Visibility enhancement in two-dimensional lensless ghost imaging with true thermal light

We report an experimental demonstration of two-dimensional（2D） lensless ghost imaging with true thermal light. An electrodeless discharge lamp with a higher light intensity than the hollow cathode lamp used before is employed as a light source. The main problem encountered by the 2D lensless ghost imaging with true thermal light is that its coherence time is much shorter than the resolution time of the detection system. To overcome this difficulty we derive a method based on the relationship between the true and measured values of the second-order optical intensity correlation, by which means the visibility of the ghost image can be dramatically enhanced. This method would also be suitable for ghost imaging with natural sunlight.

Value of two-dimensional speckle tracking imaging in quantitative assessment of left ventricular function in patients with OSAS

Objective: To research the clinical application of two-dimensional speckle tracking imaging (2D-STI) in quantitative assessment of left ventricular function in patients with obstructive sleep apnea-hypopnea syndrome (OSAS). Method: From July 2016 to December 2018, 86 patients with OSAS were selected as OSAS group. According to sleep apnea hypopnea index (AHI), they were divided into mild OSAS group (24 cases), moderate OSAS group (29 cases) and severe OSAS group (33 cases). Another 50 healthy volunteers who underwent physical examination in our hospital during the same period were selected as the control group. The left ventricular function of all patients was quantitatively assessed by 2D-STI. The left ventricular function of all patients was quantitatively assessed by 2D-STI. The results of routine echocardiography and left ventricular global strain parameters of the OSAS group, the control group and the OSAS patients with different severity were compared and analyzed. Result: There were no significant differences in the levels of left ventricular ejection fraction (LVEF), left ventricular end diastolic diameter (LVEDd), left ventricular end systolic diameter (LVESd) between the two groups and OSAS patients with different severity (P>0.05). The levels of IVST, LVPW and LVMI in the OSAS group were significantly higher than those in the control group, the levels of end-diastolic interventricular septal thickness (IVS), left ventricular posterior wall thickness (LVPW), left ventricular mass index (LVMI) in the severe OSAS group were significantly higher than those in the mild and moderate OSAS group, and the levels of IVST, LVPW and LVMI in the moderate OSAS group were significantly higher than those in the mild OSAS group, there were significant differences between groups (P<0.05). The levels of GLS, GRS and GCS in the OSAS group were significantly lower than those in the control group (P<0.05). GLS, GRS and GCS levels in the severe OSAS group were significantly lower than those in the mild OSAS group and the moderate OSAS group, while the levels of global longitudinal strain (GLS), global radial strain (GRS) and global circumferential strain (GCS) in the moderate OSAS group were significantly lower than those in the mild OSAS group (P<0.05). Conclusion: The left ventricular systolic function of OSAS patients is obviously impaired. Left ventricular function in OSAS patients can be assessed timely and accurately by two-dimensional speckle tracking imaging.

Two-dimensional horizontal visibility graph analysis of human brain aging on gray matter

Characterizing the trajectory of the healthy aging brain and exploring age-related structural changes in the brain can help deepen our understanding of the mechanism of brain aging.Currently,most structural magnetic resonance imaging literature explores brain aging merely from the perspective of morphological features,which cannot fully utilize the grayscale values containing important intrinsic information about brain structure.In this study,we propose the construction of two-dimensional horizontal visibility graphs based on the pixel intensity values of the gray matter slices directly.Normalized network structure entropy(NNSE)is then introduced to quantify the overall heterogeneities of these graphs.The results demonstrate a decrease in the NNSEs of gray matter with age.Compared with the middle-aged and the elderly,the larger values of the NNSE in the younger group may indicate more homogeneous network structures,smaller differences in importance between nodes and thus a more powerful ability to tolerate intrusion.In addition,the hub nodes of different adult age groups are primarily located in the precuneus,cingulate gyrus,superior temporal gyrus,inferior temporal gyrus,parahippocampal gyrus,insula,precentral gyrus and postcentral gyrus.Our study can provide a new perspective for understanding and exploring the structural mechanism of brain aging.

