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PubMed2005

Bulk characterization of pharmaceutical powders by low-pressure compression.

Low-pressure compression of pharmaceutical powders using small amounts of sample (50 mg) was evaluated as an alternative to traditional bulk powder characterization by tapping volumetry. Material parameters were extrapolated directly from the compression data and by fitting with the Walker, the Kawakita, and the Log-Exp compression models. The compression-derived material parameters were compared to the poured and tapped density and the Compressibility Index determined by tapping. The repeatability of the compression-derived parameters was generally high, supporting their potential for characterization purposes. Significant correlation was demonstrated between several of the compression and tapping-derived parameters. The discriminative power of the low-pressure compression test was discussed using the compressed density at 0.2 MPa, correlated with the tapped density, and the relative Walker coefficient, correlated with the Compressibility Index, as examples. The compressed density at 0.2 MPa and the relative Walker coefficient demonstrated excellent discriminative power, superior to the discriminative power of the correlated tapping derived parameters. The low-pressure compression test was concluded to provide a cost-effective and sensitive alternative to traditional tapping volumetry.

Algorithms↗
PubMed2006

Seamless image stitching by minimizing false edges.

Various applications such as mosaicing and object insertion require stitching of image parts. The stitching quality is measured visually by the similarity of the stitched image to each of the input images, and by the visibility of the seam between the stitched images. In order to define and get the best possible stitching, we introduce several formal cost functions for the evaluation of the stitching quality. In these cost functions the similarity to the input images and the visibility of the seam are defined in the gradient domain, minimizing the disturbing edges along the seam. A good image stitching will optimize these cost functions, overcoming both photometric inconsistencies and geometric misalignments between the stitched images. We study the cost functions and compare their performance for different scenarios both theoretically and practically. Our approach is demonstrated in various applications including generation of panoramic images, object blending and removal of compression artifacts. Comparisons with existing methods show the benefits of optimizing the measures in the gradient domain.

Algorithms↗
PubMed2006

Two-dimensional correlation study of uniaxially drawn poly(ethylene terephthalate) films by using attenuated total reflection based dynamic compression modulation step-scan fourier transform infrared in combination with spectral simulation analysis by density functional theory.

Attenuated total reflection (ATR) based dynamic compression modulation two-dimensional (2D) correlation studies of uniaxially drawn poly(ethylene terephthalate) (PET) films have been performed in combination with spectral simulation analysis by density functional theory (DFT). The dynamic 2D infrared (IR) correlation spectra in the region of the CCO stretching mode vibrations show four distinct correlation peaks located around 1290, 1265, 1248, and 1234 cm(-1). These bands can be clearly assigned to the combination bands or coupling modes of the CH in-plane bend of the benzene ring or the CH(2) deformation of the ethylene glycol unit, as well as CCO stretching vibrations, which are gauche conformer's characteristic bands, by DFT analysis. The sequential analysis of 2D correlation data shows that, upon applying the dynamic compression, the response of the side chain regions (ester groups) occurs first, followed by that of the backbone regions (benzene rings). The ATR based dynamic compression modulation 2D correlation spectroscopy in combination with DFT analysis can be a powerful tool for various polymer characterizations.

Algorithms↗
PubMedDate not supplied

Managing joint pain in primary care.

Joint pain is a common problem seen by family physicians. Although many pain complaints arise from self-limited conditions, a substantial number require immediate and ongoing care. Prompt appropriate treatment can help limit symptoms, prevent disability, and improve outcomes. The differential diagnosis is varied, with both laboratory studies and diagnostic imaging available to help evaluate the joint. At the initial evaluation and at each subsequent re-evaluation, there should be efforts to identify dangerous conditions and distinguish conditions with a disease-specific pathogenesis. Treatment of joint pain consists of both pharmacologic and nonpharmacologic modalities. Pharmacologic therapies may include medications specific for pain, inflammation, and adjuncts specific to the diagnosis. Treatment of pain should proceed in a step-wise fashion providing medications appropriate for treating the level of pain. Inflammation is treated with physical modalities and nonsteroidal anti-inflammatory or cyclo-oxygenase-2 inhibitors. Nonpharmacologic therapies may include protection, rest, ice, compression, elevation, and simple office procedures. Physical therapy and education can assist in the recovery process, and prevent recurrence.

