Automatic full field analysis of perfusion images gained by scanning laser Doppler flowmetry

BACKGROUND: Scanning laser Doppler flowmetry (SLDF) enables the measurement of the laser Doppler frequency shift in retinal tissue. This process allows the quantification of retinal and optic nerve head perfusion in an area of 2.7 mm x 0.7 mm within 2 seconds and with a spatial resolution of 10 microns x 10 microns. Owing to the local heterogeneity of the retinal microcirculation itself and to heart associated pulsation the capillary retinal blood flow depends on location and time. Because of technical limitations measurements of flow are only valid in retinal points with adequate brightness and focus, and away from big vessels. To include the heart beat associated pulsation and the spatial heterogeneity of retinal blood flow into the evaluation of blood flow an algorithm was developed examining automatically the whole SLDF perfusion image. AIM: To report intraobserver reliability and interobserver reliability of a new method for analysing automatically full field perfusion images. METHOD: The base of blood flow calculation by the automatic full field perfusion image analyser (AFFPIA) was 16,384 intensity time curves of all pixels of the whole perfusion image gained by the SLDF. AFFPIA calculates the Doppler frequency shift and the haemodynamic variables flow, volume, and velocity of each pixel. The resulting perfusion image was processed with respect to (1) underexposed and overexposed pixels, (2) saccades, and (3) the retinal vessel tree. The rim area and the saccades were marked interactively by the operator. The capillaries and vessels of the retinal vessel tree were identified automatically by pattern analysis. Retinal vessels with a diameter greater than 30 microns, underexposed or overexposed areas, and saccades were excluded automatically. Based on the whole perfusion image total mean flow, total mean volume, total mean velocity, standard deviation, cumulative distribution curve of flow, and the capillary pulsation index were calculated automatically. Heart beat associated pulsation of capillary blood flow was estimated by plotting the mean capillary flow of each horizontal line against time. Intraobserver reliability was estimated by measuring 10 eyes of 10 subjects on five different days by one observer. Interobserver reliability of AFFPIA was evaluated by analysing 10 perfusion maps by five different operators. To find a baseline of retinal blood flow, perfusion maps of 67 eyes of normal subjects with a mean age of 40.4 (SD 15) years were evaluated by AFFPIA. RESULTS: The coefficient of reliability of the intraobserver reproducibility of flow was 0.74. The coefficient of reliability of the interobserver reproducibility was 0.95. The juxtapapillary retinal capillary flow was temporally 484 (SD 125), nasally 450 (117); the rim area capillary flow was 443 (110). The mean capillary pulsation index of retinal flow was 0.56 (0.14). CONCLUSION: Retinal blood flow evaluation by the AFFPIA increases significantly the interobserver reliability compared with conventional evaluation of 100 microns x 100 microns areas in SLDF images with the original Heidelberg retina flowmeter software. The intraobserver reliability of AFFPIA was in the same range as conventional evaluation.     

Segmentation and tracking in echocardiographic sequences: active contours guided by optical flow estimates

This paper presents a method for segmentation and tracking of cardiac structures in ultrasound image sequences. The developed algorithm is based on the active contour framework. This approach requires initial placement of the contour close to the desired position in the image, usually an object outline. Best contour shape and position are then calculated, assuming that at this configuration a global energy function, associated with a contour, attains its minimum. Active contours can be used for tracking by selecting a solution from a previous frame as an initial position in a present frame. Such an approach, however, fails for large displacements of the object of interest. This paper presents a technique that incorporates the information on pixel velocities (optical flow) into the estimate of initial contour to enable tracking of fast-moving objects. The algorithm was tested on several ultrasound image sequences, each covering one complete cardiac cycle. The contour successfully tracked boundaries of mitral valve leaflets, aortic root and endocardial borders of the left ventricle. The algorithm-generated outlines were compared against manual tracings by expert physicians. The automated method resulted in contours that were within the boundaries of intraobserver variability.     

