Imaging Scheme Research Articles

Privacy protection scheme for batch medical images based on double memristor cellular neural network

Privacy protection scheme for batch medical images based on double memristor cellular neural network

Reciprocity-assisted ghost imaging through dynamic random media.

Ghost imaging enables the imaging of an object using intensity correlations between a single-pixel detector placed behind the object and a camera that records the light that did not interact with the object. The object and the camera are often placed at conjugate planes to ensure correlated illumination patterns. Here, we show how the combined effect of optical reciprocity and the memory effect in a random medium gives rise to correlations between two beams that traverse the random medium in opposite directions. In a proof-of-principle experiment, we observe such correlations when the beams traverse two thin diffusers separated by a variable distance. We find that the angular width of the region over which the beams are correlated decreases as the distance between the diffusers is increased. We then utilize these correlations to demonstrate a ghost imaging scheme in which the object and camera are placed at opposite ends of the random medium and illuminated by counter-propagating beams that can potentially be emitted by two different sources.

Mid-infrared edge-enhanced imaging via angle-selective nonlinear filtering.

We propose a novel, to the best of our knowledge, scheme for mid-infrared upconversion imaging with high tunability between bright-field and edge-enhanced modalities. The involved engineering of the nonlinear process favors shaping the optical transfer function of the imaging system. Consequently, a nonlinear angle-selective filter can be configured to perform an all-optical Fourier processing of the image, which highly depends on phase-matching parameters. We numerically demonstrate the ability to switch modalities between the bright-field and edge-enhanced imaging by tuning the crystal temperature and simultaneously acquiring both information by dichromatic illumination. Notably, the achieved reconfigurability is realized without changing the imaging settings, which contrasts with previous instantiations based on pump adaptation. Therefore, the proposed architecture of upconversion imagers would pave a novel way to implement layout-compact and all-optical processing for infrared images.

Ultrafast 3D synthetic aperture imaging with Hadamard-encoded aperiodic interval codes and aperiodic sparse arrays with separate transmitters and receivers

3D synthetic aperture (SA) imaging of volumes can be obtained using sparse 2D ultrasound arrays. However, even with just 256 elements, the volumetric imaging rate can be relatively slow due to having to transmit on each element in succession. Hadamard Aperiodic Interval (HAPI) codes can be used to image the full SA dataset in one extended transmit to speed up the synthetic aperture imaging, but their long nature produces large deadzones if the same elements are used as both transmitters and receivers. In this simulation study, we use a 2D Costas sparse array with separate transmitters and receivers to remedy the deadzone problem, and use it with the HAPI-coded imaging scheme to obtain fully transmit-receive focused, wide field-of-view 3D volumes with high-resolution and high SNR at ultrafast volumetric imaging rates of more than 500 volumes per second, almost nine times faster than non-coded SA imaging with the same imaging parameters. We show similar PSF performance compared to non-coded SA, and a 26 dB improvement in SNR with order-256 HAPI codes. We also present cyst simulations showing similar contrast for the HAPI-coded SA method compared to non-coded SA in the context of no noise, and improved contrast in the context of noise.

Data Hiding Scheme for Spatial Domain Images Using Fuzzy Logic and Modulus Operation

Data Hiding Scheme for Spatial Domain Images Using Fuzzy Logic and Modulus Operation

Anomaly detection scheme for lung CT images using vector quantized variational auto-encoder with support vector data description.

This study aims to develop an anomaly-detection scheme for lesions in CT images. Our database consists of lung CT images obtained from 1500 examinees. It includes 1200 normal and 300 abnormal cases. In this study, SVDD (Support Vector Data Description) mapping the normal latent variables into a hypersphere as small as possible on the latent space is introduced to VQ-VAE (Vector Quantized-Variational Auto-Encoder). VQ-VAE with SVDD is constructed from two encoders, two decoders, and an embedding space. The first encoder compresses the input image into the latent-variable map, whereas the second encoder maps the normal latent variables into a hypersphere as small as possible. The first decoder then up-samples the mapped latent variables into a latent-variable map with the original size. The second decoder finally reconstructs the input image from the latent-variable map replaced by the embedding representations. The data of each examinee is classified as abnormal or normal based on the anomaly score defined as the combination of the difference between the input image and the reconstructed image and the distance between the latent variables and the center of the hypersphere. The area under the ROC curve for VQ-VAE with SVDD was 0.76, showing an improvement when compared with the conventional VAE (0.63, p < .001). VQ-VAE with SVDD developed in this study can yield higher anomaly-detection accuracy than the conventional VAE. The proposed method is expected to be useful for identifying examinees with lesions and reducing interpretation time in CT screening.

