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PubMed2001

A new hybrid algorithm for ECG signal compression based on the wavelet transformation of the linearly predicted error.

This paper describes a hybrid technique based on the combination of wavelet transform and linear prediction to achieve very effective electrocardiogram (ECG) data compression. First, the ECG signal is wavelet transformed using four different discrete wavelet transforms (Daubechies, Coiflet, Biorthogonal and Symmlet). All the wavelet transforms are based on dyadic scales and decompose the ECG signals into five detailed levels and one approximation. Then, the wavelet coefficients are linearly predicted, where the error corresponding to the difference between these coefficients and the predicted ones is minimized in order to get the best predictor. In particular, the residuals of the wavelet coefficients are uncorrelated and hence can be represented with fewer bits compared to the original signal. To further increase the compression rate, the residual sequence obtained after linear prediction is coded using a newly developed coding technique. As a result, a compression ratio (Cr) of 20 to 1 is achieved with percentage root-mean square difference (PRD) less than 4%. The algorithm is compared to an alternative compression algorithm based on the direct use of wavelet transforms. Experiments on selected records from the MIT-BIH arrhythmia database reveal that the proposed method is significantly more efficient in compression. The proposed compression scheme may find applications in digital Holter recording, in ECG signal archiving and in ECG data transmission through communication channels.

Algorithms↗

PubMed1980

Minimisation of data transfer losses in the display of digitised scintigraphic images.

The transfer of scintigraphic data to any type of display, and ultimately to the eye, is a data compression procedure which invariably leads to information loss. Unless this information loss can be minimised, valuable image data may well be discarded. Attempts to achieve data loss minimisation have led to procedures such as the use of statistically equal levels for display, and the more recent histogram modification techniques such as equalisation and hyperbolisation. The method discussed here uses information theory to obtain the mean uncertainty (or entropy) per pixel in the intensity of the displayed image. Statistical noise and the characteristics of the image are taken into account. Calculation of the best choice of grey or colour levels for transfer loss minimisation is then possible: that is, the best conditions for data transfer to the display can be set up. A computer algorithm which carries out this function has been written. Several different types of simulated phantom, and clinical images, have been investigated. Improved perceptibility of many of these images has been obtained, correlating with reduction in mean pixel uncertainty. Although the technique still requires some refinement, it appears that optimisation of display characteristics for any transmitted image is potentially feasible.

Computers↗

PubMed1995

A desk top computer program for visualized statistical analysis of lesional images in intracerebral hemorrhage.

Statistically identified information on the relationships between the sites of lesions in intracerebral hemorrhage (ICH), risk factors such as a smoking or drinking habit, anamnesis, and biochemical data through blood tests will extend assistance to neuromedical clinicians on their daily clinical duties. It will provide them with a useful guide to determine the method of treatment. Also, it will be a basic research material for their clinical studies on diagnosis, progress, or prognosis in ICH. In order to obtain such statistics with the help of the computer, we need to have a computationally effective image database system. As is generally known, medical image data especially requires a great amount of storage; high-speed processing techniques are therefore also needed to deal with such data effectively. In addition, it is desired that we have outputs from the analysis edited with well-visualized effect, using 3D computer graphics, etc. These are why most existing image processing systems have been designed to work on comparatively large-scale computers. So far as we know, it is hard to find a practical and inexpensive personal computer-based application system for visualized statistical analysis of lesional images in ICH. We have developed a desk top computer-based program for statistical analysis of lesional image data of ICH. With this system, we can organize a medical image database that consists of the personal data of patients with ICH (sex, age, occupation, diagnosis, symptoms, part of physical disorder, etc.), risk factors, anamnesis (cerebral apoplexy, hypertension, hypotension, corpulence, diabetes, hyperlipidemia, atrial fibrillation, valvular endocarditis, etc.), biochemical data of blood, and lesional image data from CT or MRI. This system consists of the following components: 1) database management, 2) information retrieval (IR), 3) lesional image processing, 4) statistical analysis, and 5) prognostic prediction. The images are drawn manually on prescribed data sheets by tracing CT or MRI films and are read through the image scanner; then the compressed data of the digitized images is recorded in the database. Each recorded image data consists of the following two components: the frame image that corresponds to the contour of tissues of interest on the corresponding sliced section, and the actual image that corresponds to the lesion itself. In our system, these two images are separately stored and managed so that we can effectively perform subsequent image analysis. Other variables in the database (risk factors, anamnesis, etc.) are mainly used as search keys for making the aggregate of image data by the IR subsystem. In any aggregate, its elements, namely image data, have common medical background descriptions with the search keys. These aggregates can be used as input for the lesional image processing subsystem. With this subsystem, we can obtain the accumulated distribution of frequencies within a specified range of any sliced section, display planar color maps and profiles associated with the distribution, reconstruct it in 3D form, perform transformations of 3D images (zooming, enhancement, rotation, etc.), and test the significant difference of frequencies between any two different sites. We have been making practical use of this system to find the neurological relationship between the symptom (dysarthria, and paralysis of upper/lower limbs) and the site of lesion with cerebral infarction in pons. This study is quite important since the distributions of pyramidal tract related to the above symptom in pons are not well-known compared to those in cerebral cortex, internal capsule, or cerebral peduncle. With our system, we have obtained several findings expected to be helpful for this study. However, since this study is still in the initial phases, we will only present the outcome as a working example of our system. Our system was originally developed for analyzing lesional images with ICH. However, it could

