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At least 757 records · Page 42Linked to original sources
PubMed1997

Diagnosis of breast cancer by measuring nuclear disorder using planar graphs.

OBJECTIVE: To achieve a classifier of breast lesions to distinguish benign from malignant mammary lesions by quantifying nuclear disorder in epithelial cell groups from smears obtained by fine needle aspiration. STUDY DESIGN: The study included 95 cases of breast cancer (289 groups) and 47 of benign breast lesions (150 groups), diagnosed by cytology. Information from planar graphs (mean of nuclear distances, standard deviation, maximum and minimum distance between nuclei) was used, and an algorithm constructed for this purpose was applied. The data were classified by double methodology--discriminant analysis, and classification and regression trees (CART)--to determine which achieved the best results. RESULTS: CART selected the standard deviation of nuclear distances with accurate classification in 95.7% of benign lesions and 97.9% of malignant. Discriminant analysis constructed the discriminant function using the mean of nuclear distances and its standard deviation, with results similar to those of CART. CONCLUSION: The classifier based on nuclear disorder that we constructed proved to be rapid, simple and effective for malignant-benign discrimination in breast lesions and should be of diagnostic assistance.

Breast Neoplasms↗
PubMed1999

Segmentation of tissue architecture by distance graph matching.

BACKGROUND: Characterization of tissues can be based on the topographical relationship between the cells. Such characterization should be insensitive to distortions intrinsic to the acquisition of biological preparation. In this paper, a method for the robust segmentation of tissues based on the spatial distribution of cells is proposed. MATERIALS AND METHODS: The neighborhood of each cell in the tissue is modeled by the distances to the surrounding cells. Comparison with an example or prototype neighborhood reveals topographical similarity between tissue and prototype. Processing of all cells in the tissue extracts the regions with tissue architecture similar to the given example. RESULTS: Comparison with other topographical-segmentation methods shows that the proposed method is better suited for partitioning tissue architecture. As an example, the quantification of the structural integrity in rat hippocampi after ischemia is demonstrated. In contrast to other methods, the algorithm correlates well with expert evaluation. CONCLUSIONS: The present method reduces the nonbiological variation in the analysis of tissue sections and thus improves confidence in the result. The method can be applied to any field where regular patterns have to be detected, as long as the directional distribution of neighbors may be neglected.

Algorithms↗
PubMed1986

Number of receptor sites from Scatchard and Klotz graphs: complementary approaches.

Estimates of number of receptor sites and evaluation of the complexity of the binding process require collection of a spectrum of binding measurements and selection of a theoretical model to fit the experimental data. The appropriateness of the measurements and of the model can be visually judged on graphic displays of the model-data fitting curves in Scatchard and semilogarithmic coordinates. This approach is helpful for detecting the two types of errors most frequently found in reports of binding studies: (1) underestimating the number of binding sites, and (2) failure to recognize the complexity of the binding process. While the former is readily recognizable on semilogarithmic but not on Scatchard plots of the model fitting the data, the latter might not be apparent on either plot. Collection of extensive measurements over a wide range of ligand concentrations with graphic display of the model-data fitting curves in Scatchard and semilogarithmic coordinates should be used to recognize and prevent both errors.

Humans↗
PubMed2002

Graphing survival curve estimates for time-dependent covariates.

Graphical representation of statistical results is often used to assist readers in the interpretation of the findings. This is especially true for survival analysis where there is an interest in explaining the patterns of survival over time for specific covariates. For fixed categorical covariates, such as a group membership indicator, Kaplan-Meier estimates (1958) can be used to display the curves. For time-dependent covariates this method may not be adequate. Simon and Makuch (1984) proposed a technique that evaluates the covariate status of the individuals remaining at risk at each event time. The method takes into account the change in an individual's covariate status over time. The survival computations are the same as the Kaplan-Meier method, in that the conditional survival estimates are the function of the ratio of the number of events to the number at risk at each event time. The difference between the two methods is that the individuals at risk within each level defined by the covariate is not fixed at time 0 in the Simon and Makuch method as it is with the Kaplan-Meier method. Examples of how the two methods can differ for time dependent covariates in Cox proportional hazards regression analysis are presented.

Adolescent↗
PubMed1982

Linkage graphs.

Explore the source record for details and available documents.

Biopolymers↗
PubMed2003

Estimation of the Hemodynamic Response Function in event-related functional MRI: directed acyclic graphs for a general Bayesian inference framework.

A convenient way to analyze BOLD fMRI data consists of modeling the whole brain as a stationary, linear system characterized by its transfer function: the Hemodynamic Response Function (HRF). HRF estimation, though of the greatest interest, is still under investigation, for the problem is ill-conditioned. In this paper, we recall the most general Bayesian model for HRF estimation and show how it can beneficially be translated in terms of graphical models, leading to (i) a clear and efficient representation of all structural and functional relationships entailed by the model, and (ii) a straightforward numerical scheme to approximate the joint posterior distribution, allowing for estimation of the HRF, as well as all other model parameters. We finally apply this novel technique on both simulations and real data.

Adolescent↗
PubMed1990

The exploration of pharmacokinetic and pharmacodynamic data using interactive three-dimensional graphs, a tool borrowed from particle physics.

Computerized interactive 3-dimensional graphical displays were originally developed to aid in the exploration of multidimensional data from particle physics experiments. This technique can be equally well applied to speed the analysis of multivariate pharmaco-kinetic and pharmacodynamic data. The application of this technique to the results of a drug study demonstrated its effectiveness in providing a rapid overview of the data and in displaying new perspectives on the multivariate data, helping to identify sources of variability within the study. Multiple concentration-time curves from a given administration period can be distinguished within a single plot, using visual cues provided by rotating the display. Simultaneous comparison of large numbers of curves allows rapid evaluation of intersubject variability. Comparing the concentration-time curves from a single subject, each in succession, quickly identifies sources of intra-subject variability. Manipulating the display by a fourth dimensional parameter shows the degree of relationship between the concentration-time curves and associated dynamic variables. Exploratory analysis using such kinematic display software, provides a rapid, visually concrete impression of the relationships present in kinetic and dynamic data before the application of standard statistical routines.

Data Display↗
PubMed1979

A note on computer graph plots of physician practice locations.

This note examines the distribution of a medical school's physician graduates among states. Computer graphy plots of this distribution are shown to be an alternative way of providing information to health care administration decision-makers concerned with physician practice location.

Computers↗