Applications of computer graphics in craniofacial surgery.

Three-dimensional surface images can be reconstructed from CT scans. These are particularly useful in the study and management of patients with congenital and acquired craniofacial deformities. The principles of 3-D reformation, the production of the surface images, and recent advances in modification of these images for specific clinical needs are presented.

A microcomputer-based graphical reconstruction technique for serial sectioned objects, with hidden line removal.

The presented software package fulfills the need for processing serial sections with a microcomputer configuration, enabling three-dimensional reconstruction with hidden line removal. The language used is an interpreted BASIC-dialect (HPL). The input is performed via an interactive program. The object can be rotated in space. The Hidden Line algorithm does not depend upon a raster technique. Points of intersection of successive contours are calculated and inserted, thus providing drawings of high resolution and quality. The handling time can be said to be short, especially when considering the capacities of the microcomputer configuration used.

On-line three-parameter data uptake, analysis, and display device for flow cytometry and other applications.

Multiparameter flow cytometric measurements are of growing interest in the study of complex features of biological cells. With state of the art instrumentation, three-parameter (3-P) data handling is relatively complicated and time consuming and the display methods are not satisfactory. As an alternative, an interactive 3-P analyzing module, Cytomic 123 is described, which displays 3-P fields during and immediately after data uptake in the form of a cubic array of 32,768 channels. The fields can be randomly rotated by hardware and software. The event frequencies in the field are primarily visualized by brightness modulation of the display dots. Additionally, the display of the field may be confined to user selected ranges of event frequencies, which may also be superposed to mixed frequency displays. A set of preprogrammed functions is available for the following tasks: (a) uptake of 3-P histograms combined with on-line control of the transducer pulses, (b) automatic uptake of a series of 2-P time correlated histograms in the cube, (c) generation and numerical evaluation of sections and projections of cube histograms, (d) interactive generation and evaluation of spatial subfields for integration, or as sorting matrix by successive erosion of section planes, or reprojection of projection windows, and (e) isometric display of sections and projections and exchange of data sets with other Cytomic modules or other data systems, especially the Cytomic 12 module, whose 2-P capabilities can be used. The module is built with low cost Z80 microprocessor eurocards. A standard oscilloscope serves as a display unit.

Programming for the DNA analysis of FCM data on an IBM microcomputer.

The analysis of data generated on a flow cytometer (FCM) is often performed on a computer obtained especially for dedicated use with the flow cytometer. This computer component can be expensive and also presents the FCM user with the added burden of mastering specialized programming language or of accepting the secret analytical processes of protected proprietary program routines. We believe that the evolution of more accurate and efficient FCM analyses that have the power to consider complex signal distributions can be assisted by the availability of analysis programs written in languages common to many users. DNA analysis routines written for a relatively inexpensive microcomputer (IBM PC/XT) in Basic and Pascal are described here. The routines can automatically process multiple FCM data files and can provide high-resolution graphic hardcopy. A foreground/background utilization is also described that allows the computer to be available for other uses in the laboratory.

Integration of data obtained at fixed intervals.

This article discusses the design and implementation of a program well suited to integrating experimental or simulated data obtained at fixed intervals. The program uses Simpson's method and produces substantially better accuracy than trapezoidal rule integration at little extra computational cost. It accepts command line specification of integration parameters (step size and/or number) and source files. Multiple source files and integration parameters can be specified at runtime. Output can be displayed on the console or redirected to an ASCII file.

Computer faces: the human Lorenz matrix.

Realistic Ekman-type faces were generated by a computer program. Twenty primary parameters (muscle tensions and opening factors), each continuous, were used. Non-linear combination of the primary parameters permits the generation of meaningful faces each governed by a single combined parameter (intensity-parameter). Five major meaningful faces were distinguished, "friendliness", "surprise", "disgust", "anger" and "grief". In contrast to the experiments of Ekman, who combined subregions of photographed meaningful faces by hand, mixing can be done in the computer both more easily and, it turns out, more naturally. Mixed facial expressions in an animal were first drawn in matrix form by Lorenz. A consistent interpretation is possible if the linearly superposed displays are assumed to indicate the state of an autonomous optimizer with n linearly independent subfunctionals. An instant display of a vector in n-dimensional space using faces was already proposed by Chernoff. The present faces have the asset that only "natural" parameters are used. This means that no longer only a single point in n-dimensional space can be displayed, but also a meaningful succession of such points--that is, a whole trajectory.

Use of the personal computer in clinical research.

Personal computers are quickly becoming items of everyday use. More physicians' offices are using computers for billing and patients' records. Others have purchased computers for their word processing capabilities. These computers can be used for archives of medical case records or to collect and collate data for clinical research. This article focuses on how we use a personal computer for organization and management of clinical research projects. Included is a description of how we organize a research project, gather data, write computer programs, enter data into the computer, and generate and display reports. The use of a template program and a personal computer permits creation of individual programs without the aid of a professional programmer. When a single data-management program is used, five or six research projects can be carried out at a cost comparable to that of one project using a large computer and professional programmers.

A rapid, universal TI-59 model-independent pharmacokinetic analysis program based on statistical moment theory.

A model-independent program for pharmacokinetic analyses based on statistical moment theory is presented and demonstrated. The program uses an inexpensive and portable TI-59; a PC-100A printer adds convenience but is optional. The program may be used in analysis of blood, serum, or plasma concentration vs. time curves originating from iv, im, po, sl, or sc administration. Drug input can be zero or first order; both single-dose and multiple-dose steady-state conditions can be evaluated. A comparison between results generated using moment analysis and traditional two-compartment nonlinear regression showed excellent agreement.

