Improve Image Contrast Research Articles

Simulation of Single Grid-based Phase-contrast Digital Tomosynthesis (PC-DTS)

Digital tomosynthesis (DTS) is a geometric tomography technique by a limited-angle scan which has been popularly used in both medical and industrial X-ray imaging applications. However, conventional DTS remains limited by low contrast especially in imaging samples of low atomic number Z such as breast and cartilage tissues. In this work, we applied the recently proposed phase-contrast imaging (PCI) technique, the so-called single grid-based PCI, to DTS in attempt to overcome this limitation. PCI has superior soft-tissue imaging capability while DTS has improved image contrast. Combining the two techniques can therefore considerably improve the X-ray imaging performance. We developed a useful simulation platform for single grid-based phase-contrast DTS reconstruction and performed a systematic simulation using a three-dimensional (3D) numerical breast phantom. In the simulation, an X-ray grid having a lead strip density of 200 lines/inch was used and the DTS scan comprised 41 projections within an angle range of θ = ±40° at an X-ray energy of 25 keV. We successfully reconstructed DTS images of much improved contrast, compared to conventional DTS images, which demonstrates the viability of the proposed approach.

PERBAIKAN KONTRAS CITRA MENGGUNAKAN TEKNIK BRIGHTNESS ADJUSTMENT UNTUK SISTEM EKSTRAKSI GARIS PANTAI

This study has evaluated the application of brightness adjustment technique to improve image contrast in the framework of coastline extraction on video-based shoreline monitoring system. In this monitoring system, the shoreline detection mechanism is done by introducing the land and sea objects in the video image. Changes in sea conditions due to weather changes cause a change in the contrast in the coastal image. The change in contrast will lead to inaccurate coastline detection. The brightness adjustment technique is applied to the image pre-processing to produce stable contrast in all conditions so that the coastal monitoring system can extract the coastline accurately. The brightness adjustment technique can adjust the brightness of the coastal image by setting the upper and lower threshold values of each pixel intensity. This study used 3 (three) sample video test images taken on morning, noon and afternoon to obtain different video image characteristics. The simulation results show that the application of brightness adjustment technique can increase the accuracy of shoreline extraction when using the threshold value of each at -20% for morning image condition, -40% for daytime image condition, and -35% for afternoon image condition .

Abstract ID: 242 Simulation of a Fast Timing Micro-Pattern Gaseous Detector for TOF-PET

Micro-Pattern Gas Detectors (MPGDs) are a new generation of gaseous detectors that have been developed thanks to advances in micro-structure technology. The main features of the MPGDs are: high rate capability (>50 MHz/cm2); excellent spatial resolution (down to 50 μm); good time resolution (down to 3 ns); reduced radiation length, affordable costs, and possible flexible geometries. A new detector layout has been recently proposed that aims at combining both the high spatial resolution and high rate capability (100 MHz/cm2) of the current state-of-the-art MPGDs with a high time resolution. This new type of MPGD is named the Fast Timing MPGD (FTM) detector [1,2]. The FTM developed for detecting charged particles can potentially reach sub-millimeter spatial resolution and 100 ps time resolution. This contribution introduces a Fast Timing MPGD technology optimized to detect photons, as an innovative PET imaging detector concept and emphases the importance of full detector simulation to guide the design of the detector geometry. The design and development of a new FTM, combining excellent time and spatial resolution, while exploiting the advantages of a reasonable energy resolution, will be a boost for the design of affordable TOF-PET scanner with improved image contrast. The use of such an affordable gas detector allows to instrument large areas in a cost-effective way, and to increase in image contrast for shorter scanning times (lowering the risk for the patient) and better diagnosis of the disease. In this report a dedicated simulation study is performed to optimize the detector design in the contest of the INFN project MPGD-Fatima. Results are obtained with ANSYS, COMSOL, GARFIELD++ and GEANT4 simulation tools. The final detector layout will be trade-off between fast time and good energy resolution.

