Gray Level Changes Research Articles

An Ordinal Co-occurrence Matrix Framework for Texture Retrieval

We present a novel ordinal co-occurrence matrix framework for the purpose of content-based texture retrieval. Several particularizations of the framework will be derived and tested for retrieval purposes. Features obtained using the framework represent the occurrence frequency of certain ordinal relationships at different distances and orientations. In the ordinal co-occurrence matrix framework, the actual pixel values do not affect the features, instead, the ordinal relationships between the pixels are taken into account. Therefore, the derived features are invariant to monotonic gray-level changes in the pixel values and can thus be applied to textures which may be obtained, for example, under different illumination conditions. Described ordinal co-occurrence matrix approaches are tested and compared against other well-known ordinal and nonordinal methods.

Mineral content changes in bone associated with damage induced by the electron beam

Energy-dispersive x-ray (EDX) spectroscopy and backscattered electron (BSE) imaging are finding increased use for determining mineral content in microscopic regions of bone. Electron beam bombardment, however, can damage the tissue, leading to erroneous interpretations of mineral content. We performed elemental (EDX) and mineral content (BSE) analyses on bone tissue in order to quantify observable deleterious effects in the context of (1) prolonged scanning time, (2) scan versus point (spot) mode, (3) low versus high magnification, and (4) embedding in poly-methylmethacrylate (PMMA). Undemineralized cortical bone specimens from adult human femora were examined in three groups: 200x embedded, 200x unembedded, and 1000x embedded. Coupled BSE/EDX analyses were conducted five consecutive times, with no location analyzed more than five times. Variation in the relative proportions of calcium (Ca), phosphorous (P), and carbon (C) were measured using EDX spectroscopy, and mineral content variations were inferred from changes in mean gray levels ("atomic number contrast") in BSE images captured at 20 keV. In point mode at 200x, the embedded specimens exhibited a significant increase in Ca by the second measurement (7.2%, p < 0.05); in scan mode, a small and statistically nonsignificant increase (1.0%) was seen by the second measurement. Changes in P were similar, although the increases were less. The apparent increases in Ca and P likely result from decreases in C: -3.2% (p < 0.05) in point mode and -0.3% in scan mode by the second measurement. Analysis of unembedded specimens showed similar results. In contrast to embedded specimens at 200x, 1000x data showed significantly larger variations in the proportions of Ca, P, and C by the second or third measurement in scan and point mode. At both magnifications, BSE image gray level values increased (suggesting increased mineral content) by the second measurement, with increases up to 23% in point mode. These results show that mineral content measurements can be reliable when using coupled BSE/EDX analyses in PMMA-embedded bone if lower magnifications are used in scan mode and if prolonged exposure to the electron beam is avoided. When point mode is used to analyze minute regions, adjustments in accelerating voltages and probe current may be required to minimize damage.

ON THE HIERARCHICAL ASSIGNMENT TO THE FOREGROUND OF GRAY-LEVEL IMAGE SUBSETS

We present a method to assign to either the foreground or the background the regions into which a gray-level image is partitioned by watershed transformation. Our method is inspired by visual perception in the sense that the border separating any foreground component from the background is detected in correspondence with the locally maximal gray-level changes through the image. The method is implemented as consisting of three steps. The first two steps perform a basic assignment of the regions, while the remaining step examines again some regions tentatively assigned to the background during the second step and possibly changes their status. A feature of the method is that a hierarchical ranking of the regions assigned to the foreground is also accomplished.

