Changes In Pixel Intensity Research Articles

Laser-Speckle-Photometry – A Method for Non-Contact Evaluation of Material Damage, Hardness and Porosity

Abstract The Laser Speckle Photometry is a newly developed non-contact non-destructive testing method which is based on the detection and analysis of thermal or mechanical activated characteristically speckle dynamics. The determination of the material damaged state is based on the understanding of structural changes on different scaling levels given by the physical mesomechanics. The hierarchical behavior of the mesomechanical structures (meso-structures) leads to the hypothesis of the fractal nature of the deformation structure. The fractal dimension D F is a suitable parameter to characterize the fatigued material state. In the case of the laser speckle photometry method the modified auto-correlation function from the pixel intensity changes of the speckles images was used for the computation of Parameter D F . The hardness or porosity of materials is defined by micro-structural variation and is combined with several thermal properties of the material. Therefore the speckle thermal diffusivity parameter K was determined using thermal conduction equation from the pixel intensity of speckle images changes during thermal activation. Afterwards correlation between the norm K and hardness and porosity, respectively was found. Results of this research will be presented in the present contribution.

Method of calibration of a fluorescence microscope for quantitative studies

Confocal microscopy is based on measurement of intensity of fluorescence originating from a limited volume in the imaged specimen. The intensity is quantized in absolute (albeit arbitrary) units, producing a digital 3D micrograph. Thus, one may obtain quantitative information on local concentration of biomolecules in cells and tissues. This approach requires estimation of precision of light measurement (limited by noise) and conversion of the digital intensity units to absolute values of concentration (or number) of molecules of interest. To meet the first prerequisite we propose a technique for measurement of signal and noise. This method involves registration of a time series of images of any stationary microscope specimen. The analysis is a multistep process, which separates monotonic, periodic and random components of pixel intensity change. This approach permits simultaneous determination of dark and photonic components of noise. Consequently, confidence interval (total noise estimation) is obtained for every level of signal. The algorithm can also be applied to detect mechanical instability of a microscope and instability of illumination source. The presented technique is combined with a simple intensity standard to provide conversion of relative intensity units into their absolute counterparts (the second prerequisite of quantitative imaging). Moreover, photobleaching kinetics of the standard is used to estimate the power of light delivered to a microscope specimen. Thus, the proposed method provides in one step an absolute intensity calibration, estimate of precision and sensitivity of a microscope system.

Physiology of the small bowel: A new approach using MRI and proposal for a new metric of function

Background The mechanics of small bowel motility are extremely complex. Routine clinical access to small bowel has been restricted to radiological enteric contrast studies which have not contributed significantly to the understanding of small bowel physiology. Small bowel mechanics are understood within a framework of individual visible or measurable elements such as peristaltic wave formation, intra-luminal pressure gradients and transit times. There are no global measures of small bowel function that can be readily obtained in vivo in humans. Magnetic resonance imaging (MRI) is playing an increasingly important role in radiological diagnosis of small bowel disease and dynamic MRI offers the possibility of capturing small bowel movement in three-dimensional cinematic datasets. The metrics that are used to describe small bowel mechanics, typically anatomical measures in isolated segments, are not suited to analysing these large dynamic datasets. The proposal in this paper is to leave behind all previously described anatomical metrics and to describe anew the mechanics of small bowel movement in mathematical terms derived from changes in pixel intensity within dynamic MRI datasets so that global small bowel activity might be summarised in a single novel metric. Hypothesis The hypothesis of this paper is that global small bowel activity can be quantified by a new dynamic MR based metric. Evaluation A proposed strategy for evaluation includes a progression through feasibility, optimisation, reliability and validation studies. Thereafter normal volunteers would be required in order to define normal ranges for the new metric. These ranges would describe small bowel activity during fasting or after ingestion of fluids and standard meals. Mathematical modelling of the data could follow a two stage approach. The first stage could be to study segmentation or extraction techniques by which the small bowel activity could be isolated from MRI signal generated by the rest of the abdomen. The second stage would be to apply a number of data mining techniques that would identify significant features within the datasets. Conclusion If this approach proves to be a useful model for studying small bowel physiology in humans, it would afford significant new avenues of research and treatment particularly in areas such as enteric drug delivery, the ageing gut, and nutrition.

