Digital Image Analysis Techniques Research Articles

Experimental analysis of bubble size distributions in 2D gas fluidized beds

The present work focuses on the development of a novel statistical approach for the analysis of the behavior of a 2D fluidized bed operating under bubbling and slugging conditions. Experimental data were collected by means of a purposely built lab-scale 2D fluidized bed and an original digital image analysis technique (DIAT), allowing the acquisition of a number of data sufficient to perform a statistical analysis of bubble dynamics. In particular, measurements of bubble size distributions (BSD) along the bed were performed. The analysis allowed to characterize the shape of BSD for different particle systems and fluidization gas velocities; interestingly a bimodal shape of BSD is observed, likely due to the simultaneous presence of coalescence and splitting phenomena. Linear combination of two Gamma distributions was used to describe the data. Also bubble size distributions weighed on bubble area were computed, and for all cases a characteristic negatively skewed distribution shape was found. Preliminary assessment of available data allowed to point out the effectiveness of the new approach proposed for a more in-depth description of bubble dynamics in 2D gas fluidized beds.

Dense-phase velocity fluctuation in a 2-D fluidized bed

Abstract This work presents an investigation of the perturbations induced by the bubbles in a 2-D fluidized bed. A combination of Digital Image Analysis (DIA) and Particle Image Velocimetry (PIV) techniques was developed to characterize the dense and bubble phases. The analysis of the mean and the instantaneous fluctuations of the velocity of the dense phase, together with the solid movement around bubbles, allowed for the measurement of the influence region, distinguishing an upward moving dense phase in the nose and the wake of the bubble (drift) and a downward moving dense phase in the sides of the bubble. For an isolated bubble, we measured the drift area within the total influence region and related the size of these regions to the equivalent diameter of the bubble. This work also presents results on the volumetric dissipation of kinetic energy, where we concluded that the energy dissipation in the dense phase is proportional to the square of the bubble velocity.

Deformation behavior of clay cap barriers of hazardous waste containment systems: Full-scale and centrifuge tests

The objective of this paper is to study the deformation behavior of a clay cap barrier of waste containment system for storing hazardous waste. The risk of bending of a clay barrier in case of differential settlements within underlying waste is focused in the present study. Field bending “bursting tests” were performed in France on clay barriers of 0.7 m thickness at different water contents. An attempt has been made to determine limiting distortion level at which cracks are initiated. The cap clay barrier configuration tested through field bursting tests was simulated at 12.5 g in a geo-centrifuge on model cap clay barriers of 56 mm thickness subjected to bursting mode of failure. Digital image analysis technique was used to ascertain initiation and propagation of cracking at the onset of differential settlements. Further influence of discrete and randomly distributed polypropylene tape fibers in restraining cracking tendency of the clay barrier was evaluated through a centrifuge model test. With an increase in the molding water content and the presence of randomly distributed fibers, an increase in limiting distortion level was observed. Use of 0.5% of fiber dosage and 90 mm long discrete fibers was found to restrain propagation of cracking of a clay barrier subjected to differential movements. Analysis and interpretation of field bursting tests was found to be in good agreement with physically observed centrifuge model test results.

Yarn twist measurement using digital imaging

Digital image analysis techniques in the spatial and frequency domains for twist measurement of yarns are described. A spatial technique is developed to extract the twist angle through the analysis of the yarn core image. Then, a Fourier transformation technique is applied to yarn images to measure the orientation of the fibre on the yarn surface. Finally, a hybrid method that incorporates frequency domain filtering prior to spatial analysis is proposed. The trials show that spatial analysis is a fast method and can successfully predict the twist in the yarn. Fourier transformation technique is quite sensitive to the protruding fibres obstructing the yarn surface, which may result in measurements having high variations. For yarns having little amount of hairs protruding from the core, the results agreed reasonably well with actual twist levels. Frequency domain filtering in conjunction with the spatial analysis of the yarn surface is found to be superior in terms of accuracy. The twist values calculated using the more reliable diameter measurements with back-lit images together with twist angles from the front-lit images are found to be more accurate when compared with the actual values.

Is Oil Red-O Staining and Digital Image Analysis the Gold Standard for Quantifying Steatosis in the Liver?