Strain whitening of a thermoplastic olefin material

This paper presents research work on the characteristics and micro mechanism of strain whitening of a thermoplastic olefin material. Systematic tensile tests have been carried out to investigate the relation between strain whitening extent and external factors, including the deformation employed and the environmental temperature. A new optical method has been developed for the measurement of strain on polymer tensile samples. Applying this method relation between whitening level (grey level change) and strain has been studied. A new concept of ‘strain whitening sensitivity’ has been proposed and defined as the strain whitening induced by unit deformation or strain. Non-monotonic relation between whitening level and strain has been found. Strained and fractured samples were observed with A JEOL 5800 LV SEM for the micro mechanism investigation. The change of microstructure on the sample surface has been extensively observed and the combined effects of small ridges and micro-voids on the scattering efficiency of the strained surface were regarded as reasons for the non-monotonic relation between whitening level and strain.

Reduced susceptibility to stress whitening during tensile deformation of calcium carbonate-reinforced high density polyethylene composites

The micromechanism of plastic deformation and susceptibility to stress whitening during tensile straining of 20% calcium carbonate-reinforced polyethylene micrometric composites is investigated and compared with the un-reinforced polyethylene under identical conditions of processing. The adoption of calcium carbonate in polyethylene has two mutually opposite effects: the reinforcement and the nucleating effect. The reinforcement effect increases the bulk crystallinity and modulus, while the nucleating effect decreases the spherulite size and has a negative influence on yield stress, neutralizing the positive influence of increase in percentage crystallinity. The effective reinforcement of polyethylene by calcium carbonate reduces the susceptibility to stress whitening, and is characterized by lower change in gray level in the plastically deformed stress whitened zone in comparison to neat polyethylene. Also, the reinforcement of polyethylene alters the primary micromechanism of plastic deformation and stress whitening from predominantly crazing–tearing in neat polyethylene to wedge/ridge tearing and fibrillation in calcium carbonate-reinforced polyethylene composites. This is related to the cumulative contribution of small spherulite size and the amorphous nature of the interface.

On stress whitening during surface deformation in clay-containing polymer nanocomposites: A microstructural approach

The study describes the surface deformation behavior and susceptibility to surface damage in two clay-reinforced intercalated polymer nanocomposite systems that have significant differences in ductility. Neat polybutene (PB) experiences a severe and distinct ‘quasi-periodic psiloma-type’ deformation process that was absent on reinforcement with clay. In clay-PB nanocomposite system, ‘ironing,’ a less severe surface damage mechanism is dominant. While in the less ductile polymethylpentene (PMP) polymer system, ploughing–tearing and micro-voiding constitute the surface deformation mechanism. Both the clay-reinforced polymer nanocomposite systems experience significantly reduced stress whitening and is characterized by a lower change in gray level. The optical transparency of the polymeric systems is governed by the micromechanism of deformation and is greater for the ductile PB system. The difference in the susceptibility to surface deformation behavior is discussed in terms of mechanical properties and clay-induced structural changes. The reinforcement of polymers with nanoclay has a positive overriding positive influence on the modulus and yield strength that increases the resistance to surface deformation.

Nuclear Mean Gray Level and Chromatin Distribution Changes in Cardiomyocytes of Heart Transplant Recipients Suffering From Acute Cellular Rejection

Background Distribution and staining of the nuclear chromatin are sensitive indicators of changes in physiology and pathology of cells. However, their use in heart transplant recipients is rare. The aim of this study was to compare cardiomyocyte status in heart transplant recipients suffering from moderate acute cellular rejection and subjects without signs of active cellular rejection. Materials and Methods One hundred twenty-nine endomyocardial biopsy samples from 43 heart transplant recipients (no later than 6 months after surgery) were evaluated. Overall, 3235 cardiomyocytic nuclei were analyzed using the Quantimet image analysis system to assess the mean gray level: 1584 nuclei were found in biopsies without signs of rejection or with nonsignificant rejection (ISHLT grades 0, 1A, and 1B), whereas the remaining 1651 nuclei were measured from biopsies showing ISHLT grade 3A (significant rejection). Additionally, the chromatin distribution was assessed in all eligible nuclei. Results The mean gray level was markedly increased in nuclei from biopsy samples with significant rejection (182.6 vs 112.5, P < .001, Mann-Whitney U test). Moreover, the analysis of chromatin distribution revealed significantly more frequent chromatin marginalization and irregular distribution in rejecting subjects ( P < .001, chi-square test). Conclusion Inflammatory stimulation of cardiomyocytes during acute cellular rejection of the transplanted heart influences the chromatin distribution in the nuclei, which may have an additional value, when assessing the severity of rejection.