Acetaminophen↗
PubMedDate not supplied

Evaluation of compressed lung CT image quality using quantitative analysis.

The goals of this study were (1) to evaluate the quality of compressed lung CT images obtained using high resolution CT (HRCT: 2 mm slice thickness) for degree of compression and conventional CT (10 mm slice thickness) images by using physical and subjective evaluations, and (2) to analyze the distortion of density distribution on lung CT images using histogram analysis for each compression ratio. The coding method was performed according to the Joint Photographic Experts Group (JPEG). We physically evaluated the quality of compressed lung CT images using the peak signal-to-noise ratio (PSNR) as given by the square root of the ratio of the peak value of the gray level squared to the mean square error (dB) and subjectively evaluated the CT images using the mean opinion score (MOS). The acceptable compression ratio for diagnosis was about 1:6 to 1:7 for conventional CT images and about 1:4 to 1:5 for HRCT images as determined by MOS. The PSNR corresponding to acceptable compression ratios was about 50 dB. The difference in density distribution between HRCT and conventional CT was statistically significant (Friedman test: p<0.02) in histogram analysis. Results suggested that, in comparison with conventional CT, a high compression ratio was not suitable for HRCT.

Algorithms↗
PubMedDate not supplied

Lossy compression techniques, medical images, and the clinician.

There has been increasing interest in the storage and retrieval of medical images in hospitals and clinics here in Brazil and elsewhere. At the Heart Institute of São Paulo, with thousands of image-based procedures performed each month, the pursuit of optimal transmission and storage methods for digital images is a major concern. The use of data-compression techniques can reduce the enormous amount of imaging data to be stored or transmitted across a computer network, so that the efficiency of the computing system is preserved. The techniques for image compression can be categorized as "lossless" or "lossy," with "lossy" techniques being those in which some, supposedly irrelevant information is lost. Lossy techniques are much more efficient than lossless ones, achieving data-compression ratios as high as 100:1.

Algorithms↗
PubMed1995

1H-NMR microscopy of tablets.

A 1H-nuclear magnetic resonance (NMR) microscopy method was utilized for the first time to determine the porosity distribution of physically intact tablets. The main advantage of this newly developed method was that porosity cross sections through whole tablets or specific locations could be obtained without mechanically destroying the tested tablet. This was achieved by filling tablet cavities with silicone oil under vacuum. The amount of silicone oil locally within the tablet was then determined by 1H-NMR microscopy, revealing the inverse inner structure. To reduce the measuring time, a paramagnetic gadolinium complex was added to the silicone oil. The cross sectional signals produced by 1H-NMR microscopy through the tablet were transformed into a color image by a specially designed computer graphic program. To improve the signal-noise ratio an algorithm of 3D-filtering was introduced. The maximal spatial resolution achieved with this method was about 95 microns for a cube's edge length corresponding to some 380,000 positions in a 9-mm-diameter compression-coated tablet. Uneven porosity distributions within tablets, cracks, or cavities could be visualized with this newly developed method. Different compaction mechanisms were observed with plastic- or brittle-type tablets. The different states of densification during compaction of powders could be detected. The integrity of compression coatings was determined to be dependent on the pressure load and the location of the core within the coat.

Magnetic Resonance Imaging↗
PubMed2005

A nonlinear biphasic viscohyperelastic model for articular cartilage.