Determination of senescent spotting in banana ( Musa cavendish) using fractal texture Fourier image

The analysis of fractal texture reflects a change in pixel intensity, and this might contain information about the structure of objects since a great change in intensity might usually indicate changes in the object. In the images of banana surfaces, the texture image can, to some extent, reflect changes and thus it can be used as an indicator of the last stage during the ripening process (over-ripening). In this experiment, bananas ( Musa cavendish) were stored during 10 days at 20 °C. Images of banana surfaces were recorded using a computational vision system. The over-ripening process of bananas was represented by an increment in the fractal value derived from texture fractal Fourier analysis. The result shows that fractal texture derived from the spectral Fourier analysis increased monotonically and it can be used as an indicator of the senescence process also called “senescent spotting” of the banana peel.

QUANTITATIVE ULTRASOUND, MAGNETIC RESONANCE IMAGING, AND HISTOLOGIC IMAGE ANALYSIS OF HEPATIC IRON ACCUMULATION IN PIGEONS (COLUMBIA LIVIA)

Iron overload was induced by iron dextran i.v. in clinically healthy adult pigeons, Columbia livia, (n = 8). Hemosiderosis was induced in all treated birds. Two control pigeons received no iron injections. Pigeons did not show clinical signs of iron overload during the 6-wk study. Ultrasound examination of the liver in the pigeons receiving iron dextran was performed on days 0, 13, 28, and 42. No ultrasound images were collected on the control pigeons. Magnetic resonance imaging was performed on days 0, 13, 28, and 42 on all study pigeons and imaging sequences were collected in three different imaging formats: T1, T2, and gradient-recalled echo (GRE). Surgical liver biopsies were performed on pigeons receiving iron dextran on days 2, 16, and 45 (at necropsy). A single liver sample was collected at necropsy from the control birds. Histologic examination, quantitative image analysis, and tissue iron analysis by thin-layer chromatography were performed on each liver sample and compared to the imaging studies. Although hemosiderosis was confirmed histologically in each experimental pigeon, no significant change in pixel intensity of the ultrasound images was seen at any point in the study. Signal intensity, in all magnetic resonance imaging formats, significantly decreased in a linear fashion as the accumulation of iron increased.

Precision of light intensity measurement in biological optical microscopy

Standardization and calibration of optical microscopy systems have become an important issue owing to the increasing role of biological imaging in high-content screening technology. The proper interpretation of data from high-content screening imaging experiments requires detailed information about the capabilities of the systems, including their available dynamic range, sensitivity and noise. Currently available techniques for calibration and standardization of digital microscopes commonly used in cell biology laboratories provide an estimation of stability and measurement precision (noise) of an imaging system at a single level of signal intensity. In addition, only the total noise level, not its characteristics (spectrum), is measured. We propose a novel technique for estimation of temporal variability of signal and noise in microscopic imaging. The method requires registration of a time series of images of any stationary biological specimen. The subsequent analysis involves a multi-step process, which separates monotonic, periodic and random components of every pixel intensity change in time. The technique allows simultaneous determination of dark, photonic and multiplicative components of noise present in biological measurements. Consequently, a respective confidence interval (noise level) is obtained for each level of signal. The technique is validated using test sets of biological images with known signal and noise characteristics. The method is also applied to assess uncertainty of measurement obtained with two CCD cameras in a wide-field microscope.

