a cryo‐spun encapsulation strategy. The as‐obtained PPH@SIS fiber exhibited high stretchability (>200% strain), large conductivity (0.51 mS.cm−1) and high‐yet‐linear sensitivity (gauge factor of 2.4) when being directly used as a fibrous strain sensor. The resultant PPH@SIS fibrous strain sensor showed a stable response at a broad temperature range from −50 to 50°C to various strains (0% ~ 100%) and frequencies (0 ~ 2 Hz). As a demonstration, the PPH@SIS fibrous strain sensors are capable of identifying fast and slow bendings of dummy joints, showing excellent wearability, high sensitivity, and wide detecting range. This work therefore provides a unique cryo‐spun encapsulation strategy for fabricating coaxial conductive fibers promising for wearable sensors with high sensitivity, excellent wearing comfort, and resistance to extreme environments.
Bouncing Cosmology in Extended Gravity and Its Reconstruction as Dark Energy Model
Authors: Agrawal A. S. , Tello‐Ortiz Francisco , Mishra B. , Tripathy S.K. 
Published: November 2021

AbstractIn this paper, we have presented a bouncing cosmological model of the Universe in an extended theory of gravity. The dynamical behaviour of the model obtained from the flat FLRW space‐time along with the violation of null energy condition have been shown. The geometrical parameters show singularity behaviour at the bouncing epoch. The parameters involved in the scale factor play a major role in the bouncing behaviour. In addition, the coupling parameter that resulted in the minimal matter‐geometry coupling in the extended gravity has significant role to avoid the singularity of equation of state parameter at the bouncing epoch. Using a linear homogeneous perturbation calculation, we show the dynamical stability of the model.
Optimal estimation of total precipitable water from INSAT‐3D/3DR Imagers
Authors: Gangwar Rishi Kumar , Thapliyal Pradeep Kumar 
Published: November 2021

AbstractTotal precipitable water (TPW) is an important parameter for weather prediction apart from study of the hydrological cycle and climate change. Presently, TPW is generated operationally from infrared sounders on board INSAT‐3D and 3DR. However, the Sounder provides observations at a coarser resolution of 10 km over a limited region of coverage, and takes about 60 min to scan the Indian landmass. The Imager, in contrast, provides observation over a larger geographical region (full disc) at the interval of 30 min and a finer spatial resolution of 4 km. To exploit this advantage, an optimal estimation (OE) technique has been attempted to retrieve TPW from thermal infrared split‐window observations of INSAT‐3D/3DR Imagers in clear‐sky conditions. Assessment of the retrieved TPW is carried out for data of one year over land and ocean regions, separately against the three independent reference TPW products, acquired from radiosondes, Special Sensor Microwave Imager Sounder (SSMIS) on board Defense Meteorological Satellite Program (DMSP) F17 satellite, and fifth‐generation European Centre for Medium‐Range Weather Forecasts ReAnalysis (ERA5). The validation analysis of the retrieved TPW over land against the radiosonde observations and ERA5 TPW products for the entire period shows a root‐mean‐square error (RMSE) of less than 6 mm. An RMSE of better than 4 mm is observed over ocean, when compared with the operational TPW products of the SSMIS and ERA5 TPW products. Moreover, the RMSE of the retrieved TPW shows consistency for each month that clearly implies the robustness of the developed algorithm. The developed algorithm has been proposed for operational implementation at the Meteorological and Oceanographic Data Archival and Dissemination Centre (MOSDAC) hosted by Space Applications Centre, Ahmedabad and India Meteorological Department (IMD), New Delhi, India.
Separation and characterization of two series of unknown degradation impurities caused by light irradiation and autoclaving in xinfujunsu injection using liquid chromatography tandem mass spectrometry
Authors: Huang Qiaoqiao , Tang Kaixian , Ren Xiaojuan , Wang Jian 
Published: November 2021

RationaleA series of photodegradation impurities and a series of degradation impurities produced in autoclaving in xinfujunsu injection were discovered, and these unknown impurities were separated and characterized thoroughly using liquid chromatography tandem quadrupole time‐of‐flight mass spectrometry.MethodsThe column was a Platisil 5 μm ODS (4.6 × 250 mm, 5 μm). For the analysis of degradation impurities caused by light irradiation and autoclaving, the mobile phase was composed of 0.01 M ammonium formate aqueous solution and acetonitrile/isopropanol (90:10, V/V). Full scan LC–MS and LC–MS2 was carried out to obtain as much structural information as possible. The fragmentation behavior of actinomycin D, actinomycin S3, and its impurities was studied and used to obtain information about the structures of these impurities.ResultsBased on MS2 spectral data and exact mass measurements, the chemical structures of two series of degradation impurities were characterized, among which five unknown impurities were photodegradation impurities and seven unknown impurities were degradation impurities produced in autoclaving of xinfujunsu injection.ConclusionsBased on characterization of impurities, this study also revealed the cause of impurity production and provided guidance for enterprises to improve the process and drug packaging material to reduce impurity content. Furthermore, this study also provided scientific basis for further improvement of official monographs in pharmacopoeias.