To characterize the spatial patterns of vertical crustal movement of Chinese mainland,GNSS imaging technology was applied to map the tectonic deformation of the region.In this study,the vertical crustal velocities inf...To characterize the spatial patterns of vertical crustal movement of Chinese mainland,GNSS imaging technology was applied to map the tectonic deformation of the region.In this study,the vertical crustal velocities inferred from GNSS data for Chinese mainland over two decades were rigorously estimated.First,by analyzing the vertical displacement time series from continuous GNSS stations and environmental load data,we found that the annual and semi-annual vertical displacements are highly correlated.This indicates that the vertical seasonal variations on the ground surface are mainly caused by environmental loading.After removing the seasonal variations caused by environmental loads from the GNSS time series,we applied an improved PCA technique to filter out common mode errors.Next,we estimated the optimal noise models for the filtered time series and derived the vertical velocity field of Chinese mainland.Finally,we employed an empirical Spatial Structure Function(SSF)to image the tectonic deformation of Chinese mainland.This method effectively mitigates issues with abrupt circular arc-shaped boundaries in GNSS imaging caused by sparse station networks.The imaging results show that vertical crustal deformation in Chinese mainland generally ranges from-3 to 3 mm/yr,with significant spatial variability.The central and northern parts of Qinghai-Xizang Plateau are identified as primary subsidence zones,indicating that plate boundaries and tectonic compression continue to shape the crustal movement in these regions.The major uplift zones are located in northern and central China,likely linked to regional tectonic activity and plate compression.Subsidence deformation in parts of eastern China appears to be influenced by human activities.展开更多
BACKGROUND Currently,adolescent depression is one of the most significant public health concerns,markedly influencing emotional,cognitive,and social maturation.Despite advancements in distinguish the neurobiological s...BACKGROUND Currently,adolescent depression is one of the most significant public health concerns,markedly influencing emotional,cognitive,and social maturation.Despite advancements in distinguish the neurobiological substrates underlying depression,the intricate patterns of disrupted brain network connectivity in adolescents warrant further exploration.AIM To elucidate the neural correlates of adolescent depression by examining brain network connectivity using resting-state functional magnetic resonance imaging(rs-fMRI).METHODS The study cohort comprised 74 depressed adolescents and 59 healthy controls aged 12 to 17 years.Participants underwent rs-fMRI to evaluate functional connectivity within and across critical brain networks,including the visual,default mode network(DMN),dorsal attention,salience,somatomotor,and frontoparietal control networks.RESULTS Analyses revealed pronounced functional disparities within key neural circuits among adolescents with depression.The results demonstrated existence of hemispheric asymmetries characterized by enhanced activity in the left visual network,which contrasted the diminished activity in the right hemisphere.The DMN facilitated increased activity within the left prefrontal cortex and reduced engagement in the right hemisphere,implicating disrupted self-referential and emotional processing mechanisms.Additionally,an overactive right dorsal attention network and a hypoactive salience network were identified,underscoring significant abnormalities in attentional and emotional regulation in adolescent depression.CONCLUSION The findings from this study underscore distinct neural connectivity disruptions in adolescent depression,underscoring the critical role of specific neurobiological markers for precise early diagnosis of adolescent depression.The observed functional asymmetries and network-specific deviations elucidate the complex neurobiological architecture of adolescent depression,supporting the development of targeted therapeutic strategies.展开更多
The high-density,vertically aligned retinal neuron array provides effective vision,a feature we aim to replicate with electronic devices.However,the conventional complementary metal-oxide-semiconductor(CMOS)image sens...The high-density,vertically aligned retinal neuron array provides effective vision,a feature we aim to replicate with electronic devices.However,the conventional complementary metal-oxide-semiconductor(CMOS)image sensor,based on separate designs for sensing,memory,and processing units,limits its integration density.Moreover,redundant signal communication significantly increases energy consumption.Current neuromorphic devices integrating sensing and signal processing show promise in various computer vision applications,but there is still a need for frame-based imaging with good compatibility.In this study,we developed a dual-mode image sensor based on a high-density all-inorganic perovskite nanowire array.The device can switch between frame-based standard imaging mode and neuromorphic imaging mode by applying different biases.This unique bias-dependent photo response is based on a well-designed energy band diagram.The biomimetic alignment of nanowires ensures the potential for high-resolution imaging.To further demonstrate the imaging ability,we conducted pattern reconstruction in both modes with a 10×10 crossbar device.This study introduces a novel image sensor with high compatibility and efficiency,suitable for various applications including computer vision,surveillance,and robotics.展开更多
The periodic impact force induced by tip-sample contact in a tapping mode atomic force microscope （AFM） gives rise to the non-harmonic response of a micro-cantilever. These non-harmonic signals contain the full char...The periodic impact force induced by tip-sample contact in a tapping mode atomic force microscope （AFM） gives rise to the non-harmonic response of a micro-cantilever. These non-harmonic signals contain the full characteristics of tip-sample interaction. A complete theoretical model describing the dynamical behaviour of tip-sample system was developed in this paper. An analytic formula was introduced to describe the relationship between time-varying tip-sample impact force and tip motion. The theoretical analysis and numerical results both show that the timevarying tip-sample impact force can be reconstructed by recording tip motion. This allows for the reconstruction of the characteristics of the tip-sample force, like contact time and maximum contact force. It can also explain the ability of AFM higher harmonics imaging in mapping stiffness and surface energy variations.展开更多
Probability-based diagnostic imaging(PDI)is one of the most well-known damage identification methods using guided waves.It is usually applied to diagnose damage in plates.The previous studies were dependent on the cer...Probability-based diagnostic imaging(PDI)is one of the most well-known damage identification methods using guided waves.It is usually applied to diagnose damage in plates.The previous studies were dependent on the certain damage index(DI)which is always calculated from the guided wave signals.In conventional methods,DI is simply defined by comparing the real-time data with the baseline data as reference.However,the baseline signal is easily affected by varying environmental conditions of structures.In this paper,a reference-free diagnostic imaging method is developed to avoid the influence of environmental factors,such as temperature and load conditions.The DI is defined based on the mode conversion of multi-mode guided waves with realtime signals without baseline signals.To improve the accuracy of diagnosis,two terms are included in the reference-free DI.One is called energy DI,which is defined based on the feature of signal energy.The other is called correlation DI and is defined based on the correlation coefficient.Then the PDI algorithm can be carried out instantaneously according to the reference-free DI.The real-time signals which are used to calculate DI are collected by the piezoelectric lead zirconate titanate(PZT)transducers placed on both sides of a plate.The numerical simulations by the finite element(FE)method on aluminum plates with PZT arrays are performed to validate the effectiveness of the reference-free damage diagnostic imaging.The approach is validated by two different arrays:a circle network and a square network.The results of diagnostic imaging are demonstrated and discussed in this paper.Furthermore,the advantage of reference-free DI is investigated by comparing the accuracy of defined reference-free DI and energy DI.展开更多