Image encryption technique based on new two-dimensional fractional-order discrete chaotic map and Menezes–Vanstone elliptic curve cryptosystem

We propose a new fractional two-dimensional triangle function combination discrete chaotic map （2D-TFCDM） with the discrete fractional difference. Moreover, the chaos behaviors of the proposed map are observed and the bifurcation diagrams, the largest Lyapunov exponent plot, and the phase portraits are derived, respectively. Finally, with the secret keys generated by Menezes-Vanstone elliptic curve cryptosystem, we apply the discrete fractional map into color image encryption. After that, the image encryption algorithm is analyzed in four aspects and the result indicates that the proposed algorithm is more superior than the other algorithms.

Hydrophobic long-chain two-dimensional perovskite scintillators for underwater X-ray imaging

The underwater X-ray imaging technology development is significant to subaqueous target reconnaissance/detection/identification, subfluvial archaeology,submerged resource exploration, etc. As the core of X-ray imaging detection, the scintillator has been plagued by inherent moisture absorption and decomposition, and strict requirements for seamless packaging and waterproofing.Here, we designed a manganese-doped two-dimensional(2D) perovskite scintillator modified by hydrophobic longchain organic amine through the combination of component and doping engineering. The modified perovskites show high water repellency that can be used as an underwater X-ray scintillator. X-ray images of aquatic organisms or other objects with a high spatial resolution of10 lp·mm^(-1) at a big view field(32 mm × 32 mm) were obtained by scintillation screen. This hydrophobic perovskite scintillator based on molecular design is of great promise in underwater X-ray nondestructive testing technology development.

A color image encryption scheme based on a 2D coupled chaotic system and diagonal scrambling algorithm

A novel color image encryption scheme is developed to enhance the security of encryption without increasing the complexity. Firstly, the plain color image is decomposed into three grayscale plain images, which are converted into the frequency domain coefficient matrices(FDCM) with discrete cosine transform(DCT) operation. After that, a twodimensional(2D) coupled chaotic system is developed and used to generate one group of embedded matrices and another group of encryption matrices, respectively. The embedded matrices are integrated with the FDCM to fulfill the frequency domain encryption, and then the inverse DCT processing is implemented to recover the spatial domain signal. Eventually,under the function of the encryption matrices and the proposed diagonal scrambling algorithm, the final color ciphertext is obtained. The experimental results show that the proposed method can not only ensure efficient encryption but also satisfy various sizes of image encryption. Besides, it has better performance than other similar techniques in statistical feature analysis, such as key space, key sensitivity, anti-differential attack, information entropy, noise attack, etc.

An Analysis of Two-Dimensional Image Data Using a Grouping Estimator

Machine learning methods, one type of methods used in artificial intelligence, are now widely used to analyze two-dimensional (2D) images in various fields. In these analyses, estimating the boundary between two regions is basic but important. If the model contains stochastic factors such as random observation errors, determining the boundary is not easy. When the probability distributions are mis-specified, ordinal methods such as probit and logit maximum likelihood estimators (MLE) have large biases. The grouping estimator is a semiparametric estimator based on the grouping of data that does not require specific probability distributions. For 2D images, the grouping is simple. Monte Carlo experiments show that the grouping estimator clearly improves the probit MLE in many cases. The grouping estimator essentially makes the resolution density lower, and the present findings imply that methods using low-resolution image analyses might not be the proper ones in high-density image analyses. It is necessary to combine and compare the results of high- and low-resolution image analyses. The grouping estimator may provide theoretical justifications for such analysis.

A two-dimensional MoS_(2) array based on artificial neural network learning for high-quality imaging

As the basis of machine vision,the biomimetic image sensing devices are the eyes of artificial intelligence.In recent years,with the development of two-dimensional(2D)materials,many new optoelectronic devices are developed for their outstanding performance.However,there are still little sensing arrays based on 2D materials with high imaging quality,due to the poor uniformity of pixels caused by material defects and fabrication technique.Here,we propose a 2D MoS_(2)sensing array based on artificial neural network(ANN)learning.By equipping the MoS_(2)sensing array with a“brain”(ANN),the imaging quality can be effectively improved.In the test,the relative standard deviation(RSD)between pixels decreased from about 34.3%to 6.2%and 5.49%after adjustment by the back propagation(BP)and Elman neural networks,respectively.The peak signal to noise ratio(PSNR)and structural similarity(SSIM)of the image are improved by about 2.5 times,which realizes the re-recognition of the distorted image.This provides a feasible approach for the application of 2D sensing array by integrating ANN to achieve high quality imaging.

