Search

The article considers the possibility of controlling the brightness and contrast of the digital image by transformation of the pixel brightness through the power function. Analysis of the parameters of the converted images on the simple model of dark low contrast image has been carried out. The preferred values of parameters and possible ranges of brightness and contrast are determined. The results of transformation of the dark low contrast images compared with the results of image processing by other methods (approximated by reduction of a histogram to a uniform distribution and a television algorithm) are investigated. It has been stated that the parameters of the considered transformation can be chosen, so that the improvement of the distinguishability of the image details will be much better than using the methods with which the comparison is made.

Cattle in high-elevation rangelands experience cold and hot extremes. Given the increase in black hided cattle globally, thermoregulation options on rangelands, and hide color function affecting mammal thermal ecology, this study quantified winter albedo, external cattle temperatures (Tempcow), and differences (ΔT) between Tempcow and ambient air temperature (Tempamb), for different color cattle along a thermal gradient (≈−33 °C to +33 °C). From 2016 to 2018, I measured 638 individual Tempcow × Tempamb combinations for white (n = 183), red (n = 158), and black (n = 297) Bos taurus female cattle free roaming extensive Wyoming, USA rangelands. Pixel brightness of cow images relative to snow indicated mean (±standard error) albedo for white, red, and black cows (n = 3 of each) was 0.69 (±0.15), 0.16 (±0.04), and 0.04 (±0.01), respectively (p = 0.0027). Tempcow was explained by Tempamb (+), clear sky insolation index (+), and cow albedo (−). However, ΔT was explained by Tempamb (−), long-wave radiation (infrared, RadLW (−)), Tempcow (+), and cow albedo (+). Tempamb relative to ΔT was correlated for all hide colors (all p-values &lt, 0.0001, all r2 values &gt, 0.7)), yet slopes (m) were ~2× greater for red and black cows than white cows.

DNA is increasingly used in skeletal remains cases for identification and to resolve commingling. The implementation of a sampling strategy based on the likelihood of obtaining viable DNA profiles could minimize destruction of bones, expedite identification, and save time and resources by reducing the need to resample. Here we test whether bone fluorescence is a good indicator of potential DNA yield. Samples consisted of remains from seven different burial sites analyzed by the Committee on Missing Persons in Cyprus Anthropological Laboratory that were submitted for DNA analysis to an external DNA laboratory. Fluorescence was assessed as a function of pixel brightness values using images of bone and tooth samples captured using an alternate light source and measured in ImageJ. Across seven pooled sites, no relationship was apparent between fluorescence and DNA extracted, but there was a positive relationship when certain sites were considered in isolation. These results appear to suggest no overall relationship between fluorescence and DNA extracted; however, given the mixed nature of these results, additional research using a more controlled sample is needed.

Automatic crack detection is a critical task that has the potential to drastically reduce labor-intensive building and road inspections currently being done manually. Recent studies in this field have significantly improved the detection accuracy. However, the methods often heavily rely on costly annotation processes. In addition, to handle a wide variety of target domains, new batches of annotations are usually required for each new environment. This makes the data annotation cost a significant bottleneck when deploying crack detection systems in real life. To resolve this issue, we formulate the crack detection problem as a weakly-supervised problem and propose a two-branched framework. By combining predictions of a supervised model trained on low quality annotations with predictions based on pixel brightness, our framework is less affected by the annotation quality. Experimental results show that the proposed framework retains high detection accuracy even when provided with low quality annotations. Implementation of the proposed framework is publicly available at https://github.com/hitachi-rd-cv/weakly-sup-crackdet., Accepted to ICPR 2020

On the base of the first-order disproportion functions, an algorithm recognizing fragments of standard images under conditions when the analyzed signal contains these fragments in a distorted form due to passing through a nonlinear device, the static characteristic of which can be represented by a polynomial with unknown coefficients, is developed. Both, continuous signals and those, described by discrete pixel brightness values of a video image, are considered with the presence of additive impulse noises.

