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131.
Quiles J Tahoces PG Souto M Vidal JJ 《Computer methods and programs in biomedicine》2003,71(3):243-259
The development of a total digital high resolution mammography display system must meet a number of requirements that remain a challenge nowadays, most probably because of the special nature of breast imaging. In this paper, we discuss our particular approach to address some problems concerning the complexity of soft-copy diagnosis in digital mammography, such as image quality and user interface evaluation. Based on the experience obtained in the previous implementation of a medical image browser, a more ambitious project is being developed at the Department of Radiology of the University of Santiago de Compostela (Spain) in collaboration with the Department of Medical Informatics of INTELSIS, an emerging software company in our country. This new system will provide complete support to display, store and analyze mammographic studies in digital format. 相似文献
132.
Flow-mediated dilation (FMD) offers a mechanism to characterize endothelial function and, therefore, may play a role in the diagnosis of cardiovascular diseases. Computerized analysis techniques are very desirable to give accuracy and objectivity to the measurements. Virtually all methods proposed up to now to measure FMD rely on accurate edge detection of the arterial wall, and they are not always robust in the presence of poor image quality or image artifacts. A novel method for automatic dilation assessment based on a global image analysis strategy is presented. We model interframe arterial dilation as a superposition of a rigid motion and a scaling factor perpendicular to the artery. Rigid motion can be interpreted as a global compensation for patient and probe movements, an aspect that has not been sufficiently studied before. The scaling factor explains arterial dilation. The ultrasound sequence is analyzed in two phases using image registration to recover both transformation models. Temporal continuity in the registration parameters along the sequence is enforced with a Kalman filter since the dilation process is known to be a gradual physiological phenomenon. Comparing automated and gold standard measurements (average of manual measurements) we found a negligible bias (0.05%FMD) and a small standard deviation (SD) of the differences (1.05%FMD). These values are comparable with those obtained from manual measurements (bias = 0.23%FMD, SD(intra-obs) = 1.13%FMD, SD(inter-obs) 1.20%FMD). The proposed method offers also better reproducibility (CV = 0.40%) than the manual measurements (CV = 1.04%). 相似文献
133.
Region-based wavelet coding methods for digital mammography 总被引:6,自引:0,他引:6
Penedo M Pearlman WA Tahoces PG Souto M Vidal JJ 《IEEE transactions on medical imaging》2003,22(10):1288-1296
Spatial resolution and contrast sensitivity requirements for some types of medical image techniques, including mammography, delay the implementation of new digital technologies, namely, computer-aided diagnosis, picture archiving and communications systems, or teleradiology. In order to reduce transmission time and storage cost, an efficient data-compression scheme to reduce digital data without significant degradation of medical image quality is needed. In this study, we have applied two region-based compression methods to digital mammograms. In both methods, after segmenting the breast region, a region-based discrete wavelet transform is applied, followed by an object-based extension of the set partitioning in hierarchical trees (OB-SPIHT) coding algorithm in one method, and an object-based extension of the set partitioned embedded block (OB-SPECK) coding algorithm in the other. We have compared these specific implementations against the original SPIHT and the new standard JPEG 2000, both using reversible and irreversible filters, on five digital mammograms compressed at rates ranging from 0.1 to 1.0 bit per pixel (bbp). Distortion was evaluated for all images and compression rates by the peak signal-to-noise ratio. For all images, OB-SPIHT and OB-SPECK performed substantially better than the traditional SPIHT and JPEG 2000, and a slight difference in performance was found between them. A comparison applying SPIHT and the standard JPEG 2000 to the same set of images with the background pixels fixed to zero was also carried out, obtaining similar implementation as region-based methods. For digital mammography, region-based compression methods represent an improvement in compression efficiency from full-image methods, also providing the possibility of encoding multiple regions of interest independently. 相似文献
134.
Martínez A García A Sanchis P Martí J 《Journal of the Optical Society of America. A, Optics, image science, and vision》2003,20(1):147-150
A theoretical model of the group velocity, dispersion parameter, and dispersion slope of coupled-cavity waveguides in photonic crystals is reported. Results arising from closed-form expressions show a good agreement with simulation results obtained by employing a plane-wave expansion method. Coupled-cavity waveguides present interesting dispersion properties that may be employed in applications such as optical signal processing, dispersion compensation, and optical delay lines. 相似文献
135.
Ultrasound image segmentation with shape priors: application to automatic cattle rib-eye area estimation. 总被引:1,自引:0,他引:1
Pablo Arias Alejandro Pini Gonzalo Sanguinetti Pablo Sprechmann Pablo Cancela Alicia Fernández Alvaro Gómez Gregory Randall 《IEEE transactions on image processing》2007,16(6):1637-1645
Automatic ultrasound (US) image segmentation is a difficult task due to the quantity of noise present in the images and the lack of information in several zones produced by the acquisition conditions. In this paper, we propose a method that combines shape priors and image information to achieve this task. In particular, we introduce knowledge about the rib-eye shape using a set of images manually segmented by experts. A method is proposed for the automatic segmentation of new samples in which a closed curve is fitted taking into account both the US image information and the geodesic distance between the evolving curve and the estimated mean rib-eye shape in a shape space. This method can be used to solve similar problems that arise when dealing with US images in other fields. The method was successfully tested over a database composed of 610 US images, for which we have the manual segmentations of two experts. 相似文献
136.
