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PubMed1978

Performance of various mathematical methods for computer-aided processing of radioimmunoassay results.

Interpolation and regression methods are available for computer aided determination of radioimmunological end results. We compared the performance of 6 algorithms (weighted and unweighted linear logit log regression; quadratic logit log regression, smoothing spline interpolation with a large and small smoothing factor, respectively, and polygonal interpolation and the manual curve fitting on the basis of three radioimmunoassays with different reference curve characteristics (digoxin, estriol, human chorionic somatomammotrophin (HCS)). Great store was set by the accuracy of the approximation at the intermediate points on the curve, i.e. those points that lie midway between two standard concentrations. These concentrations were obtained by weighing and inserted as unknown samples. In the case of digoxin and estriol the polygonal interpolation provided the best results, while the weighted logit log regression proved superior in the case of HCS.

Computers↗
PubMed1987

Interactive statistical analysis of survival data.

This paper describes a SAS macro which facilitates the interactive analysis of right-censored survival data. Such data commonly occur in medical studies. The program produces Kaplan-Meier survival curves on a wide variety of graphics devices. The program also performs log-rank and generalized Wilcoxon significance tests among all plotted curves and for each pairwise contrast if desired. Because the program is intelligent and does not prompt the user for information that it can independently obtain, it is quite easy to use.

Computer Graphics↗
PubMed1987

Balancing allocation of subjects in biomedical research: a minimization strategy based on ranks.

A new method for ensuring the comparability of groups of experimental subjects is proposed. All subjects are ranked on each measured pretreatment variable and differences between groups in the means and the standard deviations of these ranks are minimized by systematically exchanging subjects when those exchanges yield less imbalance between groups. This method was designed for small studies in which pretreatment data from all subjects are known before the start of the experiment. A series of computer simulations suggests that this procedure is effective in balancing groups on several variables although the amount of computer time required becomes excessive as the number of subjects is increased.

Computer Simulation↗
PubMed1989

A new method for aligning histological serial sections for three-dimensional reconstruction.

A new method for aligning histological serial sections for three-dimensional reconstruction by computer is introduced. This method is particularly suited for embedding structures in celloidine or paraplast. Prior to sectioning, at least three reference markers are affixed to the preparation in a direction perpendicular to the section plane, for easy identification on the finished sections. An algorithm translates and rotates the serial sections until all the reference markers are congruent. The main advantage of this method, however, is its capability to eliminate deformations caused by compression or stretching during sectioning by the determination of correction factors.

Algorithms↗
PubMed1990

Automatic geometrical registration of fluorescein retinal angiograms.

Changes in retinal microvascular perfusion revealed by fluorescein angiography have been reported in patients undergoing coronary artery surgery. Quantification of these changes is important and current techniques depend on careful visual inspection of the angiograms by humans. Computer image processing methods can be used to identify and highlight differences, but geometrical registration of the images is a prerequisite to the comparisons. Automatic methods for locating and matching reference points have therefore been developed. In combination with an iterative process which used least-squares error to calculate the transformation coefficients, subsets of reference points were selected and used to register successfully 20 image pairs.

Coronary Artery Bypass↗
PubMed1990

Tooth surface fitting and three-dimensional display using hidden surface removal technique.

Bi-cubic parametric spline surface is applied for surface-fitting of the external surface and canal of tooth based on its crown-to-root, cross-sectional data obtained by X-ray scanning. For three-dimensional display of the fitted surfaces, a technique for fast removal of the hidden surfaces is also reported. The selection of the accumulated chord length or coordinate component as parameter make it possible to fit any kind of surface smoothly. For displaying or plotting a well-fitted surface, a method capable of discriminating the grades for sequential removal of the hidden surfaces is developed for substantial reduction of computing time.

Algorithms↗
PubMed1990

Algorithms for the computation of spatial statistics.

Algorithms are described for the calculation of spatial statistics. The statistics are the functions K(t), G(y), F(x), and K12(t). They can be used to determine (a) which type of spatial process ('random', 'clustered', 'regular', etc.) best fits a data set and whether the spatial pattern changes with distance, and (b) whether two types of events are correlated with each other, and if so, at which distances the correlation occurs. These functions provide a powerful tool for analysing the spatial distribution of biomedical and biological phenomena. An interactive, command-driven program that incorporates these algorithms is described.

Algorithms↗
PubMed1989

A program for simulation of nerve equations with branching geometries.

A computer program has been developed for simulation of electrical activity in neurons with complex branching morphology, multiple channel types, and inhomogeneous channel distribution. The program is based around an interpreter and screen editor for flexible specification of nerve properties and analysis of simulation results. Efficient simulation of the nerve specification is accomplished with procedure calls to fast, compiled routines for integration of the nerve equations.

Cell Membrane↗
PubMed1988

High-precision three-dimensional photogrammetric calibration and object space reconstruction using a modified DLT-approach.