Silver Filler Pre-embedding to Enhance Resolution and Contrast in Multidimensional SEM: A Nanoscale Imaging Study on Liver Tissue.

Contemporarily, serial block-face scanning electron microscopy (SBF-SEM) has emerged as an immensely powerful nanoscopic imaging technique, capable of generating large-volume three-dimensional information on a variety of biological specimens in a semiautomated manner. Despite the plethora of insights and advantages provided by SBF-SEM, a major challenge inherent to the technique is that of electron charging, which ultimately reduces attainable resolution and detracts from overall image quality. In this chapter, we describe a pre-embedding approach that involves infiltration of tissue with a highly conductive silver filler suspension following primary fixation. Such an approach is demonstrated to improve overall sample conductivity, resulting in the minimization of charging under high-vacuum conditions and an improvement in lateral resolution and image contrast. The strength of this sample preparation approach for SBF-SEM is illustrated on liver tissue.

Efficient OCT Image Enhancement Based on Collaborative Shock Filtering.

Efficient enhancement of noisy optical coherence tomography (OCT) images is a key task for interpreting them correctly. In this paper, to better enhance details and layered structures of a human retina image, we propose a collaborative shock filtering for OCT image denoising and enhancement. Noisy OCT image is first denoised by a collaborative filtering method with new similarity measure, and then the denoised image is sharpened by a shock-type filtering for edge and detail enhancement. For dim OCT images, in order to improve image contrast for the detection of tiny lesions, a gamma transformation is first used to enhance the images within proper gray levels. The proposed method integrating image smoothing and sharpening simultaneously obtains better visual results in experiments.

Multipoint scanning dual-detection confocal microscopy for fast 3D volumetric measurement.

We propose a multipoint scanning dual-detection confocal microscopy (MS-DDCM) system for fast 3D volumetric measurements. Unlike conventional confocal microscopy, MS-DDCM can accomplish surface profiling without axial scanning. Also, to rapidly obtain 2D images, the MS-DDCM employs a multipoint scanning technique, with a digital micromirror device used to produce arrays of effective pinholes, which are then scanned. The MS-DDCM is composed of two CCDs: one collects the conjugate images and the other collects nonconjugate images. The ratio of the axial response curves, measured by the two detectors, provides a linear relationship between the height of the sample surface and the ratio of the intensity signals. Furthermore, the difference between the two images results in enhanced contrast. The normalising effect of the MS-DDCM provides accurate sample heights, even when the reflectance distribution of the surface varies. Experimental results confirmed that the MS-DDCM achieved high-speed surface profiling with improved image contrast capability.

The effect of an ultra-low frame rate and antiscatter grid-less radiation protocol for cardiac device implantations.

Antiscatter grids improve image contrast by absorbing scattered x-ray beams, although by removing the antiscatter grid patient dose can be reduced as more x-ray beams reach the image receptor. Additionally, there is a trend toward ultra-low frame rates for radiation dose reduction during various electrophysiology procedures. As for most cardiac device implantations (CIED) image quality demands are usually modest, the purpose of this study was to assess the safety and efficacy of an ultra-low frame rate and scatter grid-less radiation protocol. A total of 140 patients undergoing CIED implantation between 2014 and 2017 were included in the study. Seventy patients (50%) implanted after implementation of the antiscatter grid-less and ultra-low frame rate protocol were matched to controls before the dose-reduction protocol was established. Forty patients (28.6%) had a one-chamber pacemaker or one-chamber implantable cardioverter defibrillator (ICD) implantation/revision, 60 (42.9%) had a two-chamber pacemaker or two-chamber ICD implantation/revision, and 40 (28.6%) patients had a cardiac resynchronization therapy device implantation/revision. Removing the antiscatter-grid and lowering the frame rate led to a 73% reduction of the overall dose area product (1,206 ± 2,015vs 324 ± 422 μGym, P<0.001). Procedural duration (95 ± 51minutes vs 82 ± 44 minutes, P=0.053) and rate of complications were not significantly different between the two groups. The use of an ultra-low frame rate and antiscatter grid-less radiation protocol significantly reduced radiation dose for implantation of CIED and led to very low average patient doses, while procedural duration and complication rates did not increase.