Evaluating the use of three-dimensional reconstruction visualization technology for precise laparoscopic resection in gastroesophageal junction cancer

BACKGROUND Laparoscopic gastrectomy for esophagogastric junction(EGJ)carcinoma enables the removal of the carcinoma at the junction between the stomach and esophagus while preserving the gastric function,thereby providing patients with better treatment outcomes and quality of life.Nonetheless,this surgical technique also presents some challenges and limitations.Therefore,three-dimensional reconstruction visualization technology(3D RVT)has been introduced into the procedure,providing doctors with more comprehensive and intuitive anatomical information that helps with surgical planning,navigation,and outcome evaluation.AIM To discuss the application and advantages of 3D RVT in precise laparoscopic resection of EGJ carcinomas.METHODS Data were obtained from the electronic or paper-based medical records at The First Affiliated Hospital of Hebei North University from January 2020 to June 2022.A total of 120 patients diagnosed with EGJ carcinoma were included in the study.Of these,68 underwent laparoscopic resection after computed tomography(CT)-enhanced scanning and were categorized into the 2D group,whereas 52 underwent laparoscopic resection after CT-enhanced scanning and 3D RVT and were categorized into the 3D group.This study had two outcome measures:the deviation between tumor-related factors(such as maximum tumor diameter and infiltration length)in 3D RVT and clinical reality,and surgical outcome indicators(such as operative time,intraoperative blood loss,number of lymph node dissections,R0 resection rate,postoperative hospital stay,postoperative gas discharge time,drainage tube removal time,and related complications)between the 2D and 3D groups.RESULTS Among patients included in the 3D group,27 had a maximum tumor diameter of less than 3 cm,whereas 25 had a diameter of 3 cm or more.In actual surgical observations,24 had a diameter of less than 3 cm,whereas 28 had a diameter of 3 cm or more.The findings were consistent between the two methods(χ^(2)=0.346,P=0.556),with a kappa consistency coefficient of 0.808.With respect to infiltration length,in the 3D group,23 patients had a length of less than 5 cm,whereas 29 had a length of 5 cm or more.In actual surgical observations,20 cases had a length of less than 5 cm,whereas 32 had a length of 5 cm or more.The findings were consistent between the two methods(χ^(2)=0.357,P=0.550),with a kappa consistency coefficient of 0.486.Pearson correlation analysis showed that the maximum tumor diameter and infiltration length measured using 3D RVT were positively correlated with clinical observations during surgery(r=0.814 and 0.490,both P<0.05).The 3D group had a shorter operative time(157.02±8.38 vs 183.16±23.87),less intraoperative blood loss(83.65±14.22 vs 110.94±22.05),and higher number of lymph node dissections(28.98±2.82 vs 23.56±2.77)and R0 resection rate(80.77%vs 61.64%)than the 2D group.Furthermore,the 3D group had shorter hospital stay[8(8,9)vs 13(14,16)],time to gas passage[3(3,4)vs 4(5,5)],and drainage tube removal time[4(4,5)vs 6(6,7)]than the 2D group.The complication rate was lower in the 3D group(11.54%)than in the 2D group(26.47%)(χ^(2)=4.106,P<0.05).CONCLUSION Using 3D RVT,doctors can gain a more comprehensive and intuitive understanding of the anatomy and related lesions of EGJ carcinomas,thus enabling more accurate surgical planning.

A reliable algorithm for image matching based on SIFT

A novel algorithm is presented to make the results of image matching more reliable and accurate based on SIFT (Scale Invariant Feature Transform). SIFT algorithm has been identified as the most resistant matching algorithm to common image deformations; however, if there are similar regions in images, SIFT algorithm still generates some analogical descriptors and provides many mismatches. This paper examines the local image descriptor used by SIFT and presents a new algorithm by integrating SIFT with two-dimensional moment invariants and disparity gradient to improve the matching results. In the new algorithm, decision tree is used, and the whole matching process is divided into three levels with different primitives. Matching points are considered as correct ones only when they satisfy all the three similarity measurements. Experiment results demonstrate that the new approach is more reliable and accurate.