A new multi-mode resistivity imaging sonde, with toroidal coils as source, can conduct three resistivity measurements: azimuthal resistivity, lateral resistivity, and bit resistivity measurements. Thus, the logging ti...A new multi-mode resistivity imaging sonde, with toroidal coils as source, can conduct three resistivity measurements: azimuthal resistivity, lateral resistivity, and bit resistivity measurements. Thus, the logging time and cost are greatly saved. The toroidal coils are simplified as an extended voltage dipole and the response equations are derived for a homogenous formation. Based on 3D FEM, the depth of investigation(DOI), vertical resolution, circumferential azimuthal capacity, borehole diameter, mud resistivity, thickness of target formation, and the resistivity of the surrounding formation and mud invasion are simulated. The results suggest that the three measurement modes of the new sonde are different in vertical resolutions and DOIs. The circumferential detection ability of the azimuth button depends on the contrast between the anomaly and formation resistivity and the open angle of the anomaly. Whether the borehole is truncated at the bit or not has a great influence on the simulation results. The borehole and mud invasion affect the apparent resistivity in all modes, but the effects of resistivity of surrounding formation and thickness of the target formation are only corrected for lateral resistivity measurement.展开更多
The coherent-mode representation theory is firstly used to analyze lensless two-color ghost imaging. A quite complicated expression about the point-spread function（PSF） needs to be given to analyze which wavelength ...The coherent-mode representation theory is firstly used to analyze lensless two-color ghost imaging. A quite complicated expression about the point-spread function（PSF） needs to be given to analyze which wavelength has a stronger affect on imaging quality when the usual integral representation theory is used to ghost imaging. Unlike this theory, the coherent-mode representation theory shows that imaging quality depends crucially on the distribution of the decomposition coefficients of the object imaged in a two-color ghost imaging. The analytical expression of the decomposition coefficients of the object is unconcerned with the wavelength of the light used in the reference arm, but has relevance with the wavelength in the object arm. In other words, imaging quality of two-color ghost imaging depends primarily on the wavelength of the light illuminating the object. Our simulation results also demonstrate this conclusion.展开更多
A facile strategy to fabricate gold nanorod@polyacrylic acid/calcium phosphate(Au NR@-PAA/Ca P) yolk–shell nanoparticles(NPs) composed with a PAA/Ca P shell and an Au NR yolk is reported. The asobtained Au NR@PAA/Ca ...A facile strategy to fabricate gold nanorod@polyacrylic acid/calcium phosphate(Au NR@-PAA/Ca P) yolk–shell nanoparticles(NPs) composed with a PAA/Ca P shell and an Au NR yolk is reported. The asobtained Au NR@PAA/Ca P yolk–shell NPs possess ultrahigh doxorubicin(DOX) loading capability(1 mg DOX/mg NPs), superior photothermal conversion property(26%)and p H/near-infrared(NIR) dual-responsive drug delivery performance. The released DOX continuously increased due to the damage of the Ca P shell at low p H values. When the DOX-loaded Au NR@PAA/Ca P yolk–shell NPs wereexposed to NIR irradiation, a burst-like drug release occurs owing to the heat produced by the Au NRs. Furthermore,Au NR@PAA/Ca P yolk–shell NPs are successfully employed for synergic dual-mode X-ray computed tomography/photoacoustic imaging and chemo-photothermal cancer therapy. Therefore, this work brings new insights for the synthesis of multifunctional nanomaterials and extends theranostic applications.展开更多
AIM: To experimentally investigate the acoustical behavior of different dual-mode nanosized contrast agents(NPCAs) for echographic medical imaging at low ultrasound(US) frequency. METHODS: We synthesized three differe...AIM: To experimentally investigate the acoustical behavior of different dual-mode nanosized contrast agents(NPCAs) for echographic medical imaging at low ultrasound(US) frequency. METHODS: We synthesized three different nanosized structures:(1) Pure silica nanospheres(SiNSs);(2) FePt-iron oxide(FePt-IO)-coated SiNSs; and(3) IOcoated SiNSs, employing three different diameter of SiNS-core(160, 330 and 660 nm). Tissue mimicking phantoms made of agarose gel solution containing 5 mg of different NPCAs in 2 mL-Eppendorf tubes, were insonified by a commercial echographic system at three different low US pulse values(2.5, 3.5 and 4.5 MHz). The raw radiofrequency signal, backscattered from each considered NPCA containing sample, has been processed in order to calculate the US average backscatter intensity and compare the acoustic behavior of the different NPCA types. RESULTS: The highest US contrast was exhibited by pure SiNSs; FePt-IO-coated SiNSs acoustical behavior followed a similar trend of pure SiNSs with a slight difference in terms of brightness values. The acoustic response of the examined NPCAs resulted function of both SiNS diameter and US frequency. Specifically, higher US frequencies determined higher value of the backscatter for a given SiNS diameter. Frequencydependent enhancement was marked for pure SiNSs and became less remarkable for FePt-IO-coated SiNSs, whereas IO-coated SiNSs resulted almost unaffected by such frequency variations. Pure and FePt-IO-coated SiNSs evidenced an image backscatter increasing with the diameter up to 330 nm. Conversely, among the types of NPCA tested, IO-coated SiNSs showed the lowest acoustical response for each synthesized diameter and employed US frequency, although a diameter-dependent raising trend was evidenced. CONCLUSION: The US characterization of magnetically covered SiNS shows that FePt-IO, rather than IO, was the best magnetic coating for realizing NPCAs suitable for dual mode imaging of deep organs, combining US and magnetic resonance imaging.展开更多
Sediment incipient velocity （SIV） is a vital parameter for sediment research and river dynamics. This paper describes a novel method of estimating SIV based on the known flow velocity in the movable-bed model experi...Sediment incipient velocity （SIV） is a vital parameter for sediment research and river dynamics. This paper describes a novel method of estimating SIV based on the known flow velocity in the movable-bed model experiment. In this method, we use B-mode ultrasound imaging technique to get video images of moving particles and topography under water. By statistical analysis of video images, the relationship between the average number of imaging particles and flow velocity is obtained. The relationship between the change rate of average number and flow velocity is analyzed in sediment incipient process. These relationships are used to estimate the SIV. Lastly, the changed topography verifies the estimated velocity. The results show there is a sudden change in these relationships which can be used to estimate the SIV with high resolution by using a B-mode ultrasound device. The estimated SIV of plastic sands （particle size is about 0.25 mm） is 3.64 cm · s^-1 and the estimated SIV of natural sands （particle size is about 0.25 mm） is 5.47 cm · s^-1in the same condition.展开更多