Cerebral Hemorrhage↗

PubMed1993

Sequencing two DNA templates in five channels by digital compression.

By applying algebraic coding methods to the Sanger dideoxynucleotide procedure, DNA sequences of two templates can be determined simultaneously in only five reactions and data channels. A 5:2 data compression is accomplished by instantaneous source coding of nucleotide sequence pairs into one set of 5-bit block codes. A general algebraic expression, 2n-1 > or = 4f, describes conditions under which f DNA templates can be sequenced using n channels. Such compression sequencing is accurate and efficient, as demonstrated by manual 35S autoradiographic detection and automated on-line analysis using fluorescent-labeled primers. Symmetric 5:2 compression is especially useful when comparing two closely related sequences.

Automation↗

PubMed1986

Is diagnostic severity grading for head injuries possible?

The classification of head injured patients is more difficult than that for most other disease processes. The quantum of data to be embedded into each patient's grading code depends on the purpose to which that grading is used. If the information is merely required for broad epidemiological surveys, it may be confined to a double rubric which represents the most significant diagnostic component and an arbitrary index of associated severity. For this purpose, diagnostic severity grading is possible provided the task is delegated to experienced members of the neurosurgical team. If the grading is to be used in attempts to compare one patient group with another or for predictions of complications or outcome, a more detailed data-set is required. This may be accomplished with the use of multiple ICD diagnostic codes but assignations of severity to each diagnostic component requires very subjective judgement. Such an approach is unlikely to be successful and the only alternative is to define a data-set of "pure" information which includes all the relevant clinical, radiological, and operative findings without resorting to artificial data compression by using potentially misinterpretable deduced codes.

Craniocerebral Trauma↗

PubMed1999

A follower load increases the load-carrying capacity of the lumbar spine in compression.

STUDY DESIGN: An experimental approach was used to test human cadaveric spine specimens. OBJECTIVE: To assess the response of the whole lumbar spine to a compressive follower load whose path approximates the tangent to the curve of the lumbar spine. SUMMARY OF BACKGROUND DATA: Compression on the lumbar spine is 1000 N for standing and walking and is higher during lifting. Ex vivo experiments show it buckles at 80-100 N. Differences between maximum ex vivo and in vivo loads have not been satisfactorily explained. METHODS: A new experimental technique was developed for applying a compressive follower load of physiologic magnitudes up to 1200 N. The experimental technique applied loads that minimized the internal shear forces and bending moments, made the resultant internal force compressive, and caused the load path to approximate the tangent to the curve of the lumbar spine. RESULTS: A compressive vertical load applied in the neutral lordotic and forward-flexed postures caused large changes in lumbar lordosis at small load magnitudes. The specimen approached its extension or flexion limits at a vertical load of 100 N. In sharp contrast, the lumbar spine supported a load of up to 1200 N without damage or instability when the load path was tangent to the spinal curve. CONCLUSIONS: Until this study, an experimental technique for applying compressive loads of in vivo magnitudes to the whole lumbar spine was unavailable. The load-carrying capacity of the lumbar spine sharply increased under a compressive follower load, as long as the load path remained within a small range around the centers of rotation of the lumbar segments. The follower load path provides an explanation of how the whole lumbar spine can be lordotic and yet resist large compressive loads. This study may have implications for determining the role of trunk muscles in stabilizing the lumbar spine.