Beyond simple identification of either the presence or absence of microplastic particles in the environment, quantitative accuracy has been criticised as being neither comparable nor reproducible. This is, in part, due to difficulties in the identification of synthetic particles amidst naturally occurring organic and inorganic components. The fluorescent stain Nile red has been proposed as a tool to overcome this issue, but to date, has been used without consideration of polymer specific fluorescent variability. The aim of this study was to evaluate the efficacy of Nile red for microplastic detection by systematically investigating what drives variations in particle pixel brightness (PPB). The results showed that PPB varied between polymer type, shape, size, colour and by staining procedure. Sand, an inorganic component of the sample matrix does not fluoresce when stained with Nile red. In contrast the organic components, wood and chitin, fluoresce between 1.40 and 12 arbitrary units (a.u.) and 32 and 74 a.u. after Nile red staining, respectively. These data informed the use of a PPB threshold limit of 100 a.u., which improved the detection of EPS, HDPE, PP and PA-6 from the 6 polymers tested and reduced analysis time by 30-58% compared to unstained samples. Conversely, as with traditional illumination, PET and PVC were not accurately estimated using this approach. This study shows that picking a threshold limit is not arbitrary but rather must be informed by polymer specific fluorescent variability and matrix considerations. This is an essential step needed to facilitate comparability and reproducibility between individual studies.

Ultrasound tissue characterization (UTC) is an imaging tool used to quantify tendon structural integrity. UTC has quantified Achilles tendon (AT) acute response to load in athletes; however, AT response to cumulative load over a season is unknown. The purpose of this study was to evaluate AT response across a four-month competitive season in collegiate cross-country (XC) runners. Participants (n=21; male=9, female=12; age=19.8±1.2 years; height=171.9±8.9 cm; weight=60.2±8.5 kg) were imaged using the UTC device with a 10-MHz linear-array transducer mounted in a tracking device. The device captures images at 0.2 mm intervals along the AT. UTC algorithms quantified the stability of pixel brightness over every 17 contiguous transverse images into four echo types (I-IV). A total of 168 scans (n=21, bilateral limbs) were performed monthly across the four-month season (Aug=M1, Sep=M2, Oct=M3, Nov=M4). Echo-type percentages (%) were calculated from each scan. Generalized estimating equations (GEE) linear regression models evaluated echo-type % change (β) over the season (M1=reference). Type I increased from M1 to M4 (β=9.10, P

Mechanical damage of hair can serve as an indicator of health status and its assessment relies on the measurement of morphological features via microscopic analysis, yet few studies have categorized the extent of damage sustained, and instead have depended on qualitative profiling based on the presence or absence of specific features. We describe the development and application of a novel quantitative measure for scoring hair surface damage in scanning electron microscopic (SEM) images without predefined features, and automation of image analysis for characterization of morphological hair damage after exposure to an explosive blast. Application of an automated normalization procedure for SEM images revealed features indicative of contact with materials in an explosive device and characteristic of heat damage, though many were similar to features from physical and chemical weathering. Assessment of hair damage with tailing factor, a measure of asymmetry in pixel brightness histograms and proxy for surface roughness, yielded 81% classification accuracy to an existing damage classification system, indicating good agreement between the two metrics. Further ability of the tailing factor to score features of hair damage reflecting explosion conditions demonstrates the broad applicability of the metric to assess damage to hairs containing a diverse set of morphological features.