Pablo S. Rivadeneira Alejandro H. González 《International journal of systems science》2013,44(15):3082-3093
Linear impulsive systems have been extensively studied in the last decades, mainly in the field of biomedical research. However, a proper characterisation of the equilibria of such a systems - when they are out of the origin - and its use by optimising control strategies is still a matter of discussion. In this work, a novel characterisation of the system equilibria and invariant regions - derived from the definition of two underlying discrete-time systems - is given, and based on this characterisation impulsive affine feedback control strategies for non-zero set-points are designed. The closed-loop performance and benefits of the strategies are assessed through two biomedical examples: the Lithium ions distribution in the human body and the HIV treatment. 相似文献
137.
Domingo A. Gagliardini Corresponding author Pablo Clemente Colón 《International journal of remote sensing》2013,34(7-8):1271-1275
A comparison of Synthetic Aperture Radar (SAR) images acquired by the ERS-2 and RADARSAT-1 satellites with Landsat Thematic Mapper (TM) images acquired close in time is presented. Similarities and differences on the kind of ocean information they provide are discussed. The images were acquired over the Brazil–Malvinas (Falkland) Confluence under different solar elevation and azimuth angles. Ocean features observed by both types of sensors are discussed. These observations show that (1) at high solar angles, sun glint prevails over upwelled water-leaving radiance resulting in optical images that tend to provide dynamical information similar to that obtained from SAR imagery and (2) at low solar zenith and azimuth angles, upwelled radiation tends to prevail over sun glint, providing typical ocean colour and water quality information that can still complement and aid in the interpretation of SAR observations. 相似文献
138.
Pablo Sevilla Clara Sandino Milena Arciniegas Jordi Martínez-Gomis Maria Peraire Francisco Javier Gil 《Materials science & engineering. C, Materials for biological applications》2010,30(1):14-19
Lately new biomedical grade yttria stabilized zirconia (YTZP) dental implants have appeared in the implantology market. This material has better aesthetical properties than conventional titanium used for implants but long term behaviour of these new implants is not yet well known. The aim of this paper is to quantify the mechanical response of YTZP dental implants previously degraded under different time conditions and compare the toughness and fatigue strength with titanium implants. Mechanical response has been studied by means of mechanical testing following the ISO 14801 for Standards for dental implants and by finite element analysis. Accelerated hydrothermal degradation has been achieved by means of water vapour and studied by X-ray diffraction and nanoindentation tests. The results show that the degradation suffered by YTZP dental implants will not have a significant effect on the mechanical behaviour. Otherwise the fracture toughness of YTZP ceramics is still insufficient in certain implantation conditions. 相似文献
139.
Federico Peinado Virginia Francisco Raquel Hervás Pablo Gervás 《Minds and Machines》2010,20(4):565-588
Novelty is a key concept to understand creativity. Evaluating a piece of artwork or other creation in terms of novelty requires
comparisons to other works and considerations about the elements that have been reused in the creative process. Human beings
perform this analysis intuitively, but in order to simulate it using computers, the objects to be compared and the similarity
metrics to be used should be formalized and explicitly implemented. In this paper we present a study on relevant elements
for the assessment of novelty in computer-generated narratives. We focus on the domain of folk-tales, working with simple
plots and basic narrative elements: events, characters, props and scenarios. Based on the empirical results of this study
we propose a set of computational metrics for the automatic assessment of novelty. Although oriented to the implementation
of our own story generation system, the measurement methodology we propose can be easily generalized to other creative systems. 相似文献
140.
In this work we report the results of a combined biochemical and electrochemical study aimed to analyze both the growth of biofilms of Pseudomonas fluorescens on copper samples and its possible role in the instability of the metal/electrolyte interface.DNA and RNA were quantified along the time for biofilms grown on copper and glass to estimate both the growth of the bacterial population and its metabolic state (through the RNA/DNA ratio). The expression and specific activity of catalase were also determined to gain insight into their possible role in corrosion acceleration. The electrochemical behavior of the biofilm/copper interface was monitored by Linear Polarization Resistance (Rp) and electrochemical impedance spectroscopy (EIS) along the experiments.Results showed a longer lag phase for biofilms developing on copper that included a period of high metabolic activity (as measured by the RNA/DNA ratio) without biomass growth. Biological activity introduced a new time constant at intermediate frequencies in EIS spectra whose capacitive behavior increased with the biofilm development. The increment in this biofilm-related signal was accompanied by a strong limitation to charge transfer through a diffusion controlled process probably due to oxygen exhaustion by cells respiration, while the resistance of the interface decreased presumably due to oxide dissolution by local acidification under the colonies. In addition, catalase activity was found to be high in mature copper-tolerant biofilms, which differentially express a catalase isoform not present in biofilms growing on glass. 相似文献