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At least 127 records · Page 7Linked to original sources
PubMed1991

Image data compression using a new floating-point digital signal processor.

A new dual-ported, floating-point, digital signal processor has been evaluated for compressing 512 and 1,024 digital radiographic images using a full-frame, two-dimensional, discrete cosine transform (2D-DCT). The floating point digital signal processor operates at 49.5 million floating point instructions per second (MFLOPS). The level of compression can be changed by varying four parameters in the lossy compression algorithm. Throughput times were measured for both 2D-DCT compression and decompression. For a 1,024 x 1,024 x 10-bit image with a compression ratio of 316:1, the throughput was 75.73 seconds (compression plus decompression throughput). For a digital fluorography 1,024 x 1,024 x 8-bit image and a compression ratio of 26:1, the total throughput time was 63.23 seconds. For a computed tomography image of 512 x 512 x 12 bits and a compression ratio of 10:1 the throughput time was 19.65 seconds.

Algorithms↗
PubMed1990

Comparison and evaluation of a disease activity index for use in patients with rheumatoid arthritis.

An algorithm (Stoke index) has been designed to give a global measure of disease activity in rheumatoid arthritis. This algorithm has been created as an easy to use flow diagram based on two objective laboratory measures (C-reactive protein and erythrocyte sedimentation rate), one subjective and two semi-objective clinical measures (morning stiffness, synovitis score and Ritchie articular index). Results of six clinical markers and seven laboratory markers of disease activity on a cohort of 371 rheumatoid patients have been used to evaluate the algorithm and compare it with a previously described index of disease activity (Mallya-Mace index). Principal component analysis validates its ability to measure disease activity. Sensitivity is described by the distribution of patients between the two index scores. Change in index score by patients over a 6-month period indicates reversibility. The Stoke index demonstrates greater sensitivity and reversibility than the Mallya-Mace index. These findings indicate that the algorithm described provides a useful index of global disease activity for use in the assessment of rheumatoid arthritis.

Adult↗
PubMed1986

Count-dependent filter for smoothing bivariate FCM histograms.

A data-smoothing filter has been developed that permits the improvement in accuracy of individual elements of a bivariate flow cytometry (FCM) histogram by making use of data from adjacent elements, a knowledge of the two-dimensional measurement system point spread function (PSF), and the local count density. For FCM data, the PSF is assumed to be a set of two-dimensional Gaussian functions with a constant coefficient of variation for each axis. A set of space variant smoothing kernels are developed from the basic PSF by adjusting the orthogonal standard deviations of each Gaussian smoothing kernel according to the local count density. This adjustment in kernel size matches the degree of smoothing to the local reliability of the data. When the count density is high, a small kernel is sufficient. When the density is low, however, a broader kernel should be used. The local count density is taken from a region defined by the measurement PSF. The smoothing algorithm permits the reduction in statistical fluctuations present in bivariate FCM histograms due to the low count densities often encountered in some elements. This reduction in high-frequency spatial noise aids in the visual interpretation of the data. Additionally, by making more efficient use of smaller samples, systematic errors due to system drift may be minimized.

Cell Count↗
PubMed2026

Discovery and validation of novel plasma protein biomarkers for severe tuberculosis patients.

OBJECTIVE: Severe tuberculosis (STB) imposes a substantial disease burden, yet reliable biomarkers for distinguishing STB from mild/moderate tuberculosis (MTB) remain scarce. This study aimed to identify and independently validate plasma protein biomarkers associated with tuberculosis severity. METHODS: In this multicenter prospective study, 298 adults with confirmed pulmonary tuberculosis were enrolled into screening (n = 128) and independent validation (n = 170) cohorts. Plasma samples were analysed using data-independent acquisition proteomics. Differentially expressed proteins were screened via Limma and four machine-learning algorithms, with candidate proteins measured by enzyme-linked immunosorbent assays. Receiver operating characteristic analysis assessed individual and combined diagnostic performance. RESULTS: STB patients were older and presented with lymphopenia, hypoalbuminemia, neutrophilia, and elevated lactate dehydrogenase. Among 166 differentially expressed proteins, HSPA5, HSP90B1, EEF1D, and SULT1A1 were selected for validation. In STB patients, HSPA5, HSP90B1, and EEF1D were upregulated, whereas SULT1A1 was downregulated. The four-protein panel achieved an AUC of 0.908 (95% CI 0.864-0.952), with 87.5% sensitivity and 83.8% specificity, modestly outperforming HSPA5 alone (AUC = 0.894). Functional enrichment implicated cholesterol metabolism, immune-inflammatory pathways, and endoplasmic reticulum stress. CONCLUSIONS: The four-protein panel effectively discriminated STB from MTB; however, its marginal improvement over HSPA5 alone suggests that an HSPA5-based assay may offer a simpler, more practical, and potentially cost-effective strategy for severity stratification.