Experiments on articular cartilage have shown nonlinear stress-strain curves under finite deformations as well as intrinsic viscous effects of the solid phase. The aim of this study was to propose a nonlinear biphasic viscohyperelastic model that combines the intrinsic viscous effects of the proteoglycan matrix with a nonlinear hyperelastic constitutive equation. The proposed equation satisfies objectivity and reduces for uniaxial loading to a solid type viscous model in which the actions of the springs are represented by the hyperelastic function proposed by Holmes and Mow [1990. J. Biomechanics 23, 1145-1156.]. Results of the model, that were efficiently implemented in an updated Lagrangian algorithm, were compared with experimental infinitesimal data reported by DiSilverstro and Suh [2001. J. Biomechanics 34, 519-525.] and showed acceptable fitting for the axial force (R(2)=0.991) and lateral displacement (R(2)=0.914) curves in unconfined compression as well as a good fitting of the axial indentation force curve (R(2)=0.982). In addition, the model showed an excellent fitting of finite-deformation confined compression stress relaxation data reported by Ateshian et al. [1997. J. Biomechanics 30, 1157-1164.] and Huang et al. [2005. J. Biomechanics 38, 799-809.] (R(2)=0.993 and R(2)=0.995, respectively). The constitutive equation may be used to represent the mechanical behavior of the proteoglycan matrix in a fiber reinforced model of articular cartilage.

Animals↗
PubMed2005

Medical and surgical palliative care of patients with urological malignancies.

PURPOSE: Urological malignancies are relatively common and patients often live many years with disease. There are many effective medical and surgical palliative treatments, although few comprehensive guidelines have been published. We reviewed the various palliative treatments available for the 3 most common urological malignancies, namely prostate cancer, bladder cancer and renal cancer. MATERIALS AND METHODS: A literature search of the last 15 years was performed using MEDLINE/PubMed. In addition, relevant journals were targeted for specific information related to this review. Our clinical experience was combined with the current literature to create guidelines for palliative care. RESULTS: Several effective treatments are available for the palliative care of patients with prostate, bladder or renal cancer. Options in palliative care are varied with regard to invasiveness, morbidity, risks and benefits. The algorithms described provide a framework to a sequential approach to achieving palliation. Urologists are central to initiating care and referrals to improve outcomes in these patients. CONCLUSIONS: Palliative care includes disease directed treatment as well as functional, psychosocial and spiritual support. Disease directed therapy and palliative care should be provided simultaneously throughout illness. Improved quality of care and quality of life as well as physician satisfaction are frequent outcomes of this approach. Supportive care begins at initial diagnosis and it should be flexible to meet the changing needs of patients with cancer and their families.

Algorithms↗
PubMed2006

Diagnosis of pulmonary embolism: in transition.

PURPOSE OF REVIEW: To discuss reports published in 2005 on the diagnosis of clinically suspected nonmassive pulmonary embolism. RECENT FINDINGS: Progress has been made in assessing the clinical probability of pulmonary embolism, in addressing diagnosis in the elderly, in evaluating the diagnostic performance of single-detector and multidetector row helical computed tomography, and in the role of D-dimer measurement and lower limb venous compression ultrasonography in the diagnostic work-up of pulmonary embolism. SUMMARY: Diagnosing venous thromboembolism depends mainly on noninvasive diagnostic tools that are used sequentially. In most patients, a noninvasive work-up is feasible and the diagnostic algorithms are becoming simpler. This review focuses on developments in clinical probability assessment, pulmonary embolism in the elderly, potential new uses of D-dimer measurement, advent of multidetector row helical computed tomography, and utility of ultrasonography in detecting deep vein thrombosis in patients with suspected pulmonary embolism. With the development of potentially more sensitive diagnostic tests for pulmonary embolism, physicians are now facing the risk of overdiagnosis and hence overtreatment. The issue will no longer be just to detect clots but to identify patients who must be treated using anticoagulants, a complicated question.

Aged↗
PubMed2004

Thouless-Anderson-Palmer approach for lossy compression.

We study an ill-posed linear inverse problem, where a binary sequence will be reproduced using a sparse matrix. According to the previous study, this model can theoretically provide an optimal compression scheme for an arbitrary distortion level, though the encoding procedure remains an NP-complete problem. In this paper, we focus on the consistency condition for a dynamics model of Markov-type to derive an iterative algorithm, following the steps of Thouless-Anderson-Palmer approach. Numerical results show that the algorithm can empirically saturate the theoretical limit for the sparse construction of our codes, which is also very close to the rate-distortion function.

Journal Article↗
PubMed2001

Advanced digital photoelastic investigations on the tooth-bone interface.