Photoluminescent two-dimensional SiC quantum dots for cellular imaging and transport

Two-dimensional （2D） ultrathin SiC has received intense attention due to its broad band gap and resistance to large mechanical deformation and external chemical corrosion. However, the synthesis and application of ultrasmall 2D SiC quantum dots （QDs） has not been explored. Herein, we synthesize a type of monolayered 2D SiC QDs with advanced photoluminescence （PL） properties via a facile hydrothermal route. Their average size and thickness can be easily adjusted by altering the reaction time. The ultrasmall 2D SiC QDs exhibit a long fluorescence lifetime of 2.59 ps due to efficient quantum confinement. The applications of SiC QDs are demonstrated through labeling A549, HeLa, and NHDF cells and delivering agents for intracellular low-abundant microRNA （miRNA） detection. This advance in preparing photoluminescent SiC QDs is of great significance for broadening their potential in biomedical and optical applications.

Light trapping enhanced broadband photodetection and imaging based on MoSe_(2)/pyramid Si vdW heterojunction

Two-dimensional(2D)layered materials have been considered promising candidates for next-generation optoelectronics.However,the performance of 2D photodetectors still has much room for improvement due to weak light absorption of planar 2D materials and lack of high-quality heterojunction preparation technology.Notably,2D materials integrating with mature bulk semiconductors are a promising pathway to overcome this limitation and promote the practical application on optoelectronics.In this work,we present the patterned assembly of MoSe_(2)/pyramid Si mixed-dimensional van der Waals(vdW)heterojunction arrays for broadband photodetection and imaging.Benefited from the light trapping effect induced enhanced optical absorption and high-quality vdW heterojunction,the photodetector demonstrates a wide spectral response range from 265 to 1550 nm,large responsivity up to 0.67 A·W^(-1),high specific detectivity of 1.84×10^(13)Jones,and ultrafast response time of 0.34/5.6μs at 0 V.Moreover,the photodetector array exhibits outstanding broadband image sensing capability.This study offers a novel development route for high-performance and broadband photodetector array by MoSe_(2)/pyramid Si mixed-dimensional heterojunction.

Bi_(2)O_(2)Se nanoplates for broadband photodetector and full-color imaging applications

Broadband light detection and sensing are widely applied in modern technology.As a promising candidate for next-generation two-dimensional(2D)optoelectronic material,bismuth oxyselenide(Bi_(2)O_(2)Se)nanoplates exhibit many prospects in the application of visible light detection due to their peculiar properties.In this work,we report the photodetection performance of single-crystal 2D Bi_(2)O_(2)Se nanoplates grown on SiO_(2)based on a ternary-alloy growth model by utilizing chemical vapor deposition(CVD).The Bi_(2)O_(2)Se nanoplates were found to have an even and uniform square shape with side lengths up to 15μm and an approximate thickness of 15 nm.A visible-light photodetector was fabricated based on a CVD-grown Bi_(2)O_(2)Se nanoplate,and characterized by a set of illumination experiments using a 400 nm laser at temperatures ranging from 77 to 370 K.The device exhibited superior performance at the temperature of 77 K,with a responsivity of 523 A/W,a specific detectivity of 1.37×10^(11)Jones,a response time of 0.2175 ms,an external quantum efficiency of 162,119.44%,resulting in high-quality and fullcolor imaging in the visible spectrum.These results indicate that the single-crystalline Bi_(2)O_(2)Se nanoplates have excellent potential in broadband photodetection and non-cryogenic imaging.

Two-dimensional pixel image lag simulation and optimization in a 4-T CMOS image sensor

Pixel image lag in a 4-T CMOS image sensor is analyzed and simulated in a two-dimensional model.Strategies of reducing image lag are discussed from transfer gate channel threshold voltage doping adjustment,PPD N-type doping dose/implant tilt adjustment and transfer gate operation voltage adjustment for signal electron transfer.With the computer analysis tool ISE-TCAD,simulation results show that minimum image lag can be obtained at a pinned photodiode n-type doping dose of 7.0×10^12 cm^-2,an implant tilt of -2°,a transfer gate channel doping dose of 3.0×10^12 cm^-2 and an operation voltage of 3.4 V.The conclusions of this theoretical analysis can be a guideline for pixel design to improve the performance of 4-T CMOS image sensors.