Background and Aims. Linked color imaging (LCI) helps screen and diagnose for early gastric cancer by color contrast in different mucosa. RGB (red, green, and blue) pixel brightness quantifies colors, which is relatively objective. Limited studies have combined LCI images with RGB to help screen for early gastric cancer (EGC). We aimed to evaluate the RGB pixel brightness characteristics of EGC and noncancer areas in LCI images. Methods. We retrospectively reviewed early gastric cancer (EGC) patients and LCI images. All pictures were evaluated by at least two endoscopic physicians. RGB pixel brightness analysis of LCI images was performed in MATLAB software to compare the cancer with noncancer areas. Receiver operating characteristic (ROC) curve was analyzed for sensitivity, specificity, cut-off, and area under the curve (AUC). Results. Overall, 38 early gastric cancer patients were enrolled with 38 LCI images. Pixel brightness of red, green, and blue in cancer was remarkably higher than those in noncancer areas (190.24±37.10 vs. 160.00±40.35, p<0.001; 117.96±33.91 vs. 105.33±30.01, p=0.039; 114.36±34.88 vs. 90.93±30.14, p<0.001, respectively). Helicobacter plyori (Hp) infection was not relevant to RGB distribution of EGC. Whether the score of Kyoto Classification of Gastritis (KCG) is ≥4 or p>0.05). Receiver operating characteristic (ROC) curve for differentiating cancer from noncancer was calculated. The maximum area under the curve (AUC) was 0.767 in B/G, with a sensitivity of 0.605, a specificity of 0.921, and a cut-off of 0.97. Conclusions. RGB pixel brightness was useful and more objective in distinguishing early gastric cancer for LCI images.

Many solar forecast algorithms based on ground based sky imagery apply the red-blue ratio (RBR) method to classify image pixels as clear or cloudy, by comparing the current image with the corresponding image from a clear sky library (CSL). The CSL needs to be updated regularly due to changes in clear sky readings over time caused by aerosols and imager dome properties. This clear sky library is typically created by visually scrutinizing daily sky videos and selecting appropriate clear sky periods. This practice takes a significant amount of time and manual intervention can result in human errors. To avoid this, an automated CSL algorithm (ACSL) was developed which filters each image for clear sky features including maximum green pixel brightness, average RBR, and red channel difference by pixel with respect to the previous image. The root mean square difference (RMSD) between the image RBR of the manually created CSL and the ACSL for November and April 2013 at UC San Diego were observed to be less than 6% over the full range of solar zenith angles. The ACSL was found to be more representative of clear conditions than its manual counterpart.

Purpose: To enhance the current standards of subclinical keratoconus screening based on the statistical modeling of the pixel intensity distribution of Scheimpflug images. Methods: Scheimpflug corneal tomographies corresponding to 25 corneal meridians of 60 participants were retrospectively collected and divided into three groups: controls (20 eyes), subclinical keratoconus (20 eyes), and clinical keratoconus (20 eyes). Only right eyes were selected. After corneal segmentation, pixel intensities of the stromal tissue were statistically modeled using a Weibull probability density function from which parameter a (pixel brightness) was derived. Further, data were transformed to polar coordinates, smoothed, and interpolated to build a map of the corneal a parameter. The discriminative power of the method was analyzed using receiver operating characteristic curves. Results: The proposed platform-independent method achieved a higher performance in discriminating subclinical keratoconus from control eyes (90.0% sensitivity, 95.0% specificity, 0.97 area under the curve [AUC]) than the standard method (Belin–Ambrósio enhanced ectasia display), which uses only corneal morphometry (85.0% sensitivity, 85.0% specificity, 0.80 AUC). Conclusions: Analysis of light backscatter at the cornea successfully discriminates subclinical keratoconus from control eyes, upgrading the results previously reported in the literature. Translational Relevance: The proposed methodology has the potential to support clinicians in the detection of keratoconus before showing clinical signs. © 2021 The Authors.

Problems encountered in diagnosis of blood diseases are considered, and an analysis of existing methods for measuring blood parameters is presented. A new approach to screenings is proposed that is based on recording images of the gas-discharge emission from blood droplets in an electromagnetic field, and also a method for automated computer processing of the images obtained, making it possible to generate the pixel brightness histogram, to estimate the values of the medians in the brightness ranges, and to carry out fuzzy c-means cluster analysis.