We read with great interest the randomized placebo-controlled trial by Abdelmalek et al.,1 in which the effects of betaine were studied in nonalcoholic fatty liver disease (NAFLD). The authors used the widely employed NAFLD activity score (NAS)2 as part of the inclusion criteria to their study and as the “gold-standard” endpoint to define treatment response. One of the major outcomes identified in the trial was change in the steatosis grade. The NAS is a well-validated, pragmatic, semiquantitative scoring system for determining the severity of NAFLD.3 The degree of steatosis contributes up to 3 of the 8 points to this score, and hepatocyte ballooning (which may be confused with small-droplet steatosis) contributes a further 2 points. Given the large contribution of steatosis to the overall score, it is important to correctly identify steatosis in a liver biopsy. During the study of both human tissue and tissue from mouse models of NAFLD, we have found that accurately determining the amount of steatosis on hematoxylin and eosin (H&E) staining, especially when the fat droplets are small, is extremely challenging. Consequently, we have explored an alternative approach adopting Oil red-O (ORO) as the “gold standard” histochemical stain for specifically identifying lipids.4 Using steatotic murine liver tissue from C57BL/6 mice, we compared the assessment of steatosis in H&E-stained sections by two expert liver pathologists with digital image analysis (DIA) quantification of ORO-stained sections. Hepatic triglyceride levels were quantified in the same tissues (triglyceride quantification kit, ab65336; Abcam Inc., Cambridge, MA). We found that, although ORO DIA assessment correlates well with the total liver triglyceride concentration and is therefore an accurate reflection of liver steatosis (Pearson correlation R = 0.706, P = 0.001), assessment by the expert pathologists showed poor correlation (R = −0.422). In samples with macrovesicular steatosis, we found that liver pathologists overestimated the amount of steatosis present on H&E stain as compared with ORO DIA (71.8% versus 46.7%, P < 0.01). In 67% of cases, the NAS steatosis score decreased from 3 to 2 when using ORO DIA. We conclude that the ORO DIA technique provides a more accurate quantification of microvesicular and macrovesicular steatosis. The NAS score is a useful and pragmatic tool in clinical practice and for patient selection for trial entry, but when the score is used as an outcome measure in a clinical trial setting, its performance is less robust. When, as Abdelmalek et al.1 report, steatosis changes are the major study outcome, it is therefore difficult to know whether inaccurate scoring of H&E-stained sections by expert pathologists confounds these observations. ORO DIA is the most reliable way to accurately assess and quantify histological liver steatosis. We accept that ORO staining is not practical for everyday use. It is optimally performed on frozen tissue because processing removes the lipids, hence the stain is not routinely performed on liver biopsies. However, its use may be of merit in clinical trials. Indeed, we have been able to successfully perform ORO staining on frozen sections of formalin-fixed human liver biopsies prior to processing, making wider adoption of this technique viable. Adam P. Levene MBChB Hons*, Hiromi Kudo MSc*, Mark R. Thursz M.D, FRCP , Quentin M. Anstee Ph.D., FRCP , Robert D. Goldin M.D., FRCPATH*, * Department of Histopathology, Imperial College Faculty of Medicine at St Mary's Hospital, London, UK, Department of Gastroenterology and Hepatology, Imperial College Faculty of Medicine at St Mary's Hospital, London, UK.

Virtual-reality-assisted surgery using CNN paradigm and image-processing techniques

The scope of this paper is to stress the two important application areas of medical imaging such as Image-guided Neurosurgery and Image-guided Vascular Surgery through image-processing techniques under Cellular Neural Network (CNN) environment. In real-time, it is very important to have in computer-aided surgery using Computed Tomography (CT), Magnetic Resonance Imaging (MRI), Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT) and Ultrasonography with the help of digital image processing and analysis techniques. The significant advantage of virtual-reality-assisted surgery is to preoperatively plan a complex reconstruction, visualise the plan during the operation on the operative site and make correct comparisons between the preoperative plans qualitatively and quantitatively.