Adult↗

PubMed1995

Finding the "natural" vector bases for multidimensional reference values.

The concept of reference values can be extended to multidimensional results. A probability function describes the relative density of the observations in the multivariate space. When the density of a given point is measured relative to all other points, we get an estimate of the density rank of a given point. If the rank of a point is lower than 95 per cent of all points, the multidimensional result is outside the multidimensional reference range. The single-dimensional case is a special case of this general concept. Many observations are needed to define multidimensional distributions. However, less points are needed if the dimensionality of the data matrix is reduced by statistical methods such as principal component analysis (PCA). Also other vector bases than the orthogonal solution produced by PCA are possible, and all of them compress data equally well. So the choice must be based on other criteria than compression. We propose using a vector basis that consists of positive numbers. The positive vectors can be found by direct methods such as Alternating Regression (AR) or they can be modified from the results of the PCA. Positive vectors resemble the spectra that are familiar in chemistry and physics. They are a "natural" way to describe multidimensional results. It is easier to name the positive vectors than the purely statistical vectors of PCA. To obtain a unique positive solution, additional constraints besides positivity are needed.

Clinical Laboratory Techniques↗

PubMed2000

Networking of three dimensional sonography volume data.

Three-dimensioned (3D) sonography enables the examiner to store, instead of copies from single B-scan planes, a volume consisting of 300 scan planes. The volume is displayed on a monitor in form of three orthogonal planes--longitudinal, axial and coronal. Translation and rotation facilitates anatomical orientation and provides any arbitrary plane within the volume to generate organ optimized scan planes. Different algorithms allow the extraction of different information such as surface, or bone structures by maximum mode, or fluid filled structures, such as vessels by the minimum mode. The volume may contain as well color information of vessels. The digitized information is stored on a magnetic optical disc. This allows virtual scanning in absence of the patient under the same conditions as the volume was primarily stored. The volume size is dependent on different, examiner-controlled settings. A volume may need a storage capacity between 2 and 16 MB of 8-bit gray level information. As such huge data sets are unsuitable for network transfer, data compression is of paramount interest. 100 stored volumes were submitted to JPEG, MPEG, and biorthogonal wavelet compression. The original and compressed volumes were randomly shown on two monitors. In case of noticeable image degradation, information on the location of the original and compressed volume and the ratio of compression was read. Numerical values for proving compression fidelity as pixel error calculation and computation of square root error have been unsuitable for evaluating image degradation. The best results in recognizing image degradation were achieved by image experts. The experts disagreed on the ratio where image degradation became visible in only 4% of the volumes. Wavelet compression ratios of 20:1 or 30:1 could be performed without discernible information reduction. The effect of volume compression is reflected both in the reduction of transfer time and in storage capacity. Transmission time for a volume of 6 MB using a normal telephone with a data flow of 56 kB/s was reduced from 14 min to 28 s at a compression rate of 30:1. Compression reduced storage requirements from 6 MB uncompressed to 200 kB at a compression rate of 30:1. This successful compression opens new possibilities of intra- and extra-hospital and global information for 3D sonography. The key to this communication is not only volume compression, but also the fact that the 3D examination can be simulated on any PC by the developed 3D software. PACS teleradiology using digitized radiographs transmitted over standard telephone lines. Systems in combination with the management systems of HIS and RIS are available for archiving, retrieval of images and reports and for local and global communication. This form of tele-medicine will have an impact on cost reduction in hospitals, reduction of transport costs. On this fundament worldwide education and multi-center studies becomes possible.