Multiple-Input Multiple-Output Microwave Tomographic Imaging for Distributed Photonic Radar Network

This paper deals with the imaging problem from data collected by means of a microwave photonics-based distributed radar network. The radar network is leveraged on a centralized architecture, which is composed of one central unit (CU) and two transmitting and receiving dual-band remote radar peripherals (RPs), it is capable of collecting monostatic and multistatic phase-coherent data. The imaging is herein formulated as a linear inverse scattering problem and solved in a regularized way through the truncated singular value decomposition inversion scheme. Specifically, two different imaging schemes based on an incoherent fusion of the tomographic images or a fully coherent data processing are herein developed and compared. Experimental tests carried out in a port scenario for imaging both a stationary and a moving target are reported to validate the imaging approach.

Hippocampal recording with a soft microelectrode array in a cranial window imaging scheme: a validation study

The hippocampus has a crucial role in the formation, consolidation and recall of memories as well as in navigation related processes. These functions are in the focus of neuroscience and different disciplines have contributed to this research field for decades. Two-photon imaging in awake animals is a valuable new aspect for these observations, especially when it is supported by electrophysiology. In this study, we applied high speed two-photon hippocampal imaging through a chronically implanted, soft, transparent microelectrode (STM) device incorporated into a cranial window chamber in awake mice. We monitored the impedance of the recording sites over the course of the experiments to observe long-term changes in recording quality. The large-scale ipsilateral local field potential (LFP) recordings from the dorsal hippocampus provided reliable sharp wave-ripples (SPW-Rs), multi-unit activity (MUA) and single-unit activity (SUA) for up to two months. Calcium imaging of GCaMP6f. labeled cells from the CA1 pyramidal layer under the transparent device was possible even after six months in thy1-GCaMP6f. transgenic mice. We investigated the immune response with GFAP staining after the end of the long-term experiments. Based on our results, this dedicated transparent electrode device proved to be suitable for simultaneous two-photon imaging and large-scale electrophysiological measurements in chronic experiments in mice.

Novel Statistical Analysis Schemes for Frequency-Modulated Thermal Wave Imaging for Inspection of Ship Hull Materials

Novel Statistical Analysis Schemes for Frequency-Modulated Thermal Wave Imaging for Inspection of Ship Hull Materials

CONCEPT IMAGE AND CONCEPT DEFINITION SCHEMES AS TOOLS FOR ANALYZING STUDENTS’ COMPREHENSION OF LIMIT OF A FUNCTION

This paper aims to analyze one’s understanding of limit of a function based on Concept Image and Concept Definition schemes, which can be used as powerful tools in research that have mathematical comprehension as part of their object of study. For that, we developed and applied a set of tasks involving limits of functions to students who had already been in a Calculus course. Vinner’s study about concept image and concept definition was the theoretical framework of this paper. The results obtained let us observe the plurality of interpretations about limits and other adjacent concepts, which allowed us to trace, in this paper, a reflection upon the cognitive conflicts concerning the (lack of) understanding of these concepts.

Full-Waveform Inversion Imaging of Cortical Bone Using Phased Array Tomography.

Classic ultrasound bone imaging modalities usually demand either a prior knowledge or an advanced estimation on speed of sound (SoS), which not only renders to a burdensome imaging process but also supplies a limited resolution. To overcome these drawbacks, this article proposed a frequency-domain full-waveform inversion (FDFWI) modality using phased array tomography for high-accuracy cortical bone imaging. A transmission scenario of ultrasound wave in 2-D space was presented in the frequency domain to simulate the forward wavefield propagation. Iterations in the inversion process were performed by matching the simulation wavefield to the experimental one from low to high discrete frequency points. Moreover, the association between the maximum initial frequency and the initial SoS model was explored to prevent the occurrence of cycle-skipping phenomenon, which could lead to the outcomes being trapped in local minima. The feasibility and effectiveness of the proposed imaging scheme were testified by simulation, phantom, and ex-vivo studies, with mean relative errors of cortical part being 3.18%, 8.71%, and 9.36%, respectively. It is verified that the proposed FDFWI method is an effective way for parametric imaging of cortical bone without any prior knowledge of sound speed.