This study evaluated the impact of various cosmetics on the surface properties of silicone hydrogel (SiHy) contact lens materials.In this in vitro experiment, 7 SiHy contact lens materials were coated with 1 of 9 cosmetics, including common hand creams (3), eye makeup removers (3), and mascaras (3). Dark-field microscopy images were taken to determine pixel brightness (PB) after cosmetic exposure, which describes the visible surface deposition (n=6 for each lens type), with a higher PB indicating increased deposition. The sessile drop technique was used to determine the advancing contact angle (CA). Measurements were repeated for both methods after a single peroxide-based cleaning cycle.Pixel brightness was significantly higher for mascara-coated lenses compared with the other cosmetic products (P0.01). The peroxide-based lens care solution removed most deposits from the nonwaterproof mascara for 4 lens types, whereas deposits remained relatively unchanged for 1 waterproof mascara (P0.05). Hand creams and makeup remover had minimal impact on PB. Changes in CA measurements after cosmetic application were highly lens dependent. Hand creams caused primarily a decrease in CA for 5 of the 7 lens types, whereas 1 of the waterproof mascaras caused a significant increase of 30 to 50° for 3 lens types.Some mascara-lens combinations resulted in increased CA and PB, which could have an impact on in vivo lens performance. Nonwaterproof mascara was mostly removed after a cleaning cycle. Further research is needed to understand the clinical implications for SiHy lens wearers using cosmetics.

At the suggestion of the NASA Meteoroid Environment Office (NASA/MEO), which promotes lunar impact monitoring worldwide during NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) mission period (launched Sept. 2013), we set up a video observation system for lunar impact flashes using a 16-inch educational telescope at Chungnam National University. From Oct. 2013 through Apr. 2014, we recorded 80 hours of video observation of the unilluminated part of the crescent moon in the evening hours. We found a plausible candidate impact flash on Feb. 3, 2014 at selenographic longitude 2.1° and latitude 25.4°. The flash lasted for 0.2 s and the light curve was asymmetric with a slow decrease after a peak brightness of 8.7 ± 0.3 mag. Based on a star-like distribution of pixel brightness and asymmetric light curve, we conclude that the observed flash was due to a meteoroid impact on the lunar surface. Since unequivocal detection of an impact flash requires simultaneous observation from at least two sites, we strongly recommend that other institutes and universities in Korea set up similar inexpensive monitoring systems involving educational or amateur telescopes, and that they collaborate in the near future.

In this paper, the approach of changing bit depth of images is considered. This type of operation is required when performing primary processing operations, identifying parameters and stitching images. The process of changing bits depth of images is performed in three stages. At each stage, the error minimization criterion is tested Result of applying the approach allows obtaining numerical region characteristics including the number of clusters, the number of minimum and maximum cluster sizes. To perform the process of minimizing some of the criteria, it is necessary to divide the image into areas. The paper presents a mathematical description of the approach, as well as flowcharts for performing operations of data processing steps. The article gives recommendations for choosing coefficients to obtain optimal minimizing parameters. The test images give an example of performing bit changes on image areas.

© 2017 IEEE. Commercial off-the-shelf 12-Megapixel CMOS image sensors were irradiated with 105 MeV protons - one part to a fluence of 4×1011 protons/cm2, and a second part to 2×1011 protons/cm2. Pixel brightness increases with fluence along with annealing effects are reported. No latch-up events or hangs occurred.

Results of a study of automatic recognition of pathological resorption zones in the image of the jawbone are presented. A criterion for the presence of pathological resorption in the bone is formulated based on statistical investigation. The pathological resorption search method is described as a sequence of algorithmic steps.

Within the context of photometric stereo reconstruction, flatfielding may be used to compensate for the effect of the inverse-square law of light propagation on the pixel brightness. This would require capturing a set of reference images at an off-line imaging session, which employs a calibrating device that should be captured under the exact conditions as the main session. Similarly, the illumination vectors, on which photometric stereo relies, are typically precomputed based on another dedicated calibration session. In practice, implementing such off-line sessions is inconvenient and often infeasible. This work aims at enabling accurate photometric stereo reconstruction for the case of non-interactive on-line capturing of human faces. We propose unsupervised methodologies, which extract all information that is required for accurate face reconstruction from the images of interest themselves. Specifically, we propose an uncalibrated flatfielding and an uncalibrated illumination vector estimation methodology, and we assess their effect on photometric stereo face reconstruction. Results demonstrate that incorporating our methodologies into the photometric stereo framework halves the reconstruction error, while eliminating the need of off-line calibration.

