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At least 1,063 records · Page 59Linked to original sources
PubMed2004

Clinical validation of different echocardiographic motion pictures expert group-4 algorythms and compression levels for telemedicine.

Tele-echocardiography is not widely used because of lengthy transmission times when using standard Motion Pictures Expert Groups (MPEG)-2 lossy compression algorythms, unless expensive high bandwidth lines are used. We sought to validate the newer MPEG-4 algorythms to allow further reduction in echocardiographic motion video file size. Four cardiologists expert in echocardiography read blindly 165 randomized uncompressed and compressed 2D and color Doppler normal and pathologic motion images. One Digital Video and 3 MPEG-4 compression algorythms were tested, the latter at 3 decreasing compression quality levels (100%, 65% and 40%). Mean diagnostic and image quality scores were computed for each file and compared across the 3 compression levels using uncompressed files as controls. File dimensions decreased from a range of uncompressed 12-83 MB to MPEG-4 0.03-2.3 MB. All algorythms showed mean scores that were not significantly different from uncompressed source, except the MPEG-4 DivX algorythm at the highest selected compression (40%, p=.002). These data support the use of MPEG-4 compression to reduce echocardiographic motion image size for transmission purposes, allowing cost reduction through use of low bandwidth lines.

Algorithms↗
PubMed2006

Fully 3-D PET reconstruction with system matrix derived from point source measurements.

The quality of images reconstructed by statistical iterative methods depends on an accurate model of the relationship between image space and projection space through the system matrix The elements of the system matrix for the clinical Hi-Rez scanner were derived by processing the data measured for a point source at different positions in a portion of the field of view. These measured data included axial compression and azimuthal interleaving of adjacent projections. Measured data were corrected for crystal and geometrical efficiency. Then, a whole system matrix was derived by processing the responses in projection space. Such responses included both geometrical and detection physics components of the system matrix. The response was parameterized to correct for point source location and to smooth for projection noise. The model also accounts for axial compression (span) used on the scanner. The forward projector for iterative reconstruction was constructed using the estimated response parameters. This paper extends our previous work to fully three-dimensional. Experimental data were used to compare images reconstructed by the standard iterative reconstruction software and the one modeling the response function. The results showed that the modeling of the response function improves both spatial resolution and noise properties.

Algorithms↗
PubMed2006

Hydrophobic hydration in cyclodextrin complexation.

We report temperature-dependent acoustic and densimetric data on changes in volume, expansibility, and adiabatic compressibility accompanying the binding of 1-adamantanecarboxylic acid (AD) to beta-cyclodextrin (beta-CD). We interpret our volumetric results in terms of hydration. Based on our compressibility and expansibility data, we estimate that, at 25 degrees C, the binding of AD to beta-CD is accompanied by displacement of 20 to 25 water molecules from the hydration shells of the two interacting species. Comparison of the temperature-dependent compressibility changes accompanying the binding of AD to beta-CD with the compressibility contribution of aliphatic groups suggests that displaced water molecules predominantly come from the hydrophobic loci of AD and beta-CD. Thus, we conclude that hydrophobic interactions play a major role in stabilizing the AD-beta-CD complex. Our estimate of the number of water molecules released to the bulk is consistent with structural considerations. There is also good agreement between our volumetric data and osmotic stress results reported by Harries et al. (Harries, D.; Rau, D. C.; Parsegian, V. A. J. Am. Chem. Soc. 2005, 127, 2184). This observation is consistent with the picture in which the two techniques probe the same population of water molecules solvating AD and beta-CD.

Cyclodextrins↗
PubMedDate not supplied

A randomized, controlled comparison of cardiopulmonary resuscitation performed on the floor and on a moving ambulance stretcher.

