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排序方式: 共有136条查询结果,搜索用时 15 毫秒
1.
We have developed an IT governance disclosure framework to examine how firms communicate their IT governance activities. Using this framework for a sample of 200 commercial banking firms, our empirical assessment indicates that differences in the level of disclosure are systematically related to differences in institutional settings. We also find that firms with relatively good corporate governance practices consider IT performance measurement matters to be highly important when informing and communicating with shareholders. 相似文献
2.
Robert Toth Justin Ribault John Gentile Dan Sperling Anant Madabhushi 《Computer Vision and Image Understanding》2013,117(9):1051-1060
In this work we present an improvement to the popular Active Appearance Model (AAM) algorithm, that we call the Multiple-Levelset AAM (MLA). The MLA can simultaneously segment multiple objects, and makes use of multiple levelsets, rather than anatomical landmarks, to define the shapes. AAMs traditionally define the shape of each object using a set of anatomical landmarks. However, landmarks can be difficult to identify, and AAMs traditionally only allow for segmentation of a single object of interest. The MLA, which is a landmark independent AAM, allows for levelsets of multiple objects to be determined and allows for them to be coupled with image intensities. This gives the MLA the flexibility to simulataneously segmentation multiple objects of interest in a new image.In this work we apply the MLA to segment the prostate capsule, the prostate peripheral zone (PZ), and the prostate central gland (CG), from a set of 40 endorectal, T2-weighted MRI images. The MLA system we employ in this work leverages a hierarchical segmentation framework, so constructed as to exploit domain specific attributes, by utilizing a given prostate segmentation to help drive the segmentations of the CG and PZ, which are embedded within the prostate. Our coupled MLA scheme yielded mean Dice accuracy values of .81, .79 and .68 for the prostate, CG, and PZ, respectively using a leave-one-out cross validation scheme over 40 patient studies. When only considering the midgland of the prostate, the mean DSC values were .89, .84, and .76 for the prostate, CG, and PZ respectively. 相似文献
3.
4.
Anant K. Singh Wentong Lu Dulal Senapati Sadia Afrin Khan Zhen Fan Tapas Senapati Teresa Demeritte Lule Beqa Paresh Chandra Ray 《Small (Weinheim an der Bergstrasse, Germany)》2011,7(17):2517-2525
A recent gold nanotechnology‐driven approach opens up a new possibility for the destruction of cancer cells through photothermal therapy. Ultimately, photothermal therapy may enter into clinical therapy and, as a result, there is an urgent need for techniques to monitor the tumor response to therapy. Driven by this need, a nanoparticle surface‐energy‐transfer (NSET) approach to monitor the photothermal therapy process by measuring a simple fluorescence intensity change is reported. The fluorescence intensity change is due to the light‐controlled photothermal release of single‐stranded DNA/RNA via dehybridization during the therapy process. Time‐dependent results show that just by measuring the fluorescence intensity change, the photothermal therapy response during the therapy process can be monitored. The possible mechanism and operating principle of the NSET assay are discussed. Ultimately, this NSET assay could have enormous potential applications in rapid, on‐site monitoring of the photothermal therapy process, which is critical to providing effective treatment of cancer and multidrug‐resistant bacterial infections. 相似文献
5.
Anant Hegde Jose C. Principe Deniz Erdogmus Umut Ozertem Yadunandana N. Rao Hemanth Peddaneni 《The Journal of VLSI Signal Processing》2006,45(1-2):85-95
Principal components analysis is an important and well-studied subject in statistics and signal processing. Several algorithms
for solving this problem exist, and could be mostly grouped into one of the following three approaches: adaptation based on
Hebbian updates and deflation, optimization of a second order statistical criterion (like reconstruction error or output variance),
and fixed point update rules with deflation. In this study, we propose an alternate approach that avoids deflation and gradient-search
techniques. The proposed method is an on-line procedure based on recursively updating the eigenvector and eigenvalue matrices
with every new sample such that the estimates approximately track their true values as would be calculated analytically from
the current sample estimate of the data covariance matrix. The perturbation technique is theoretically shown to be applicable
for recursive canonical correlation analysis, as well. The performance of this algorithm is compared with that of a structurally
similar matrix perturbation-based method and also with a few other traditional methods like Sanger’s rule and APEX.
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6.
Combining low-, high-level and empirical domain knowledge for automated segmentation of ultrasonic breast lesions 总被引:11,自引:0,他引:11
Breast cancer is the most frequently diagnosed malignancy and the second leading cause of mortality in women. In the last decade, ultrasound along with digital mammography has come to be regarded as the gold standard for breast cancer diagnosis. Automatically detecting tumors and extracting lesion boundaries in ultrasound images is difficult due to their specular nature and the variance in shape and appearance of sonographic lesions. Past work on automated ultrasonic breast lesion segmentation has not addressed important issues such as shadowing artifacts or dealing with similar tumor like structures in the sonogram. Algorithms that claim to automatically classify ultrasonic breast lesions, rely on manual delineation of the tumor boundaries. In this paper, we present a novel technique to automatically find lesion margins in ultrasound images, by combining intensity and texture with empirical domain specific knowledge along with directional gradient and a deformable shape-based model. The images are first filtered to remove speckle noise and then contrast enhanced to emphasize the tumor regions. For the first time, a mathematical formulation of the empirical rules used by radiologists in detecting ultrasonic breast lesions, popularly known as the "Stavros Criteria" is presented in this paper. We have applied this formulation to automatically determine a seed point within the image. Probabilistic classification of image pixels based on intensity and texture is followed by region growing using the automatically determined seed point to obtain an initial segmentation of the lesion. Boundary points are found on the directional gradient of the image. Outliers are removed by a process of recursive refinement. These boundary points are then supplied as an initial estimate to a deformable model. Incorporating empirical domain specific knowledge along with low and high-level knowledge makes it possible to avoid shadowing artifacts and lowers the chance of confusing similar tumor like structures for the lesion. The system was validated on a database of breast sonograms for 42 patients. The average mean boundary error between manual and automated segmentation was 6.6 pixels and the normalized true positive area overlap was 75.1%. The algorithm was found to be robust to 1) variations in system parameters, 2) number of training samples used, and 3) the position of the seed point within the tumor. Running time for segmenting a single sonogram was 18 s on a 1.8-GHz Pentium machine. 相似文献
7.