잡음영상에서 로버스트 순위-순서 검정을 이용한 효과적인 에지검출

에지검출은 컴퓨터비전과 영상처리 시스템에서 널리 사용되는 단계이다. 본 논문에서는 잡음영상에서 효율적인 에지검출을 위해 이표본 위치 문제에서 월콕슨 검정의 대안인 로버스트 순위-순서 검정에 기초한 새로운 검출법을 제안하였다. 제안된 방법은 <TEX>$\delta$</TEX>-에지모형하에서 <TEX>$5\times5$</TEX> 윈도우의 부분 픽셀만으로 구성된 근방영역 간에 통계적으로 유의한 차이가 있는지를 조사하였다. 제안된 에지 검출법의 성능을 평가하기 위해 실제영상과 인조영상을 가지고 영상실험을 통하여 얻은 에지맵과 객관적인 척도하에서 양적으로 비교 분석하였다. Edge detection has been widely used in computer vision and image processing. We describe a new edge detector based on the robust rank-order test which is a useful alternative to Wilcoxon test. Our method is based on detecting pixel intensity changes between two neighborhoods with a <TEX>$r{\times}r$</TEX> window using an edge-height model to perform effectively on noisy images. Some experiments of our robust rank-order detector with several existing edge detectors are carried out on both synthetic images and real images with and without noise.

Evaluation of the Time Course of Plasma Extravasation in the Skin by Digital Image Analysis

Plasma extravasation (PE) can be triggered by neurotransmitters as part of a neuroinflammatory response. We present a technique based on video digital image processing that provides a simple, noninvasive, reliable, and quantitative method for measuring the time course and extent of PE in the skin. After intravenous infusion of Evans Blue dye, stimulation of the saphenous nerve caused the skin on the dorsomedial region of the hind paw to become dark blue. The change in reflectance of the skin was recorded with a monochrome video camera. Images were digitized and analyzed with inexpensive or public domain software. The change in pixel intensity was determined in a selected region. Stimulation at 4 Hz caused greater darkening of the skin than at 1 Hz, and this was confirmed with spectrophotometric measurements of Evans Blue content. The NK1 receptor antagonist CP-99, 994 blocked saphenous nerve and substance P–induced darkening of the skin. The results indicate that our measurement gives results similar to those obtained with classic methods that are widely accepted as an indication of PE. This simple and quick method reveals the extent, time course, and location of PE, is cheap to implement and easy to learn, and thus represents a useful and alternative tool for studies of PE and its modulation. Perspective This article presents a simple technique with which to evaluate the time course and extent of plasma extravasation in the skin of animal models of neuroinflammation. The technique is well suited to answer questions about basic physiologic mechanisms of neuroinflammation and should also be useful in drug testing studies.

What's in a “Smile?” Intra-operative Observations of Contralateral Smiles Induced by Deep Brain Stimulation

Objective: To descirbe smiling and euphoria induced by deep brain stimulation (DBS). Background and Significance: The brain systems inducing emotional experiences and displays are not entirely known, but the ventral striatum including the nucleus accumbens have been posited to play a critical role in mediating emotions with positive valence. DBS has been successfully employed for the treatment of movement disorders, and most recently obsessive compulsive disorder (OCD). The purpose of this report is to describe the emotional changes associated with stimulation of the ventral striatum. Methods: A single patient with intractable OCD had electrode arrays placed in the right and left anterior limbs of the internal capsule and region of the nucleus accumbens. Changes in facial movement during stimulation were quantified by video recording. Ten video segments, time locked to the onset of stimulation, were digitized and changes in pixel intensity that occurred over both sides of the lower face, on a frame by frame basis, following stimulation onset were computed. These summed changes in pixel intensity represented the dependent variable of “entropy” and directly corresponded to changes in light reflectance that occur during facial movement. Results: During stimulation on both the right and left side, the patient consistently developed a half smile on the side of the face contralateral to the stimulating electrode, and also became euphoric. The effect ceased when DBS was discontinued. Conclusions: DBS in the region of the nucleus accumbens produced smile and euphoria suggesting that alterations in the ventral striatum may result in emotional experience and displays. We hypothesize the existence of a limbic-motor network responsible for such changes. This observation suggests that DBS may be useful as a therapy for mood disorders.

RADIOMETRIC NORMALIZATION OF MULTI–TEMPORAL IMAGES BASED ON IMAGE SOIL LINES

A radiometric normalization procedure utilizing the soil line concept is developed and tested. The routine, referredto as the soil line transformation (SLT) technique, is developed to provide a system for transforming multitemporal imagesto a common reference scene. The routine involves developing soil lines not only for the bare soil images, but also for imageswith vegetative cover, assuming that some pixels within the entire image would represent bare soil conditions orpseudoinvariant features. The procedure uses the soil lines developed for the imagetobetransformed and the referenceimage to form transforming equations using pixels within a specified interval of both soil lines. In this research, the SLTtechnique is evaluated using multitemporal images of crop development. Digital aerial images of two corn (Zea mays L.)fields are used to test the SLT routine based on expected change in pixel intensity due to crop development. The SLT techniqueis also compared against an alternative histogram matching technique based on the percentage of pixels matching theexpected growth pattern away from the soil line. For two fields over two growing seasons, the SLT technique outperformedhistogram matching, resulting in at least 87% of pixels demonstrating the expected growth pattern between the images.

