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Results for “Numerical Analysis, Computer-Assisted”

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PubMedDate not supplied

Combining evidence from multiple imaging modalities: a feature-analysis method.

This study was designed to develop methods to improve radiologists' ability to detect and diagnose breast cancer. We evaluated the ability of a feature-analysis method to help radiologists merge judgements constructively from two rather disparate breast imaging tests. To accomplish these goals, we developed a list of perceptual features and quantitated the importance of each in the diagnosis of patients having both diaphanography (Test 1) and mammography (Test 2). Then, two decision aids were developed: One was a checklist of the critical diagnostic visual features from both tests that also assisted readers in rating these features numerically. The second was a computer-based classifier that assisted readers in merging the assessments of the two tests into one overall diagnostic probability. The value of these aids was assessed by comparing radiologists' accuracy in reading a set of proven cases in their standard fashion with their accuracy when reading in an enhanced mode, utilizing the checklist and computer classifier. When Test 1 was read adjunctively with Test 2, use of the decision aids led to a significant improvement in accuracy (p = .013) over the unenhanced, combined readings. For Test 1 alone, the aids led to a significant improvement over its low level of unenhanced reading (p = .046). For Test 2 alone, the enhancements provided little gain in accuracy over an already high level of performance on the full case set (p = .081), although significant gains were realized on the most difficult ones. We conclude that methods to aid standardization and merging of feature-based judgements can improve radiologists performance on complex diagnostic tasks.

Breast Neoplasms↗

PubMed1992

[New aspects in the evaluation of Doppler blood flow curves: three- dimensional image and analysis of Doppler shift frequencies within the heart cycle].

Since the introduction of Doppler ultrasound to the area of medical diagnostics, there have been numerous improvements and important technical refinements. In obstetrics, Doppler examination allows a more accurate and encompassing evaluation of the foetal condition than was previously possible. Combined with today's sophisticated computer technology, it has a great potential in research and to expand our knowledge about the physiology and pathophysiology of foetal and maternal haemodynamics. This paper describes a new way of integrating another factor into the evaluation of Doppler blood flow waveforms, namely, the intensities of various frequencies. One result should be more detailed information about the given haemodynamic situation; another, a valuable tool for the quality control of Doppler blood flow measurements. Although our work was on applications in the field of obstetrics, the method we have developed can be used in all medical areas.

Blood Flow Velocity↗

PubMed1992

Relationship of tumor cell motility and morphologic patterns. Part 1. Melanocytic skin tumors.

In the diagnosis of melanocytic skin tumors, the assessment of the overall architectural pattern (silhouette) is often essential. We have previously shown by a computer simulation model that tumor patterns are likely to depend on the relative degrees of proliferation and motility of the tumor cells. In this study, we examined the morphological pattern of 12 cases each of nevocellular nevi, primary melanoma, and metastatic melanoma by image analysis. The patterns of the individual melanocytic skin tumors were compared statistically with patterns generated by computer simulation, which facilitates estimates of biological properties of the tumor cells. Additionally, mitotic counts were made to measure tumor cell proliferation. A comparison of the three diagnostic groups revealed that the cells of nevocellular nevi show a low degree of motility, which, however, still exceeds the very low degree of proliferation. Thus, an "invasive" pattern with numerous small nests and single cells at the base of the lesion is common. In primary malignant melanoma, tumor cell motility and tumor cell proliferation are significantly increased in various proportions, thus leading to varying morphological patterns. In metastatic melanoma, a strikingly elevated degree of proliferation exceeds the only slightly elevated degree of motility and leads to sharply demarcated, "expansive" lesions. To check the validity of the technical procedure, estimates of proliferation based on pattern analysis alone were compared with the results obtained by mitotic counts. There was a significant correlation, indicating that the assumptions of the computer model and the image analysis procedure are in fact applicable to real-life melanocytic skin tumors.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Division↗

PubMed1991

Gender recognition from speech. Part II: Fine analysis.