This paper considers the optimization of a set of brightness gradations for pixel images of the tissue morphology of patients with oncological pathology. The influence of a set of pixel brightness gradations on the functional performance of training a system for the recognition of images of oncological diseases is analyzed. It is established that a change in the collection of pixel brightnesses in the receptive field increases the value of the criterion of functional efficiency and, as a result, the reliability of recognition.

Improved color channel comparison method (ICCCM) is an effective method to transformcolor images into gray-scale ones. Based on the ICCCM, black or white insects could be effectively extracted and recognized from the real color images with bright background. Howeverit is difficult to use the ICCCM to extract and recognize the black insects from the realcolorimage with dark background. In this paper, the ICCCM is modified to transformthe color images into the gray ones, extracting and recognizing the black insectson the dark background. The ICCCM is modified as follows: (1) A threshold of the gray image is an average brightness value ofred (R), green (G) and blue (B) in all the image pixels.(2) The bright pixels and the color pixels have the highest brightness value 255 in the gray image.(3) A pixel brightness value of the dark area in the gray image equals to a minimum of R, G and B in the pixel. (4) After deleted all the pixels with a brightness value of 255, a threshold of the binary image is determined by Otsus theory. The modified ICCCM more effectively extracts and recognizes the black insects from the realcolorimages with dark background compared with the ICCCM.

Shot boundary detection is an essential step for efficient browsing, sorting, and classification of video data. Robust shot detection method should overcome the disturbances caused by pixel brightness and object movement between frames. In this paper, two shot boundary detection methods are presented to address these problem by using segmentation, object movement, and pixel brightness. The first method is based on the histogram that reflects object movements and the morphological dilation operation that considers pixel brightness. The second method uses the pixel brightness information of segmented and whole blocks between frames. Experiments on digitized video data of National Archive of Korea show that the proposed methods outperforms the existing pixel-based and histogram-based methods.

BackgroundThere is growing evidence that maximal surgical resection of primary intrinsic brain tumours is beneficial, both by improving progression free and overall survival and also by facilitating postoperative chemotherapy and radiotherapy. Hence, there has been an increase in the popularity of real-time intraoperative imaging in brain tumour surgery. The complex theatre arrangements, prohibitive cost and prolonged theatre time of intraoperative MRI have restricted its application. By comparison, intraoperative three-dimensional ultrasound (i3DUS) is user friendly, cost-effective and portable and adds little to surgical time. However, operator-dependent image quality and image interpretation remain limiting factors to the wider application of this technique. The aim of this study was to explore objective i3DUS image analysis and its potential therapeutic role in brain tumour surgery.MethodsA prospective, observational study was undertaken (approved by the local Research and Ethics Committee prior to recruitment). Biopsies were taken from the solid, necrotic, periphery and brain/tumour interface of intrinsic primary brain tumours. Digital i3DUS images were analysed to extract quantitative parameters from these regions of interest (ROI) in the i3DUS images. These were then correlated with the histology of the relevant specimens. The histopathologist was blinded to the imaging findings.ResultsNinety-seven patients (62 males; mean 54 years) with varying gliomas (84 high grade) were included. Two hundred and ninety regions of interest were analysed. Mean pixel brightness (MPB) and standard deviation (SD) were correlated with histological features. Close correlations were noted between MPB and cellularity, and SD and intrinsic cellular diversity.ConclusionsMPB and SD are objective measures reflecting the sensitivity of i3DUS in detecting the presence and extent of intrinsic brain tumours. They indirectly suggest heterogeneity, cellularity and invasiveness, providing information of the nature of the tumour, and also reflect the sensitivity of intraoperative US to detect the presence of residual intrinsic brain tumours. Development of this paradigm will enhance i3DUS use as an adjunct in brain tumour surgery. Optimizing its intraoperative application will impact surgical resection and, hence, patient outcome.