After drawbacks and shortages of using conventional kV or MV imaging mode were analyzed, this study proposes a new position verification mode with using the energy larger than 15 MeV or nominal accelerating potential ...After drawbacks and shortages of using conventional kV or MV imaging mode were analyzed, this study proposes a new position verification mode with using the energy larger than 15 MeV or nominal accelerating potential greater than 25 MV X-Ray. The new position verification mode is named HMV imaging mode. Along with the comparison of theoretical analyses, phantom experiments and clinical results to the original imaging modes, this report is going to demonstrate the HMV imaging mode is superior to traditional kV and MV imaging modes. This report first theoretically analyzed three main effects of X-ray interacting with medium by numerous equations and compared their mass attenuation coefficient with different types of tissue. X-ray irradiated on a “Catphan 500” cylinder phantom with different energies to verify these theoretical results. Furthermore, based on phantom experiments’ results, we have done numerous clinical trials and comparisons with patient’s clinical results. The theoretical and experimental results illustrate that the scanned images from HMV mode have a good quality and have ability to identify different tissue components clearly. HMV imaging mode overcomes drawbacks of position verification from both kV and MV level imaging mode as well as keeping advantages of kV and MV imaging mode. The result indicates that HMV is a good position verification mode in radiotherapy.展开更多
First we present a theoretical analysis of classical noise in ghost imaging system based on the coherent-mode representation theory. The classical noise depends crucially on the distribution of the eigenvalues of the ...First we present a theoretical analysis of classical noise in ghost imaging system based on the coherent-mode representation theory. The classical noise depends crucially on the distribution of the eigenvalues of the coherent-mode representation of the source and the decomposition coefficients of the object imaged. We show that both decreasing the distribution of the decomposition coefficients and increasing the distribution of the eigenvalues can lead to the decrease of classical noise.展开更多
Based on an avalanche photodiode（ APD） detecting array working in Geiger mode（ GM-APD）, a high-performance infrared sensor readout integrated circuit（ ROIC） used for infrared 3D（ three-dimensional） imaging is ...Based on an avalanche photodiode（ APD） detecting array working in Geiger mode（ GM-APD）, a high-performance infrared sensor readout integrated circuit（ ROIC） used for infrared 3D（ three-dimensional） imaging is proposed. The system mainly consists of three functional modules, including active quenching circuit（ AQC）, time-to-digital converter（ TDC） circuit and other timing controller circuit. Each AQC and TDC circuit together constitutes the pixel circuit. Under the cooperation with other modules, the current signal generated by the GM-APD sensor is detected by the AQC, and the photon time-of-flight（ TOF） is measured and converted to a digital signal output to achieve a better noise suppression and a higher detection sensitivity by the TDC. The ROIC circuit is fabricated by the CSMC 0. 5 μm standard CMOS technology. The array size is 8 × 8, and the center distance of two adjacent cells is 100μm. The measurement results of the chip showthat the performance of the circuit is good, and the chip can achieve 1 ns time resolution with a 250 MHz reference clock, and the circuit can be used in the array structure of the infrared detection system or focal plane array（ FPA）.展开更多
Due to the data acquired by most optical earth observation satellite such as IKONOS, QuickBird-2 and GF-1 consist of a panchromatic image with high spatial resolution and multiple multispectral images with low spatial...Due to the data acquired by most optical earth observation satellite such as IKONOS, QuickBird-2 and GF-1 consist of a panchromatic image with high spatial resolution and multiple multispectral images with low spatial resolution. Many image fusion techniques have been developed to produce high resolution multispectral image. Considering panchromatic image and multispectral images contain the same spatial information with different accuracy, using the least square theory could estimate optimal spatial information. Compared with previous spatial details injection mode, this mode is more accurate and robust. In this paper, an image fusion method using Bidimensional Empirical Mode Decomposition (BEMD) and the least square theory is proposed to merge multispectral images and panchromatic image. After multi-spectral images were transformed from RGB space into IHS space, next I component and Panchromatic are decomposed by BEMD, then using the least squares theory to evaluate optimal spatial information and inject spatial information, finally completing fusion through inverse BEMD and inverse intensity-hue-saturation transform. Two data sets are used to evaluate the proposed fusion method, GF-1 images and QuickBird-2 images. The fusion images were evaluated visually and statistically. The evaluation results show the method proposed in this paper achieves the best performance compared with the conventional method.展开更多
OBJECTIVE:To examine the brain effects of transcutaneous auricular vagus nerve stimulation(ta VNS)treatment of recurrent depression based on the functional brain network by using resting-state functional magnetic reso...OBJECTIVE:To examine the brain effects of transcutaneous auricular vagus nerve stimulation(ta VNS)treatment of recurrent depression based on the functional brain network by using resting-state functional magnetic resonance imaging(f MRI).METHODS:Twenty-five patients with recurrent depression were enrolled in a single-arm trial of ta VNS treatment for eight weeks.Clinical results were assessed by 17-item Hamilton Depression Rating Scale(HAMD-17),Hamilton Anxiety Scale(HAMA),Self-Rating Depression Scale(SDS),Self-Rating Anxiety Scale(SAS),and Ruminative Response Scale(RRS)scales.Resting-state f MRI was conducted to explore the brain effects before and after treatment.For the functional connectivity(FC)analysis,the bilateral nucleus accumbens,globus pallidus,caudate,and putamen were selected as seeds.Finally,the correlations between FC and the clinical scale scores were calculated.RESULTS:After treatment,the patients’scores of HAMD-17,HAMA,SDS,SAS,and RRS were significantly decreased(P<0.05).FC was considerably decreased between the following areas:the left globus pallidus and the right postcentral gyrus,inferior parietal gyrus,the right globus pallidus and the left superior marginal gyrus,postcentral gyrus,superior parietal gyrus,inferior parietal gyrus,precuneus,right postcentral gyrus,superior marginal gyrus,and inferior parietal gyrus,between the right caudate and the right lingual gyrus,calcarine gyrus,and cerebellum.Changes in FC between the right globus pallidus and the left inferior parietal gyrus,between the left globus pallidus and the right postcentral gyrus were negatively correlated with HAMD-17 scores change before and after treatment(before,P=0.003,r=-0.6;after,P=0.009,r=-0.54).The change of FC between the right globus pallidus and the right postcentral gyrus was negatively correlated with the change in SDS(P=0.026,r=-0.474).The difference in FC between the right globus pallidus and the right postcentral gyrus was negatively correlated with the change in SAS(P=0.016,r=-0.513).CONCLUSIONS:Recurrent depression could be effectively treated with ta VNS.The changes in brain FC involving the basal ganglia,default mode,and sensorimotor networks provide insight into the effects of ta VNS treatment on recurrent depression.展开更多