The purpose of this research was to investigate the potential effectiveness of digital speech processing and pattern recognition techniques for the automatic recognition of gender from speech. In part I Coarse Analysis [K. Wu and D. G. Childers, J. Acoust. Soc. Am. 90, 1828-1840 (1991)] various feature vectors and distance measures were examined to determine their appropriateness for recognizing a speaker's gender from vowels, unvoiced fricatives, and voiced fricatives. One recognition scheme based on feature vectors extracted from vowels achieved 100% correct recognition of the speaker's gender using a database of 52 speakers (27 male and 25 female). In this paper a detailed, fine analysis of the characteristics of vowels is performed, including formant frequencies, bandwidths, and amplitudes, as well as speaker fundamental frequency of voicing. The fine analysis used a pitch synchronous closed-phase analysis technique. Detailed formant features, including frequencies, bandwidths, and amplitudes, were extracted by a closed-phase weighted recursive least-squares method that employed a variable forgetting factor, i.e., WRLS-VFF. The electroglottograph signal was used to locate the closed-phase portion of the speech signal. A two-way statistical analysis of variance (ANOVA) was performed to test the differences between gender features. The relative importance of grouped vowel features was evaluated by a pattern recognition approach. Numerous interesting results were obtained, including the fact that the second formant frequency was a slightly better recognizer of gender than fundamental frequency, giving 98.1% versus 96.2% correct recognition, respectively. The statistical tests indicated that the spectra for female speakers had a steeper slope (or tilt) than that for males. The results suggest that redundant gender information was imbedded in the fundamental frequency and vocal tract resonance characteristics. The feature vectors for female voices were observed to have higher within-group variations than those for male voices. The data in this study were also used to replicate portions of the Peterson and Barney [J. Acoust. Soc. Am. 24, 175-184 (1952)] study of vowels for male and female speakers.

Computer Graphics↗

PubMed1977

Automated, rapid identification of bacteria by pattern analysis of growth inhibition profiles obtained with Autobac 1.

A scheme for identifying bacteria has been devised which utilizes the inhibition patterns obtained by Autobac 1 with routine and unusual antimicrobial agents and with other differentially inhibitory chemical compounds. Over 600 compounds were initially identified from the literature, and over 125 of these were selected for further testing on the basis of antibacterial activity most conducive to the instrument-generated differential scheme. Numerical growth index information derived by light scatter comparisons from the instrument were analyzed by computer, utilizing the quadratic discriminant function statistical technique. In comparison with conventional methods, accuracy for the 10 bacterial genera studied was 95% or greater. Results indicate a potential for both bacterial identification and antimicrobial agent susceptibility testing in the clinical laboratory within 3 to 5 h when using this automated approach.

Acinetobacter↗

PubMed1977

Results of computer-aided diagnosis of peripheral bronchial carcinoma.

Radiographic images can be converted into numerical sequences that can be evalueate by computer to determine the significance of certain radiographic findings in peripheral pulmonary nodules. Of three methods (discriminant analysis. Bayes' theoroem, and the Calm system), discriminant analysis has proven the best with an accuracy rate of 85%. By taking into account serial radiographs and statements on the possible growth of the neoplasm, the accuracy of the method can be increased to 90%. A simplified, inexpensive and effective method for application of this diagnostic tool is described.

Adult↗

PubMed1992

The measurement of blood flow waveforms from X-ray angiography. Part 1: Principles of the method and preliminary validation.

The principles and implementation of a method for measurement of blood flow waveforms from X-ray angiography are described. Contrast medium mass values are obtained at multitudinous positions along individual vessels and from numerous images in a time sequence. These values are represented as a matrix of grey levels in a parametric image. This image is normalized to represent contrast medium concentration, and the movement over time of isoconcentration portions of the contrast bolus is recovered to determine blood flow. Preliminary validation has been undertaken using parametric images generated in two ways: synthesis from a computer model of vascular pulsatile flow and analysis of cine-angiograms of physical models (plastic and perspex tubes) carrying known pulsatile flows. Two distinct methods for interrogation of parametric images by digital image processing were employed; both provided accurate flow measurements.

Blood Flow Velocity↗

PubMed1992

[Numerical analysis of orthodontic treatment elements of pseudo-elastic NiTi alloys].

In orthodontic treatment malpositions of teeth are often corrected by fixed appliances, consisting, in part, of loops made by the orthodontist. The most important alloys in use are steel, cobalt-chromium, or titanium-molybdenium alloys. The static force systems of fixed appliances made of these materials are well known from experimental and numerical studies, but as they may change during tooth movement, we are often confronted with problems in therapy. The introduction of pseudoelastic nickel titanium alloys (NiTi) into orthodontic treatment, offers the chance of improving the effectiveness and reliability of orthodontic devices. In the present paper a plane finite element (FE) for the analysis of orthodontic loops is presented. It enables the determination of the nonlinear behaviour of pseudoelastic NiTi-alloys and is capable of simulating large structural displacements and rotations accompanied by moderate strains. A comparative numerical and experimental study shows the efficiency of this element. The associated results reflect pseudoelastic effects on certain loop designs, and reveal the benefits for the orthodontist and his patients.

Computer Simulation↗

PubMed1975

Computer analysis of defined populations of lymphocytes irradiated in vitro. II. Analysis of thymus-dependent versus bone marrow-dependent cells.

