Spine Localization in X-ray Images Using Interest Point Detection

This study was conducted to evaluate a new method used to calculate vertebra orientation in medical x-ray images. The goal of this work is to develop an x-ray image segmentation approach used to identify the location and the orientation of the cervical vertebrae in medical images. We propose a method for localization of vertebrae by extracting the anterior—left—faces of vertebra contours. This approach is based on automatic corner points of interest detection. For this task, we use the Harris corner detector. The final goal is to determine vertebral motion induced by their movement between two or several positions. The proposed system proceeds in several phases as follows: (a) image acquisition, (b) corner detection, (c) extracting of the corners belonging to vertebra left sides, (d) global estimation of the spine curvature, and (e) anterior face vertebra detection.     

基于MRI图像纹理特征的膀胱肿瘤浸润深度检测

对膀胱肿瘤浸润深度进行无创检测,为膀胱肿瘤的检测及分期判断提供参考。基于膀胱MRI图像,利用尿液和膀胱壁的天然密度对比,结合统计分析,得到在肿瘤及膀胱壁组织有统计差异的纹理特征。通过提取肿瘤及周围膀胱壁组织的均值、均匀度、标准差、粗糙度、自协方差系数和对比度等特征,再经分类器判断,得到感兴趣区域肿瘤浸润情况的伪彩图。就16位患者MRI扫描数据及术后病理分析结果,用于测试的56幅图像中,判断准确率为82.1%;15位患者的标记结果与病理分期相符,正确率为93.8%,与病理分析吻合较好。利用分类器和纹理特征判别肿瘤区域的属性,实现了膀胱肿瘤浸润深度标记和边界的初步划分,为膀胱肿瘤的无创检测提供了新的可能手段。     

Novel Approach to Segment the Inner and Outer Boundaries of the Bladder Wall in T2-Weighted Magnetic Resonance Images

Diagnosis of bladder-related conditions needs critical measurements which require the segmentation of the inner and outer boundaries of the bladder wall. In T2-weighted MR images, the low-signal intensity bladder wall can be identified due to the large contrast with the high-signal intensity urine and perivesical fat. In this article, two deformable models are proposed to segment the bladder wall. Based on the imaging features of the bladder, a modified geodesic active contour is proposed to segment the inner boundary. This method uses the statistical information of the bladder lumen and can handle the intensity variation in MR images. Having obtained the inner boundary, a shape influence field is formed and integrated with the Chan–Vese (C–V) model to segment the outer boundary. The shape-guided C–V model can prevent the overlapping between the two boundaries when the appearance of the bladder wall is blurred. Segmentation examples are presented and analyzed to demonstrate the effectiveness of this novel approach.     

A Computer-Aided Type-II Fuzzy Image Processing for Diagnosis of Meniscus Tear

Meniscal tear is one of the prevalent knee disorders among young athletes and the aging population, and requires correct diagnosis and surgical intervention, if necessary. Not only the errors followed by human intervention but also the obstacles of manual meniscal tear detection highlight the need for automatic detection techniques. This paper presents a type-2 fuzzy expert system for meniscal tear diagnosis using PD magnetic resonance images (MRI). The scheme of the proposed type-2 fuzzy image processing model is composed of three distinct modules: Pre-processing, Segmentation, and Classification. λ-nhancement algorithm is used to perform the pre-processing step. For the segmentation step, first, Interval Type-2 Fuzzy C-Means (IT2FCM) is applied to the images, outputs of which are then employed by Interval Type-2 Possibilistic C-Means (IT2PCM) to perform post-processes. Second stage concludes with re-estimation of “η” value to enhance IT2PCM. Finally, a Perceptron neural network with two hidden layers is used for Classification stage. The results of the proposed type-2 expert system have been compared with a well-known segmentation algorithm, approving the superiority of the proposed system in meniscal tear recognition.     