High-performance photodetectors based on two-dimensional perovskite crystals with alternating interlayer cations

Organic-inorganic halide perovskite,as a low-cost,solution-processable material with remarkable optoelectronic properties,is ideal candidate to fabricate high-performance photodetectors and is expected to significantly reduce device costs.Compared to the common Dion-Jacobson and Ruddlesden-Popper two-dimensional(2D)layered hybrid perovskite compounds,the perovskites with alternating cations in the interlayer(ACI)phase show higher crystal symmetry and narrower optical bandgaps,which exhibit great potential for excellent photodetection performance.Herein,we report a high-performance photodetector based on the 2D bilayered hybrid lead halide perovskite single crystal with the ACI phase(GAMA_(2)Pb_(2)I_(7);GA=C(NH_(2))_(3)and MA=CH_(3)NH_(3)).The single-crystal photodetector exhibits high photoresponsivity of 1.56,2.54,and 2.60 A/W for incident light wavelengths of 405,532,and 635 nm under 9.82 nW,respectively,together with the correspondingly high detectivity values of 1.86×10^(12),3.04×10^(12),and 3.11×10^(12)Jones under the same operating conditions.Meanwhile,a high-resolution imaging sensor is built based on the GAMA_(2)Pb_(2)I_(7)single-crystal photodetector,confirming the high stability and photosensitivity of the imaging system.These results show that the 2D hybrid lead halide perovskites with alternating interlayer cations are promising for high-performance visible light photodetectors and imaging systems.

Hierarchical MPS-Based Three-Dimensional Geological Structure Reconstruction with Two-Dimensional Image(s)

Multiple-point statistics(MPS)is a useful approach to reconstruct three-dimensional models in the macroscopic or microscopic field.Extracting spatial features for three-dimensional reconstruction from two-dimensional training images(TIs),and characterizing non-stationary features with directional ductility are two key issues in MPS simulation.This study presents a step-wise MPS-based three-dimensional structures reconstruction algorithm with the sequential process and hierarchical strategy based on two-dimensional images.An extension method is proposed to construct three-dimensional TIs.With a sequential simulation process,an initial guess at the coarsest scale is simulated,in which hierarchical strategy is used according to the characteristics of TIs.To obtain a more refined realization,an expectation-maximization like iterative process with global optimization is implemented.A concrete example of chondrite micro-structure simulation,in which one scanning electron microscopy(SEM)image of the Heyetang meteorite is used as TI,shows that the presented algorithm can simulate complex non-stationary structures.

Recent advances on two-dimensional metal halide perovskite x-ray detectors

In recent years,two-dimensional metal halide perovskites(MHPs)have attracted increased attention for radiation detection and imaging.Their detection efficiencies are almost comparable to three-dimensional(3D)perovskites.Meanwhile,they demonstrate superior stability to 3D perovskites.The pursuit of high-quality,phase-pure and lead-free two-dimensional MHP materials and large-area fabrication capability for x-ray detectors are among the research hotspots.In this review,we first give a brief introduction of the crystallographic structure,optoelectronic characteristics and preparation methods of high-quality two-dimensional perovskites.In addition,we overview the general working principles of direct and indirect x-ray detection processes and the corresponding performance metrics from the perspective of detection and imaging.Furthermore,we provide a comprehensive discussion on the recent advances in 2D perovskite x-ray detectors and imaging devices.Finally,we pinpoint several major obstacles of 2D x-ray detectors that should be overcome in the near future.

Real-time SERS monitoring anticancer drug release along with SERS/MR imaging for pH-sensitive chemo-phototherapy

In situ and real-time monitoring of responsive drug release is critical for the assessment of pharmacodynamics in chemotherapy.In this study,a novel pH-responsive nanosystem is proposed for real-time monitoring of drug release and chemo-phototherapy by surface-enhanced Raman spectroscopy(SERS).The Fe3O4@Au@Ag nanoparticles(NPs)deposited graphene oxide(GO)nanocomposites with a high SERS activity and stability are synthesized and labeled with a Raman reporter 4-mercaptophenylboronic acid(4-MPBA)to form SERS probes(GO-Fe3O4@Au@Ag-MPBA).Furthermore,doxorubicin(DOX)is attached to SERS probes through a pH-responsive linker boronic ester(GO-Fe3O4@Au@Ag-MPBA-DOX),accompanying the 4-MPBA signal change in SERS.After the entry into tumor,the breakage of boronic ester in the acidic environment gives rise to the release of DOX and the recovery of 4-MPBA SERS signal.Thus,the DOX dynamic release can be monitored by the real-time changes of 4-MPBA SERS spectra.Additionally,the strong T2 magnetic resonance(MR)signal and NIR photothermal transduction efficiency of the nanocomposites make it available for MR imaging and photothermal therapy(PTT).Altogether,this GO-Fe3O4@Au@Ag-MPBA-DOX can simultaneously fulfill the synergistic combination of cancer cell targeting,pH-sensitive drug release,SERS-traceable detection and MR imaging,endowing it great potential for SERS/MR imaging-guided efficient chemo-phototherapy on cancer treatment.