Specialized nanowhisker probes for high-precision investigation of native bio-objects in liquid by means of atomic force microscopy

Fabrication and investigation of specialized Pt-C single nanowhisker probes are carried out for high-precision study of objects with organic and inorganic nature in liquids by atomic force microscopy. The best modes and buffered media were revealed on calibration lattice TGQ1 choosing as reference inorganic structure. Preliminary results of the study of the structure of bacteria E.Coli in the native state were received in the PBS liquid. Fixation of the bacteria was performed on agar-agar with a mass fraction of 1.8%. The significant improvement of image contrast and resolution was found when using nanowhisker probes compare to standard Si tips.

Short-lag spatial coherence combined with eigenspace-based minimum variance beamformer for synthetic aperture ultrasound imaging

Recently, short-lag spatial coherence (SLSC) imaging has been widely studied to improve image contrast and contrast-to-noise ratio (CNR) in ultrasound imaging. Nevertheless, SLSC is unable to provide a good imaging resolution. Eigenspace-based minimum variance (ESBMV) beamformer was previously devised to promote imaging resolution, while enhancing imaging contrast. However, ESBMV will cause black-spot artifact problem under a high threshold of eigenvalues. Given their complementary properties, in this study, we propose an imaging method with synthetic aperture (SA) ultrasound imaging by combining SLSC weighting (SLSCw) and ESBMV, to improve imaging quality at all depth. Based on the spatial coherence of different sources, adaptive threshold of eigenvalues is designed for ESBMV. In the proposed method, receive aperture data are directly summed to get the receive aperture synthesized data, and then SLSC and ESBMV are applied in transmit aperture based on the receive synthesized data. After that, the estimated SLSC value is adopted as a weighting factor for ESBMV beamforming output. We demonstrate the performance of the proposed method based on simulated and experimental data. The results show that the proposed method can not only achieve satisfactory improvement in resolution and contrast but also remove the black-spot artifacts.

Development of a New FR-Targeting Agent 99mTc-HYNFA with Improved Imaging Contrast and Comparison of Multimerization and/or PEGylation Strategies for Radio-Folate Modification.

This study aims to develop a new folate receptor (FR)-targeting agent for SPECT imaging with improved contrast and evaluate the modification strategies of multimerization and/or PEGylation in the development of new radio-folates. A series of novel folate derivatives have been synthesized and radiolabeled with 99mTc using tricine and TPPTS as coligands. To better investigate their pharmacokinetics, cell uptake, biodistribution, and microSPECT/CT imaging were evaluated. Four radioligands displayed high KB cell uptake after incubation for 2 and 4 h. Presaturated with excess folic acid (FA) resulted in a significant blocking effect in KB cells, indicating specificity of these radioligands toward FR. Biodistribution and microSPECT imaging studies in KB tumor-bearing mice showed that the folate conjugate 99mTc-HYNFA with poly(ethylene glycol) (PEG) and triazole linkage displayed the highest tumor uptake (16.30 ± 2.01 %ID/g at 2 h p.i. and 14.9 ± 0.62 %ID/g at 4 h p.i. in mice biodistribution) and best imaging contrast, indicating promising application prospect. More interestingly, the in vivo performance of this monomeric 99mTc-HYNFA was much better than that of FA multimers and non-PEGylated monomers, suggesting that multimerization may not be a feasible method for the design of radio-folates. PEG linkage rather than FA multimerization should be taken into consideration in the development of folate-based radiopharmaceuticals in the future.