Humans↗
PubMed1986

Test of a versatile on-line distortion corrector for a gamma-camera.

A gamma-camera on-line distortion corrector, based on a fast microprocessor, has been tested on two cameras. The original electronic design and the software algorithm are described. Performance measurements on phantoms and clinical results show an improvement of the pictures.

Computers↗
PubMed1987

[Classification of spot-shaped lung changes by texture analysis].

Classification of opacities in pneumoconiosis was accomplished by textural analysis in digitised chest x-rays. A good discrimination was achieved by a set of 10 parameters. These texture measures were computed by algorithms for edge detection, local extremes, difference statistics, the co-occurrence matrix and the power spectrum. The classes of the training set were classified correctly at 99%. A test set comprising additional classes that were not contained in the training set, was classified at 82%.

Algorithms↗
PubMed1988

Discriminant analysis of promoter regions in Escherichia coli sequences.

We have previously developed a general method based on the statistical technique of discriminant analysis to predict splice junctions in eukaryotic mRNA sequences [Nakata, K., Kanehisa, M. and DeLisi, C. (1985) Nucleic Acids Res., 13, 5327-5340]. In order to evaluate further applicability of this method, we now analyze the promoter region of Escherichia coli sequences. The attributes used for discrimination include the accuracy of consensus sequence patterns measured by the perceptron algorithm, the thermal stability map, the base composition and the Calladine-Dickerson rules for helical twist angle, roll angle, torsion angle and propeller twist angle. When applied to selected E. coli sequences in the GenBank database, the method correctly identifies 75% of the true promoter regions.

Algorithms↗
PubMed1990

Comparison of pattern recognition methods for computer-assisted classification of spectra of heart sounds in patients with a porcine bioprosthetic valve implanted in the mitral position.

The diagnostic performance of two pattern recognition methods (or classifiers) to detect valvular degeneration was evaluated in 48 patients with a porcine bioprosthetic heart valve inserted in the mitral position. Twenty patients had a normal porcine bioprosthetic valve and 28 patients had a degenerated bioprosthetic valve. One method was based on the Gaussian-Bayes model and the second on the "nearest neighbor" algorithm using three distance measurements. Eighteen diagnostic features were extracted from the sound spectrum of each patient and, for each method, a two-class supervised learning approach was used to determine the most discriminant diagnostic patterns composed of 6 features or less. The probability of error of the classifiers was estimated with the leave-one-out approach. The performance of each method to discriminate between normal and degenerated bioprosthetic valves was verified by clinical evaluation of the valves. The best performance in evaluation of the sound spectrum (98% correct classifications) was obtained with the Bayes classifier and two patterns of six features each. The percentage of false positive classifications of valve degeneration was 0% and the percentage of false negative classifications was 4%. Sensitivity for the detection of valve degeneration was 96%, specificity was 100%, positive predictive value was 100%, and negative predictive value was 95%. The best performance of the nearest neighbor method (94% correct classifications) was obtained by using the Mahalanobis distance and five patterns composed of three, four, five, or six diagnostic features. Using a pattern composed of only three features, the percentage of false positive classifications for degeneration was 10% and the percentage of false negative classifications was 4%.(ABSTRACT TRUNCATED AT 250 WORDS)

Bayes Theorem↗
PubMed1991

Evaluation and treatment of ventricular arrhythmias: an update.