Rescue of Caenorhabditis elegans pharyngeal development by a vertebrate heart specification gene

Development of pharyngeal muscle in nematodes and cardiac muscle in vertebrates and insects involves the related homeobox genes ceh-22, nkx2.5, and tinman, respectively. To determine whether the nematode and vertebrate genes perform similar functions, we examined activity of the zebrafish nkx2.5 gene in transgenic Caenorhabditis elegans. Here, we report that ectopic expression of nkx2.5 in C. elegans body wall muscle can directly activate expression of both the endogenous myo-2 gene, a ceh-22 target normally expressed only in pharyngeal muscle, and a synthetic reporter construct controlled by a multimerized CEH-22 binding site. nkx2.5 also efficiently rescues a ceh-22 mutant when expressed in pharyngeal muscle. Together, these results indicate that nkx2.5 and ceh-22 provide a single conserved molecular function. Further, they suggest that an evolutionarily conserved mechanism underlies heart development in vertebrates and insects and pharyngeal development in nematodes.     

冷轧带钢边部偏移量对原始板形信号的影响

 在板形检测过程中,针对冷轧带钢两侧边部经常不能完全覆盖检测通道及可能发生偏移的现象,建立了适应在线计算的带钢边部板形信号误差补偿模型。利用该模型,根据带钢横向偏移量自动计算检测辊的起始通道号、有效通道数量及带钢边部的通道覆盖率,合理选择比例补偿和差分补偿2种方法,对带钢边部在线板形信号进行必要的误差补偿,使板形曲线更真实地反映实际板形状况。经物理测试和工业验证,该方法可靠有效,有效防止因异常板形信号引起的误调事故,满足轧机的精细板形调控要求。     

Swallowing performance in patients with vocal fold motion impairment

Twenty-seven patients with vocal fold motion impairment underwent detailed pharyngoesophagel manometry with a strain gauge assembly linked to a computer recorder. Nine were known to have lesions of the central vagal trunk or nucleus, 9 had recurrent laryngeal nerve (RLN) palsy, and the remainder were idiopathic. The site of the lesion was a more important determinant of subjective swallowing performance than the position of the involved cord at laryngoscopy. Patients with central lesions had lower tonic and contraction upper esophageal sphincter (UES) pressures than 25 age-matched controls, suggesting that high cervical branches of the lower cranial nerves are important in UES excitatory innervation. RLN palsy patients showed significantly increased pharyngeal contraction amplitude and reduced pharyngoesophageal wave durations. The results suggest that the dysphagia associated with vocal fold motion impairment is not simply due to the disruption of laryngeal deglutitive kinetics, but to independent effects on pharyngeal function.     

Novel Approach to Pavement Cracking Detection Based on Fuzzy Set Theory

Conventional visual and manual pavement cracking analysis approaches are very costly, time-consuming, dangerous, labor-intensive, and subjective. They possess various drawbacks such as having a high degree of variability, being unable to provide meaningful quantitative information, and almost always leading to inconsistencies in cracking details over space and across evaluations. In this paper, a novel pavement cracking detection algorithm based on fuzzy logic is proposed. The main idea of the proposed method is based on the fact that the crack pixels in pavement images are “darker than their surroundings and continuous.” First, the proposed method determines how much darker the pixels are than the surroundings by deciding the brightness membership function for gray levels in the difference image. Second, we map the fuzzified image into the crack domain by finding the crack membership values of the pixels. Third, we check the connectivity of the darker pixels to eliminate the pixels lacking in connectivity. Finally, an image projection algorithm is employed to classify cracks. The experimental results have demonstrated that the cracks are correctly and effectively detected by the proposed method. The main advantages of the proposed method are: (1) it can correctly discover thin cracks, even from very noisy pavement images; (2) the necessary parameters can be determined automatically; (3) the efficiency and accuracy of the proposed algorithm are superior; and (4) its application-dependent nature can simplify the design of the entire system.     

Integration of physical and semantic information in object processing

Physiological studies report independent processing pathways for form and colour information. A more-complex picture on human subjects has previously been reported. A sequential matching task was used that was based on a physical property of an object and in which semantic relations between stimuli were manipulated. Performance was affected by semantic information when matching was based on a property of the form of an object (its orientation, shape, or size). Effects of semantic information were eliminated when matching was based on the colour of a local part of an object but were found again when subjects matched pictures on the basis of the percentage of a colour integrated across the shape boundary. The results suggest independent selection mechanisms in vision in which selection by local colour can be based on inhibition of the form-processing pathway whilst processing of the global configuration of the form of an object activates automatically the identification process.     