An authentication scheme for color images with grayscale invariance and recoverability using image demosaicing

This paper proposes a novel recoverable authentication scheme for color images that ensures the consistency of grayscale values after embedment. In the proposed scheme, the color image is sub-sampled based on the Bayer pattern, and the most significant bits (MSBs) of the sub-sampled image are used as the recovery codes. Image blocks are divided into two categories, feasible and infeasible. Feasible blocks are utilized for embedding both authentication and recovery codes, whereas infeasible ones are only used for embedding authentication codes. In case of tampering, the authentication codes are employed to detect the tampered regions, and the undamaged recovery codes can be utilized to reconstruct the sub-sampled image. The demosaicing algorithm is applied to the sub-sampled image to obtain the demosaicked image, which is then used to recover the tampered regions. Experiments demonstrate that the proposed scheme yields an acceptable image quality even when the tampering rate is as high as 40 %.

Layer multiplexing and DNA based color image encryption

Abstract A layer multiplexing-based encrypted image scheme for DNA color images is proposed. Firstly, a memristor is added to the Sprott-B chaotic system to make it a fourth-order memristorised hyper-chaotic system. The hyperchaotic system has better pseudo-randomness. The encryption system proposed generates the initial value of the system by SHA3-256 function to achieve “One image, one secret”. The chaotic sequence is generated by a memory hyperchaotic system for encrypting the image. The encryption process includes image zero complements, image chunking, DNA encryption, layer multiplexing, DNA decryption, and improved XOR diffusion. The encrypted images are analyzed by Matlab. The pixel distribution of the encrypted image is verified to be homogeneous by pixel histogram analysis. The encryption system is tested to have good resistance to shear attacks and noise attacks. The encryption system also has a good encryption effect by information entropy test. Experiments show that the encryption system proposed has a short encryption time and decryption time.

ChiSCAT: Unsupervised Learning of Recurrent Cellular Micromotion Patterns from a Chaotic Speckle Pattern.

There is considerable evidence that action potentials are accompanied by "intrinsic optical signals", such as a nanometer-scale motion of the cell membrane. Here we present ChiSCAT, a technically simple imaging scheme that detects such signals with interferometric sensitivity. ChiSCAT combines illumination by a chaotic speckle pattern and interferometric scattering microscopy (iSCAT) to sensitively detect motion in any direction. The technique features reflective high-NA illumination, common-path suppression of vibrations, and a large field of view. This approach maximizes sensitivity to motion, but does not produce a visually interpretable image. We show that unsupervised learning based on matched filtering and motif discovery can recover underlying motion patterns and detect action potentials. We demonstrate these claims in an experiment on blebbistatin-paralyzed cardiomyocytes. ChiSCAT opens the door to action potential measurement in scattering tissue, including a living brain.

Quantum ghost imaging microscopy depth-of-field study

Quantum ghost imaging approaches have been proposed to enhance biological microscopy, for example, using 2D visible detectors to provide IR images or providing additional dimensions of spatial or spectral information. Toward the goal of making such imaging schemes practical, we compare image quality and depth-of-field between traditional images and ghost images at the same excitation levels. We measure how image quality and depth-of-field depend on the parameters of the entangled light produced using type-I spontaneous parametric down-conversion (SPDC). We use a pair of time-synchronized, photon-timing single-photon avalanche diode (SPAD) array detectors to capture two distinct microscope imaging paths simultaneously on a photon-pair-by-photon-pair basis: one in a traditional imaging pathway and the other a quantum ghost imaging pathway. We calculate the depth-of-field, resolution, contrast, and signal-to-noise ratio (SNR) through the parameter space of a β-Barium Borate (BBO) type-I bulk non-linear crystal length and angle. Our results provide a basis for choosing parameters for quantum ghost imaging with type-I SPDC sources.