Three uniform populations of T and B cells exposed to varying amounts of x-irradiation are examined utilizing computer-assisted morphometric analysis. These populations are: thoracic duct lymphocytes (TDL) from congenitally athymic (nude) mice (B cells); TDL from CBA mice treated with anti-Ig plus complement (T cells); and computer-selected untreated T cells from CBA TDL. Irradiated B cells show a more even dispersion of the nuclear chromatin and a dose-dependent increase in relative nuclear area beginning with the lowest dose evaluated (50 rads); no significan change in total optical density (OD) is demonstrable over the dose range evaluated (0 to 2000 rads). Anti-Ig-treated irradiated T cells demonstrate an initial shift toward lower OD values as a function of dose followed by a marked rise of OD values at 2000 rads, where numerous densely staining Feulgen-positive aggregates are identified. The relative nuclear area of this cell population also shows a biphasic response to radiation injury with an initial increase at the lower dose levels followed by a progressive decline to approximate control levels at 2000 rads. This effect is mirrored by the alteration in total OD which, after a decrease at low dose levels, approximates control values at 2000 rads. The computer-selected T cells show little change in OD values at the low-dose levels but show a marked increase in the more densely staining Feulgen-positive material following 2000 rads. This population reveals no apparent change in either relative nuclear area or total OD as a function of dose. Thus, untreated computer-selected T cells exhibit remarkably little evidence, morphologically, of radiation injury of doses associated with pronounced alterations on the part of B cells. In addition, treatment of a mixed cell population (CBA TDL) with anti-Ig plus complement to remove the B cells appears to alter the response of the residual T cells to radiation injury. These results, in conjunction with recent evidence to support the concept that T cells possess surface Ig, suggest that an Ig-anti-Ig interaction may alter the radiosensitivity of T cells.

Animals↗

PubMed1992

Computer-aided classification of malignancy in astrocytomas. I. The value of nuclear parameters obtained by automated black and white image analysis.

Ninety-three selected cases of astrocytomas including glioblastomas (astrocytomas grades 1-4) were evaluated by means of Feulgen-stained microscopic slides for nuclear parameters obtained by automated black and white image analysis (ABWIA). The goal was to determine to what extent nuclear features evaluated by ABWIA were applicable as classifiers for the computer-aided numerical classification of malignancy in astrocytomas. Before the automated evaluation, all tumours had been subjectively graded according to the Mayo Clinic grading rules as delineated by Ringertz. Twenty-three nuclear parameters were evaluated and tested for their classification impact. With a model of five parameters (number of nuclei per area, mean of the convex form factor, extinction sum, extinction variation, and full-width-half-maximum of the extinction distribution) the highest reclassification rate of 75% correctly reclassified cases was obtained. Although this is a good result for a classification using only nuclear parameters, it is too poor for practical application. Thus, nuclear parameters evaluated by ABWIA alone are insufficient for numerical classification models assessing the malignant expression of astrocytomas.

Astrocytoma↗

PubMed1992

Computer-aided classification of malignancy in astrocytomas. II. The value of categorically evaluated histologic and non-histologic features for a numerical classifier.

The present study was carried out in order to obtain a numerical classifier for the assessment of the malignancy in astrocytomas including glioblastomas ('astrocytomas grade 4'). The attempt resulted in 'TESTAST 268', a classifier based on a reference sample of 268 tumours, 67 in each of four malignancy classes. TESTAST 268 aids the identification of astrocytomas with one of four malignancy classes by means of eight classification variables, five histologic and three non-histologic. Identification is achieved with the aid of linear discriminant functions, both according to Bayes' decision rule (BAYTEST) and by canonical discriminant analysis (CANTEST) using the squared Mahalanobis distance. The discriminant functions with the calibration of the reference sample of the 268 tumours may be implemented on personal and even small pocket computers for practical application.

Astrocytoma↗

PubMed1992

[Neurophysiologic monitoring in neurosurgical vascular operations: specific technical requirements and their conversion].

Several authors have presented evidence for a strict relation between regional cerebral blood flow and EEG. Therefore the EEG can serve as an adequate physiological parameter when monitoring cerebral function in the operating room. However, to exploit the inherent information as far as possible, both multichannel EEG and somatosensory evoked potentials should be recorded simultaneously. In the present article we describe a monitoring system which is capable to handle this task under the conditions of an operating room. In the first step some numerically simple algorithms are applied to detect gross artifacts. In the subsequent processing stage an analysis procedure is performed which is robust with respect to the remaining more subtile artifacts. In addition the raw signals are continually displayed on a monitor to allow for a visual evaluation of the EEG. The results of a trend analysis procedure are presented on the same graphical display by means of a compact topographical scheme. The system has been running under routine conditions for approximately two years now.

Artifacts↗

PubMed1992

An analysis of vitreous tamponade effect in encircling surgery by means of finite element method.