The purpose of this study was to investigate the behavior of the tooth-bone interface on the nature of stress distribution in the tooth and its supporting alveolar bone for various occlusal loads using an advanced digital photoelastic technique. A digital image processing system coupled with a circular polariscope was used for the stress analysis. The phase shift technique and a phase unwrapping algorithm was utilized for fringe processing. This aids in obtaining qualitative and quantitative information on the nature of stress distribution within the dento-osseous structures. The experiments revealed bending stresses within dento-osseous structures. However, the compressive stress magnitude was larger than the tensile stress. Zero stress regions were also identified within the dento-osseous structures. The results suggest that the geometry of the dento-osseous structures and the structural gradients at the tooth-bone interface play a significant role in the distribution of stresses without stress concentrations. Further, the application of an advanced image-processing system with the circular polariscope showed notable advantages and could be applied in other biomechanical investigations.

Alveolar Process↗
PubMed2005

3-D correlation-based speckle tracking.

Widely-used 1-D/2-D speckle tracking techniques in elasticity imaging often experience significant speckle decorrelation in applications involving large elevational motion (i.e., out of plane motion). The problem is more pronounced for cardiac strain rate imaging (SRI) since it is very difficult to confine cardiac motion to a single image plane. Here, we present a 3-D correlation-based speckle tracking algorithm. Conceptually, 3-D speckle tracking is just an extension of 2-D phase-sensitive correlation-based speckle tracking. However, due to its high computational cost, optimization schemes, such as dynamic programming, decimation and two-path processing, are introduced to reduce the computational burden. To evaluate the proposed approach, a 3-D bar phantom under uniaxial compression was simulated for benchmark tests. A more sophisticated 3-D simulation of the left ventricle of the heart was also made to test the applicability of 3-D speckle tracking in cardiac SRI. Results from both simulations clearly demonstrated the feasibility of 3-D correlation-based speckle tracking. With the ability to follow 3-D speckle in 3-D space, 3-D speckle tracking outperforms lower-dimensional speckle tracking by minimizing decorrelation caused by pure elevational translation. In other words, 3-D tracking can push toward solely deformation-limited, decorrelation-optimized speckle tracking. Hardware implementation of the proposed 3-D speckle tracking algorithm using field programmable gate arrays (FPGA) is also discussed.

Algorithms↗
PubMed2002

Slow local movements of collagen fibers by fibroblasts drive the rapid global self-organization of collagen gels.

Aclassic model for tissue morphogenesis is the formation of ligament-like straps between explants of fibroblasts placed in collagen gels. The patterns arise from mechanical forces exerted by cells on their substrates (Harris et al., 1981). However, where do such straps come from, and how are slow local movements of cells transduced into dramatic long-distance redistributions of collagen? We embedded primary mouse skin and human periodontal ligament fibroblasts in collagen gels and measured the time course of patterning by using a novel computer algorithm to calculate anisotropy, and by tracking glass beads dispersed in the gel. As fibroblasts began to spread into their immediate environments, a coordinated rearrangement of collagen commenced throughout the gel, producing a strap on a time scale of minutes. Killing of cells afterwards resulted in a partial relaxation of the matrix strain. Surprisingly, relatively small movements of collagen molecules on the tensile axis between two pulling explants induced a much larger concomitant compression of the gel perpendicular to the axis, organizing and aligning fibers into a strap. We propose that this amplification is due to the geometry of the collagen matrix, and that analogous amplified movements may drive morphological changes in other biological meshes, both outside and inside the cell.

Algorithms↗
PubMedDate not supplied

Low-cost telepresence for collaborative virtual environments.

We present a novel low-cost method for visual communication and telepresence in a CAVE -like environment, relying on 2D stereo-based video avatars. The system combines a selection of proven efficient algorithms and approximations in a unique way, resulting in a convincing stereoscopic real-time representation of a remote user acquired in a spatially immersive display. The system was designed to extend existing projection systems with acquisition capabilities requiring minimal hardware modifications and cost. The system uses infrared-based image segmentation to enable concurrent acquisition and projection in an immersive environment without a static background. The system consists of two color cameras and two additional b/w cameras used for segmentation in the near-IR spectrum. There is no need for special optics as the mask and color image are merged using image-warping based on a depth estimation. The resulting stereo image stream is compressed, streamed across a network, and displayed as a frame-sequential stereo texture on a billboard in the remote virtual environment.