Influence of transducer frequency and imaging modality on the intraoperative assessment of myocardial perfusion with transesophageal echocardiography

Objective: To determine factors that improve intraoperative myocardial perfusion assessment with conventional ultrasound imaging and intravenous ultrasound agents. Design: Prospective cohort study with repeated interventions on each patient. Setting: Single university hospital. Participants: Fourteen patients scheduled for elective coronary artery bypass graft surgery. Interventions: Myocardial perfusion was evaluated with contrast transesophageal echocardiography during conventional imaging after central venous injections of the contrast agent Optison (0.3 mL) before cardiopulmonary bypass. Eight patients received the injection during continuous sampling at each of 4 transducer frequency settings (3.5, 5.0, 6.0, 7.0 MHz). In another 6 patients, injections were administered during continuous and intermittent sampling (electrocardiogram-gated) at 3.5 and 5.0 MHz. Generalized estimating equations were used to compare mean responses, with p ≤ 0.05 considered significant. Measurements and Main Results: All recorded images were analyzed with off-line videodensitometry. Background-corrected peak pixel intensity (PPIcorr) and rate of change in pixel intensity (PPIcorr/TPPI) were determined for each injection. PPIcorr was greater at 3.5 MHz than at 5.0, 6.0, and 7.0 MHz (p < 0.001). PPIcorr/TPPI was greater at 3.5 MHz than at 5.0 (p < 0.001), 6.0 (p = 0.003), and 7.0 MHz (p < 0.001). PPIcorr was greater for gated than for nongated sampling conditions at 3.5 (p < 0.05) and 5.0 MHz (p < 0.05). Conclusion: To optimize myocardial contrast opacification, intraoperative transesophageal echocardiography should be performed with intermittent sampling at a transducer frequency close to the intrinsic frequency of the contrast agent. Copyright © 2001 by W.B. Saunders Company

Adaptive Supersampling in Object Space Using Pyramidal Rays

We introduce a new approach to three important problems in ray tracing: antialiasing, distributed light sources, and fuzzy reflections of lights and other surfaces. For antialiasing, our approach combines the quality of supersampling with the advantages of adaptive supersampling. In adaptive supersampling, the decision to partition a ray is taken in image‐space, which means that small or thin objects may be missed entirely. This is particularly problematic in animation, where the intensity of such objects may appear to vary. Our approach is based on considering pyramidal rays (pyrays) formed by the viewpoint and the pixel. We test the proximity of a pyray to the boundary of an object, and if it is close (or marginal), the pyray splits into 4 sub‐pyrays; this continues recursively with each marginal sub‐pyray until the estimated change in pixel intensity is sufficiently small.The same idea also solves the problem of soft shadows from distributed light sources, which can be calculated to any required precision. Our approach also enables a method of defocusing reflected pyrays, thereby producing realistic fuzzy reflections of light sources and other objects. An interesting byproduct of our method is a substantial speedup over regular supersampling even when all pixels are supersampled. Our algorithm was implemented on polygonal and circular objects, and produced images comparable in quality to stochastic sampling, but with greatly reduced run times.

Analysis of regional cerebral blood flow in dogs, with an experimental microbubble-based US contrast agent.