An overall approach to evaluating and treating ventricular arrhythmias based on objective monitoring criteria is described. A clinically useful system classifies patients based on whether their ventricular arrhythmias are benign, potentially lethal, or lethal. Some clinicians believe that antiarrhythmic drug therapy improves survival in patients with potentially lethal arrhythmias. However, disappointing results from the Cardiac Arrhythmia Suppression Trial have led to a greater awareness of the potential adverse effects of antiarrhythmics. Various risk factors for arrhythmia-related death have been identified, such as the presence of frequent and complex ventricular ectopy, abnormal signal-averaged electrocardiography (SAECG) tracings, and poor left ventricular ejection fraction (LVEF). Antiarrhythmic drugs remain the primary mode of therapy for patients with recurrent symptomatic tachycardias. Antiarrhythmic drug efficacy has been evaluated by methods including symptom assessment, continuous ambulatory electrocardiographic monitoring (Holter monitoring), exercise testing, and invasive electrophysiologic testing. There may be an extremely wide range of effective serum concentrations for the class IA agents. Individual target concentrations of antiarrhythmic agents may be determined for individual patients and should assist the clinician in optimizing long-term antiarrhythmic drug therapy. The risk-to-benefit ratio of treatment should be weighed before antiarrhythmic drug therapy is begun, and careful, objective monitoring of drug efficacy should be performed. When pharmacologic treatment of ventricular arrhythmias is considered, treatment algorithms that incorporate LVEF measurements, Holter monitor recordings, and SAECG may aid the clinician.

Anti-Arrhythmia Agents↗
PubMed1990

[A rapid radiotherapy planning program in intracavitary afterloading therapy].

A recently developed program for the irradiation planning of intracavitary afterloading applications in the treatment of gynecological diseases is presented. On the basis of measured data, a rapid algorithm for calculating the dose within the field near to ray emitters is introduced which avoids any uncertainties as to the greatest activity and the dose rate constant. Distance- and direction-dependent corrections of the inverse square law are performed by means of polynomials easy to calculate or by tables. The structure and performance of the program are described. Some examples are given in order to illustrate the possible applications of the irradiation planning program.

Algorithms↗
PubMed1989

[Combination radiodiagnosis of the functional state of the urinary tract in cancer of the kidney].

The results of combined radiodiagnosis of the urinary system in patients with renal tumors before and after nephrectomy were analyzed. Investigations included excretory urography and renography with the processing of the results of measurements by a common algorithm and on the basis of 3 mathematical models of RP body transport. The results were correlated with the findings of biochemical blood and urine tests and pathoanatomical investigation of the removed kidney. Ample potentialities of renography for the detection of latent renal insufficiency in the preoperative period and for accurate and exhaustive assessment of function of the urinary system were shown.

Humans↗
PubMed1987

[Method of determining separate kidney clearance].

The task was to develop a simple and effective method of radionuclide determination of separate clearance of the kidneys (SCK), i.e. separate assessment of secretory-excretory function of each kidney. The other earlier known methods of SCK determination were either methodologically incorrect or very difficult. A method of SCK determination intended both for gamma-chambers and standard radiographic units based on common renographic methods, was proposed. An algorithm for processing of measurement results was based on the generalization of the mathematical apparatus of circulation models usually employed for a study of the central and organ hemodynamics, and on its development for transitory nephrotropic radiopharmaceuticals (RP). An investigation of 21 healthy persons and 51 patients with renal tumors using 131I-hippuran showed that the proposed method possessed sufficient sensitivity for its clinical use. Advantages and shortcomings of the method were analysed. All the allowances were justifiable.

Humans↗
PubMed1985

[Separate measurements of compact and spongy bone density using a transverse rotation scanner. Determination of mineral content of the radius using a least squares algorithm].

The absorption profile of the distal forearm, which depends on bone mineralisation, was measured using a high resolution microcomputer-controlled transverse rotational scanner with a tightly collimated I-125 photon source and a scintillation counter. Reconstruction of the anatomical structures within the measured area occurred in two stages. Subsequently the linear attenuation coefficient for soft tissues, compacta and spongiosa was obtained by a "least-square" algorithm. The absorption coefficient of the compacta and spongiosa provided a measure of bone mineralisation. Correlation between the reconstructed images and the calculated results and measurements was tested by calculation. Ten measurements of a model and of in vivo bones resulted in a coefficient of variation of 1.8% and 3.3% for the compacta and 2.5% and 3.8% for the spongiosa. Relative deviation from the standard varied from +1.3% to -1.0%, depending on mineral content. This new, technically simple procedure for the separate determination of the compacta and spongiosa in the distal radius is useful for the early recognition of changes in bone mineralisation which are usually apparent first in the spongiosa.