A high-speed vacuum ultraviolet(VUV) imaging system has been developed on the Experimental Advanced Superconducting Tokamak(EAST), which selectively measures line emission with a central wavelength of 13.5 nm(CVI, n=4...A high-speed vacuum ultraviolet(VUV) imaging system has been developed on the Experimental Advanced Superconducting Tokamak(EAST), which selectively measures line emission with a central wavelength of 13.5 nm(CVI, n=4–2). It has been employed to study edge/pedestal plasma behavior in EAST. Edge localized mode(ELM)-induced filament structures have been captured by the VUV imaging system during the ELMy high confinement mode discharge with both high temporal and spatial resolutions. The typical features(i.e.poloidal width and pitch angle) of the observed filaments are quantitatively characterized based on the VUV imaging data, and the dependence of these features on basic plasma parameters is analyzed. It is found that the poloidal width is proportional to the heating power, and the pitch angle is inversely proportional to the edge safety factor q.95 The scatterplot shows a positive trend between the poloidal width and the ELM amplitude defined by the relative change in stored energy. These results are based on the condition that the perturbation induced by ELMs is confined to a narrow layer in the plasma.展开更多
Empirical mode decomposition (EMD) is a data-driven and multi-scale transform theory, and it is a nonlinear and non-stationary signal processing theory. But each EMD decomposition theory has its advantages and disadva...Empirical mode decomposition (EMD) is a data-driven and multi-scale transform theory, and it is a nonlinear and non-stationary signal processing theory. But each EMD decomposition theory has its advantages and disadvantages. Synthetic aperture radar (SAR) imaging is an important remote sensing technique to obtain the change information, and SAR image data belongs to non-stationary signal. So EMD is very suitable for SAR image processing. There are two kinds of typical EMD theories, which are the ensemble empirical mode decomposition (EEMD) and bidimensional empirical mode decomposition (BEMD). Based on the deep study of the two methods, this paper proposed a new SAR image change detection algorithm, which is called the FCD-EMD algorithm, i.e. fusion change detection based on EMD. So FCD-EMD algorithm can obtain more accurate information, which not only includes the directional information obtained by EEMD, but also can contain the spatial information got by BEMD. The main contribution of the FCD-EMD algorithm is to fuse the detail information in different directions, so that the results obtained are more accurate than the individual method. On the other hand, it can reduce the influence of speckle noise in SAR images by feature selections. The actual SAR image data verify the algorithm proposed in this paper and good experimental results are obtained, which show that the new method is feasible.展开更多
Oil spills pose a major threat to ocean ecosystems and their health. Synthetic aperture radar（SAR） sensors can detect oil spills on the sea surface. These oil spills appear as dark spots in SAR images. However, dark...Oil spills pose a major threat to ocean ecosystems and their health. Synthetic aperture radar（SAR） sensors can detect oil spills on the sea surface. These oil spills appear as dark spots in SAR images. However, dark formations can be caused by a number of phenomena. It is aimed to distinguishing oil spills or look-alike objects. A novel method based on a bidimensional empirical mode decomposition is proposed. The selected dark formations are first decomposed into several bidimensional intrinsic mode functions and the residue. Subsequently, 64 dimension feature sets are calculated using the Hilbert spectral analysis and five new features are extracted with a relief algorithm. Mahalanobis distances are then used for classification. Three data sets containing oil spills or look-alikes are used to test the accuracy rate of the method. The accuracy rate is more than 90%. The experimental results demonstrate that the novel method can detect oil spills validly and accurately.展开更多
In this paper a millimeter-wave （MMW） squint indirect holographic method is presented, which is suitable for imaging with a large field-of-view. The proposed system employs the squint operation mode to remove the ba...In this paper a millimeter-wave （MMW） squint indirect holographic method is presented, which is suitable for imaging with a large field-of-view. The proposed system employs the squint operation mode to remove the background and twin- image interferences, which achieves a similar effect to off-axis holography but leaves out the large-aperture quasi-optical component. The translational scanning manner enables a large field of view and ensures the image uniformity, which is difficult to realize in off-axis holography. In addition, a corresponding imaging algorithm for the presented scheme is developed to reconstruct the image from the recorded hologram. Some imaging results on typical objects, obtained with electromagnetic simulation, demonstrate good performance of the imaging scheme and validate the effectiveness of the image reconstruction algorithm.展开更多
Magnetic resonance imaging(MRI),as a noninvasive and powerful method in modern diagnostics,has been advancing in leaps and bounds.Conventional methods to improve MRI based on increasing the static magnetic field stren...Magnetic resonance imaging(MRI),as a noninvasive and powerful method in modern diagnostics,has been advancing in leaps and bounds.Conventional methods to improve MRI based on increasing the static magnetic field strength are restricted by safety concerns,cost issues,and the impact on patient experience;as such,innovative approaches are required.It has been suggested that metamaterials featuring subwavelength unit cells can be used to take full control of electromagnetic waves and redistribute electromagnetic fields,achieve abundant counterintuitive phenomena,and construct versatile devices.Recently,metamaterials with exotic effective electromagnetic parameters,peculiar dispersion relations,or tailored field distribution of resonant modes have shown promising capabilities in MRI.Herein,we outline the principle of the MRI process,review recent advances in enhancing MRI by employing the unique physical mechanisms of metamaterials,and demystify ways in which metamaterial designs could improve MRI,such as by enhancing the imaging quality,reducing the scanning time,alleviating field inhomogeneities,and increasing patient safety.We conclude by providing our vision for the future of improving MRI with metamaterials.展开更多
基金National Natural Science Foundation of China(42274012,42004001)the Science and Technology Innovation Project of Anhui Surveying and Mapping Bureau(2025-KJ-08)+1 种基金the Open Fund of Wuhan Gravitation and Solid Earth Tides,National Observation and Research Station(WHYWZ202107)the Fundamental Research Funds for the Central Universities(JZ2022HGTB0268)。
文摘To characterize the spatial patterns of vertical crustal movement of Chinese mainland,GNSS imaging technology was applied to map the tectonic deformation of the region.In this study,the vertical crustal velocities inferred from GNSS data for Chinese mainland over two decades were rigorously estimated.First,by analyzing the vertical displacement time series from continuous GNSS stations and environmental load data,we found that the annual and semi-annual vertical displacements are highly correlated.This indicates that the vertical seasonal variations on the ground surface are mainly caused by environmental loading.After removing the seasonal variations caused by environmental loads from the GNSS time series,we applied an improved PCA technique to filter out common mode errors.Next,we estimated the optimal noise models for the filtered time series and derived the vertical velocity field of Chinese mainland.Finally,we employed an empirical Spatial Structure Function(SSF)to image the tectonic deformation of Chinese mainland.This method effectively mitigates issues with abrupt circular arc-shaped boundaries in GNSS imaging caused by sparse station networks.The imaging results show that vertical crustal deformation in Chinese mainland generally ranges from-3 to 3 mm/yr,with significant spatial variability.The central and northern parts of Qinghai-Xizang Plateau are identified as primary subsidence zones,indicating that plate boundaries and tectonic compression continue to shape the crustal movement in these regions.The major uplift zones are located in northern and central China,likely linked to regional tectonic activity and plate compression.Subsidence deformation in parts of eastern China appears to be influenced by human activities.