To evaluate a perfluorochemical stabilized microbubble-based ultrasound (US) contrast agent (Imagent US, formulation AF0145) create regional cerebral blood flow (CBF) maps. Intravenous injections of the contrast agent (0.16-0.20 mL/kg) were performed in four anesthetized dogs (9-14 kg). Serial coronal color-Doppler-amplitude and gray-scale US scans were obtained through a cranial window during injection of contrast material. Mean pixel intensity was analyzed on digitized images. Regional CBF was varied by modifying arterial partial pressure of carbon dioxide (PaCO2). Color-Doppler-amplitude and gray-scale mean pixel intensity and percentage change in mean pixel intensity after injection of contrast material were analyzed, by means of a bolus injection curve that plotted color mean pixel intensity per unit area versus time. Contrast material injection resulted in a statistically significant difference in color-Doppler-amplitude and gray-scale enhancement of brain. Color mean pixel intensity increased from 1.4 units +/- 1 (standard error) to 122 units +/- 6 in thalamus and from 9.7 units +/- 4.0 to 107 units +/- 9 in cortex (P < .0001). Gray-scale mean pixel intensity increased from 0.55 units +/- 0.20 to 33 units +/- 11 in thalamus and from 0.42 units +/- .06 to 10.5 units +/- 2.0 in cortex (P < .005). Correlation between the area under the color-Doppler-amplitude mean-pixelintensity curve and regional CBF in thalamus and cortex was significant (r = .815, P < .0001). Color-Doppler-amplitude US can be used to create regional CBF maps and shows potential for noninvasive evaluation of CBF in the critically ill newborn.

Renal cortical perfusion in rabbits: visualization with color amplitude imaging and an experimental microbubble-based US contrast agent.

To evaluate an experimental microbubble-based ultrasound (US) contrast agent (Imagent US, formulation AF0150) in the kidney to help identify focal perfusion abnormalities. Six incremental doses (0.007-0.2 mL/kg) of contrast material were injected intravenously in six New Zealand rabbits (3.1-3.5 kg), with experimental focal renal ischemia in five kidneys. Unenhanced and contrast material-enhanced color amplitude and gray-scale images of the kidney were analyzed for changes in mean pixel intensity. Kidneys were harvested and examined pathologically. On contrast-enhanced color amplitude images, mean pixel intensity increased significantly in cortex and medulla at every dose level (P < .0005) (with doses as low as 0.007 mL/kg), and differences were significant in cortical peak intensity and duration of enhancement with incremental increases in dose (P < .006). On contrast-enhanced gray-scale images, renal cortical enhancement reached statistical significance only at the highest dose (0.2 mL/kg). Duration of gray-scale tissue enhancement was not dose related. Color mean pixel intensity markedly increased in areas of normally perfused kidney (P = .002) but remained essentially unchanged in ischemic areas (P = .34). Color Doppler and gray-scale images enhanced with this microbubble-based US contrast agent depict renal cortical perfusion clearly in rabbits.

Evaluation of changes in skeletal muscle blood flow in the dog with contrast ultrasonography.

Intraoperative methods to assess skeletal muscle blood flow or muscle-flap perfusion during vascular reconstructive surgery are limited. At present, techniques enable only anatomic identification of the degree of patency of large vessels. We report here the first use of ultrasonography to assess dynamic changes in skeletal muscle perfusion. Baseline blood flow in the adductor muscle group of the hindlimbs of seven dogs was measured with an electromagnetic flow probe and with contrast ultrasound using the contrast agent Albunex. Blood flow was manipulated in each dog pharmacologically with random administration of intraarterial injections of Neo-Synephrine and papaverine. After each change in blood flow detected by electromagnetic flow probe, flow also was assessed qualitatively by four independent observers who graded video-recorded contrast enhancement in the muscle group on a 0 to 4 scale. Videodensitometry also was used to generate time versus intensity curves in the adductor muscle region of interest. Peak pixel intensity was determined during each flow condition. A total of 21 flow measurements were made with each assessment scheme (electromagnetic flow probe, video enhancement, videodensitometry) for each condition (7 control, 7 papaverine, 7 Neo-Synephrine). Changes in blood flow assessed by video enhancement scores and changes in peak pixel intensity correlated with changes measured by electromagnetic flow probe (r = 0.84 and 0.66, respectively). We conclude that contrast ultrasound may be used to detect changes in skeletal muscle perfusion intraoperatively. Measures of muscle perfused by visual inspection of contrast enhancement and videodensitometric data were in agreement with direct measurements of changes in skeletal muscle blood flow.