A hybrid strategy to integrate surface-based and mutual-information-based methods for co-registering brain SPECT and MR images

Co-registration of brain SPECT and MR images has been used extensively in clinical applications. The complementary features of two major co-registration methods—surface- and mutual-information-based (MI-based)—motivated us to study a hybrid-based scheme that uses the surface-based method to achieve a quick alignment, followed by the MI-based method for fine tuning. Computer simulations were conducted to evaluate the accuracy and robustness of surface-, MI-, and hybrid-based registration methods by designing different levels of noise and mismatch in the registration experiments. Results demonstrated that the hybrid surface-MI-based scheme outperforms both the surface- and MI-based methods in providing superior accuracy and success rates. Specifically, the translational and rotational errors were no more than 1 mm and 2°, respectively, with consistent success rates over 98%. Besides, the hybrid-based method saved 12–53% of the computation efforts, compared with using the MI-based method alone. We recommend the use of hybrid-based method when the orientational differences between the floating and reference images exceed 10°.     

Left ventricular image processing

Left ventricular image processing methods of x-ray cineangiocardiograms and ultrasound echocardiograms are discussed. 3-D reconstruction methods of the left ventricle from ultrasound echocardiograms and magnetic resonance images are also discussed. Boundary detection of the left ventricle and the quantitative analysis of the left ventricular function and wall motion are discussed. To reconstruct 3-D shapes, we need several cross sectional shapes or silhouettes of the left ventricle. Several cross sectional echo images of apical long axis view are taken by changing the angles of rotation of the probe of echo transducer around its axis. Gated multi-phase MRI method is used to obtain each 2 cross sectional images in transverse, coronal and sagittal directions. Some results of 3-D shapes of the left ventricle and myocardium reconstructed are shown and 3-D functional images which give us regional functions of the left ventricular wall on three dimensional shape are shown.     

<Emphasis Type="Italic">In Vitro</Emphasis> Accumulation of Complexes of Endotoxin and Low-Density Lipoproteins by Macrophages and Arterial Wall

Binding and uptake of complexes of endotoxin and low-density lipoproteins (LPS—LDL) in the arterial wall and mononuclear phagocytes were studied under in vitro conditions. Incubation of aortic explants from Wistar rats with complexes of ¹²⁵I—LDL and S. minnesota R595 LPS or ¹²⁵I--LDL was accompanied by a 6-fold increase in binding (0°C) and 2-fold increase in the uptake (37°C) of LDL—LPS complexes as compared to free LDL. Binding and degradation of ¹²⁵I—LDL—LPS complexes in the culture of peritoneal macrophages were higher compared to the corresponding parameters for free ¹²⁵I—LDL. Our results suggest that the formation of LDL—LPS complexes is followed by the increased binding and accumulation of LDL in the arterial wall and macrophages. These changes probably induce the cascade of major atherogenic events in the vascular wall. Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 147, No. 2, pp. 148–151, February, 2009     

Completely automated robust edge snapper for carotid ultrasound IMT measurement on a multi-institutional database of 300 images

The carotid intima-media thickness (IMT) is the most used marker for the progression of atherosclerosis and onset of cardiovascular diseases. Computer-aided measurements improve accuracy and precision, but usually require user interaction. In this paper we characterized a new and completely automated technique for carotid segmentation and IMT measurement based on the merits of two previously developed techniques. We used an integrated approach of intelligent image feature extraction and line fitting for automatically locating the carotid artery in the image frame, followed by wall interfaces extraction based on a Gaussian edge operator. We called our system—CARES. We validated CARES on a multi-institutional database of 300 carotid ultrasound images. The IMT measurement bias was 0.032 ± 0.141 mm. Our novel approach of CARES processed 96% of the images in the database taken from two different institutions. In order to evaluate its performance, the figure-of-merit (FoM) was defined as the percent ratio between the average IMT computed by CARES and the one obtained from manual tracings by expert sonographers. The estimated FoM by CARES was 95.7%. Comparing the IMT bias of CARES with our previously published method CALEX that showed an IMT bias equal to 0.099 ± 0.137 mm, CARES improved the IMT accuracy by 67%, while increasing the standard deviation by 3%. CARES could be a useful research tool for processing large datasets in multi-center studies involving atherosclerosis.     