Bone and Bones↗
PubMed1984

The inertial and geometrical properties of helmets.

The center of gravity (CG) and the principal mass moments of inertia about the CG of Army aviator, American football, and bicycle helmets were experimentally determined by a variation of the classic differential weighing and torsional pendulum techniques. In the course of these experiments, an innovative method for three-dimensional (3D) digitization was found. An electronic caliper, which measured length, was used with a computer algorithm to achieve 3D digitization. The results of the above measurements show that the weight of the helmet and the distances from the CG to the orthogonal coordinate axes intercepts with the outer shell surface were highly correlated with its principal mass moments of inertia. A set of regression equations was derived on theoretical considerations and served to unify the experimentally obtained data. Our results indicate that the principal mass moments of inertia of helmets vary linearly with its mass but nonlinearly with size and shape. For a helmet, given its weight and certain geometrical distances, the regression equations estimate the principal mass moments of inertia to within 5% of its experimentally-determined values. For the helmets studied in this series, a modified linear-regression relationship between the principal mass moments of inertia and its mass was found. This result is reasonable because the mass distribution of the current generation of helmets are set primarily by the head size and secondarily by helmet size, shape, and materials.

Aviation↗
PubMed1988

Three-dimensional reconstruction in electrical impedance tomography.

We have developed a three-dimensional, computer-simulated, electrical impedance tomographic imaging system using the four-electrode measurement technique. The reconstruction process finds the numerical solution of Laplace's equation by using the finite element method and the Newton-Raphson algorithm. A new diagonal electrodes measurement method provides lower error than the usual neighbouring electrodes measurement method. For a three-layer, 4 x 4 model, the number of iterations increased from 3 to 16 as the number of randomly placed, high-resistivity voxels increased from 3 to 18.

Electric Conductivity↗
PubMed1989

Nonparametric comparison of entire ROC curves for computerized ECG left ventricular hypertrophy algorithms using data from the Framingham Heart Study.

A computer program may be capable of several different statements for left ventricular hypertrophy (eg, possible LVH, probable LVH, consistent with LVH), but such statements resulting from discretized levels of sensitivity/specificity would represent only isolated points on a receiver-operating characteristic (ROC) curve, which is a plot of all levels of sensitivity versus specificity. Even if two algorithms use the same discrete scales, their performances may not readily be compared. The authors present a comparison methodology for ROC curves using ROC area as a nonparametric measure of the ability of the algorithm to separate the two populations; the ROC area ranges from 0.5 (no ability) to 1.0 (perfect separation) and is unbiased if the normal versus abnormal populations have no common values for the measurement. The methodology compares the performance of ECG algorithms on the same population of cases by testing for significant differences of ROC areas and incorporating correlation of the algorithms in a nonparametric way. To illustrate this methodology, they use ECG and echocardiographic data from the Framingham Heart Study.

Algorithms↗
PubMed1992

Maximal dynamic range electrotactile stimulation waveforms.

A new method to measure the dynamic range of electrotactile (electrocutaneous) stimulation uses both steepest ascent (gradient) and one-variable-at-a-time methods to determine the waveform variables that maximize the subjective magnitude (intensity) of the electrotactile percept at the maximal current without discomfort for balanced-biphasic pulse bursts presented at a 15-Hz rate. The magnitude at the maximal current without discomfort is maximized by the following waveform (range tested in parentheses): number of pulses/burst = 6 (1-20), pulse repetition rate within a burst = 350 Hz (200-1500), and phase width = 150 microseconds (40-350). The interphase interval (separation between positive and negative phases in a biphasic pulse) does not affect dynamic range from 0-500 microseconds. The number of pulses/burst has a large effect on the perceived dynamic range when this is measured using a subjective-magnitude-based algorithm, whereas it has little effect on the traditional dynamic range measure, i.e., (maximal current without discomfort)/(sensation threshold current). The perceived stimulus magnitude at the maximal current without discomfort is approximately twice as strong with 6 pulses/burst as it is with 1 pulse/burst (a frequently-used waveform).

Bias↗