Reversible data hiding in JPEG images based on improved frequency selection and mapping strategy

JPEG images have become ubiquitous in our daily lives due to their ability to strike a balance between visual quality and file size. Consequently, reversible data hiding (RDH) schemes for JPEG images have emerged. However, existing methods by modifying discrete cosine transform (DCT) coefficients still have room for improvement in terms of distortion reduction and file size preservation. This paper proposes a novel two-dimensional (2D) histogram mapping strategy for RDH in JPEG images. Firstly, the quantized DCT coefficient blocks are sorted based on the count of zero alternating current (AC) coefficients in each block. This enables the estimation of distortion in non-zero AC coefficients at different locations within the block, facilitating the selection of frequency coefficients with minimal distortion for embedding. Additionally, leveraging statistical characteristics, six mapping types with different embedding efficiency are created and the improved 2D histogram mapping method is proposed. Furthermore, The unit distortion-increase ratio (UDIR) is employed as a comprehensive evaluation metric. Extensive experiments are conducted on four representative images and two widely-used image databases to validate the proposed scheme. The results consistently demonstrate superior visual quality, minimal file size increase (FSI), and higher UDIR in comparison to state-of-the-art RDH schemes for JPEG images.

Remote sensing ghost imaging based on Hadamard modulated Gaussian array beam

A ghost imaging (GI) scheme by using Hadamard modulated Gaussian array beam (HMGAB) is proposed. Compared to traditional light sources modulated using ground glass, DMD, or SLM, HMGAB has higher emitting energy, making it advantageous for remote sensing GI. Moreover, the incoherent superposition of array sub-beams makes our scheme avoid the periodic aliasing which usually occurs in GI systems using optical phased array beam. The relationship between imaging maximum distance and target size is established and verified. In addition, GANs are used to address the issue of point-like reconstructed images caused by the spacing between array sub-beams.

Multiplexed Shortwave Infrared Imaging Highlights Anatomical Structures in Mice

AbstractMultiplexed fluorescence in vivo imaging remains challenging due to the attenuation and scattering of visible and traditional near infrared (NIR‐I, 650–950 nm) wavelengths. Fluorescence imaging using shortwave infrared (SWIR, 1000–1700 nm, a.k.a. NIR‐II) light enables deeper tissue penetration due to reduced tissue scattering as well as minimal background autofluorescence. SWIR‐emitting semiconductor quantum dots (QDs) with tunable emission peaks and optical stability are powerful contrast agents, yet few imaging demonstrations exclusively use SWIR emission beyond two‐color imaging schemes. In this study, we engineered three high quality lead sulfide/cadmium sulfide (PbS/CdS) core/shell QDs with distinct SWIR emission peaks ranging from 1100–1550 nm for simultaneous three‐color imaging in mice. We first use the exceptional photostability of QDs to non‐invasively track lymphatic drainage with longitudinal imaging, highlighting the detailed networks of lymphatic vessels with widefield imaging over a 2 hr period. We then perform multiplexed imaging with all three QDs to distinctly visualize the lymphatic system and spatially overlapping vasculature networks, including clearly distinguishing the liver and spleen. This work establishes optimized SWIR QDs for next generation multiplexed and longitudinal preclinical imaging, unlocking numerous opportunities for preclinical studies of disease progression, drug biodistribution, and cell trafficking dynamics in living organisms.

Self-healing spiral phase contrast imaging

Spiral phase contrast imaging alleviates the information load by extracting the geometric features of objects and is one of the most representative branches of instant imaging processing. The self-healing capacity of edge detectors can enhance their robustness to obstacles in practical applications. Here, a self-healing spiral phase contrast imaging scheme is proposed and experimentally demonstrated by a liquid crystal edge detector combining a spiral phase, an axicon phase, and a lens phase. The spiral phase is encoded into a liquid crystal by photopatterning. Self-healing contrast imaging is characterized by a series of edge images of both high-contrast amplitude-type and low-contrast phase-type objects. This work extends the self-healing capacity of these detectors to instant imaging processing and paves the way for optical applications with self-healing features.

A novel chaotic system with one absolute term: Stability, ultimate boundedness, and image encryption

This paper proposes a system with an absolute term, exhibiting chaos. The system's dynamics are examined by computation of bifurcation and Lyapunov exponents. This system has a countable finite coexisting nested attractors. The features of the system make it suitable for secure applications. The system is combined with the 4×4 Toeplitz matrix to generate an encryption algorithm, validated using security and performance analysis. Combining the proposed system and the Toeplitz matrix improves the pixel distribution's randomness, significantly increasing security. The test results showed that the suggested image scheme is very secure and impervious to differential, statistical analysis, and other types of attacks. Furthermore, the majority assessment shows that the presented approach performs noticeably better than previous techniques.