Lens opacity detection for serious posterior subcapsular cataract

Cataract leads to visual impairment. Among different types of cataract, posterior subcapsular cataract (PSC) can develop rapidly and surgery is usually needed. An approach to detect PSC opacities in retro-illumination images is proposed. Watershed and Markov random fields (MRF) method are employed to opacities in anterior retro-illumination images. It results in a mixture of PSC, cortical opacities and noise. Then, information in both anterior and posterior retro-illumination images is utilized. Two features are extracted to identify PSC: mean gradient comparison (MGC) between anterior and posterior retro-illumination images, and spatial location. This is the first time that comparison between anterior and posterior retro-illumination images is proposed and MGC is proposed as the feature of comparison in PSC detection. Experiments show that the sensitivity and specificity of PSC screening is 91.2 and 90.1 %, respectively, based on the 519 pairs of testing images. To the best of our knowledge, it is the best performance reported in automatic detection of PSC. Compared with the methods in the literatures, considerable improvement is achieved when there are large areas of PSC opacities.     

Characterisation of structural changes in the arterial elastic matrix by a new fractal feature: directional fractal curve

A new fractal feature, the Directional Fractal Curve (DFC), defined over an arc of 180° and composed of 90 fractal dimensions determined at intervals of arc of 2°, is developed to account for the anisotropic property of a fractal texture. The DFC algorithm is first applied to two images with different textural patterns one without directional preference and one with a well-organised texture. The DFC of these images shows different patterns. The technique is then applied to quantify the structure of the elastic texture in the arterial wall where the elastic network was imaged by scanning electron microscopy following selective tissue digestion. The results suggest: (i) that images of the elastin matrix of the arterial wall exhibit fractal properties with directional preference, (ii) the DFC gives quantitative parameters which allow characterisation of structural changes in the elastin matrix of the arterial wall in terms of disorganisation and fragmentation of elastin fibres—conditions which are associated with medial degeneration due to normal ageing or presence of arterial disease.     

Quality evaluation of ultrasound imaging in the carotid artery based on normalization and speckle reduction filtering

Image quality is important when evaluating ultrasound images of the carotid for the assessment of the degree of atherosclerotic disease, or when transferring images through a telemedicine channel, and/or in other image processing tasks. The objective of this study was to investigate the usefulness of image quality evaluation based on image quality metrics and visual perception, in ultrasound imaging of the carotid artery after normalization and speckle reduction filtering. Image quality was evaluated based on statistical and texture features, image quality evaluation metrics, and visual perception evaluation made by two experts. These were computed on 80 longitudinal ultrasound images of the carotid bifurcation recorded from two different ultrasound scanners, the HDI ATL-3000 and the HDI ATL-5000 scanner, before (NF) and after (DS) speckle reduction filtering, after normalization (N), and after normalization and speckle reduction filtering (NDS). The results of this study showed that: (1) the normalized speckle reduction, NDS, images were rated visually better on both scanners; (2) the NDS images showed better statistical and texture analysis results on both scanners; (3) better image quality evaluation results were obtained between the original (NF) and normalized (N) images, i.e. NF–N, for both scanners, followed by the NF–DS images for the ATL HDI-5000 scanner and the NF–DS on the HDI ATL-3000 scanner; (4) the ATL HDI-5000 scanner images have considerable higher entropy than the ATL HDI-3000 scanner and thus more information content. However, based on the visual evaluation by the two experts, both scanners were rated similarly. The above findings are also in agreement with the visual perception evaluation, carried out by the two vascular experts. The results of this study showed that ultrasound image normalization and speckle reduction filtering are important preprocessing steps favoring image quality, and should be further investigated.     