Metrology for characterizing scratch resistance of polymer coatings

Current methods for scratch resistance assessment are often based on “relative but not quantitative” types of measurements, such as visual inspection, gloss changes, and changes in gray scale level or lightness. Most results are used for qualitative assessment purposes, which result in the lack of a repeatable and reliable standardized test method for the polymer materials community. To implement a scientifically based standardized test method for quantifying scratch resistance, it is vital to understand the relationships between material mechanical properties, morphology, and appearance (optical properties) of surface and subsurface deformation. In this article, preliminary results from a scratch testing protocol to identify the “onset” of plastic deformation in poly(methyl methacrylate) and poly(propylene) commercial samples are presented. Recent advances in optical scattering measurements to identify the onset of plastic deformation by analyzing specular and off-specular intensities are also presented.

MO-E-T-618-03: Dynamic Intraoperative Prostate Brachytherapy Using 3D TRUS Guidance with Robotic Assistance

Purpose: Develop a dynamic intraoperative prostate brachytherapy system, in which all phases of the procedure are performed in one session, including planning, monitoring of prostate changes, dynamic re-planning, optimal needle insertion including oblique trajectories and automatic seed localization in US images, to deal with variabilities in the current procedure. Method and Materials: The system consists of 3D TRUS imaging, a robot and software tools for prostate segmentation, intraoperative planning, oblique needle segmentation and tracking, seed segmentation, and 3D dose planning. The robot and 3D TRUS coordinate systems are unified with robot and image calibrations. In 3D TRUS images, the prostate is segmented using discrete dynamic contour method, and optimal implantation plan is performed by applying geometric optimization followed by simulated annealing. The robot can be controlled to guide the needle to target points in 3D TRUS images along oblique trajectories accurately and consistently. The inserted needles are segmented and tracked using grey-level change, and seed segmentation is performed using 3D line segment patterns. Results: Needle placement accuracy of the robot at “patient” skin was 0.15mm±0.06mm, and needle angulation error was 0.07°. Needle targeting accuracy was 0.79mm±0.32mm. The average difference between manual and the prostate segmentation algorithm of prostate boundaries was −0.20±0.28mm. In our needle tracking tests, errors in determining needle orientation were less than 2° in robot yaw and 0.7° in robot pitch orientations, for up to 20° needle insertion angles when the needle insertion distance was greater than 15mm. The true-positive rates for the seed segmentation algorithm in 3D TRUS images were 100% for agar and 93% for chicken phantoms. With optimal planning tools provided, 98% of prostate volume receives 80% of dose coverage. Conclusion: The result of this work provides a tool to achieve dynamic intraoperative prostate brachytherapy using 3D TRUS imaging and robotic assistance together with efficient segmentation software.

Scratch deformation characteristics of micrometric wollastonite‐reinforced ethylene‐propylene copolymer composites

AbstractThe scratch deformation behavior of neat and wollastonite‐containing ethylene‐propylene copolymer composites has been studied by electron microscopy and atomic force microscopy techniques. The study indicates that the severity of plastic deformation during scratch testing in reinforced ethylene‐propylene copolymers is a function of debonding/detachment of wollastonite mineral particles from the ethylene‐propylene matrix. The resistance to scratch deformation was evaluated in terms of scratch hardness, scratch depth, average scratch roughness, and change in gray level before and subsequent to scratching. The data suggests that resistance to scratch deformation follows the sequence: coated + coupled wollastonite‐containing EP copolymer &gt; fine wollastonite‐containing EP copolymer &gt; coated wollastonite‐containing EP copolymer &gt; coarse wollastonite‐containing EP copolymer &gt; neat EP copolymer. EP copolymer containing coated wollastonite and coupling agent is characterized by highest scratch hardness and minimum scratch depth and scratch roughness. The visibility of scratch, quantified in terms of gray level, suggests that coated + coupled wollastonite‐containing copolymer exhibits significantly reduced susceptibility to stress whitening, and is characterized by a lower gray level in the scratch‐deformed regions. In the present case of wollastonite‐containing copolymer composites, the resistance to scratch deformation follows a trend similar to that of gray level or scratch visibility. Polym. Eng. Sci. 44:1738–1748, 2004. © 2004 Society of Plastics Engineers.