Algorithms↗
PubMedDate not supplied

Boolean operations with implicit and parametric representation of primitives using R-functions.

We present a new and efficient algorithm to accurately polygonize an implicit surface generated by multiple Boolean operations with globally deformed primitives. Our algorithm is special in the sense that it can be applied to objects with both an implicit and a parametric representation, such as superquadrics, supershapes, and Dupin cyclides. The input is a Constructive Solid Geometry tree (CSG tree) that contains the Boolean operations, the parameters of the primitives, and the global deformations. At each node of the CSG tree, the implicit formulations of the subtrees are used to quickly determine the parts to be transmitted to the parent node, while the primitives' parametric definition are used to refine an intermediary mesh around the intersection curves. The output is both an implicit equation and a mesh representing its solution. For the resulting object, an implicit equation with guaranteed differential properties is obtained by simple combinations of the primitives' implicit equations using R-functions. Depending on the chosen R-function, this equation is continuous and can be differentiable everywhere. The primitives' parametric representations are used to directly polygonize the resulting surface by generating vertices that belong exactly to the zero-set of the resulting implicit equation. The proposed approach has many potential applications, ranging from mechanical engineering to shape recognition and data compression. Examples of complex objects are presented and commented on to show the potential of our approach for shape modeling.

Algorithms↗
PubMed1988

The impact of magnetic resonance on the diagnostic evaluation of acute cervicothoracic spinal trauma.

From 1984 to 1987 magnetic resonance (MR) imaging was performed on 100 patients suffering acute spinal trauma. MR demonstrated one or more injuries to the cervicothoracic region in 31 patients. It displayed a spectrum of spinal cord injury ranging from mild compression and swelling to complete transection. MR was also useful in evaluating alignment at the cervicothoracic junction, in depicting ligamentous injury, in establishing the presence of disc herniation, and in identifying unsuspected levels of injury. We present a diagnostic algorithm that incorporates the role of MR in evaluating acute cervicothoracic spinal trauma and emphasizes the replacement of myelography by MR in the initial assessment of neurologic deficit.

Acute Disease↗
PubMed1984

A technique for the detection, decomposition and analysis of the EMG signal.

In the present paper we have described a system for acquiring, processing and decomposing EMG signals for the purpose of extracting as many motor unit action potential trains as possible with the greatest level of accuracy. This system consists of 4 main sections. The first section consists of methodologies for signal acquisition and quality verification. Three channels of EMG signals are acquired using a quadripolar needle electrode designed to enhance discrimination among different MUAPs. An automated experiment control system is devised to free the experimenter from the burden of experiment detailed surveillance and bookkeeping; and to allow on-line assessment of the EMG signal quality in terms of decomposition suitability. The second section consists of methodologies for signal sampling and conditioning. The EMG signal is bandpass filtered (between 1 kHz and 10 kHz), sampled and compressed by eliminating parts of the signal under a preset threshold level. The third section consists of a signal decomposition technique where motor unit action potential trains are extracted from the EMG signal using a highly computer assisted interactive algorithm. The algorithm uses a continuously updated template matching routine and firing statistics to identify MUAPs in the EMG signal. The templates of the MUAPs are continuously updated to enable the algorithm to function even when the shape of a specific MUAP undergoes slow variations. The fourth section deals with ways in which to analyze and display the results. The more frequently used representation formats are: (1) display of MUAP wave shapes; (2) impulse trains representing motor unit firings; (3) IPI plots where time interval between successive firings of the same motor unit is plotted vs. time of the muscle contraction; (4) firing rate plots where the estimated time-varying mean firing rate of the detected motor units is plotted vs. time of the muscle contraction. The performance of the system has been tested in terms of: (1) consistency among results obtained by different operators; (2) accuracy evaluated on synthetic EMG signal; (3) indirect measure of accuracy on real EMG signal by comparing results pertaining the same motor unit action potential trains derived by two EMG signals, independently and simultaneously recorded from two different electrodes.

Action Potentials↗