Algorithms↗

PubMed1993

Compensation for the signal processing characteristics of ultrasound B-mode scanners in adaptive speckle reduction.

A systematic method to compensate for nonlinear amplification of individual ultrasound B-scanners has been investigated in order to optimise performance of an adaptive speckle reduction (ASR) filter for a wide range of clinical ultrasonic imaging equipment. Three potential methods have been investigated: (1) a method involving an appropriate selection of the speckle recognition feature was successful when the scanner signal processing executes simple logarithmic compressions; (2) an inverse transform (decompression) of the B-mode image was effective in correcting for the measured characteristics of image data compression when the algorithm was implemented in full floating point arithmetic; (3) characterising the behaviour of the statistical speckle recognition feature under conditions of speckle noise was found to be the method of choice for implementation of the adaptive speckle reduction algorithm in limited precision integer arithmetic. In this example, the statistical features of variance and mean were investigated. The third method may be implemented on commercially available fast image processing hardware and is also better suited for transfer into dedicated hardware to facilitate real-time adaptive speckle reduction. A systematic method is described for obtaining ASR calibration data from B-mode images of a speckle producing phantom.

Algorithms↗

PubMed2001

Optimal filter-based detection of microcalcifications.

This paper deals with the problem of texture feature extraction in digital mammograms. We use the extracted features to discriminate between texture representing clusters of microcalcifications and texture representing normal tissue. Having a two-class problem, we suggest a texture feature extraction method based on a single filter optimized with respect to the Fisher criterion. The advantage of this criterion is that it uses both the feature mean and the feature variance to achieve good feature separation. Image compression is desirable to facilitate electronic transmission and storage of digitized mammograms. In this paper, we also explore the effects of data compression on the performance of our proposed detection scheme. The mammograms in our test set were compressed at different ratios using the Joint Photographic Experts Group compression method. Results from an experimental study indicate that our scheme is very well suited for detecting clustered microcalcifications in both uncompressed and compressed mammograms. For the uncompressed mammograms, at a rate of 1.5 false positive clusters/image our method reaches a true positive rate of about 95%, which is comparable to the best results achieved so far. The detection performance for images compressed by a factor of about four is very similar to the performance for uncompressed images.

Biomedical Engineering↗

PubMed2000

Development of computerised procedures for the characterisation of the tableting properties with eccentric machines: extended Heckel analysis.

Heckel plots are a suitable and valuable method for analysis of powder compaction with very small amounts of powder. The determination is based upon a non-linear transformation of compression data and thus the signal errors that might be introduced into the analysis might be enlarged and become critical. The method of determination of true density affects the results dramatically as does the accuracy of the powder height determination. The porosity should be corrected for compression of the solid fraction. The accuracy of the powder height detection is the most demanding parameter. The statements are proven by simulations based on real data and analytic calculation. According to these highly corrected Heckel plots, the shape of the plots during the compression phase gives the information about fragmentation and plasticity and additionally about the time dependency of the compression behaviour within one compression on an eccentric press.

Algorithms↗

PubMed1978

Particle slippage and rearrangement during compression of pharmaceutical powders.

Compression data from different size fractions of lactose, chloroquine diphosphate, stearic acid and calcium carbonate have been analysed using the Walker and the Heckel compression equations. Points of inflection in graphs of log applied pressure vs the reciprocal of the packing fraction at low pressures corresponded closely to figures for theoretical packing conditions for equisized spheres and are attributed to a change in the stage of compression. The degree of particle slippage and rearrangement taking place during compression has been shown to increase as the particle size of the powder decreases and to be more extensive for powders composed of non-spherical particles. In addition, three types of compression behaviour have been distinguished for the four powders studied.

Calcium Carbonate↗

PubMedDate not supplied

Virtual sonography through the Internet: volume compression issues.

