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Biomedical subjects

J Mira

Publications and source records attributed to J Mira.

At least 19 recordsLinked to original sources
PubMed1992

Improved detection of HIV p24 antigen in serum after acid pretreatment.

HIV-1 p24 antigen was detected in 554 sera (509 from HIV-1 seropositive individuals and 45 sera from seronegative controls) using a conventional method with acid pretreatment of the sample in order to separate the p24 antigen/anti-p24 antibody immune complexes. In asymptomatic individuals there was a substantial increase in antigen detection (48.2% vs 8.4%). Similar results were also observed in ARC (59.1% vs 12.2%) and AIDS patients (85.7% vs 37.1%). It can be concluded that the acid treatment improves the sensitivity of conventional techniques to detect HIV-1 p24 antigen.

Female↗
PubMed1991

Fuzzy K-nearest neighbor classifiers for ventricular arrhythmia detection.

We report a study of the efficiency of 4 classifiers (the K-nearest-neighbor and single-nearest-prototype algorithms, each as parametrized by both Fuzzy C-Means and Fuzzy Covariance clustering) in the detection of ventricular arrhythmias in ECG traces characterized by 4 features derived from 7 spectral parameters. Principal components analysis was used in conjunction with a cardiologist's deterministic classification of 90 ECG traces to fix the number of trace classes to 5 (ventricular fibrillation/flutter, sinus rhythm, ventricular rhythms with aberrant complexes and 2 classes of artefact). Forty of the 90 traces were then defined as a test set; 5 different learning sets (numbering 25, 30, 35, 40 and 45 traces) were randomly selected from the remaining 50 traces; each learning set was used to parametrize both the classification algorithms using both fuzzy clustering algorithms and the parametrized classification algorithms were then applied to the test set. Optimal K for K-nearest-neighbor algorithms and optimal cluster volumes for Fuzzy Covariance algorithms were sought by trial and error to minimize classification differences with respect to the cardiologist's classification. Fuzzy Covariance clustering afforded significantly better perception of cluster structure than the Fuzzy C-Means algorithm, and the classifiers performed correspondingly with an overall empirical error ratio of just 0.10 for the K-nearest-neighbor algorithm parametrized by Fuzzy Covariance.

Algorithms↗
PubMed1990

Multimicroprocessor system for online monitoring in a CCU.

A real-time monitoring system for physiological signals, developed for patients in coronary care units (CCUs), is described. This system monitors the signals that have the greatest clinical value in a CCU environment (ECG and cardiovascular pressures), taking charge of detecting dangerous situations and of extracting information significant to the correct monitoring of the patient. The information it extracts, mainly from the ECG, is presented to the user in an ergonomic way using written reports and graphs which collect and compile the information, facilitating its interpretation. Some utilities have been developed to allow the user to modify certain monitoring conditions as well as to correct results derived from them, thereby improving the reliability of the monitoring process. The system uses a multimicroprocessor architecture (imposed by the need to perform a large number of tasks in real time) with a block based on the VME bus, charged with acquiring and processing the monitored signals, and an IBM-compatible PC/XT which is used as a system user interface and a massive storage device in which the information resulting from the monitoring of signals is stored.

Coronary Care Units↗
PubMed1990

Fuzzy beat labeling for intelligent arrhythmia monitoring.

The performance in automatic diagnosis of cardiac rhythm based on the analysis of the electrocardiographic signal (ECG) is strongly conditioned by the correct classification of each beat detected. In this work we present a fuzzy classifier of beats that applies empiric criteria and that permits it to ignore the frequent lack of clarity in the information coming from previous stages within ECG processing. The classification of each beat is performed applying diffuse conditional statements which represent the knowledge of the cardiologist expert and that use a set of descriptions of the temporal and morphological attributes of the analyzed beat. The process of classification is completed with information derived from the consideration of "families," which group beats that have QRSs of similar morphology, and with information brought in by the user himself in the monitoring process. The modularity of the classifier that has been developed facilitates the incorporation of new descriptions and classification criteria in order to increase its reliability. The design process proposed has a structure that is transferable to other analysis and event classification processes.

Arrhythmias, Cardiac↗
PubMed1989

Algorithmic sequential decision-making in the frequency domain for life threatening ventricular arrhythmias and imitative artefacts: a diagnostic system.

A preliminary study to approach the problem of reliably detecting life threatening ventricular arrhythmias in real time is described. An algorithm (DIAGNOSIS) has been developed in order to classify ECG signal records on the basis of the computation of four simple parameters calculated from a representation in the frequency domain. This algorithm uses a set of rules constituting an operative classification scheme based on the comparison of the parameters with a set of pre-established thresholds. This allows us to differentiate four general categories: ventricular fibrillation-flutter, ventricular rhythms, imitative artefacts and predominant sinus rhythm.

Algorithms↗
PubMed1987

Symbolic keyboard for computer aided instruction of deaf children.