Semiempirical, Analytical, and Computational Predictions of Dynamic Modulus of Asphalt Concrete Mixtures

Dynamic modulus is the key property used to characterize stiffness of asphaltic mixtures in pavement performance evaluation programs such as the Guide for Mechanistic–Empirical Design of New and Rehabilitated Pavement Structures. This paper investigates various models for predicting the dynamic modulus of asphalt mixtures and compares model predictions with experimental test results. The predictions of two semi-empirical models (Witczak's model, modified Hirsch model), an analytical micromechanics model (Hashin's model), and the computational micromechanics model are compared with the dynamic modulus test results obtained from cylindrical asphalt concrete specimens. For the computational micromechanics approach, the finite element method was incorporated with laboratory tests that characterize the properties of individual mixture constituents and with a digital image analysis technique to represent detailed microstructure characteristics of asphalt concrete mixtures. All predicting models investigated in this paper are in fair agreement with the test results. Witczak's equation simulates dynamic moduli somewhat greater than laboratory test results, whereas the modified Hirsch model generally underpredicts moduli. The computational micromechanics model presents a relatively higher deviation at lower loading frequencies, but it shows better predictions because the loading frequency is higher. Hashin's analytical micromechanics model is limited to accurately predicting the dynamic modulus of the asphalt mixtures because of geometric simplifications and assumptions. With further improvements, the computational micromechanics method incorporated with the testing protocol seems attractive, because it can directly account for geometric complexity due to aggregates and inelastic mixture component properties with fewer of the required laboratory tests.

Using Sharpness Image with Haar Function for Urban Atmospheric Visibility Measurement

Air quality affects human health, traffic safety and human life quality. The status of air quality can be indicated by the urban atmospheric visibility. The atmospheric visibility is traditionally the human-eye observed maximum distance at which outline of the selected target can be recognized. To replace the traditional measurement for the atmospheric visibility, digital image analysis techniques provide good visibility data which is established by the numerical index. These techniques provide good performance which is defined by the correlation between the observed visual range and the obtained index. In this paper, two high pass filters for atmospheric visibility monitoring are reviewed. Since the performance is affected by non-uniform illumination, such as shadow, a scheme which is called the sharpness image with Haar function is also introduced. Synthetic images, real images and actual atmospheric images are used to show the comparison of the performances. According to the results, the introduced method obtains higher relationship with human observed visibility than the other methods. We also show that obtaining the visibility indices with the proposed procedure can increase the similarity when the observed visibilities are the same.

The use of novel digital image analysis technique and rheological tools to characterize nanofiber nonwovens

Polyurethane (PU) solved in dimethylformamide (DMF) was electrospun under one set of conditions using five different supporting textiles. The mechanical properties of the nanofiber mats were measured by the Sentmanat extensional rheometer, and the pore size distribution was calculated by a newly proposed digital image analysis methodology applied on nanoscale SEM images taking macroscopic features of the nonwovens into account. It has been found that supporting textiles have a very high effect on mechanical properties of nanofiber mats (even if their fiber diameter distributions are similar), which can be explained by different porosity of the prepared samples.

O emprego da análise de imagem na determinação da distribuição de tamanho de partículas da areia presente no esgoto sanitário

É consensual, no meio técnico, que unidades de desarenação devem reter partículas discretas de elevada velocidade relativa de sedimentação (por exemplo: areia, silte, cinzas, semente de frutas etc); e que desarenadores capazes de remover grãos de areia de tamanho maior ou igual a 0,2 mm removem a maior parte dos materiais que ocasionam problemas operacionais em estações de tratamento de esgoto (ETE). Entretanto, não existe concordância acerca da forma de se determinar a concentração ou a distribuição granulométrica de tais materiais no esgoto sanitário. O presente artigo apresenta um método para determinar a distribuição granulométrica da areia presente no esgoto sanitário, o qual se baseia no emprego de técnicas de análise de imagens digitais. A aplicação do método proposto demonstrou que, em média, 84% da massa de areia carreada pelo esgoto sanitário afluente da ETE Jardim das Flores (Rio Claro, SP) era composta por partículas maiores ou iguais a 0,2 mm.