BACKGROUND: Three-dimensional ultrasound images allow virtual sonography even at a distance. However, the size of final 3-D files limits their transmission through slow networks such as the Internet. OBJECTIVE: To analyze compression techniques that transform ultrasound images into small 3-D volumes that can be transmitted through the Internet without loss of relevant medical information. METHODS: Samples were selected from ultrasound examinations performed during, 1999-2000, in the Obstetrics and Gynecology Department at the University Hospital in La Laguna, Canary Islands, Spain. The conventional ultrasound video output was recorded at 25 fps (frames per second) on a PC, producing 100- to 120-MB files (for from 500 to 550 frames). Processing to obtain 3-D images progressively reduced file size. RESULTS: The original frames passed through different compression stages: selecting the region of interest, rendering techniques, and compression for storage. Final 3-D volumes reached 1:25 compression rates (1.5- to 2-MB files). Those volumes need 7 to 8 minutes to be transmitted through the Internet at a mean data throughput of 6.6 Kbytes per second. At the receiving site, virtual sonography is possible using orthogonal projections or oblique cuts. CONCLUSIONS: Modern volume-rendering techniques allowed distant virtual sonography through the Internet. This is the result of their efficient data compression that maintains its attractiveness as a main criterion for distant diagnosis.

Algorithms↗

PubMed1998

Volumetric properties of nucleic acids.

Volumetric studies can yield useful new information on a myriad of intra- and intermolecular interactions that stabilize nucleic acid structures. In particular, appropriately designed volumetric measurements can characterize the conformation-dependent hydration properties of nucleic acids as a function of solution conditions, including temperature, pressure, ionic strength, pH, and cosolvent concentration. We have started to accumulate a substantial database on volumetric properties of DNA and RNA, as well as on related low molecular weight model compounds. This database already has provided unique insights into the molecular origins of various nucleic acid recognition processes, including helix-to-coil and helix-to-helix conformational transitions, as well as drug-DNA interactions. In this article, we review recent progress in volumetric investigations of nucleic acids, emphasizing how these data can be used to gain insight into intra-and intermolecular interactions, including hydration properties. Throughout this review, we underscore the importance of volume and compressibility data for characterizing the hydration properties of nucleic acids and their constituents. We also describe how such volumetric data can be interpreted at the molecular level to yield a better understanding of the role that hydration can play in modulating the stability and recognition of nucleic acids.

Animals↗

PubMed1998

Magnetic resonance imaging of the whole spine in suspected malignant spinal cord compression: impact on management.

Patients with suspected malignant spinal cord compression may present with a misleading sensory level or have multiple levels of compression that are not apparent clinically or on imaging of a limited area of the spine. To estimate how often this occurs and to evaluate a policy of magnetic resonance imaging (MRI) of the whole spine for any patient with suspected cord compression, data from 127 patients who had undergone MRI scans of the whole spine were reviewed. In 85 of 127 scans, there was evidence of compression of or impingement upon the spinal cord. A sensory level was present in 47 of these 85 patients, but in 12/47 (26%) the sensory level was four or more segments below or three or more segments above the actual lesion. Multiple levels of compression or impingement were found in 33 of 85 (39%) patients; in 24 of these, more than one region (cervical/thoracic/lumbar) of the cord was involved. For 32 patients who commenced radiotherapy to a treatment volume based on clinical criteria before the MRI scan was available, the radiotherapy fields needed modification in 16 (50%) as a result of the MRI findings. The results support a policy of MRI of the whole spine in any patient with suspected malignant spinal cord compression.

Female↗

PubMed1991

A triphasic theory for the swelling and deformation behaviors of articular cartilage.