Micro-computed tomography: high resolution imaging of bone and implants in three dimensions

<h2>Abstract</h2> The success of orthodontics and dentofacial orthopedic treatment depends on effective anchorage and a favorable osseous adaptation to applied loads. The quality of bone produced under therapeutic conditions depends on its matrix organization, degree of mineralization, and geometric distribution. To adequately assess the mechanical properties of orthodontic anchorage devices, such as dental implants, requires three-dimensional (3D) imaging of block specimens. Micro-computed tomography (micro CT) has opened new scientific frontiers for analyzing mineralized tissue. The method is particularly useful for the technically demanding task of assessing mineral density patterns for bone supporting titanium implants. However, this digital imaging technology has not been directly compared with the gold standard for that task, which is microradiography. Digital microtomographic and conventional microradiographic images of the same implant integrated in cortical bone were compared with digital subtraction radiography. A gray level concordance of 126.7 ± 11.4 (mean ± SD) demonstrated excellent agreement between the images. Because it is a 3D nondestructive method, which achieves higher resolution and is more sensitive to gray level changes than microradiography, it was concluded that the micro CT is the new gold standard for assessment of bone supporting implants. Micro CT of a threaded implant integrated into a dog femur showed intense remodeling activity at the interface and within supporting bone. Threaded implants have foci of remodeling associated with individual threads, while cylindrical devices have a more global response concentrated on the center of the endosseous portion of the implant. Micro CT is a novel digital technology that shows great promise for detecting subtle changes in osseous structure that are related to dental implants, orthodontic responses, and dentofacial orthopedics.

Past monsoon rainfall variations in peninsular India recorded in a 331-year-old speleothem

An actively growing stalagmite collected from a cave located in the hills of the Western Ghats in the Uttar Kannada District of Karnataka, India, has been studied for stable isotope ratios of oxygen and carbon, width of growth layers and grey-level changes. Distinct carbonate layers, alternate coarse and compact, are seen in cross-section. Each couplet of compact and coarse layer is found to represent a single year. A total of 331 such couplets has been counted, indicating that the stalagmite started growing in AD 1666 and continued until it was sampled. Stable isotope ratios of oxygen (δ18O) and carbon (δ13C) show variations ranging from-13.6 to-7.9%° and from-2.7 to 1.6%°, respectively. We have reconstructed past rainfall changes of the cave site using the‘amount effect’ in &amp;δ18O of rain. Speleothemδ18O and instrumental rainfall data from the associated climate subdivision show a significant correlation (r =-0.62, decadal average). Several sharp spikes of enrichment and depletion in 18O are indicative of the past deficiency and excess in rainfall. Most of the severe drought years recorded independently by meteorological observations are found registered in the stalagmite layers. During the 331-year-period, rainfall was highest at Añ 1666 and lowest around AD 1900. The stalagmite-generated past rainfall record can serve as a reasonable proxy for testing monsoon models.