Centrifuge model tests on soil-nailed slopes subjected to seepage

This paper presents the results of centrifuge model tests on the behaviour of a slope subjected to seepage with and without soil nails. For this purpose, a custom-designed seepage flow simulator was developed for evaluating the deformation behaviour of slopes with and without soil nails at the onset of seepage flow at 30g. A series of centrifuge model tests was carried out on 2V:1H slopes by varying nail layout and length of soil nails. Bored and grouted soil nails including nail heads were modelled using thin aluminium tubes covered with a thin layer of sand-coated adhesive. A soil nail inclination of 15° with the horizontal was adopted with two different layouts. All the models were thoroughly instrumented with displacement transducers for measuring settlements and using pore pressure transducers to capture the development of the phreatic surface within the slope during the centrifuge test. A digital image analysis technique was employed to arrive at displacement vectors of markers placed on the front elevation of the slope. The displacements were used to compare slopes with and without soil nails and to identify the occurrence of failure surfaces. The results indicate that stabilising the earth slope using soil nails has a significant effect in improving the stability and deformation behaviour of a slope subjected to seepage. For a soil nail layout, the stabilising effect was observed to diminish with a decrease in soil nail length and increasing vertical and horizontal spacing of the soil nails in the slope surface. Stability analysis of the slope models with and without soil nails was found to be in good agreement with physically observed centrifuge test results.

Functional effects of xanthan gum on composite cassava-wheat dough and bread

The use of composite flour for bread making is gradually gaining prominence worldwide due to some economic and nutritional reasons. However, studies on the application of functional ingredients purposely to improve composite bread quality are very few. This paper examines the functional role of xanthan gum (XG) on the properties of dough and bread from composite cassava-wheat flour. The viscoelastic properties of dough and gas retention characteristics of batter as well as the fresh and storage properties of bread from the composite flour (90% wheat plus 10% cassava) were studied. The crumb cell structure was also studied using digital image analysis technique. Inclusion of XG had significant effects on the dough tenacity and extensibility and sensory acceptability of fresh composite bread. The oven spring, specific volumes of bread loaf and crumb softness were higher at 1% XG content. Also, addition of XG made the composite bread samples had more open crumb structure and better sensory acceptability. However, moisture loss and crumb firming during bread storage were best reduced when 1% XG was added to bread formulation.

Gross Placental Structure in a Low-Risk Population of Singleton, Term, First-Born Infants

Suboptimal fetal growth has been associated with an increased risk of adult disease, which may be exacerbated by an increased placental weight-to-fetal weight ratio. Placental weight is a summary measure of placental growth and development throughout pregnancy. However, measures of placental structure, including the chorionic disk surface area and thickness and eccentricity of the umbilical cord insertion, have been shown to account for additional variance in birth weight beyond that explained by placental weight. Little is known of the variability of these placental parameters in low-risk populations; their association with maternal, pregnancy, and neonatal characteristics; and the agreement between manual and digital measures. This study used manual and digital image analysis techniques to examine gross placental anatomy in 513 low-risk, singleton, term, first-born infants. Parametric methods compared groups and examined relationships among variables. Maternal birth weight, prepregnancy weight, and body mass index were associated with increased placental and birth weight (all P < 0.005), but only maternal birth weight was associated with increased placental surface area (P < 0.0005) and thickness (P = 0.005). Smoking during pregnancy reduced birth weight and increased the eccentricity of umbilical cord insertion (P = 0.012 and 0.034, respectively). The variability in these placental parameters was consistently lower than that reported in the literature, and correlations between digital and manual measurements were reasonable (r = .87-.71). Detailed analyses of gross placental structure can provide biologically relevant information regarding placental growth and development and, potentially, their consequences.

An efficient and reproducible method for quantifying macrophages in different experimental models of central nervous system pathology

Historically, microglia/macrophages are quantified in the pathological central nervous system (CNS) by counting cell profiles then expressing the data as cells/mm2. However, because it is difficult to visualize individual cells in dense clusters and in most cases it is unimportant to know the absolute number of macrophages within lesioned tissue, alternative methods may be more efficient for quantifying the magnitude of the macrophage response in the context of different experimental variables (e.g., therapeutic intervention or time post-injury/infection). The present study provides the first in-depth comparison of different techniques commonly used to quantify microglial/macrophage reactions in the pathological spinal cord. Individuals from the same and different laboratories applied techniques of digital image analysis (DIA), standard cell profile counting and a computer-assisted cell counting method with unbiased sampling to quantify macrophages in focal inflammatory lesions, disseminated lesions caused by autoimmune inflammation or at sites of spinal trauma. Our goal was to find a simple, rapid and sensitive method with minimal variability between trials and users. DIA was consistently the least variable and most time-efficient method for assessing the magnitude of macrophage responses across lesions and between users. When used to evaluate the efficacy of an anti-inflammatory treatment, DIA was 5–35× faster than cell counting and was sensitive enough to detect group differences while eliminating inter-user variability. Since lesions are clearly defined and single profiles of microglia/macrophages are difficult to discern in most pathological specimens of brain or spinal cord, DIA offers significant advantages over other techniques for quantifying activated macrophages.