The vitreous tamponade effect in encircling surgery was investigated by means of a finite element method. We performed the simulated encircling surgery on a computer program, which could have alternative band positions, i.e. anterior or posterior band position. Computed results revealed that the band position has a great influence on the vitreous stress distribution, and that the anterior band position is more advantageous than the posterior band position with regard to the vitreous tamponade effect. To our knowledge, this is the first numerical experiment to demonstrate the advantage of the anterior band position in encircling surgery.

Computer Simulation↗

PubMedDate not supplied

A comprehensive cardiovascular waveform analysis program for IBM-compatible personal computers.

Computerized cardiovascular waveform processing has become a necessary and fundamental tool in the analysis of physiologic data. The availability of numerous commercial data-analysis programs has significantly enhanced the efficiency of waveform analysis. Many such programs come with their own programming language, which enables the researcher to create an application program suited to a specific series of calculations. Once written, an application program can significantly increase the efficiency with which data from a specific experiment can be analyzed. However, creating or modifying a program for each new experimental protocol can be time-consuming, especially in the error-detection and verification stages. Single-purpose programs also prove somewhat inflexible to unexpected changes in experimental formats. These problems suggested the need for a more flexible program, but one that is nevertheless specifically suited to the analysis of cardiovascular signals. This need led to the development of a program designed in collaboration with surgeons and physiologists. This program addresses some important analysis problems in cardiovascular research, and allows the user to survey and manipulate cardiovascular waveforms in an intuitive and spontaneous manner.

Algorithms↗

PubMed1978

Enlarged acid-base and blood gas calculations by electronical data computing in the blood gas laboratory.

A rapid anaysis of parameters of the acid-base equilibrium and blood gases during open heart surgery and emergency therapy is absolutely necessary. Computing of the several parameters of the acid-base status by slide rules or nomograms is time consuming and can be shortened by computer applications. The central blood gas laboratory consists of a blood gas analyzer for PO2, PCO2 and pH, an electronic desktop calculator, a four color X-Y-plotter and two data lines to the cardiac surgery unit and to the intensive care unit. The time needed for computing and feedback of the parameters could be decreased to one quarter. In addition to numerical data printout, a graphical representation of the several parameters is possible on a X-Y-plotter and includes the Rahn-Fenn-O2-CO2-Diagram with venous admixture, ventilation perfusion ratio, alveolar dead space ventilation and the standard and actual oxygen dissociation curve as well as the pH/HCO3- Acid-Base nomogram. Furthermore, a computer diagnosis of the actual disturbances can be plotted.

Acid-Base Equilibrium↗

PubMed1977

[Multivariant discriminance analytical computation methods for the evaluation of clinico-chemical parameters in liver and biliary tract diseases].

Multivariate variance and discriminance-analytic investigations on the value of evidence of clinico-chemical tests in the diagnostics of diseases of the liver and the biliary tract gave the following results: 1. By means of clinico-chemical methods and discriminance-analytic functions we succeed in 50% of the cases in formulating a correct diagnosis, in more than 75% of the cases a correct probability diagnosis (3 first places in the rank of diagnoses). Sensitivity and specificity of discrimination were established for 15 classes of diagnoses. 2. Due to the intercorrelations of test results biochemical maximum programmes contain numerous redundant parameters measured on diagnostic information values. With the help of a test for indispensability (redundance test) among 20 parameters owy 5-6 were characterized as indispensable. An optimal combination of parameters should not transgress an extent of 14 tests. 3. Results of reclassifications with discriminance analytic functions confirmed that the discriminance analysis is an extraordinarily suitable method for the computer-supported finding of a decision, on which basis aimed additional investigations might be performed.

Analysis of Variance↗

PubMed1977

[Nystagmus analysis by computer (author's transl)].

Automatic quantitative nystagmus analysis by means of a digital computer primarily gives a lot of data. Analysis then means reducing this amount of numerical data to a few relevant results. Because the diagnostic importance is not known yet for all available nystagmus parameters, this implies the risk of losing essential informations. Therefore, limitations of the number of parameters as well as of the duration of the investigated intervals by the method of analysis have to be avoided. This then allows studying the diagnostic value of new parameters (e.g. of the fast components) or the time course of reaction intensity. From this point of view a method of quantitative nystagmus analysis is described.

Computers↗

PubMed1979

[Objectivation of tremor and motion disorders via computerisation (author's transl)].

The quantitative analysis of motion disorders of the upper extremities can be performed by means of a joystick connected with a minicomputer. Therefore a random squarewave curve is drawn on a computer display and the patient must follow it with the joystick. The deviation of the two curves are recorded, analysed and documented numerically and graphically.

Diagnosis, Computer-Assisted↗