基金Supported by the Medical Research Project of the Chongqing Municipal Health Commission,No.2024WSJK110.
文摘BACKGROUND Currently,adolescent depression is one of the most significant public health concerns,markedly influencing emotional,cognitive,and social maturation.Despite advancements in distinguish the neurobiological substrates underlying depression,the intricate patterns of disrupted brain network connectivity in adolescents warrant further exploration.AIM To elucidate the neural correlates of adolescent depression by examining brain network connectivity using resting-state functional magnetic resonance imaging(rs-fMRI).METHODS The study cohort comprised 74 depressed adolescents and 59 healthy controls aged 12 to 17 years.Participants underwent rs-fMRI to evaluate functional connectivity within and across critical brain networks,including the visual,default mode network(DMN),dorsal attention,salience,somatomotor,and frontoparietal control networks.RESULTS Analyses revealed pronounced functional disparities within key neural circuits among adolescents with depression.The results demonstrated existence of hemispheric asymmetries characterized by enhanced activity in the left visual network,which contrasted the diminished activity in the right hemisphere.The DMN facilitated increased activity within the left prefrontal cortex and reduced engagement in the right hemisphere,implicating disrupted self-referential and emotional processing mechanisms.Additionally,an overactive right dorsal attention network and a hypoactive salience network were identified,underscoring significant abnormalities in attentional and emotional regulation in adolescent depression.CONCLUSION The findings from this study underscore distinct neural connectivity disruptions in adolescent depression,underscoring the critical role of specific neurobiological markers for precise early diagnosis of adolescent depression.The observed functional asymmetries and network-specific deviations elucidate the complex neurobiological architecture of adolescent depression,supporting the development of targeted therapeutic strategies.
基金supported by the Science and Technology Plan of Shenzhen(JCYJ20170818114107730,JCYJ20180306174923335)The General Research Fund(projects 16205321,16214619)from the Hong Kong Research Grant Council,Innovation Technology Fund(GHP/014/19SZ)+2 种基金Guangdong-Hong Kong-Macao Intelligent Micro-Nano Optoelectronic Technology Joint Laboratory(2020B1212030010)Foshan Innovative and Entrepreneurial Research Team Program(2018IT100031)the support from the Center for 1D/2D Quantum Materials and the State Key Laboratory of Advanced Displays and Optoelectronics Technologies at HKUST。
文摘The high-density,vertically aligned retinal neuron array provides effective vision,a feature we aim to replicate with electronic devices.However,the conventional complementary metal-oxide-semiconductor(CMOS)image sensor,based on separate designs for sensing,memory,and processing units,limits its integration density.Moreover,redundant signal communication significantly increases energy consumption.Current neuromorphic devices integrating sensing and signal processing show promise in various computer vision applications,but there is still a need for frame-based imaging with good compatibility.In this study,we developed a dual-mode image sensor based on a high-density all-inorganic perovskite nanowire array.The device can switch between frame-based standard imaging mode and neuromorphic imaging mode by applying different biases.This unique bias-dependent photo response is based on a well-designed energy band diagram.The biomimetic alignment of nanowires ensures the potential for high-resolution imaging.To further demonstrate the imaging ability,we conducted pattern reconstruction in both modes with a 10×10 crossbar device.This study introduces a novel image sensor with high compatibility and efficiency,suitable for various applications including computer vision,surveillance,and robotics.
基金Project supported by the National High-Tech Research and Development Program of China (Grant No. 2007AA12Z128)
文摘The periodic impact force induced by tip-sample contact in a tapping mode atomic force microscope （AFM） gives rise to the non-harmonic response of a micro-cantilever. These non-harmonic signals contain the full characteristics of tip-sample interaction. A complete theoretical model describing the dynamical behaviour of tip-sample system was developed in this paper. An analytic formula was introduced to describe the relationship between time-varying tip-sample impact force and tip motion. The theoretical analysis and numerical results both show that the timevarying tip-sample impact force can be reconstructed by recording tip motion. This allows for the reconstruction of the characteristics of the tip-sample force, like contact time and maximum contact force. It can also explain the ability of AFM higher harmonics imaging in mapping stiffness and surface energy variations.
基金This work was supported by the National Key Research and Development Program of China(Grant No.2016YFF0203002)the National Natural Science Foundation of China(Grant No.11702051)+1 种基金China Post-doctoral Science Foundation(Grant No.2017M610176)the Fundamental Research Funds for the Central Universities(DUT16ZD214).