BACKGROUND: Recent studies have demonstrated that cardiopulmonary resuscitation (CPR) of poor quality is associated with worsened outcomes. OBJECTIVE: To compare the quality of CPR delivered on the floor with the quality of CPR delivered on a moving stretcher. The authors hypothesized that CPR performed on the floor would be superior to that performed on a moving stretcher. METHODS: A randomized, crossover experimental design was used. Subjects included emergency medical technician students, paramedic students, and emergency medicine residents. Two-member teams were randomly assigned to perform two-rescuer CPR on a manikin either on the floor or on a moving stretcher. After a 5-minute rest, the teams performed CPR under the opposite condition. Compression and ventilation data were collected using a recording resuscitation manikin. Dependent variables were compression depth, compression rate per minute, percentage of correct chest compressions, tidal volume, and percentage of correct ventilations. Data were compared using two-tailed paired t-test. RESULTS: Sixty-two subjects completed the study. The mean compression depth performed on the floor (39 +/- 9 mm) was greater than that on a moving stretcher (28 +/- 9 mm) (p < 0.001). The mean rates of chest compressions on the floor (110 +/- 17 beats/min) and on a moving stretcher (113 +/- 21 beats/min) were not different (p = 0.49). The percentage of correct compressions performed on the floor (54% +/- 40%) exceeded that on a moving stretcher (21% +/- 29%)(p < 0.001). The percentage of correct ventilations performed on the floor (43% +/- 26%) was greater than that on a moving stretcher (24% +/- 21%)(p < 0.04). CONCLUSIONS: Chest compression and ventilation quality of CPR performed on the floor was superior to that of CPR performed on a moving stretcher in this manikin model. The quality of CPR while moving was significantly compromised.

Adolescent↗
PubMed1993

SCANGRAPH: a program for digitization of graphs using an image scanner.

The program SCANGRAPH has been developed for vectorizing any drawing or graph in the form of a single continuous line. With the use of the software, the raster image of a graph in the TIFF format as generated from an optical scanner or digitizing video system can be converted to the corresponding digitized graph with x and y coordinates given. The digitized data can be output in the ASCII format for importing to other software packages. Options for peak identification, data smoothing and compression, and graph comparison are also provided for data manipulation.

Algorithms↗
PubMed2006

Extraction and compression of hierarchical isocontours from image data.

In this work, we introduce a new scheme to extract hierarchical isocontours from regular and irregular 2D sampled data and to encode it at single rate or progressively. A dynamic tessellation is used to represent and adapt the 2D data to the isocontour. This adaptation induces a controlled multi-resolution representation of the isocontour. This representation can then be encoded while controlling the geometry and topology of the decoded isocontour. The resulting algorithms form an efficient and flexible isocontour extraction and compression scheme.

Algorithms↗
PubMed2002

Hair-MAP: a prototype automated system for forensic hair comparison and analysis.

This paper demonstrates the feasibility of the automation of forensic hair analysis and comparison task using neural network explanation systems (NNESs). Our system takes as input microscopic images of two hairs and produces a classification decision as to whether or not the hairs came from the same person. Hair images were captured using a NEXTDimension video board in a NEXTDimension color turbo computer, connected to a video camera. Image processing was done on an SGI indigo workstation. Each image is segmented into a number of pieces appropriate for classification of different features. A variety of image processing techniques are used to enhance this information. Use of wavelet analysis and the Haralick texture algorithm to pre-process data has allowed us to compress large amounts of data into smaller, yet representative data. Neural networks are then used for feature classification. Finally, statistical tests determine the degree of match between the resulting collection of hair feature vectors. An important issue in automation of any task in criminal investigations is the reliability and understandability of the resulting system. To address this concern, we have developed methods to facilitate explanation of neural network's behavior using a decision tree. The system was able to achieve a performance of 83% hair match accuracy, using 5 of the 21 morphological characteristics used by experts. This shows promise for the usefulness of a fuller scale system. While an automated system would not replace the expert, it would make the task easier by providing a means for pre-processing the large amount of data with which the expert must contend.

Algorithms↗
PubMed1998

Experimental data and modelling of apparent molar volumes, isentropic compressibilities and refractive indices in aqueous solutions of glycine + NaCl.