Automatic background recognition and removal (ABRR) in computed radiography images

A novel method to automatically recognize and remove background signals in computed radiography (CR) images caused by X-ray collimation during projection radiographic examinations is presented. There are three major steps in this method. In the first step, a statistical curve is derived based on many hierarchical CR sample images as a first approximation to loosely separate image and background pixels. Second, signal processing methods, including specific sampling, filtering, and angle recognition, are used to determine edges between image and background pixels. Third, adaptive parameter adjustments and consistent and reliable estimation rules are used to finalize the location of edges and remove the background. In addition, this step also evaluates the reliability of the complete background removal operation. With this novel method implemented in a clinical picture archiving and communication system (PACS) at the University of California at San Francisco, we achieved 99% correct recognition of CR image background, and 91% full background removal without removing any valid image information.     

Figure-ground discrimination from temporal information

The separation of figures from ground is achieved by the visual system based on differences in features such as luminance, colour, depth, orientation, texture or motion. Temporal information, namely phase differences between groups of spatially homogeneous points, can also lead to a clear discrimination of an object shape. The time difference needed to separate figure and ground is around 5 ms over a range of temporal frequencies between 1.3 Hz and 30 Hz, both for sharply focused and for blurred points. These short delays are clearly below the temporal integration time of the visual system. The results have implications for theories on temporal binding and object recognition.     

Foundations of spatial vision: From retinal images to perceived shapes.

Vision is based on spatial correspondences between physically different structures—in environment, retina, brain, and perception. An examination of the correspondence between environmental surfaces and their retinal images showed that this consists of 2-dimensional 2nd-order differential structure (effectively 4th-order) associated with local surface shape, suggesting that this might be a primitive form of spatial information. Next, experiments on hyperacuities for detecting relative motion and binocular disparity among separated image features showed that spatial positions are visually specified by the surrounding optical pattern rather than by retinal coordinates, minimally affected by random image perturbations produced by 3-D object motions. Retinal image space, therefore, involves 4th-order differential structure. This primitive spatial structure constitutes information about local surface shape. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A belongingness principle of motion perception

Four experiments are reported that investigated the role of the perceived coplanarity of a moving target with respect to a frame of reference in the third dimension on the perceived path of that target. When a target dot and small moving frame appeared coplanar, the dot's perceived trajectory was governed entirely by its changing position relative to the moving frame. However, when the target and a large stationary frame appeared in a different plane than the small moving frame, the motion of the dot was seen independently of the moving frame. The results support a belongingness principle of motion perception: The displacement of an object relative to a frame of reference to which it belongs governs its perceived path of motion.     

Prefabricated free jejunal transfer: a new reconstructive technique for high pharyngeal defects

A new method that uses a prefabricated free jejunal transfer has been applied to three cancer patients with pharyngoesophageal defects with a high pharyngeal deficit extending up to the nasopharynx. In this method, the jejunum harvested in the usual manner is divided into two segments with a single vascular pedicle. Its distal segment is used to reconstruct the cervical esophagus, and its proximal segment is turned over to create a mucosal patch to cover the high pharyngeal defects. The two segments are then co-apted in a side-by-side anastomosis. The esophagus can be reconstructed in a naturally straight shape without a curved portion or blind loop formation, thus leading to good swallowing function. In our series, all grafts survived well and there was no complication directly related to jejunal transfer. All patients could tolerate a soft diet without difficulty. This method is easy to perform and applicable to any shape or size of very high pharyngeal defects that cannot be reconstructed properly by other methods. Although patients with an advanced hypopharyngeal cancer usually have a poor prognosis, this technique allows a better quality of life for a probable short life span.     

The effects of depression and chronic pain on psychosocial and physical functioning

Ray tracing with a personal computer allows realistic simulation of optical properties of the human eye. Patterns of point sources are used as objects. The path of light rays is calculated between the point source and the retina for a Gullstrand eye model with improved parameters; the normal eye model has a resolution limit close to the natural resolution limit of the human eye. The image formed on the retina is projected back to a screen at the distance of the object so as to simulate image interpretation by the brain. Refractive errors are modeled by a change in eye parameters and corrected by eyeglasses or/and contact lenses or by an artificial intraocular lens. For optic correction the parameters of seeing aids can be fitted automatically by a least-squares routine. The effect of faulty eye correction on image quality is visualized by using a photograph of a realistic scene as an object.     