文摘Probability-based diagnostic imaging(PDI)is one of the most well-known damage identification methods using guided waves.It is usually applied to diagnose damage in plates.The previous studies were dependent on the certain damage index(DI)which is always calculated from the guided wave signals.In conventional methods,DI is simply defined by comparing the real-time data with the baseline data as reference.However,the baseline signal is easily affected by varying environmental conditions of structures.In this paper,a reference-free diagnostic imaging method is developed to avoid the influence of environmental factors,such as temperature and load conditions.The DI is defined based on the mode conversion of multi-mode guided waves with realtime signals without baseline signals.To improve the accuracy of diagnosis,two terms are included in the reference-free DI.One is called energy DI,which is defined based on the feature of signal energy.The other is called correlation DI and is defined based on the correlation coefficient.Then the PDI algorithm can be carried out instantaneously according to the reference-free DI.The real-time signals which are used to calculate DI are collected by the piezoelectric lead zirconate titanate(PZT)transducers placed on both sides of a plate.The numerical simulations by the finite element(FE)method on aluminum plates with PZT arrays are performed to validate the effectiveness of the reference-free damage diagnostic imaging.The approach is validated by two different arrays:a circle network and a square network.The results of diagnostic imaging are demonstrated and discussed in this paper.Furthermore,the advantage of reference-free DI is investigated by comparing the accuracy of defined reference-free DI and energy DI.
基金sponsored by Study on High-Precision Logging While Drilling Imaging Technology of Low-Permeability Reservoirs(No.2016ZX05021-002)
文摘A new multi-mode resistivity imaging sonde, with toroidal coils as source, can conduct three resistivity measurements: azimuthal resistivity, lateral resistivity, and bit resistivity measurements. Thus, the logging time and cost are greatly saved. The toroidal coils are simplified as an extended voltage dipole and the response equations are derived for a homogenous formation. Based on 3D FEM, the depth of investigation(DOI), vertical resolution, circumferential azimuthal capacity, borehole diameter, mud resistivity, thickness of target formation, and the resistivity of the surrounding formation and mud invasion are simulated. The results suggest that the three measurement modes of the new sonde are different in vertical resolutions and DOIs. The circumferential detection ability of the azimuth button depends on the contrast between the anomaly and formation resistivity and the open angle of the anomaly. Whether the borehole is truncated at the bit or not has a great influence on the simulation results. The borehole and mud invasion affect the apparent resistivity in all modes, but the effects of resistivity of surrounding formation and thickness of the target formation are only corrected for lateral resistivity measurement.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61771067,61631014,61471051,and 61401036)the Youth Research and Innovation Program of Beijing University of Posts and Telecommunications,China(Grant Nos.2015RC12 and 2017RC10)
文摘The coherent-mode representation theory is firstly used to analyze lensless two-color ghost imaging. A quite complicated expression about the point-spread function（PSF） needs to be given to analyze which wavelength has a stronger affect on imaging quality when the usual integral representation theory is used to ghost imaging. Unlike this theory, the coherent-mode representation theory shows that imaging quality depends crucially on the distribution of the decomposition coefficients of the object imaged in a two-color ghost imaging. The analytical expression of the decomposition coefficients of the object is unconcerned with the wavelength of the light used in the reference arm, but has relevance with the wavelength in the object arm. In other words, imaging quality of two-color ghost imaging depends primarily on the wavelength of the light illuminating the object. Our simulation results also demonstrate this conclusion.
基金the National Natural Science Foundation of China(Grant Nos.21573040 and 21603029)the Natural Science Foundation and Science and Technology Development Planning of Jilin Province(20150204086GX and20170520148JH)+3 种基金the Fundamental Research Funds for the Central Universities(2412016KJ007 and 2412016KJ020)the China Postdoctoral Science Foundation(2016M600224)the Jilin Provincial Research Foundation for Basic Research(20160519012JH)Jilin Provincial Key Laboratory of Advanced Energy Materials(Northeast Normal University)
文摘A facile strategy to fabricate gold nanorod@polyacrylic acid/calcium phosphate(Au NR@-PAA/Ca P) yolk–shell nanoparticles(NPs) composed with a PAA/Ca P shell and an Au NR yolk is reported. The asobtained Au NR@PAA/Ca P yolk–shell NPs possess ultrahigh doxorubicin(DOX) loading capability(1 mg DOX/mg NPs), superior photothermal conversion property(26%)and p H/near-infrared(NIR) dual-responsive drug delivery performance. The released DOX continuously increased due to the damage of the Ca P shell at low p H values. When the DOX-loaded Au NR@PAA/Ca P yolk–shell NPs wereexposed to NIR irradiation, a burst-like drug release occurs owing to the heat produced by the Au NRs. Furthermore,Au NR@PAA/Ca P yolk–shell NPs are successfully employed for synergic dual-mode X-ray computed tomography/photoacoustic imaging and chemo-photothermal cancer therapy. Therefore, this work brings new insights for the synthesis of multifunctional nanomaterials and extends theranostic applications.
基金Supported by Italian Ministry of Instruction and Research,No.DM18604-Bando Laboratori-DD MIUR 14.5.2005 n.602/Ric/2005FESR PO Apulia Region 2007-2013-Action 1.2.4,No.3Q5AX31the Progetto Bandiera NANOMAX ENCODER
文摘AIM: To experimentally investigate the acoustical behavior of different dual-mode nanosized contrast agents(NPCAs) for echographic medical imaging at low ultrasound(US) frequency. METHODS: We synthesized three different nanosized structures:(1) Pure silica nanospheres(SiNSs);(2) FePt-iron oxide(FePt-IO)-coated SiNSs; and(3) IOcoated SiNSs, employing three different diameter of SiNS-core(160, 330 and 660 nm). Tissue mimicking phantoms made of agarose gel solution containing 5 mg of different NPCAs in 2 mL-Eppendorf tubes, were insonified by a commercial echographic system at three different low US pulse values(2.5, 3.5 and 4.5 MHz). The raw radiofrequency signal, backscattered from each considered NPCA containing sample, has been processed in order to calculate the US average backscatter intensity and compare the acoustic behavior of the different NPCA types. RESULTS: The highest US contrast was exhibited by pure SiNSs; FePt-IO-coated SiNSs acoustical behavior followed a similar trend of pure SiNSs with a slight difference in terms of brightness values. The acoustic response of the examined NPCAs resulted function of both SiNS diameter and US frequency. Specifically, higher US frequencies determined higher value of the backscatter for a given SiNS diameter. Frequencydependent enhancement was marked for pure SiNSs and became less remarkable for FePt-IO-coated SiNSs, whereas IO-coated SiNSs resulted almost unaffected by such frequency variations. Pure and FePt-IO-coated SiNSs evidenced an image backscatter increasing with the diameter up to 330 nm. Conversely, among the types of NPCA tested, IO-coated SiNSs showed the lowest acoustical response for each synthesized diameter and employed US frequency, although a diameter-dependent raising trend was evidenced. CONCLUSION: The US characterization of magnetically covered SiNS shows that FePt-IO, rather than IO, was the best magnetic coating for realizing NPCAs suitable for dual mode imaging of deep organs, combining US and magnetic resonance imaging.