A total number of 270 ultrasound images of m. longissimus behind the 13th thoracic vertebrae were obtained on 90 lamb carcasses. Three different scanning frequencies were used (5.0, 7.5 and 10.0 MHz) in order to analyse how the frequency of the ultrasound wave affects the changes of pixel brightness in the ultrasound image. In the images obtained with 10 MHz probe the brightness of the 1st region was higher by 27% and 25% (P≤0.01) compared to the same region of images obtained with 5 MHz and 7.5 MHz frequency probe. The 3rd region of muscle cross-sections obtained with 10 MHz frequency was very dark, with the brightness lower by 22,5% and 28,3% compared to the same region of images obtained with 5 MHz and 7.5 MHz frequency. In the images obtained with 10 MHz scanning frequency, the decrease of brightness from the 1st to the 3rd region of the image was very sharp. While in the images obtained by means of 5 and 7.5 MHz ultrasound frequency, the brightness changes between the regions were very fluent. To conclude, the results of the presented research reveal that high ultrasound frequency has a negative impact on ultrasound image brightness and may reduce the information value of the image.

Aim: Ultrasound tissue characterization (USTC) is a precursor of ultrasound virtual histology (USVH), already applied to B-mode images of coronary, carotid, and peripheral arteries, as well as venous thrombosis. Elevated echogenicity has been described for a rejected transplanted kidney. We analyzed data from healthy young adults as reference for further renal USTC. Methods: Ultrasound kidney images of 10 volunteers were analyzed. Pixel brightness in the 0-to-255 range was rescaled to zero for black and 200 for fascia brightness before automatic classification into 14 ranges, including ‘‘blood-like’’ (0Y4), ‘‘fat-like’’ (8Y26), ‘‘hypoechoic muscle-like’’ (41Y60), ‘‘hyperechoic muscle-like’’ (61Y76), 4 ranges of ‘‘fiber-like’’ (112Y196), ‘‘calcium-like’’ (211Y255) and intermediary intervals. Nomenclature was readapted using nonechoic, hypoechoic I to IV, echoic I to IV, hyperechoic I to IV, and saturated echoes to avoid inference to actual kidney tissue. Descriptive and comparative statistics were based on percentages of pixels in specific brightness ranges. Sample Population: Eight women and 2 men, 26 T 4 years (range, 22Y34 years) old, were studied. Kidney length was 10.5 T 0.9 cm (9.0Y12.0 cm). Doppler US resistivity index was 0.67T 0.03 (0.62Y0.71). Results: Original fascia brightness converted to 200 value had a mean T SD of 206 T 16 (range, 181Y236). Kidney grayscale median averaged 37 T 6 (27Y48). Most pixels were hypoechoic II to IV (8Y60), averaging 78% T 6% (66%Y87%). Percentages for fat-like, intermediary fat/muscle-like, and hypoechoic muscle-like intervals averaged 25%, 28%, and 25%, respectively. Conclusions: A reference database for USTC/USVH of normal young kidneys was created for future comparisons with transplanted and abnormal kidneys. Normal renal echoes have low brightness. Hyperechoic pixels may represent abnormalities.

Two precedures are presented for image preprocessing, automated haze removal and the relative radiometric normalization of multitemporal optical images, to act as the data support for land cover change detection and image analysis. The developed algorithm for haze removal involves processes of feature and texture analysis of the multiresolution spatial frequency distribution of pixel brightness information content of a scene. The image contaminated by haze is decomposed into layers of different resolutions of spatial distribution frequencies. The radiometric characteristics of the corresponding layers are estimated and analyzed with topology based multiresolution spatial analysis technology. Based on the analysis, the haze component is then separated from the remaining spatial frequency components representing spectral information of actual land cover types in the scene, and a spectrally corrected image with “haze-off” characteristics is obtained. Then a method is used for radiometric normalization between multitemporal images of the same area. Case study using several different type images of Qingdao City in China proves the effectiveness of this technique except for those regions too hazy.

Consistency of pixel brightness is an important index for LED display.For LED display with un-ideal consistency of pixel brightness,to get pictures file including brightness information by taking photograph,via computer,background can be de-noised,pixel can be positioned,and even information about brightness can be obtained,thus getting file about brightness data,and finally,handled by computer and database,the Excel brightness corrected file will be made.The brightness file corrected in Excel format can be convenient to deliver to the controller of LED display where it will be corrected point by point.In this way,the visual effect of LED display could be greatly improved.