그림자 영역의 수직 경계선을 이용한 고해상도 위성 영상의 그림자 제거

The effect of shadows in very-high resolution (VHR) satellite imagery has become one of major issues in urban area analysis. The shadows in VHR satellite imagery, such as Kompsat-3A, covers a wide range of urban areas due to the buildings and affects the analysis of land cover and land use. This paper presents a shadow-removal method using the linear relationship between inner and outer intensities of shadow region borders. Vertical shadow borders, which have constant orientation in the whole image according to the altitude and azimuth of the sun at the image acquisition time, are extracted from shadow regions based on the orientation and linearity of the vertical border pixels. We estimate the pixel intensities in the shadow region based on RANdom Sample Consensus (RANSAC)-based linear transformation using only the pixels belonging to the shadow and non-shadow regions located outside a narrow border region. The pixel intensities in the narrow border region are interpolated using the least-square method which calculates the intensity plane parameters using the pixels belonging to small shadow and non-shadow regions. The proposed shadow removal method was tested using a part of WorldView-3 satellite images and showed improved shadow removal performance than the conventional linear correlation correction method in terms of image contrast and detailed-information improvement in the restored shadow region.

Adaptive enhancement for nonuniform illumination images via nonlinear mapping

Nonuniform illumination images suffer from degenerated details because of underexposure, overexposure, or a combination of both. To improve the visual quality of color images, underexposure regions should be lightened, whereas overexposure areas need to be dimmed properly. However, discriminating between underexposure and overexposure is troublesome. Compared with traditional methods that produce a fixed demarcation value throughout an image, the proposed demarcation changes as local luminance varies, thus is suitable for manipulating complicated illumination. Based on this locally adaptive demarcation, a nonlinear modification is applied to image luminance. Further, with the modified luminance, we propose a nonlinear process to reconstruct a luminance-enhanced color image. For every pixel, this nonlinear process takes the luminance change and the original chromaticity into account, thus trying to avoid exaggerated colors at dark areas and depressed colors at highly bright regions. Finally, to improve image contrast, a local and image-dependent exponential technique is designed and applied to the RGB channels of the obtained color image. Experimental results demonstrate that our method produces good contrast and vivid color for both nonuniform illumination images and images with normal illumination.

Ultrasonic Characteristics and Cellular Properties of Anabaena Gas Vesicles

Ultrasound imaging is a common modality in clinical examination and biomedical research, but has not played a significant role in molecular imaging for lack of an appropriate contrast agent. Recently, biogenic gas vesicles (GVs), naturally formed by cyanobacteria and haloarchaea, have exhibited great potential as an ultrasound molecular imaging probe with a much smaller size (∼100 nm) and improved imaging contrast. However, the basic acoustic and biological properties of GVs remain unclear, which hinders future application. Here, we studied the fundamental acoustic properties of a rod-shaped gas vesicle from Anabaena, a kind of cyanobacterium, including attenuation, oscillation resonance, and scattering, as well as biological behaviors (cellular internalization and cytotoxicity). We found that GVs have two resonance peaks (85 and 120 MHz). We also observed a significant non-linear effect and its pressure dependence as well. Ultrasound B-mode imaging reveals sufficient echogenicity of GVs for ultrasound imaging enhancement at high frequencies. Biological characterization also reveals endocytosis and non-toxicity.

Comparison between two-phase and one-phase SLIPI for instantaneous imaging of transient sprays