Evaporating characteristics of sessile droplet on hydrophobic and hydrophilic surfaces

This study investigates evaporation characteristics of water droplets on hydrophobic and hydrophilic surfaces experimentally. The time-dependent contact angle, center-height, contact radius, surface area, and volume of droplet were measured for slide glass, octadecyltricholorosilane (OTS), and alkylketene dimmer (AKD) surfaces using the digital image analysis technique. First, during the evaporation of droplet on hydrophilic surface, the measured contact angle, liquid volume, and height of droplet were in good agreements with numerical predictions. It was found that there are no three distinct stages and no pinning section during the evaporation for the super-hydrophobic surface, and the surface characteristics highly affect evaporation speed rather than the droplet surface area contact with air. Moreover, as the hydrophobicity of surfaces becomes strong, the pinning time becomes short and the total evaporation time lasts long. In particular, the edge shrinking velocity of the droplet shows nonlinear characteristics, and its magnitude becomes extremely high at the last period of total evaporating time.

Image analysis for monitoring of crack growth in hydropower concrete structures

A digital image analysis technique for crack monitoring using a standard web-camera has been further developed to acquire continuous data sets on crack development in concrete dams. The method is based on an existing robust and straightforward non-contact method for experimental deformation analysis. It allows for the measurement of suspected serious cracks, identified from inspections, through a sequence of images captured at intervals. The crack opening displacements at the surface of investigated objects are obtained by an algorithm that makes it possible to automatically track the motions of discrete markers painted on the object surface markers and compute their centre of mass in a sequence of images. The data acquisition process is straightforward and is well suited for this type of environment. Results from laboratory experiments and a field-test on a commuter bridge in Sweden are presented. The study implies that the technique can be useful for hydropower concrete structure applications.

Use of digital photography and image analysis techniques to quantify erythema in health care workers

Nosocomial infections affect up to 26% of ICU patients. Compliance with the required hand hygiene procedures remains low, rarely exceeding 50%, with skin irritation as one of the main reasons for lack of conformity. The aim was to quantify the epidermal barrier effects, particularly erythema, from repetitive exposure to hand hygiene procedures among health care workers (HCWs) using an objective, reliable clinical method that could evaluate the entire hand surface. The hand skin of HCWs was evaluated before the initial scrub and at the end of multiple 2-3 days work cycles during spring (n=54) and winter (n=60) trials. The skin condition was measured with live visual skin evaluation (LSG), digital image analysis (DIA) of high-resolution digital images, and visual perception evaluation (VPS) of image pairs. The HCWs had significantly higher values of erythema than the non-HCW control group with all methods. Knuckle erythema increased over the cycle in both seasons. It decreased during recovery in spring and continued to increase during recovery in winter. For the DIA area of excess redness, the quantitative measure of erythema, the decrease over the cycle in spring was significantly different than the increase over the cycle in winter. Minimal changes in area of excess redness occurred during recovery in both seasons. With the VPS, both judges found a decrease in erythema during recovery in spring and an increase during recovery in winter, indicating significant differences for spring vs. winter (P<0.05). No differences in VPS erythema were seen for either product set over the work cycle during spring. Correlations were observed for (1) results for the VPS vs. the LSG method and (2) between excess erythema (mu+sigma) from DIA and the VPS erythema scores. Relatively low correlations were found between the DIA and VPS methods, i.e., knuckle mu+sigma and VPS erythema. Significant work cycle effects for spring vs. winter were observed with DIA, while significant effects were found during the recovery period with VPS. DIA produced an objective quantitative measure of erythema that was not limited or influenced by other aspects of skin irritation (e.g., dryness, scaling) or texture encountered in the visual methods of LSG and VPS. The DIA method minimizes the difficulty in differentiating erythema severity. Standardization of image capture and processing allows assessment of skin condition across clinical locations. The VPS is a more reliable way to compare skin condition at different times, i.e. beginning vs. the end of a treatment cycle, because images are viewed simultaneously and can be carefully examined for differences.