Multimodal architectonic subdivision of the caudal ventrolateral prefrontal cortex of the macaque monkey

The caudal part of the macaque ventrolateral prefrontal cortex (VLPF) is part of several functionally distinct domains. In the present study we combined a cyto- and a myeloarchitectonic approach with a chemoarchitectonic approach based on the distribution of SMI-32 and Calbindin immunoreactivity, to determine the number and extent of architectonically distinct areas occupying this region. Several architectonically distinct areas, completely or partially located in the caudal VLPF, were identified. Two areas are almost completely limited to the anterior bank of the inferior arcuate sulcus, a dorsal one—8/FEF—which extends also more dorsally and should represent the architectonic counterpart of the frontal eye field, and a ventral one—45B—which occupies the ventral half of the bank. Two other areas occupy the ventral prearcuate convexity cortex, a caudal one—area 8r—located just rostral to area 8/FEF and a rostral one—area 45A—which extends as far as the inferior frontal sulcus. Area 45A borders dorsally, in the proximity of the principal sulcus, with area 46 and, ventrally, with area 12. The present data show the existence of two distinct prearcuate convexity areas (8r and 45A), extending other architectonic subdivisions of the caudal VLPF and providing a new, multiarchitectonic frame of reference for this region. The present architectonic data, together with other functional and connectional data, suggest that areas 8/FEF, 45B and 8r are part of the oculomotor frontal cortex, while area 45A is a distinct entity of the VLPF domain involved in high-order processing of nonspatial information.     

Quantification of carotid vessel wall and plaque thickness change using 3D ultrasound images

Quantitative measurements of carotid plaque burden progression or regression are important in monitoring patients and in evaluation of new treatment options. 3D ultrasound (US) has been used to monitor the progression or regression of carotid artery plaques. This paper reports on the development and application of a method used to analyze changes in carotid plaque morphology from 3D US. The technique used is evaluated using manual segmentations of the arterial wall and lumen from 3D US images acquired in two imaging sessions. To reduce the effect of segmentation variability, segmentation was performed five times each for the wall and lumen. The mean wall and lumen surfaces, computed from this set of five segmentations, were matched on a point-by-point basis, and the distance between each pair of corresponding points served as an estimate of the combined thickness of the plaque, intima, and media (vessel-wall-plus-plaque thickness or VWT). The VWT maps associated with the first and the second US images were compared and the differences of VWT were obtained at each vertex. The 3D VWT and VWT-Change maps may provide important information for evaluating the location of plaque progression in relation to the localized disturbances of flow pattern, such as oscillatory shear, and regression in response to medical treatments.     

Sound enhances touch perception

Certain sounds, such as fingernails screeching down a chalkboard, have a strong association with somatosensory percepts. In order to assess the influences of audition on somatosensory perception, three experiments measured how task-irrelevant auditory stimuli alter detection rates for near-threshold somatosensory stimuli. In Experiment 1, we showed that a simultaneous auditory stimulus increases sensitivity, but not response biases, to the detection of an electrical cutaneous stimulus delivered to the hand. Experiment 2 demonstrated that this enhancement of somatosensory perception is spatially specific—only monaural sounds on the same side increased detection. Experiment 3 revealed that the effects of audition on touch are also frequency dependent—only sounds with the same frequency as the vibrotactile frequency enhanced tactile detection. These results indicate that auditory information influences touch perception in highly systematic ways and suggest that similar coding mechanisms may underlie the processing of information from these different sensory modalities.     

