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Biomedical subjects

J Demongeot

Publications and source records attributed to J Demongeot.

11 recordsLinked to original sources
PubMed1992

Potential use of robots in endoscopic neurosurgery.

A 6-axis stereotactic robot has been designed and linked to a stereotactic frame for routine use. Robot software allows the positioning of a probe holder in order to reach a given target. A calibration step enables the robot to compute the position of the x-ray beam and correct its final position to avoid parallax errors. The co-ordinates of the target are presently taken from anteroposterior and lateral X-rays using a digitizing table. Connection with a digitized angiography system is in progress and will allow direct sampling of numerical data from the x-ray data. Further steps will include connections with a 3D-reconstructed image from MRI and CAT as well as with a resident computerized atlas. Present experience after 14 months of daily practice represents 140 stereotactic procedures which can be extended to any special use, including endoscopic approaches.

Brain Diseases↗
PubMed1992

Human reciprocal translocations: a new computer system for genetic counseling.

A new computer system for genetic counseling in reciprocal translocations is described. This system, namely RCPc (RCP counseling) is a knowledge base extracted from a data base called SCD (Structural Chromosome Data) which contains 1376 families carrying reciprocal translocations. RCPc gives key information for each translocation which allows an evaluation of the risk of unbalance at birth and a prediction of the characteristics of potential unbalances. This information could provide a useful basis for deciding whether a prenatal diagnosis is required and if so, the preferred sampling method i.e. amniocentesis or chorionic villus sampling (CVS).

Artificial Intelligence↗
PubMed1991

Formulas for threshold computations.

Given a continuous variable S, which density functions on two subgroups omega + and omega - of a population omega are known (with for instance a higher mean value on omega + than on omega -), we first define two strategies for classification in these groups; the first one (MWC) consists in determining a threshold alpha such that classifying in omega + when S greater than or equal to alpha, in omega - otherwise, leads to the highest percentage of well-classed elements. The second one consists in choosing the most probable group, given the observed value of S. We give mathematical formulas for the thresholds involved in these two strategies when the density functions, determined by the application of the maximum entropy principle, are those of normal distributions. These formulas prove that the two considered strategies are frequently equivalent, and we give simpler formulas when the partial variances of S on omega + and omega - are unknown or approximately equal. All the formulas are adapted to the case where a cost coefficient is introduced to display the unequal seriousness of the two possible errors (misclassification in omega + or omega -). Then we consider an example, where we see that the computed thresholds can be graphically validated from empirical curves and have the same performances on the learning sample and on a test sample.

Analysis of Variance↗
PubMed1991

Strategies for graphical threshold determination.

Determining a threshold for a quantitative variable (arising in biological measurements for instance) is a common problem in medical decision making. We define seven commonly used strategies: each one leads to an optimal determination. To these strategies correspond relevant empirical curves: the ROC curve for strategies involving the sensitivity or the specificity, the predictive ROC curve (P-ROC curve) for strategies involving the positive and negative predicting values, and the well classified frequencies curve (WCF curve) for classification strategies where all misclassifications have the same importance. For one of the considered strategies, there also exists a theoretical formula for the optimal threshold, elicited within a classical probabilistic model, which gives a considerable advantage to this strategy. These strategies are applied to a stimulated example containing 702 cases, where we see that they lead to different optimal threshold values. Finally, we briefly review a practical application in the determination of thresholds for glycemia measurements, leading to the choice of one of them as the optimal one to consider in the gestational diabetes mellitus prediction.

Diagnosis, Computer-Assisted↗
PubMed1990

Random field and neural information.

A representation--the Ear-Th representation--of the activity of an assembly of neurons is proposed that allows us to describe simultaneous recorded spike trains through the concept of the random field. This representation intrinsically takes into account the fundamental properties of the neuronal signal: its temporal, stochastic, and spatial nature. As a consequence, a neural network, considered as a kind of parallel random automata, delivers an output random field in response to the excitation provided by a random field that represents the activity of some input fibers. Each random field is represented by its associated Gibbs measure, whose potential is plotted in our representation. This approach is applied to the modeling of an intermediary neural network, which receives its input excitation from the auditory nerve fibers and delivers its response to the next auditory neuronal layer.

Auditory Perception↗
PubMed1988

Image cytometry of estrogen receptors in breast carcinomas.

A significant level of estrogen receptors (ER) in breast cancer cells is an indication of tumor differentiation and suggests that a homeostatic control of cell growth may persist in these cancers. In medical practice, the Dextran-coated charcoal assays (DCCA) are still the most frequently used test to characterize patients having ER-positive malignant breast tumors and for whom hormonal therapy is justified. Nevertheless, this routine biochemical technique is not satisfactory because it is a broad method unsuitable for revealing receptor tissue heterogeneity. However, immunocytochemical labeling, such as the ER-ICA method, which involves a monoclonal antibody linked to peroxidase, is a specific reaction for this purpose but which until now was not quantitative. The present study uses an original cell preparation technique combining the PAP reaction with toluidine blue counterstain for image analysis on the SAMBA system. Special software has been developed for the quantitative analysis of immunocytochemistry in cancers. Results obtained showed a high correlation between the DCCA values and the score derived from the mean ER concentration per positive tumor cell and the labeling index. In addition, intracell and intratumor heterogeneity can be displayed according to several parameters and were shown to vary according to tumor and to antiestrogen (Tamoxifen) presurgical therapy.

Breast Neoplasms↗
PubMed1988

[Extrahepatic digestive surgery in cirrhotic patients: mortality, morbidity and preoperative prognostic factors].

The purpose of this work was to study postoperative mortality and morbidity with respect to preoperative prognostic factors in 67 patients with alcoholic or posthepatitis cirrhosis. Surgical procedures involved the biliary tract (n = 20), stomach (n = 16), colon or rectum (n = 12), and hernia (n = 7). Thirteen preoperative clinical and biological variables were subjected to mono- and multivariate statistical analysis. The mortality rate was 23 p. 100. There was no statistical difference between the three main surgical procedures. No patients died after herniorrhaphy. The rate of morbidity was 37 p. 100. The most common complications were sepsis, organ failure, and ascites. Three preoperative variables were found to be different between survivors and non survivors: ascites, prothrombin time and the Child-Pugh score. Multidimensional analysis demonstrated that the only variable to have an independent unfavorable prognostic value was albuminemia. These results suggest that postoperative mortality following extrahepatic abdominal surgery in cirrhotic patients is: 1) especially high after digestive procedures, 2) increased by ascites, low prothrombin time and high Child-Pugh score. Only hypoalbuminemia had a significant independent explanatory value regarding prognosis.

Adult↗
PubMedDate not supplied

Variables processing in expert system building: application to the aetiological diagnosis of infantile meningitis.

We describe a method for the analysis and quantitative synthesis of information in a clinical data file using as an example the aetiological diagnosis of infantile meningitis. The results obtained together with the qualitative knowledge of experts in the field have enabled an experimental system to be constructed. This is performing sufficiently well to be introduced into a hospital environment to assist young doctors facing an emergency situation.

Acute Disease↗