The 21-cm PDF (i.e., distribution of pixel brightness temperatures) is expected to be highly non-Gaussian during reionization and to provide important information on the distribution of density and ionization. We measure the 21-cm PDF as a function of redshift in a large simulation of cosmic reionization and propose a simple empirical fit. Guided by the simulated PDF, we then carry out a maximum likelihood analysis of the ability of upcoming experiments to measure the shape of the 21-cm PDF and derive from it the cosmic reionization history. Under the strongest assumptions, we find that upcoming experiments can measure the reionization history in the mid to late stages of reionization to 1-10% accuracy. Under a more flexible approach that allows for four free parameters at each redshift, a similar accuracy requires the lower noise levels of second-generation 21-cm experiments.

This paper describes a reliable method developed for a view-based navigation which uses approximate planes of image pixel brightness in which edge-based information has been modified with a least-square algorithm. The system developed in this work have shown not only the robustness of this method to ambient lighting conditions due to indoor illumination or daylight from windows, but also the high capability of its noise rejection for images taken in recording runs. This method has been found to be highly tolerated in larger ambient illumination change than the used conventional method where brightness-based pixel values are utilized. Based on this scheme, the experiment has been successfully made in the navigation test even if large ambient lighting condition was given to the robot by means of the change in the number of the luminescent lamps or in the night and the day.

A robust matching scheme for computing optical flow within a sequence of grayscale images is proposed. The technique employs the gradient information in textured images for extracting features in the form of orientation codes, which are then used for matching. The proposed method has been found to be robust in cases of matching under different ill-conditionings especially illumination variations. We utilize its robustness to compute optical flow in cases where illumination fluctuation is a problem and matching pixel brightness can introduce errors. Results of computation of optical flow field on real world scenes in the cases of translation, rotation and zooming have been presented and compared with other region matching techniques.

Purpose The purpose of this study was to evaluate the ability of 4 liquid boluses to enhance pixel brightness and the ease with which the boluses could be identified during the sonographic evaluation of oral swallowing in healthy young adults. Methods Ten healthy adult volunteers (5 men and 5 women), ranging in age from 21 to 31 years, underwent sonographic evaluation of the oral phase of swallowing while sitting in their usual feeding position. We compared the ability of the 4 following liquids to improve sonographic visualization of swallowing with that of water: a carbonated cola beverage, 5.0 ml of Thick-It in 120 ml of water, 2.5 ml of Thick-It in 120 ml of water, and 7.5 ml of confectioners' sugar in 120 ml of water. Water was used as a control. In each case, 5 ml of the liquid was introduced into the subject's oral cavity using a syringe, and the subject was instructed to swallow. Digitized still images and recorded video sequences of sonographic examinations of the swallowing were analyzed. The brightness of the bolus image on selected digitized video frames was measured digitally using Image Analyst software. Pixel brightness within selected regions of interest for each of the test liquids was statistically compared with that for water. Seven clinicians rated the visualization of each test liquid and water on paired sonographic videotape sequences. These ratings and the level of agreement between them were statistically tested. Results Only the carbonated cola beverage demonstrated statistically greater pixel brightness than that of water on digitized video frames (p = 0.01), whereas both cola (with a moderate inter-rater agreement, κ = 0.50) and 5.0 ml Thick-It mixed with 120 ml of water (with a fair inter-rater agreement, κ = 0.24) were significantly better visualized on sonographic video sequences. Conclusions The digital still-frame analysis confirmed the clinicians' ratings of bolus visualization on real-time sonography, but dynamic sonography is more important than still frames in assessing sonographic swallow media because the dynamic images more closely parallel what is seen in clinical practice. Future investigations of sonographic contrast agents for use in the examination of the oral phase of swallowing should use both static digital (still-frame) and dynamic (real-time) assessment methods, as well as expert reviewers. © 2002 John Wiley & Sons, Inc. J Clin Ultrasound 30:83–87, 2002; DOI 10.1002/jcu.10034