基于超声图像的乳腺钙化点自动检测技术

当前乳腺钙化点检测方法多基于X光片,难以应用于超声图像,本研究提出基于超声图像的乳腺钙化点自动检测技术,首先将乳腺超声图像中的肿瘤区域通过勾画模板提取出来,基于简单线性迭代聚类算法进行超像素分割;然后提取表征各超像素的特征量来计算显著性图,基于钙化区域显著性进行粗钙化点分割;最终对分割后的粗钙化点进行形态学检测,达到对超声图像中的细钙化点自动检测。该方法取得了较好的分割效果,具有较强的鲁棒性,为形成具有普适性的肿瘤自动诊断方案奠定了研究基础。     

Comparative findings of voice and speech: language processing at an early ontogenetic age in quantitative EEG mapping

Quantitative EEG mapping in powers of electrical activity, concentration of main powers and area of concentration in relation to the side of presentation (left, right, and bihemisphery) and closer location was done on a 24-day-old infant first, and again when the infant was 2.5 months. EEG responses are analyzed in following acoustic modalities: (1) specific (native language speech of mother and unfamiliar female, unfamiliar female speech of foreign language); (2) unspecific (passive period). Familiar and unfamiliar texts present the contents of speech material. Comparative findings on two different ages showed that the infant maintains the processing scheme of unfamiliar stimulus (passive period, foreign language), and also very similar processing scheme of unfamiliar voice regardless if the text in native language is familiar or unfamiliar. During stimulation with familiar or unfamiliar text in native language, which is read by mother, processing type is significantly changed in relation to the age at the time of examination. While a 24-day-old infant shows a similar scheme in processing the familiar and the unfamiliar voices in native language, at the age of 2.5 months, this scheme of processing is changed, especially for theta rhythm, which now has bihemisphery presentation (at earlier stage it has right-side presentation) in the F–C–P region, what is practically the same region where also delta rhythm is processed. However, the sample of unfamiliar voice in native language observed in subsequent period, when the infant was 2.5 months old, maintains the same processing location as it has at an earlier ontogenetic stage, when the infant was 24 days old, regarding the theta rhythm processed in the F–C–P region with right-side presentation, and delta rhythm processed in C–P region with bihemisphery presentation. Post stimuli periods observed when the infant was 2.5 months old show obviously differentiation of theta and delta rhythms’ samples and their electrophysiological parameters. The samples of familiar and unfamiliar texts in native language when read by mother (familiar voice) begin to differentiate regarding to closer location and number of centers for maximal powers in theta rhythm at subsequent ontogenetic period (2.5-month-old infant). The samples of quantitative EEG mapping for a 2.5-months-old infant show the signs of complex processing of different stimuli types: known/unknown voice, foreign language, with stronger inclusion of parietal regions, bihemisphery and an increase in number of maximal powers' centers, compared to the samples when the infant was 42 days old. Quantitative EEG electrophysiological parameters are discussed in relation to side representation and closer regional location with the aim of explaining the processing of complex speech and language stimulation in relation to certain characteristics in its bases.     

Design and evaluation of an ultrasound-based bladder volume monitor

Ultrasonic bladder volume monitors have successfully been used in the diagnosis and treatment of various urological disorders. Ultrasonic bladder monitors have been developed but they have either been too bulky or too simple and inaccurate. A new, wearable ultrasonic bladder volume monitor has been designed for urological patients. The instrument consists of seven phased-array ultrasonic transducers ergonomically arranged in a circular pattern to optimise detection of the bladder walls perpendicular to the abdominal wall. A Bluetooth radio link was used to transmit data to a laptop computer, where the main signal processing was performed. After detection of bladder surface points, a three-dimensional convex hull representing the bladder was generated, and the volume was estimated. Accuracy, precision, drift over time, temperature dependency and dynamic performance were evaluated using ultrasound phantoms. Furthermore, the system was tested on one volunteer using magnetic resonance imaging (MRI) as reference. The apparatus showed no significant drift, systematic error or temperature effects. Percentage error during static volume measurements had a 95% central prediction interval of ±7.5% and mean absolute percentage error of 2.9%. The dynamic performance analysis showed linearity in the analysed volume interval. The in vivo study showed a high degree of correlation (R²=0.99) between the volume measured using MRI and that measured with the apparatus.     