LVC工作辊综合辊形预测模型和应用

 在热轧带钢板形在线控制模型中,综合辊形的计算精度直接影响板形控制模型设定的准确性。建立了LVC工作辊初始辊形、热辊形和磨损辊形的计算模型,并在此基础上建立了综合辊形的等效模型和特征参数。该综合辊形等效模型已成功应用于鞍钢2150 mm热连轧在线板形控制模型中。生产数据表明,采用该模型后板形设定模型计算出的弯辊力和窜辊量能够自动适应轧制规格、轧辊磨损和热胀的变化,带钢头部凸度和平坦度的命中率均达到95%以上。     

The Caenorhabditis elegans gene unc-25 encodes glutamic acid decarboxylase and is required for synaptic transmission but not synaptic development

The neurotransmitter GABA has been proposed to play a role during nervous system development. We show that the Caenorhabditis elegans gene unc-25 encodes glutamic acid decarboxylase (GAD), the GABA biosynthetic enzyme. unc-25 is expressed specifically in GABAergic neurons. Null mutations in unc-25 eliminate the UNC-25 protein or alter amino acids conserved in all known GADs, result in a complete lack of GABA, and cause defects in all GABA-mediated behaviors. In unc-25 mutants the GABAergic neurons have normal axonal trajectories and synaptic connectivity, and the size and shape of synaptic vesicles are normal. The number of synaptic vesicles at GABAergic neuromuscular junctions is slightly increased. Cholinergic ventral nerve cord neurons, which innervate the same muscles as GABAergic ventral cord neurons, have normal morphology, connectivity, and synaptic vesicles. We conclude that GAD activity and GABA are not necessary for the development or maintenance of neuromuscular junctions in C. elegans.     

The adjacent pixel nonlinearity: problems and solutions

The adjacent pixel nonlinearity refers to the dependence of the luminance of a given pixel on the preceding pixel or pixels. We measured this nonlinearity for two CRT displays by measuring the average luminances of a variety of test patterns with different luminance jumps. A two-stage model proposed by Mulligan and Stone was used to fit the data [Mulligan, J.B. & Stone, L. S., (1989). Journal of the Optical Society of America A, 6, 1217-1227 (1989)]. The results show that the model predicts our data well. Based on our measurements and the modeling results, a double-entry look-up table was created to compensate for this nonlinearity. This compensation method works even if the current pixel depends on more than one preceding pixel. Observers commented that at small pixel sizes the compensation results in a sharp, accurate image. Advantages and problems of this compensation will be discussed.     

板形检测辊挠度变化对冷轧带钢原始波形信号的影响

 综合考虑板形检测辊自重及其所受带钢张力的影响,利用正弦波和样条曲线虚拟各通道的零点偏差,基于截点法建立了针对检测辊挠度动态变化的原始波形零点补偿模型。对于检测辊自重造成的离线零点偏差,对其进行虚拟正弦截点补偿;对于动态大张力造成的在线零点偏差,利用样条曲线实时拟合零点偏差。从实测曲线中减去零点偏差拟合曲线,即可获得更稳定的径向压力值或板形值,应用过程中还可以采用递推平滑法使其更可靠地反映在线带钢的实际板形状况。实测数据表明,各通道的原始波形AD零点偏差从补偿前的600左右下降到补偿后的50以内,径向压力零点偏差从130N左右下降到10N以内。因此,该零点补偿方法对于提高板形检测精度和板形控制精度具有重要的意义。     

基于图象处理的棒材自动计数技术

利用面阵CCD摄象机采集打捆后棒材的端面图象，通过合适的阈值将灰度图象转换成二值图象，以消除棒材图象区域中由于油污造成的孔洞和棒材区域间的粘连现象。根据距离变换思想，提出了图象距离概念，通过计算并比较棒材区域各象素点的图象距离，确定了各根棒材的中心，从而实现了从图象中自动计算棒材的数目。对现场采集到的图象进行试验，结果验证了这种方法的有效性。