Imaging through optically dense sprays is challenging due to the detection of multiple light scattering, which blurs the recorded images and limits visibility. Structured laser illumination planar imaging (SLIPI) is a technique that is capable of reducing the intensity contribution that stems from multiple scattering in a light sheet imaging configuration. The conventional SLIPI approach is based on recording three modulated sub-images successively, each having a different spatial phase, and has, therefore, been mostly used for temporally averaged imaging. To circumvent this limitation and image spray dynamics, ‘instantaneous’ two-phase (2p) and single-phase (1p) SLIPI approaches have recently been developed. The purpose of the work presented here is to compare these two approaches in terms of optical design, image post-processing routines, multiple scattering suppression ability, and spatial resolution. The two approaches are used to image a transient direct-injection spark-ignition ethanol spray, for both liquid laser-induced fluorescence and Mie scattering detection. The capabilities of the approaches for multiple scattering suppression and image formation have also been numerically modeled by means of Monte Carlo simulation. This article shows that both approaches efficiently suppress the contribution from multiple light scattering, providing images with an intensity profile close to the corresponding single scattering case. Experimentally, this suppression renders both an improvement in image contrast and the removal of undesired stray light components that could be interpreted as signal. However, while 2p-SLIPI preserves most of the initial spatial resolution, 1p-SLIPI results in a loss of spatial resolution, where high-frequency image information is not visible anymore. Thus, there is a trade-off between preserving the most detailed information of the spray structure—with 2p-SLIPI—and being able to record an SLIPI image from a single modulated image only—with 1p-SLIPI. The comparison and technical overview of these two methods presented in this paper can facilitate in selecting which approach is the most suitable for a given application for spray visualization.

In Situ Ligation of High- and Low-Affinity Ligands to Cell Surface Receptors Enables Highly Selective Recognition.

This paper reports an entirely unexplored concept of simultaneously recognizing two receptors using high‐ and low‐affinity ligands through ligating them in situ on the target cell surface. This de novo approach is inspired by the pretargeting strategy frequently applied in molecular imaging, and has now evolved as the basis of a new paradigm for visualizing target cells with a high imaging contrast. A distinct advantage of using a labeled low‐affinity ligand such as glycan is that the excess labeled ligand can be washed away from the cells, whereas the ligand bound to the cell, even at the milli molar affinity level, can be anchored by a bioorthogonal reaction with a pretargeted high‐affinity ligand on the surface. Consequently, nonspecific background is minimized, leading to improved imaging contrast. Importantly, despite previously unexplored for molecular imaging, a notoriously weak glycan/lectin interaction can now be utilized as a highly selective ligand to the targets.

Complex decorrelation averaging in optical coherence tomography: a way to reduce the effect of multiple scattering and improve image contrast in a dynamic scattering medium.

We demonstrate that complex decorrelation averaging can reduce the effect of multiple scattering and improve optical coherence tomography (OCT) imaging contrast. Complex decorrelation averaging calculates the product of an A-scan and the complex conjugate of a subsequent A-scan. The resultant signal is the product of the amplitudes and the phase difference. All these resulting complex signals at a particular location are then averaged. We take advantage of the fact that complex averaging, in contrast to conventional magnitude averaging, is sensitive to phase decorrelation. Sample motion that increases signal phase variance results in lower signal magnitude after complex averaging. Such motion preferentially results in a faster decorrelation of the multiple scattering signal when compared to the single scattering signal with each scattering event spreading the phase. This indicates that we may reduce multiple scattering by implementing complex decorrelation averaging to preferentially reduce the magnitude of the multiply scattered light signal in OCT images. By adjusting the time between phase-differenced A-scans, one can regulate the amount of measured decorrelation. We have performed experiments on liquid phantoms that give experimental evidence for this hypothesis. A substantial improvement in OCT image contrast using complex decorrelation averaging is demonstrated.

Performance of Half-dose Chest Computed Tomography in Lung Malignancy Using an Iterative Reconstruction Technique