Experiments have been performed at 298.15 K to measure the density, sound velocity and refractive index of glycine in aqueous solutions of NaCl over a wide range of both glycine and NaCl concentrations. The values of apparent molar volume and isentropic compressibility of glycine were calculated from the measured data. The results show a positive transfer volume of glycine from an NaCl solution to a more concentrated NaCl solution. This indicates that the size of a glycine molecule is larger in a solution with higher NaCl concentration. The negative values of apparent isentropic compressibility imply that the water molecules around the glycine molecules are less compressible than the water molecules in the bulk solution. These effects are attributed to the doubly charged behaviour of glycine and to the formation of physically bonded ion-pairs between the charged groups of glycine and sodium and chloride ions. The formation of ion-pairs, whose extents of binding reactions depend on the concentrations of both NaCl and glycine, alter the hydration number of glycine. This also explains the reason for the increase in the size of glycine with an increase in the NaCl concentration. A model based on the Pitzer formalism has been developed to correlate the activity coefficient, apparent molar volume and isentropic compressibility of glycine in aqueous solutions of NaCl. The results show that the model can accurately correlate the interactions in aqueous solutions of glycine and NaCl.

Journal Article↗
PubMed2006

Reversing demosaicking and compression in color filter array image processing: performance analysis and modeling.

In the conventional processing chain of single-sensor digital still cameras (DSCs), the images are captured with color filter arrays (CFAs) and the CFA samples are demosaicked into a full color image before compression. To avoid additional data redundancy created by the demosaicking process, an alternative processing chain has been proposed to move the compression process before the demosaicking. Recent empirical studies have shown that the alternative chain can outperform the conventional one in terms of image quality at low compression ratios. To provide a theoretically sound basis for such conclusion, we propose analytical models for the reconstruction errors of the two processing chains. The models developed confirm the results of existing empirical studies and provide better understanding of DSC processing chains. The modeling also allows performance predictions for more advanced compression and demosaicking methods, thus providing important cues for future development in this area.

Algorithms↗
PubMed1977

[Biomathematical evaluation of morphometric data--presented illustrated on the example of the relationship between axon diameter and thickness of the myelin sheath. II. Nonlinear approximations].

After the process of measuring morphometrical characteristics performing empirical regressions as a first stage of data processing is treated in the foregoing part I of the paper. The morphometrical datas have to characterize a functional relationship between two variables X and Y, in the cases in question this is the connection between axon caliber and thickness of myelin sheat of nerve fibres. Based on the results of empirical regression the second data processing stage consists in performing nonlinear approximations of the measured courses by a suitable chosen mathematical function. For this purpose the generalized logistic function is chosen for a quantitative and qualitative description of the connection between axon caliber and myelin sheat thickness. The numerical procedure and the various possibilities of the ALGOL-program for performing the approximation task are sketched. The results of this second data processing stage are discussed under the aspects of information compressing, of automatic data processing, and of providing an objective basis for the further process of evaluation and interpretation.

Anthropometry↗
PubMed2006

Cosolvent effects on the micellization of oxyphenyl(copoly)ethylene oxide copolymers in aqueous solution.

In the present paper, we have analyzed how the presence of ethanol affects the micellization process of two structurally related polyoxyethylene block copolymers with diblock and triblock architectures (diblock, S15E63; triblock, E67S15E67) and the same hydrophobic block length, formed by oxyphenylethylene units, through surface tension, static and dynamic light scattering, density, ultrasound velocity, transmission electron microscopy, and steady-state fluorescence techniques. E and S denote the oxyethylene (-OCH2CH2) and oxyphenylethylene (-OCH2CH(C6H5)) units, respectively, and the subscripts the block length. The effect of increasing amounts of ethanol in solution gives rise to a progressive disruption of the micelle structures formed by these copolymers, with an increase in the critical micelle concentration (cmc) values and a decrease in the micellar aggregation number. This originated from the deswelling of the poly(ethylene oxide) (PEO) chains due to a decrease of the water content, accompanied by a reduction of the solvophobicity and an increase of the solubility of the S blocks, causing the lowering of the interfacial tension between the polyoxyphenylethylene core and the solvent, and favoring the swelling of hydrophobic blocks. Therefore, to achieve thermodynamic equilibrium, the micelle size should be smaller. A model derived from small angle neutron scattering (SANS) data is also applied to get extra information on micelle structure. With the aim of obtaining information about the hydration of micellar solutions of these block copolymers, compressibility and fluorescence data were collected. The increase of compressibility with ethanol addition confirms the swelling of the hydrophobic polyoxyphenylethylene chains. Fluorescence data show that the addition of ethanol to the solution decreases the polarity, favoring the solubilization of the oxyphenylethylene chains in the mixed solvent as single monomers. Aggregation data derived from this technique are in fair agreement with those obtained from light scattering.