Centrifuge modeling of geotextile-reinforced slopes subjected to differential settlements

Today, geosynthetic-reinforced soil structures are widely used to support bridge abutments and approach roads in place of traditional pile supports and techniques. In such situations, foundation conditions have been shown to adversely affect the stability and deformation behaviour of overlying geosynthetic-reinforced slopes and walls. This paper addresses the response of geotextile-reinforced slopes subjected to differential settlements in a geotechnical centrifuge. Centrifuge model tests were carried out on model geotextile-reinforced sand slopes with two different types of reinforcement. A wrap-around technique was used to represent a flexible facing. In order to initiate failure in the reinforcement layers, the ratio of length of reinforcement to height of the slope was maintained as 0.85. One of the objectives of this paper is to present about a special device developed for inducing differential settlements during centrifuge test at 40 g for a reinforced soil structure. A digital image analysis technique was employed to arrive at displacement vectors of markers glued to the reinforcement layers. The displacements were used to compute and analyze the strain distribution along the reinforcement layers during different settlement stages. Results of the centrifuge test indicate that even after inducing a differential settlement equivalent to 1.0 m in prototype dimensions, the geotextile-reinforced soil structure with a flexible facing was not found to experience a collapse failure. Analysis of geotextile strain results shows that the location of the maximum peak reinforcement strain occurs along the bottom-most reinforcement layer at the onset of differential settlements, at the point directly below the crest of the slope.

Analysis of the bubbling behaviour of 2D gas solid fluidized beds

In the field of gas–solid fluidization, bubbles, and all features regarding them, have a very great importance, as they significantly affect the process performance. Numerous experimental studies on bubbles, and their formation, evolution, and properties, have been performed in the past. These investigations appear particularly difficult, due to the nature of these systems, since the gas phase is distributed in both the bubble and the emulsion phase. Several experimental approaches have been developed to tackle this study. Among these, the Digital Image Analysis Technique purposely developed in Part I of the present work, based on the use of a video camera for monitoring the phenomenon coupled with image analysis has been found viable and effective.

Digital Image Analysis of Endoscopic Images of Diminutive Polyps

Purpose: Endoscopic digital images contain rich information on texture and color. There is increasing interest in differentiating tissue pathology based on the patterns of color and texture features of endoscopic images extracted by digital image analysis (DIA). Objective: In this study, we applied techniques of DIA to endoscopic images of diminutive polyps in order to identify the color and texture features of endoscopic images that may differentiate adenomatous polyps from hyperplastic polyps. Methods: Methods: Our endoscopic image database was searched to retrieve and store digital images of diminutive polyps with diagnosis confirmed by histopathology. Texture analysis was performed on multiple regions of interest (ROIs) digitally selected in these images using the MatLab image processing toolbox; the following texture parameters were extracted: histogram (first order statistics) run-length and co-occurrence matrix (measuring features of runs of pixels and distribution of pairs of pixels), gradient analysis (spatial distribution of pixels), auto-regressive analysis (measurement of local interaction amongst pixels of different grey level values) and also wavelet analysis (which measures parameters of spatial frequency). Principal component analysis (PCA) was used for data reduction, and an artificial neural network (NN) based predictive model was built, trained and validated using the extracted texture features for classification of adenomatous polyps from hyperplastic polyps. Results: Results: A total of 110 and 109 ROIs were selected from endoscopic images of 30 and 28 patients with diminutive adenomatous and hyperplastic polyps, respectively. The sensitivity and specificity of the multilayered perceptron neural network classification model were both 82% with an area under the receiver operating characteristic (ROC) curve of 0.87. Three types of features of pixel distribution had high discriminatory power: Kurtosis (measure of the steepness of the pixel distribution), angular second momentum and horizontal and vertical grey level non-uniformity (parameters estimating the second order joint conditional probability density functions of spatial distribution of two neighboring pixels) Conclusion: Conclusion: Results of this exploratory study suggest that the technique DIA may be a clinically useful adjunct for non-invasive automated diagnosis of diminutive colon polyps, particularly if available as a real-time application.