Objectives The purpose of this study was to evaluate the performance of half-dose chest CT using an iterative reconstruction technique in patients with lung malignancies. Methods The Dual-source CT scans were obtained and half-dose datasets were reconstructed with 5 different strengths in 38 adults with lung malignancies. Two radiologists graded subjective image quality; noise, contrast and sharpness at the central/peripheral lung, mediastinum and chest wall of the reconstructed half-dose images, compared with those of standard-dose images, using a three-point scale. A lesion assessment; lesion conspicuity and diagnostic confidence, was also performed. The quantitative image noises; contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) were measured and compared with those of standard-dose images. Results The subjective image noise in the half-dose images was less than that of the standard-dose images. The contrast in strengths 2 to 5 was superior, the sharpness of the lung parenchyma in strengths 3 to 5 was inferior, and the CNR/SNR in all strengths were higher than those of standard-dose images ( P &amp;lt; 0.05). The improvement of subjective image noise and contrast, the decrease in sharpness, were correlated with strength level ( P &amp;lt; 0.05). The lesion conspicuity in half-dose images of strengths 4 and 5 was decreased. The diagnostic confidence of the half-dose images of all strengths was comparable to that of the standard-dose images ( P &amp;lt; 0.05). Conclusions Half-dose chest CT images using an iterative reconstruction technique show decreased image noise, increased contrast, and diagnostic confidence comparable to standard-dose images. Images reconstructed with strength 2 and 3 appear to be the optimal choice in clinical practice.

Mueller polarimetric imaging for surgical and diagnostic applications: a review.

Polarization is a fundamental property of light and a powerful sensing tool that has been applied to many areas. A Mueller matrix is a complete mathematical description of the polarization characteristics of objects that interact with light, and is known as a transfer function of Stokes vectors which characterise the state of polarization of light. Mueller polarimetric imaging measures Mueller matrices over a field of view and thus allows for visualising the polarization characteristics of the objects. It has emerged as a promising technique in recent years for tissue imaging, improving image contrast and providing a unique perspective to reveal additional information that cannot be resolved by other optical imaging modalities. This review introduces the basis of the Stokes-Mueller formulism, interpretation methods of Mueller matrices into fundamental polarization properties, polarization properties of biological tissues, and considerations in the construction of Mueller polarimetric imaging devices for surgical and diagnostic applications, including primary configurations, optimization procedures, calibration methods as well as the instrument polarization properties of several widely-used biomedical optical devices. The paper also reviews recent progress in Mueller polarimetric endoscopes and fibre Mueller polarimeters, followed by the future outlook in applying the technique to surgery and diagnostics. Tissue polarization properties convey morphological, micro-structural and compositional information of tissue with great potential for label free characterization of tissue pathological changes. Recent progress in tissue polarimetric imaging and polarization resolved endoscopy paved the way for translation of polarimetric imaging to surgery and tissue diagnosis.

Imaging of the Finger Vein and Blood Flow for Anti-Spoofing Authentication Using a Laser and a MEMS Scanner.

A new authentication method employing a laser and a scanner is proposed to improve image contrast of the finger vein and to extract blood flow pattern for liveness detection. A micromirror reflects a laser beam and performs a uniform raster scan. Transmissive vein images were obtained, and compared with those of an LED. Blood flow patterns were also obtained based on speckle images in perfusion and occlusion. Curvature ratios of the finger vein and blood flow intensities were found to be nearly constant, regardless of the vein size, which validated the high repeatability of this scheme for identity authentication with anti-spoofing.

Tensor based multichannel reconstruction for breast tumours identification from DCE-MRIs.

A new methodology based on tensor algebra that uses a higher order singular value decomposition to perform three-dimensional voxel reconstruction from a series of temporal images obtained using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is proposed. Principal component analysis (PCA) is used to robustly extract the spatial and temporal image features and simultaneously de-noise the datasets. Tumour segmentation on enhanced scaled (ES) images performed using a fuzzy C-means (FCM) cluster algorithm is compared with that achieved using the proposed tensorial framework. The proposed algorithm explores the correlations between spatial and temporal features in the tumours. The multi-channel reconstruction enables improved breast tumour identification through enhanced de-noising and improved intensity consistency. The reconstructed tumours have clear and continuous boundaries; furthermore the reconstruction shows better voxel clustering in tumour regions of interest. A more homogenous intensity distribution is also observed, enabling improved image contrast between tumours and background, especially in places where fatty tissue is imaged. The fidelity of reconstruction is further evaluated on the basis of five new qualitative metrics. Results confirm the superiority of the tensorial approach. The proposed reconstruction metrics should also find future applications in the assessment of other reconstruction algorithms.