Helmy R Zhou GX Chen YW Crocker L Wang T Wenslow RM Vailaya A 《Analytical chemistry》2003,75(3):605-611
In this study, we report the use of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FT-IR) for the identification and quantitation of two polymorphs of Aprepitant, a substance P antagonist for chemotherapy-induced emesis. Mixtures of the polymorph pair were prepared by weight and ATR-FT-IR spectra of the powdered samples were obtained over the wavelength range of 700-1500 cm(-1). Significant spectral differences between the two polymorphs at 1140 cm(-1) show that ATR-FT-IR can provide definitive identification of the polymorphs. To investigate the feasibility of ATR-FT-IR for quantitation of polymorphic forms of Aprepitant, a calibration plot was constructed with known mixtures of the two polymorphs by plotting the peak ratio of the second derivative of absorbance spectra against the weight percent of form II in the polymorphic mixture. Using this novel approach, 3 wt % of one crystal form could be detected in mixtures of the two polymorphs. The accuracy of ATR-FT-IR in determining polymorph purity of the drug substance was tested by comparing the results with those obtained by X-ray powder diffractometry (XRPD). Indeed, polymorphic purity results obtained by ATR-FT-IR were found to be in good agreement with the predictions made by XRPD and compared favorably with actual values in the known mixtures. The present study clearly demonstrates the potential of ATR-FT-IR as a quick, easy, and inexpensive alternative to XRPD for the determination of polymorphic identity and purity of solid drug substances. The technique is ideally suited for polymorph analysis, because it is precise, accurate, and requires minimal sample preparation. 相似文献
8.
Yeh David Peh Li-Shiuan Borkar Shekhar Darringer John Agarwal Anant Hwu Wen-mei 《Design & Test of Computers, IEEE》2008,25(3):272-278
The 2007 Design Automation Conference (DAC) had a special session entitled "1000 Core Chips," which was organized by Radu Marculescu (Carnegie Mellon University) and Li-Shiuan Peh (Princeton University). This session examined some of the ramifications of multicore chip design from four perspectives: technology, architecture, programming, and design automation. In this roundtable, held immediately following the conference session, the presenters expounded on the future of multicore chips with respect to education, programming languages, operating systems, and design automation. 相似文献
9.
Active contours and active shape models (ASM) have been widely employed in image segmentation. A major limitation of active contours, however, is in their 1) inability to resolve boundaries of intersecting objects and to 2) handle occlusion. Multiple overlapping objects are typically segmented out as a single object. On the other hand, ASMs are limited by point correspondence issues since object landmarks need to be identified across multiple objects for initial object alignment. ASMs are also are constrained in that they can usually only segment a single object in an image. In this paper, we present a novel synergistic boundary and region-based active contour model that incorporates shape priors in a level set formulation with automated initialization based on watershed. We demonstrate an application of these synergistic active contour models using multiple level sets to segment nuclear and glandular structures on digitized histopathology images of breast and prostate biopsy specimens. Unlike previous related approaches, our model is able to resolve object overlap and separate occluded boundaries of multiple objects simultaneously. The energy functional of the active contour is comprised of three terms. The first term is the prior shape term, modeled on the object of interest, thereby constraining the deformation achievable by the active contour. The second term, a boundary-based term detects object boundaries from image gradients. The third term drives the shape prior and the contour towards the object boundary based on region statistics. The results of qualitative and quantitative evaluation on 100 prostate and 14 breast cancer histology images for the task of detecting and segmenting nuclei and lymphocytes reveals that the model easily outperforms two state of the art segmentation schemes (geodesic active contour and Rousson shape-based model) and on average is able to resolve up to 91% of overlapping/occluded structures in the images. 相似文献
10.
Intraocular lens power (IOL) calculation for cataract surgery has been shown to be inaccurate after photorefractive keratectomy (PRK), laser-assisted subepithelial keratectomy (LASEK) and laser in situ keratomileusis (LASIK). Many techniques exist to calculate corneal power with varying results and require the clinician to be aware of the pitfalls of IOL power calculation in post-refractive eyes. The AS biometry method proposed here is a simple method which does not rely on the calculation of corneal power. This new method is compared to the current gold standard the clinical history method (CHM). Twenty-nine eyes of 15 patients had routine biometry prior to LASIK, LASEK or PRK. The range of pre-operative spherical equivalent refractive error was -5.37 to +4.00 diopters. The post-operative refraction was measured at 3-6 months. The IOL power calculation was calculated using the AS biometry method and the CHM. The two methods were compared using the Student's paired t-test and the Bland Altman technique. There was no statistical difference between the AS biometry method and the CHM. The paired Student's t-test comparing the AS biometry method and the CHM showed no statistical difference, t=0.33 with a p-value of 0.75, at a 95% confidence interval. The authors conclude that the AS biometry technique is as accurate as the CHM. The former is a simpler method which avoids many of the pitfalls and confounding factors involved in IOL power calculation following corneal excimer laser surgery. However, like the CHM it requires measurements prior to laser surgery. 相似文献