Automated detection and quantitative assessment of pulmonary airways depicted on CT images

We developed and tested a fully automated computerized scheme that identifies pulmonary airway sections depicted on computed tomography (CT) images and computes their sizes including the lumen and airway wall areas. The scheme includes four processing modules that (1) segment left and right lung areas, (2) identify airway locations, (3) segment airway walls from neighboring pixels, and (4) compute airway sizes. The scheme uses both a raster scanning and a labeling algorithm complemented by simple classification rules for region size and circularity to automatically search for and identify airway sections of interest. A profile tracking method is used to segment airway walls from neighboring pixels including those associated with dense tissue (i.e., pulmonary arteries) along scanning radial rays. A partial pixel membership method is used to compute airway size. The scheme was tested on ten randomly selected CT studies that included 26 sets of CT images acquired using both low and conventional dose CT examinations with one of four reconstruction algorithms (namely, "bone," "lung," "soft," and "standard" convolution kernels). Three image section thicknesses (1.25, 2.5, and 5 mm) were evaluated. The scheme detected a large number of quantifiable airway sections when the CT images were reconstructed using high spatial frequency convolution kernels. The detection results demonstrated a consistent trend for all test image sets in that as airway lumen size increases, on average the airway wall area increases as well and the wall area percentage decreases. The study suggested that CT images reconstructed using high spatial frequency convolution kernels and thin-section thickness were most amenable to automated detection, reasonable segmentation, and quantified assessment when the airways are close to being perpendicular to the CT image plane.     

Evaluation of an algorithm for arterial lumen diameter measurements by means of ultrasound

We have developed an algorithm for arterial luminal diameter measurement by means of ultrasound and evaluated the algorithm on agar vessel phantoms and in vivo. The algorithm utilises relative threshold detection on the inner slopes of the arterial walls before the resolution is improved by solving the equation of a straight line between the samples around the threshold value. Further, correction distances added to compensate for the underestimation when using the inner slopes were found to be 304 μm for the near wall and 415 μm for the far wall. The measured mean diameters of ten consecutive images of 3-, 6- and 9-mm phantoms were 3,006 μm (SD 4), 5,918 μm (SD 1) and 8,936 μm (SD 2), respectively. The mean differences between the images were 0.19, 0.04 and 0.37 μm, respectively. In vivo, the intra- and inter-observer variabilities were −64 μm (2SD 358) and −57 μm (2SD 366), respectively.     

Snakes based segmentation of the common carotid artery intima media

Ultrasound measurements of the human carotid artery walls are conventionally obtained by manually tracing interfaces between tissue layers. In this study we present a snakes segmentation technique for detecting the intima-media layer of the far wall of the common carotid artery (CCA) in longitudinal ultrasound images, by applying snakes, after normalization, speckle reduction, and normalization and speckle reduction. The proposed technique utilizes an improved snake initialization method, and an improved validation of the segmentation method. We have tested and clinically validated the segmentation technique on 100 longitudinal ultrasound images of the carotid artery based on manual measurements by two vascular experts, and a set of different evaluation criteria based on statistical measures and univariate statistical analysis. The results showed that there was no significant difference between all the snakes segmentation measurements and the manual measurements. For the normalized despeckled images, better snakes segmentation results with an intra-observer error of 0.08, a coefficient of variation of 12.5%, best Bland–Altman plot with smaller differences between experts (0.01, 0.09 for Expert1 and Expert 2, respectively), and a Hausdorff distance of 5.2, were obtained. Therefore, the pre-processing of ultrasound images of the carotid artery with normalization and speckle reduction, followed by the snakes segmentation algorithm can be used successfully in the measurement of IMT complementing the manual measurements. The present results are an expansion of data published earlier as an extended abstract in IFMBE Proceedings (Loizou et al. IEEE Int X Mediterr Conf Medicon Med Biol Eng POS-03 499:1–4, 2004).