영상을 이용한 자동 유고 검지 알고리즘 개발

본 논문은 영상 검지기에서 얻은 영상을 이용하여 화면상에 보이는 차량의 사고상황을 자동 검출하는데 목적이 있다. 사고 검지를 위해 별도의 장비 설치 없이 영상 검지기를 통해 얻은 도로 영상을 토대로 추돌사고, 고장으로 인한 정차, 갓길 불법 정차 등의 돌발 상황을 자동으로 검지 하는 알고리즘을 구현한다. 차량 사고가 발생할 가능성이 높은 관심 영역을 설정하여 화면에 가상의 트랩을 설치하고, 가상의 트랩상에서 발생하는 화소값의 변화와 차량의 움직임을 분석하여 사고상황을 자동 검지 하도록 한다. 제안된 방식의 효과를 검증하기 위해 도로에서 사고 상황을 재현하고 설치된 영상 검지기를 통해 사고상황 영상을 획득하여 사고상황에 대한 자동 검지 결과를 제시한다. This paper is intended to develop an algorithm for automatic detection of traffic accidents using image sequences. This algorithm is designed for detecting stopped vehicles traffic accidents, break down, illegal stop in the road shoulder - on the range of camera view. Virtual traps are set on accident-prone spots. We analyze the changes in gray levels of pixels on the virtual traps which represent the motion of vehicles on the corresponding spots. We verify the proposed algorithm by simulating some situations and checking if it detect them correctly.

An optical method for assessing scratch damage in bulk materials and coatings

For some applications, the most important property of a scratch in a surface or coating is the visual perception of that scratch by a human observer. A method is proposed to predict the visual impact of scratch damage from measurements of geometrical dimensions and changes in grey level. A ‘logarithmic instrumental visibility’, V i , is defined by V i =log∫Δ G 2.5d A where Δ G is the difference in grey level between the scratched region and the surrounding background, and A is the area of the scratch. This objective measure is shown to correlate well with more subjective estimates of visibility, as perceived by human observers, for a wide range of simulated scratch images and also for real scratches in smooth-surfaced filled polyolefin sheets.

Physics-based flow estimation of fluids

We present a physics-based method to compute the optical flow of a fluid. In most situations, gray level changes in an image do not provide sufficient information to completely ascertain optical flow, necessitating the use of a supplementary constraint. For this, the smoothness constraint is often employed. This constraint is, however, general and does not express well a priori knowledge of a specific object. We therefore propose a method in which physical equations describing the object are used as supplementary constraints. In this way, more accurate flow estimation can be achieved. The physical model employed is a combination of the continuity equation and Navier–Stokes’ equations. After describing how we integrate these equations into fluid flow estimation, we demonstrate the effectiveness of the proposed method by presenting experimental results of its application to simulated and real Karman flows.

Precision Tone Reproduction Curve Measurement Technique for High Image Quality and Halftone Design Applications

We show that an extremely accurate tone reproduction curve (TRC), insensitive to noise in the printer and the media, can be measured using a scanner. In the scannerbased approach, two patterns are written. The first contains as many as 15,000 extremely small patches of the 256 addressable gray levels randomly placed on paper. The random placement averages over the noise and the mean of each patch gives an estimate of the TRC. The second pattern consists of 256 narrow strips with a high spatial frequency modulation between two adjacent gray levels for each strip. The scanner response at the modulation frequency for each strip gives the change in gray level between each halftone. The absolute values of the TRC from the first measurement are adjusted to best agree with the slope measurements, resulting in a highly accurate TRC measurement.

Glacial-interglacial relationship between carbonate components and sediment reflectance in the North Atlantic

A high-resolution composite sediment record from intermediate water depths in the North Atlantic, dating back to marine isotope stage (MIS) 13, was investigated in order to determine the relationship between sediment reflectance (gray level%) and carbonate content (weight%). For this purpose, a detailed analysis of the coarse (>20 µm) and fine (<20 µm) carbonate components was carried out to assess which of the two carbonate components drives glacial-interglacial changes in sediment gray level. The results indicate that the bulk carbonate component is clearly dominated by the fine carbonate fraction, regardless of glacial or interglacial climatic mode, suggesting that the sediment gray level is usually controlled by fluctuations of the fine carbonate content. However, a comparison of MIS 1 and 5.5 indicates that, besides this difference in the contents of the two carbonate size fractions, changing modes in carbonate preservation, i.e., the preservational state of planktonic Foraminifera, may also have a profound influence on total sediment reflectance.