三维斑点追踪成像技术评价乳腺癌患者接受吡柔比星化疗后右心室心肌力学特性改变

目的应用三维斑点追踪成像(3D-STI)评价乳腺癌化疗后右室心肌力学特性。方法选择术后接受吡柔比星化疗的乳腺癌36例,采用3D-STI观察化疗前及化疗第2周期、第4周期、第6周期末(下简称C2、C4、C6)右室心肌力学改变,检测血hs-c Tn I、NT-pro BNP水平,31例在C6进行^(99m)Tc-MIBI和^(18)F-FDG核素心肌灌注/代谢显像。测量参数:RV-V、FAC、TAPSE及S'、LV-V和LV-EF;RVGLS、RVGCS、RVGRS及RVGAS,根据核素显像评判心肌灌注和存活。结果 (1)与化疗前相比,C2时RVGLS明显降低,C4时RVGLS、RVGAS均明显降低(P<0.05),且C6时进一步下降,与药物剂量累计有关。TAPSE、hs-c Tn I水平及RV-FAC下降程度不同患者的RVGLS、RVGAS显著不同(P<0.05);(2)RVGLS、RVGAS与FAC,TAPSE,S'存在相关性(r=0.37,0.26;0.43,0.51;0.21,0.36;P<0.01),RVGAS、RVGLS判定RV-FAC下降>5%的敏感度和特异度高;(3)核素显像:17例右室心肌灌注正常,14例右室出现灌注异常但18F-FDG显示为存活心肌节段,且后者的RVGLS、RVGAS较前者显著减小;hs-c Tn I明显增高(P<0.05)。ROC曲线显示:RVGLS绝对值小于18.2%判断RV受损的敏感度92.9%,特异度88.2%,曲线下面积0.87;RVGAS绝对值小于26.8%判断RV受损的敏感度94.8%,特异度86.6%,曲线下面积0.86。结论 3D-STI可为评判乳腺癌接受吡柔比星化疗时右室心肌力学改变提供早期、可靠的新方法。

二维斑点追踪成像技术评价左心室不同部位心肌梗死患者右心室心肌功能

目的探讨二维斑点追踪成像技术(STI)评价左心室不同部位心肌梗死对右心室心肌功能的影响。方法收集诊断为急性心肌梗死(AMI)并接受经皮冠状动脉支架植入术的52例患者(AMI组),结合心电图、室壁运动评分指数(WMSI)及冠状动脉造影结果,分为下后壁心肌梗死亚组(A组,n=26)和非下后壁心肌梗死亚组(B组,n=26)。另选取26名健康志愿者作为对照组。对3组行超声心动图检查,采用STI技术进行评价,比较左、右心室心肌功能。结果与对照组比较,B组右心室纵向峰值应变(RV-LS)、右心室面积变化率(RVFAC)、左心室纵向峰值应变(LV-LS)、室间隔纵向峰值应变(Sep-LS)、左心室射血分数(LVEF)减小(P均<0.05),WMSI增大(P<0.05);与A组比较,B组RV-LS、RVFAC、LV-LS、Sep-LS减小(P均<0.05),二尖瓣舒张早期血流速度与二尖瓣瓣环舒张早期运动速度的比值增大(P<0.05)。RV-LS与LV-LS、Sep-LS和LVEF均呈正相关(r=0.48、0.55、0.39,P均<0.05)。结论非下后壁心肌梗死患者右心室心肌收缩功能减低,且右心室心肌收缩功能主要受室间隔心肌收缩功能的影响。