Journal Article↗
PubMed2006

An adaptive signal compression system with pre-specified reconstruction quality and compression rate.

Two essential properties of a signal compression method are the compression rate and the distance between the original signal and the reconstruction from the compressed signal. These two properties are used to assess the performance and quality of the method. In a recent work [B. Tümer, B. Demiröz, Lecture Notes in Computer Science-Computer and Information Sciences, volume 2869, chapter Signal Compression Using Growing Cell Structures: A Transformational Approach, Springer Verlag, 2003, pp. 952-959], an adaptive signal compression system (ACS) is presented which defines the performance of the system as a function of the system complexity, system sensitivity and data size. For a compression method, it is desirable to formulate the performance of the system as a function of the system complexity and sensitivity to optimize the performance of the system. It would be further desirable to express the reconstruction quality in terms of the same system parameters so as to know up front what compression rate to end up with for a specific reconstruction quality. In this work, we modify ACS such that the modified ACS (MACS) estimates the reconstruction quality for a given system complexity and sensitivity. Once this relation is identified it is possible to optimize either compression rate or reconstruction quality with respect to system sensitivity and system complexity while limiting the other one.

Algorithms↗
PubMed2005

Error concealment for shape in MPEG-4 object-based video coding.

In asynchronus transfer mode networks, cell loss or channel errors can cause data to be dropped in the channel. When digital images/videos are transmitted over these networks, one must be able to reconstruct the missing data so that the impact of the errors is minimized. In this paper, we present an error-concealment technique for shape in MPEG-4 object-based video coding. This method, which is based on using global motion estimation and compensation techniques for boundary recovery, consists of three steps: (1) boundary extraction from shape; (2) boundary patching using global motion compensation; and (3) boundary filling to reconstruct the shape of the damaged video object planes. Global motion parameters are inserted as part of the USER_DATA field in the compressed stream and are utilized in reconstructing the damaged boundaries of compressed video object planes.

Algorithms↗
PubMed2006

Unbiased pattern detection in microarray data series.

MOTIVATION: Following the advent of microarray technology in recent years, the challenge for biologists is to identify genes of interest from the thousands of genetic expression levels measured in each microarray experiment. In many cases the aim is to identify pattern in the data series generated by successive microarray measurements. RESULTS: Here we introduce a new method of detecting pattern in microarray data series which is independent of the nature of this pattern. Our approach provides a measure of the algorithmic compressibility of each data series. A series which is significantly compressible is much more likely to result from simple underlying mechanisms than series which are incompressible. Accordingly, the gene associated with a compressible series is more likely to be biologically significant. We test our method on microarray time series of yeast cell cycle and show that it blindly selects genes exhibiting the expected cyclic behaviour as well as detecting other forms of pattern. Our results successfully predict two independent non-microarray experimental studies.

Algorithms↗
PubMed2004

Kinematic response of lumbar functional spinal units to axial torsion with and without superimposed compression and flexion/extension.

Experimental data suggest that lumbar torsion contributes to lumbar disc degenerative changes, such as instability, spondylolisthesis and spinal canal stenosis. However, some basic mechanical characteristics of the lumbar spine under torsional loading have not yet been reported in detail. For example, the function of the facet joints under combined mechanical loads such as torsion with superimposed flexion or extension postures is an area of interest about which little biomechanical data have been reported. In this study, the kinematic response to axial torsion with superimposed axial compression (200 N), compression-flexion (3 and 6 Nm) and compression-extension (3 and 6 Nm) was investigated in 10 cadaveric lumbar functional spinal units. Range of motion (ROM), and helical axes of motion (HAM), were analyzed. There was no difference in ROM between no preload, pure compressive and flexion-compression preload conditions. The ROM was significantly reduced by both extension-compression preload conditions (11% reduction for 3 Nm and 19% reduction for 6 Nm of extension) compared to the pure compressive preload. For no preload, the average HAM position in the transverse plane of the intervertebral disc was near the posteriormost part of the disc and located laterally on the side contralateral to the applied torsional moment. In the transverse plane, the HAM position showed a discrete trend towards the posterior part of the specimens during extension. Kinematic data were visualized using computer animation techniques and CT-based reconstructions of the respective specimens. This information may be used for identifying and characterizing physiologic and pathologic motion and for specifying conservative and surgical treatment concepts and, thus, may find application to identifying indications for spinal fusion or in evaluating the effect of future semi-flexible instrumentation.