Swelling of articular cartilage depends on its fixed charge density and distribution, the stiffness of its collagen-proteoglycan matrix, and the ion concentrations in the interstitium. A theory for a tertiary mixture has been developed, including the two fluid-solid phases (biphasic), and an ion phase, representing cation and anion of a single salt, to describe the deformation and stress fields for cartilage under chemical and/or mechanical loads. This triphasic theory combines the physico-chemical theory for ionic and polyionic (proteoglycan) solutions with the biphasic theory for cartilage. The present model assumes the fixed charge groups to remain unchanged, and that the counter-ions are the cations of a single-salt of the bathing solution. The momentum equation for the neutral salt and for the intersitial water are expressed in terms of their chemical potentials whose gradients are the driving forces for their movements. These chemical potentials depend on fluid pressure p, salt concentration c, solid matrix dilatation e and fixed charge density cF. For a uni-uni valent salt such as NaCl, they are given by mu i = mu io + (RT/Mi)ln[gamma 2 +/- c(c + cF)] and mu w = mu wo + [p-RT phi (2c + cF) + Bwe]/pwT, where R, T, Mi, gamma +/-, phi, pwT and Bw are universal gas constant, absolute temperature, molecular weight, mean activity coefficient of salt, osmotic coefficient, true density of water, and a coupling material coefficient, respectively. For infinitesimal strains and material isotropy, the stress-strain relationship for the total mixture stress is sigma = - pI-TcI + lambda s(trE)I + 2 musE, where E is the strain tensor and (lambda s, mu s) are the Lamé constants of the elastic solid matrix. The chemical-expansion stress (-Tc) derives from the charge-to-charge repulsive forces within the solid matrix. This theory can be applied to both equilibrium and non-equilibrium problems. For equilibrium free swelling problems, the theory yields the well known Donnan equilibrium ion distribution and osmotic pressure equations, along with an analytical expression for the "pre-stress" in the solid matrix. For the confined-compression swelling problem, it predicts that the applied compressive stress is shared by three load support mechanisms: 1) the Donnan osmotic pressure; 2) the chemical-expansion stress; and 3) the solid matrix elastic stress. Numerical calculations have been made, based on a set of equilibrium free-swelling and confined-compression data, to assess the relative contribution of each mechanism to load support. Our results show that all three mechanisms are important in determining the overall compressive stiffness of cartilage.

Biomechanical Phenomena↗

PubMed2026

Non-destructive prediction of lead content in oilseed rape leaves by fluorescence hyperspectral technology based on neural network.

Based on fluorescence hyperspectral imaging (FHSI), this study targeted rapid, non-destructive quantification of lead (Pb) content in oilseed rape leaves treated with varying silicon (Si) concentrations, acquiring fluorescence spectra over the 484.43-1001.61 nm wavelength range. To optimize spectral data quality, preprocessing methods (Savitzky-Golay smoothing, first derivative, detrending) were comprehensively compared. Characteristic wavelengths were then selected via interval variable iterative shrinkage, which effectively compressed data dimensionality and reduced computational load. A hybrid SE-CL1DA model, fusing a 1D convolutional neural network, a long short-term memory network and SE attention mechanism was constructed, with Bayesian optimization tuning hyperparameters to boost stability. The BO-SE-CL1DA outperformed both traditional machine learning and insufficiently optimized deep learning model (Rp2=0.9609, RMSE = 0.0377 mg/kg, RPD = 5.1736), thus enabling accurate Pb estimation, supporting Si-regulated heavy metal stress management and facilitating agricultural contamination monitoring.

Plant Leaves↗

PubMed1996

Compressibility as a means to detect and characterize globular protein states.

We report compressibility data on single-domain, globular proteins which suggest a general relationship between protein conformational transitions and delta kzeroS, the change in the partial specific adiabatic compressibility which accompanies the transition. Specifically, we find transitions between native and compact intermediate states to be accompanied by small increases in kzeroS of +(1-4) x 10(-6) cm3.g-1.bar-1 (1 bar = 100 kPa). By contrast, transitions between native and partially unfolded states are accompanied by small decreases in kzeroS of -(3-7) x 10(-6) cm3.g-1.bar-1, while native-to-fully unfolded transitions result in large decreases in kzeroS of -(18-20) x 10(-6) cm3.g-1.bar-1. Thus, for the single-domain, globular proteins studied here, changes in kzeroS correlate with the type of transition being monitored, independent of the specific protein. Consequently, kzeroS measurements may provide a convenient approach for detecting the existence of and for defining the nature of protein transitions, while also characterizing the hydration properties of individual protein states.

Chymotrypsinogen↗