基金Supported by the Fundamental Research Funds for the Central Universities(2014212020205)
文摘Sediment incipient velocity （SIV） is a vital parameter for sediment research and river dynamics. This paper describes a novel method of estimating SIV based on the known flow velocity in the movable-bed model experiment. In this method, we use B-mode ultrasound imaging technique to get video images of moving particles and topography under water. By statistical analysis of video images, the relationship between the average number of imaging particles and flow velocity is obtained. The relationship between the change rate of average number and flow velocity is analyzed in sediment incipient process. These relationships are used to estimate the SIV. Lastly, the changed topography verifies the estimated velocity. The results show there is a sudden change in these relationships which can be used to estimate the SIV with high resolution by using a B-mode ultrasound device. The estimated SIV of plastic sands （particle size is about 0.25 mm） is 3.64 cm · s^-1 and the estimated SIV of natural sands （particle size is about 0.25 mm） is 5.47 cm · s^-1in the same condition.
文摘After drawbacks and shortages of using conventional kV or MV imaging mode were analyzed, this study proposes a new position verification mode with using the energy larger than 15 MeV or nominal accelerating potential greater than 25 MV X-Ray. The new position verification mode is named HMV imaging mode. Along with the comparison of theoretical analyses, phantom experiments and clinical results to the original imaging modes, this report is going to demonstrate the HMV imaging mode is superior to traditional kV and MV imaging modes. This report first theoretically analyzed three main effects of X-ray interacting with medium by numerous equations and compared their mass attenuation coefficient with different types of tissue. X-ray irradiated on a “Catphan 500” cylinder phantom with different energies to verify these theoretical results. Furthermore, based on phantom experiments’ results, we have done numerous clinical trials and comparisons with patient’s clinical results. The theoretical and experimental results illustrate that the scanned images from HMV mode have a good quality and have ability to identify different tissue components clearly. HMV imaging mode overcomes drawbacks of position verification from both kV and MV level imaging mode as well as keeping advantages of kV and MV imaging mode. The result indicates that HMV is a good position verification mode in radiotherapy.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10904015, 11074036, and 11004030)
文摘First we present a theoretical analysis of classical noise in ghost imaging system based on the coherent-mode representation theory. The classical noise depends crucially on the distribution of the eigenvalues of the coherent-mode representation of the source and the decomposition coefficients of the object imaged. We show that both decreasing the distribution of the decomposition coefficients and increasing the distribution of the eigenvalues can lead to the decrease of classical noise.
基金The Natural Science Foundation of Jiangsu Province(No.BK2012559)Qing Lan Project of Jiangsu Province
文摘Based on an avalanche photodiode（ APD） detecting array working in Geiger mode（ GM-APD）, a high-performance infrared sensor readout integrated circuit（ ROIC） used for infrared 3D（ three-dimensional） imaging is proposed. The system mainly consists of three functional modules, including active quenching circuit（ AQC）, time-to-digital converter（ TDC） circuit and other timing controller circuit. Each AQC and TDC circuit together constitutes the pixel circuit. Under the cooperation with other modules, the current signal generated by the GM-APD sensor is detected by the AQC, and the photon time-of-flight（ TOF） is measured and converted to a digital signal output to achieve a better noise suppression and a higher detection sensitivity by the TDC. The ROIC circuit is fabricated by the CSMC 0. 5 μm standard CMOS technology. The array size is 8 × 8, and the center distance of two adjacent cells is 100μm. The measurement results of the chip showthat the performance of the circuit is good, and the chip can achieve 1 ns time resolution with a 250 MHz reference clock, and the circuit can be used in the array structure of the infrared detection system or focal plane array（ FPA）.
文摘Due to the data acquired by most optical earth observation satellite such as IKONOS, QuickBird-2 and GF-1 consist of a panchromatic image with high spatial resolution and multiple multispectral images with low spatial resolution. Many image fusion techniques have been developed to produce high resolution multispectral image. Considering panchromatic image and multispectral images contain the same spatial information with different accuracy, using the least square theory could estimate optimal spatial information. Compared with previous spatial details injection mode, this mode is more accurate and robust. In this paper, an image fusion method using Bidimensional Empirical Mode Decomposition (BEMD) and the least square theory is proposed to merge multispectral images and panchromatic image. After multi-spectral images were transformed from RGB space into IHS space, next I component and Panchromatic are decomposed by BEMD, then using the least squares theory to evaluate optimal spatial information and inject spatial information, finally completing fusion through inverse BEMD and inverse intensity-hue-saturation transform. Two data sets are used to evaluate the proposed fusion method, GF-1 images and QuickBird-2 images. The fusion images were evaluated visually and statistically. The evaluation results show the method proposed in this paper achieves the best performance compared with the conventional method.
基金Supported by the National Natural Science Foundation of China:Neuroimaging Study of Transcutaneous Auricular Vagus Nerve Stimulation in Treatment of Refractory Depression Based on Emotion Cognition Circuit(No.81774433)Prediction of Curative Effect of Transcutaneous Auricular Vagus Nerve Stimulation on Depression based on MRI and Machine Learning Technology(No.82174282)Scientific and Technological Innovation Project of China Academy of Chinese Medical Sciences:Study on the Mechanism and Efficacy Prediction of Transcutaneous Auricular Vagus Nerve Stimulation in the Treatment of Depression based on MRI Brain Imaging and Intestinal Flora(No.CI2021A03316)。
文摘OBJECTIVE:To examine the brain effects of transcutaneous auricular vagus nerve stimulation(ta VNS)treatment of recurrent depression based on the functional brain network by using resting-state functional magnetic resonance imaging(f MRI).METHODS:Twenty-five patients with recurrent depression were enrolled in a single-arm trial of ta VNS treatment for eight weeks.Clinical results were assessed by 17-item Hamilton Depression Rating Scale(HAMD-17),Hamilton Anxiety Scale(HAMA),Self-Rating Depression Scale(SDS),Self-Rating Anxiety Scale(SAS),and Ruminative Response Scale(RRS)scales.Resting-state f MRI was conducted to explore the brain effects before and after treatment.For the functional connectivity(FC)analysis,the bilateral nucleus accumbens,globus pallidus,caudate,and putamen were selected as seeds.Finally,the correlations between FC and the clinical scale scores were calculated.RESULTS:After treatment,the patients’scores of HAMD-17,HAMA,SDS,SAS,and RRS were significantly decreased(P<0.05).FC was considerably decreased between the following areas:the left globus pallidus and the right postcentral gyrus,inferior parietal gyrus,the right globus pallidus and the left superior marginal gyrus,postcentral gyrus,superior parietal gyrus,inferior parietal gyrus,precuneus,right postcentral gyrus,superior marginal gyrus,and inferior parietal gyrus,between the right caudate and the right lingual gyrus,calcarine gyrus,and cerebellum.Changes in FC between the right globus pallidus and the left inferior parietal gyrus,between the left globus pallidus and the right postcentral gyrus were negatively correlated with HAMD-17 scores change before and after treatment(before,P=0.003,r=-0.6;after,P=0.009,r=-0.54).The change of FC between the right globus pallidus and the right postcentral gyrus was negatively correlated with the change in SDS(P=0.026,r=-0.474).The difference in FC between the right globus pallidus and the right postcentral gyrus was negatively correlated with the change in SAS(P=0.016,r=-0.513).CONCLUSIONS:Recurrent depression could be effectively treated with ta VNS.The changes in brain FC involving the basal ganglia,default mode,and sensorimotor networks provide insight into the effects of ta VNS treatment on recurrent depression.