Two modified DLT algorithms are presented that improve the accuracy of three-dimensional object space reconstruction by almost an order of magnitude when compared with conventional methods. The improvement in the linear modified DLT (MDLT) algorithm is achieved by satisfying certain orthogonality conditions in the form of a non-linear constraint, thereby effectively eliminating a redundant DLT parameter. In the non-linear MDLT algorithm, the improvement and computational stability results from the appropriate elimination of implicit variables from one side of the approximating relations and the corresponding reformulation of the objective function to be minimized. The highest reconstruction accuracy of 0.733 mm rms mean error was obtained with the non-linear MDLT algorithm. This corresponds to a spatial resolution of about one part in 2860 or 0.035% overall accuracy. The accuracy obtainable with the linear MDLT was found to be slightly less and about 0.041% (0.833 mm rms mean error).

Algorithms↗
PubMed1987

Intersection of shaped radiation beams with arbitrary image sections.

Display of the intersection of a shaped radiation beam with an arbitrarily oriented image plane is a very useful tool in three-dimensional external beam radiation treatment planning. Coverage of the tumor (or target) region can be graphically investigated, as well as the radiation received by the surrounding healthy tissues. An algorithm is presented that obtains and displays these intersections by projecting contour points defining the beam's aperture on the plane. A general procedure is given, as well as provisions for special cases in which a straightforward projection is not sufficient.

Algorithms↗
PubMed1989

CONFREG: a BASIC program for calculating and plotting confidence regions based on correlational analyses.

Many observations encountered in biological and medical research are randomly distributed in bivariate scales, and thus not susceptible to simple regression analyses. Since such data are depicted by ellipses in scatter diagrams, a computer program to calculate the confidence regions for the means or the total data of bivariate samples was written in BASIC for correlational analyses. The program, based on the principal axes algorithm, plots the calculated confidence regions as an elliptic area, using the fitted equations for its major and minor axes. The program displays the sample parameters required to perform comparisons between different groups of experimental conditions.

Animals↗
PubMed1989

BOOMER, a simulation and modeling program for pharmacokinetic and pharmacodynamic data analysis.

BOOMER is an improved version of an earlier non-linear regression program, MULTI-FORTE. Rather than the user writing a FORTRAN subroutine, models are defined by means of the parameters which make up the model. Models based on differential equations are specified by means of zero-order, first-order, or Michaelis-Menten-type rate constants. Doses (in units of mass) are translated into the usually observed concentration units by a reciprocal volume parameter. Integrated equation models are specified in terms of baseline terms, exponential terms, or the emax function with slope term as described by the Hill equation. Time points can be specified as parameters to specify dose times, infusion start/stop times, or lag times. With careful selection of parameters quite complex models can be specified. The user has a choice of differential equation solvers and fitting algorithms.

Computer Simulation↗
PubMedDate not supplied

Evaluation of Monte Carlo generation of long-tailed symmetric and contaminated symmetric distributions.

Generating random variables from a specific distribution, whether symmetric or asymmetric, is a concern of investigators involved in Monte Carlo studies. Of particular interest to those concerned with robustness is the generation of contaminated symmetric distributions such as those used in the Princeton Robustness Study. A reliable composite uniform U(0,1) generator is described and algorithms for transforming U(0,1) to symmetric long-tailed and contaminated symmetric distributions are given. Goodness-of-fit tests and graphical illustrations demonstrate the adequacy of the empirical distributions.

Algorithms↗
PubMed1990

An application of the D-optimal criterion to define the experimental design for a particular class of semi-parametric models.

An updated version of the computer program EXCAD [1] allows the user to optimize experimental design to estimate parameters of particular semi-parametric models. The semi-parametric models take the general form of a function of time (t): Y(t) = NL (c(t,alpha),beta). The function NL(C(t,alpha),beta), is, in general, a non-linear transformation of a function, C(t,alpha), that in turn is the convolution of two others. One of these two functions is expressed in a non-parametric form, and is not of direct interest to the experimenter. The other is of direct interest: it is a parametric function depending on a set of parameters alpha. This semi-parametric model applies to numerous kinds of biological experiments, such as pharmacokinetic/pharmacodynamic, physiological, circulatory flow experiments. This paper presents a new method for determining an optimal experimental design to estimate the parameters alpha and beta. The new approach adopts the D-optimal criterion, and is illustrated using real thiopental data.

Animals↗
PubMed1994

A knowledge acquisition tool in analytical pathology based on multi-media relational database.

The need for a knowledge based expert system for efficient decision making in the field of pathology has been well accepted. To build the knowledge-base for such an expert system is a painstaking task. This work is an attempt to provide the pathologists a powerful and user-friendly tool that will help them in the process of building the knowledge-base for medical diagnosis by closely looking at the specimen images and their extracted feature values. The tool is based on multi-media relational database and software like VAX Rally (4GL), ILIAD and SAS to provide a wide-range comparative study between feature data and image data; and also their statistical analysis.

Artificial Intelligence↗