Adult↗
PubMed1998

Chronic double-level cauda equina compression. An experimental study on the dog cauda equina with analyses of nerve conduction velocity.

STUDY DESIGN: Nerve conduction velocity was studied in the dog cauda equina subjected to chronic double-level compression. OBJECTIVES: To analyze the effects of chronic double-level cauda equina compression. SUMMARY OF BACKGROUND DATA: Double-level cauda equina compression produces more symptoms in patients and more changes in acute experimental set-ups than does single-level compression. However, there have been no controlled, experimental studies on chronic double-level compression. METHODS: A total of 20 dogs were anesthetized. Two balloons were placed under the lamina of the seventh lumbar vertebra and the first sacral vertebra, respectively. One week (10 mm Hg, n = 5; 0 mm Hg, n = 5) and 1 month (10 mm Hg, n = 5; 0 mm Hg, n = 5) after inflation with a viscous substance, nerve conduction velocity was studied by local electrical stimulation and recording of muscle action potentials in the tail muscles. RESULTS: Nerve conduction velocity was determined over the cranial balloon, the caudal balloon, and both balloons. The data were similar for all three recordings. After 1 week there was a significant reduction in nerve conduction velocity induced by 10 mm Hg, compared with that induced by 0 mm Hg, which showed normal conditions. However, after 1 month this initial reduction in nerve conduction velocity had recovered partially. The reduction was similar to that described for single-level compression in a previous study in which the same compression model was used. CONCLUSIONS: Unlike the acute situation, chronic double-level compression does not induce more changes than single-level compression after 1 week, although the recovery after 1 month of compression is less complete after double-level compression. This less complete recovery may be a result of an adaptation of the nerve tissue and the vascularization of the cauda equina nerve roots to the applied pressure.

Action Potentials↗
PubMedDate not supplied

Adaptive compression of the ambulatory electrocardiogram.

Previous use of the MIT/BIH arrhythmia database, on analog tape, to investigate compression of ambulatory ECG data by average beat subtraction, residual differencing, and Huffman coding of the residuals had shown that with a quantization level of 35 mu V and a sample rate of 100 samples per second, it was possible to store ECG data with average data rates of 174 bits per second (bps), but because of the variation in ECG signals, data rates for different records ranged from 144 bps to 230 bps. In a practical storage system, it is desirable to fix the maximum data rate and store data with a minimum of distortion. For this study the previous compression algorithm was modified to adapt its quantization level to different ECG signal conditions. Two adaptation strategies were investigated. Both adapt the quantization-step size according to the number of bytes required for storing the coded signal, beat arrival times, and beat classifications. The new compression algorithm was tested with data from the MIT/BIH database on CD ROM. With the more successful of the two strategies, the adaptive compression algorithm stored MIT/BIH records with a difference of only 0.8 bps between the record with the highest data rate and the record with the lowest data rate. The average data rate for the entire database was 193.3 bps. Signal-to-compression noise ratios varied from record to record and varied over time for a given record. Average signal to compression noise ratios varied from 26.82 to 532.83.

Algorithms↗
PubMed1987

Mechanical strength of tibial trabecular bone evaluated by X-ray computed tomography.

The prospects for the use of quantitative computed tomography (QCT) for evaluation of mechanical properties of tibial trabecular bone were investigated. Computed tomography (CT) data from the proximal tibial epi- and metaphysis of six human cadaver knees were correlated with mechanical data obtained from compression tests and penetration strength measurements. In addition CT and intraoperative penetration data were compared in 20 patients. If spatial agreement between CT and mechanical measurement sites is optimized, close correlations are found between the relative linear attenuation coefficient determined by CT and the ultimate strength (r = 0.84), the yield strength (r = 0.85), the elastic modulus (r = 0.78), the ultimate energy absorption (r = 0.83), the yield energy absorption (r = 0.81), and the penetration strength (r = 0.82). It is concluded that these correlations are sufficient to make QCT a valuable tool for non-invasive evaluation of the spatial distribution of bone properties in several clinical applications.

Aged↗