Digital Subtraction Radiography for Monitoring Dental Demineralization

The aim of the present study was to evaluate the assessment of progression of demineralization by digital subtraction radiography. In each of 14 extracted human teeth, 2 approximal enamel demineralization lesions were induced in vitro to simulate dental caries. A modified tunnel preparation with glass ionomer fillings was performed on one lesion of every tooth as a model of caries inhibition. Every week, radiographs were obtained under standardized conditions over a period of 42 days. The radiographs were digitized and calibrated for grayscales. Reference landmarks were chosen and aligned for the different pictures by computer–assisted imaging to adjust the images for projective distortions. The images of the 7th, 14th, 21st, 28th, 35th and 42nd day were subtracted from the baseline radiograph. The mean value of gray values of the subtraction images was calculated and ANOVA tests for repeated measurements and paired t tests were used for statistical analysis. The results of the present study indicate that statistically significant gray level changes due to progression of demineralization could be detected in the radiographic images by subtraction analysis. Differences between glass ionomer–filled and nonfilled lesions failed to reach significance. The introduced method may have the potential to detect and document minute caries progression.

Determination of Background Gray-level for Accurate Measurement of Particles in using Image Processing Method

In this study, experiments have been performed to examine the effects of background gray-level on the depth-of-field and on the in-focus criteria. The normalized value of contrast(VC) and the gradient indicator(GI) were used as the in-focus criteria for the small and the large size-ranges of particles, respectively. The slightly larger number of pixels were detected with the brighter background. The maximum of the normalized value of contrast(VCmax) is decreased with the brighter background and its deviation from that with the background gray-level of 160 turned out to be about 15% when the background gray-level changes from 100 to 200. However, the maximum gradient indicator(GImax) changes with the background gray-level within only 5%. The depth-of-field for the VC-applicable particle-size range is largely dependent on the background gray-level. On the other hand, the depth-of-field for the GI-applicable particle-size range changes only slightly with the background gray-level. To keep the normalized standard deviation of the particle size within 0.1, the background gray-level should be set 16020 for both the VC-applicable and GI-applicable ranges which cover the particle size between and .

Glacial-interglacial records of the reflectance of sediments from the Norwegian-Greenland-Iceland Sea (Nordic seas)

The reflectance of sediments (gray level) were measured on 11 sediment cores from the Norwegian–Greenland–Iceland Sea (Nordic seas). The analyzed time interval covers the past five glacial–interglacial cycles. Although the results demonstrate that the gray-level method has a potential for stratigraphic purposes, it is indicated that gray-level changes in the Nordic seas are not necessarily driven by variations in the content of biogenic calcite. A detailed comparison of gray-level values with contents of total CaCO3 (carbonate) and total organic carbon (TOC) reveals no overall causal link between these proxies. However, specific glacial core sections with layers containing organic-rich sediment clasts as a consequence of iceberg-rafting seem to correlate well with law gray-level values. Of those cores which show relatively high and comparable carbonate values in the last three main interglacial intervals (stages 11, 5.5, and 1), stage 11 is always marked by the highest gray-level values. A close inspection of the surface structure of the foraminiferal tests as well as the conduction of reflectance measurements on these tests leads to the conclusion that enhanced carbonate corrosion occurred during stage 11. The test corrosion not only affected the reflectance of the tests by making them appear whiter, it also seems responsible for the comparatively high gray-level values of the total sediment in stage 11. In contrast, the relatively low gray-level values found in stages 5.5, and 1 are not associated with enhanced test corrosion. This observation implies that variable degrees of carbonate corrosion can have a profound effect on total sediment reflectance.