基金supported in part by the National Key R&D Program of China (No. 2017YFE0301205)National Natural Science Foundation of China (Nos. 11975271, 12075284 and 12075283)partly supported by Chinese Academy of President’s International Fellowship Initiative (Grant No. 2021 VMA0022)。
文摘A high-speed vacuum ultraviolet(VUV) imaging system has been developed on the Experimental Advanced Superconducting Tokamak(EAST), which selectively measures line emission with a central wavelength of 13.5 nm(CVI, n=4–2). It has been employed to study edge/pedestal plasma behavior in EAST. Edge localized mode(ELM)-induced filament structures have been captured by the VUV imaging system during the ELMy high confinement mode discharge with both high temporal and spatial resolutions. The typical features(i.e.poloidal width and pitch angle) of the observed filaments are quantitatively characterized based on the VUV imaging data, and the dependence of these features on basic plasma parameters is analyzed. It is found that the poloidal width is proportional to the heating power, and the pitch angle is inversely proportional to the edge safety factor q.95 The scatterplot shows a positive trend between the poloidal width and the ELM amplitude defined by the relative change in stored energy. These results are based on the condition that the perturbation induced by ELMs is confined to a narrow layer in the plasma.
文摘Empirical mode decomposition (EMD) is a data-driven and multi-scale transform theory, and it is a nonlinear and non-stationary signal processing theory. But each EMD decomposition theory has its advantages and disadvantages. Synthetic aperture radar (SAR) imaging is an important remote sensing technique to obtain the change information, and SAR image data belongs to non-stationary signal. So EMD is very suitable for SAR image processing. There are two kinds of typical EMD theories, which are the ensemble empirical mode decomposition (EEMD) and bidimensional empirical mode decomposition (BEMD). Based on the deep study of the two methods, this paper proposed a new SAR image change detection algorithm, which is called the FCD-EMD algorithm, i.e. fusion change detection based on EMD. So FCD-EMD algorithm can obtain more accurate information, which not only includes the directional information obtained by EEMD, but also can contain the spatial information got by BEMD. The main contribution of the FCD-EMD algorithm is to fuse the detail information in different directions, so that the results obtained are more accurate than the individual method. On the other hand, it can reduce the influence of speckle noise in SAR images by feature selections. The actual SAR image data verify the algorithm proposed in this paper and good experimental results are obtained, which show that the new method is feasible.
基金The National Science and Technology Support Project under contract No.2014BAB12B02the Natural Science Foundation of Liaoning Province under contract No.201602042
文摘Oil spills pose a major threat to ocean ecosystems and their health. Synthetic aperture radar（SAR） sensors can detect oil spills on the sea surface. These oil spills appear as dark spots in SAR images. However, dark formations can be caused by a number of phenomena. It is aimed to distinguishing oil spills or look-alike objects. A novel method based on a bidimensional empirical mode decomposition is proposed. The selected dark formations are first decomposed into several bidimensional intrinsic mode functions and the residue. Subsequently, 64 dimension feature sets are calculated using the Hilbert spectral analysis and five new features are extracted with a relief algorithm. Mahalanobis distances are then used for classification. Three data sets containing oil spills or look-alikes are used to test the accuracy rate of the method. The accuracy rate is more than 90%. The experimental results demonstrate that the novel method can detect oil spills validly and accurately.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.11174280,60990323,and 60990320)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No.YYYJ-1123)
文摘In this paper a millimeter-wave （MMW） squint indirect holographic method is presented, which is suitable for imaging with a large field-of-view. The proposed system employs the squint operation mode to remove the background and twin- image interferences, which achieves a similar effect to off-axis holography but leaves out the large-aperture quasi-optical component. The translational scanning manner enables a large field of view and ensures the image uniformity, which is difficult to realize in off-axis holography. In addition, a corresponding imaging algorithm for the presented scheme is developed to reconstruct the image from the recorded hologram. Some imaging results on typical objects, obtained with electromagnetic simulation, demonstrate good performance of the imaging scheme and validate the effectiveness of the image reconstruction algorithm.
基金supported by the National Key R&D Program of China(Grant Nos.2021YFA1400602 and 2023YFA1407600)the National Natural Science Foundation of China(Grant Nos.91850206,12374294,and 12004284)the Chenguang Program of Shanghai(Grant No.21CGA22).
文摘Magnetic resonance imaging(MRI),as a noninvasive and powerful method in modern diagnostics,has been advancing in leaps and bounds.Conventional methods to improve MRI based on increasing the static magnetic field strength are restricted by safety concerns,cost issues,and the impact on patient experience;as such,innovative approaches are required.It has been suggested that metamaterials featuring subwavelength unit cells can be used to take full control of electromagnetic waves and redistribute electromagnetic fields,achieve abundant counterintuitive phenomena,and construct versatile devices.Recently,metamaterials with exotic effective electromagnetic parameters,peculiar dispersion relations,or tailored field distribution of resonant modes have shown promising capabilities in MRI.Herein,we outline the principle of the MRI process,review recent advances in enhancing MRI by employing the unique physical mechanisms of metamaterials,and demystify ways in which metamaterial designs could improve MRI,such as by enhancing the imaging quality,reducing the scanning time,alleviating field inhomogeneities,and increasing patient safety.We conclude by providing our vision for the future of improving MRI with metamaterials.