We describe a computer-based method for the special education of deaf children in their stage of expanding an initial vocabulary; the method uses a symbolic keyboard to facilitate real-time communication between the deaf child and the machine. The lack of auditory feedback is partially compensated by using visual and proprioceptive sensorial modalities as alternative representations of words and concepts. To illustrate the use of the computer with display and symbolic keyboard we comment on a program for the teaching of spatial relationships. The same method is used in teaching the structure of sentences and other conventional educational material such as Geography and Physics.

Biomedical Engineering↗
PubMed1986

A computational frame to study social behaviour in animals.

This paper presents new methods and procedures for studying collective behaviour in rats. The animals are assumed to be indistinguishable one from another and the behaviour of the group is represented analysed and interpreted in terms of the temporal evolution of a finite state probabilistic automaton. The automaton states are defined by measures on the clustering degree considered as a social response variable. The electronic system developed to carry out the cluster analysis and the automatic control of the social behaviour in the experimental environment includes a multimicroprocessor interacting with a 'social box' in which, together with classical sensors and effectors, a phototransistor based position sensor is included. Preliminary experiments show the discriminative power of the cluster automaton concerning sexual differences and emotivity, as well as the extensive of a basic mechanism of clustering as a collective response to stress. Pharmacologically, the new experimental medium proposed in this paper may be used to detect a new range of products affecting social but not individual behaviour. Also, well-known products, which in normal doses produce no detectable modification of individual behaviour, might have detectable effects on the collective level. Be this as it may, the experimental environment described constitutes a further experimental facility for the analysis and control of animal behaviour.

Animals↗
PubMed1986

On fast algorithms for interval selection in event related potentials.

In this paper a computational algorithm is proposed which allows one to detect event related potentials (ERP) components and the way these components modify their amplitude with electrode location and with the variation in experimental conditions. The results of applying this algorithm to the ERPs obtained in two experimental situations (which require different modes of cognitive processing of a same visual information) are also exposed.

Algorithms↗
PubMed1982

The influence of radiation therapy quality control on survival, response and sites of relapse in oat cell carcinoma of the lung: preliminary report of a Southwest Oncology Group study.

Two hundred and ninety-eight patients with limited (confined to chest and supraclavicular area, encompassable by a single radiation portal) small cell carcinoma of the lung were entered on Southwest Oncology Group Protocol 7628. Patients were treated with multi-agent chemotherapy and radiation therapy with or without BCG. Radiation therapy quality control analysis, including dosimetric reconstruction and port film review was introduced after the protocol was activated and was retrospectively applied. Patients who were considered major protocol variations had statistically worse survival (40 weeks versus 60 weeks; P = .002), a lesser improvement in response rate after induction chemotherapy (27 versus 48%; P = .05) and a higher chest failure rate (77 versus 55%; P = .047) than evaluable patients. Five patients relapsed in the brain, all associated with chest failure. Quality control is essential in cooperative group studies.

Antineoplastic Agents↗
PubMed1982

Limited squamous cell carcinoma of the lung: a Southwest Oncology Group randomized study of radiation with or without doxorubicin chemotherapy and with or without levamisole immunotherapy.

In 1976, the Southwest Oncology Group activated a four-arm randomized study of limited squamous cell carcinoma of the lung. The purpose of this study was to determine if doxorubicin and/or levamisole added to radiation therapy improved the local control rate and survival in patients with limited squamous cell carcinoma of the lung. Of the 107 eligible patients, 15 (14%) had complete responses and 20 (19%) had partial responses. When compared by chemotherapy, immunotherapy, and performance status, no statistically significant difference was found in response rates or in survival. Although not statistically significant, the survival and response rates of patients in the combined levamisole arms were shorter than those of patients in the combined arms not containing levamisole. Patients receiving radiation therapy alone had the best survival. The irradiated field was the site of failure in 68 (88%) of the 77 patients in whom the site of failure was specified. Fifty (65%) of the patients failed in the radiation therapy field only. Chemotherapy and/or immunotherapy as employed in this protocol were of no benefit.

Carcinoma, Squamous Cell↗
PubMedDate not supplied

Grammatic representation of beat sequences for fuzzy arrhythmia diagnosis.

The final stage of a system for automatic monitoring of cardiac arrhythmias is the diagnosis of the rhythm or arrhythmia present in the patient during the monitoring process. In this paper we approach the detection process by means of the analysis of the electrocardiographic signal (ECG) on a surface lead produced by those arrhythmias which can be recognized by identifying specific beat sequences and taking into account contextual information, mainly rhythm information. We have developed a diagnosis process for arrhythmias which uses a fuzzy classification of beats according to their etiology or focus of origin. The process we describe permits a more adequate consideration by the user of the arrhythmias diagnosed by the system, mainly in those cases in which the information derived from ECG analysis is not determinant.

Arrhythmias, Cardiac↗