Modeling the electrical behavior of anatomically complex neurons using a network analysis program: passive membrane.

We describe the application of a popular and widely available electrical circuit simulation program called SPICE to modeling the electrical behavior of neurons with passive membrane properties and arbitrarily complex dendritic trees. Transient responses may be calculated at any location in the cell model following current, voltage or conductance perturbations at any point. A numbering method is described for binary trees which is helpful in transforming complex dendritic structures into a coded list of short cylindrical dendritic segments suitable for input to SPICE. Individual segments are modeled as isopotential compartments comprised of a parallel resistor and capacitor, representing the transmembrane impedance, in series with one or two core resistors. Synaptic current is modeled by a current source controlled by the local membrane potential and an "alpha-shaped" voltage, thus simulating a conductance change in series with a driving potential. Extensively branched test cell circuits were constructed which satisfied the equivalent cylinder constraints (Rall 1959). These model neurons were perturbed by independent current sources and by synaptic currents. Responses calculated by SPICE are compared with analytical results. With appropriately chosen model parameters, extremely accurate transient calculations may be obtained. Details of the SPICE circuit elements are presented, along with illustrative examples sufficient to allow implementation of passive nerve cell models on a number of common computers. Methods for modeling excitable membrane are presented in the companion paper (Bunow et al. 1985).

Modeling the electrical behavior of anatomically complex neurons using a network analysis program: excitable membrane.

We present methods for using the general-purpose network analysis program, SPICE, to construct computer models of excitable membrane displaying Hodgkin-Huxley-like kinetics. The four non-linear partial differential equations of Hodgkin and Huxley (H-H; 1952) are implemented using electrical circuit elements. The H-H rate constants, alpha and beta, are approximated by polynomial functions rather than exponential functions, since the former are handled more efficiently by SPICE. The process of developing code to implement the H-H sodium conductance is described in detail. The Appendix contains a complete listing of the code required to simulate an H-H action potential. The behavior of models so constructed is validated by comparison with the space-clamped and propagating action potentials of Hodgkin and Huxley. SPICE models of multiply branched axons were tested and found to behave as predicted by previous numerical solutions for propagation in inhomogeneous axons. New results are presented for two cases. First, a detailed, anatomically based model is constructed of group Ia input to an alpha-motoneuron with an excitable soma, a myelinated axon and passive dendrites. Second, we simulate interactions among clusters of mixed excitable and passive dendritic spines on an idealized neuron. The methods presented in this paper and its companion (Segev et al. 1985) should permit neurobiologists to construct and explore models which simulate much more closely the real morphological and physiological characteristics of nerve cells.

APL programs for outcome probabilities and confidence limits in sequential binomial trials.

For closed sequential binomial sampling plans (including plans for multistage sampling), the probability of reaching each terminal point is calculated. These probabilities are cumulated from "each side" of the plan. Thus, the power function obtainable by defining any (reasonable) acceptance region can be studied. Corresponding to a given outcome of the trial confidence limits can be calculated by an auxiliary program.

Computer-assisted multiple categorization of absorbance values in ELISA through pictorial emulation of 96-well plates.

A simple algorithm is proposed by which multiple categorization of absorbance values from ELISA plates is performed under a microcomputer control. The printed output is a pictorial emulation of a 96-well plate with the color intensities represented for each reaction. Although the method is presented as a colorimeter computer interfaced system, a provision for manual entry of absorbance values via keyboard is also included. Simulation is based solely on the magnitude of absorbance values. Therefore, it is possible to utilize any enzyme/substrate combination within the range of filters of the colorimeter. We have tested the present system for titration of anti-malarial antibodies in human serum and for the screening of mouse hybridoma culture supernatants.

Computer software design for pediatric practice. A modular approach.

Practical applications for using computers in everyday medical practice have not kept pace with the technical developments that now make this tool available to the pediatric practitioner. A modular approach to user-developed applications software is presented as a model for computerizing the pediatric office. Benefits have included lower cost, greater data reliability and validity, standardization of office and medical procedures, and automation of jobs formerly requiring much personnel time. Some patient services have improved, and other new services have become possible, through the application of computer software designed in accordance with our practice philosophy.

Experimental intravenous digital subtraction angiography (DSA) of orbital and choroidal circulation: preliminary study.

The development of the radiologic technique, digital subtraction angiography (DSA), has substantial importance in studying the uveal vasculature and its orbital blood supply. After rapid intravenous injection of commercially available contrast material, images of the orbital and uveal vessels of rabbits, cats, and the nonhuman primate can be observed. Advantages and limitations of this new technique for visualization of uveal and orbital vasculature were evaluated in serial experimental animal studies. Future potential clinical applications are discussed.

Competing models for the analysis of red cell survival obtained with 51Cr labelling technique.

A computer program for the analysis of 51Cr labelled red cell survival data was used in 84 patients and 8 normal subjects to estimate the parameters of 7 competing models derived from different hypotheses of the red cell destruction process. The purpose was to establish the optimal complexity of a red cell survival model to be used. Senescence or random destruction were the most common identified patterns of red cell death (79% of the cases). Models assuming different levels of death probability according to the age of cells, or 2 populations of cells with different death probabilities, were selected in 21% of the cases. These latter patients were characterized by the lowest values of MRCL. The conclusion of the work was that an automatic procedure for selecting the best model of red cell destruction is necessary when information concerning the mechanism of red cell death is required. For the more practical aim of obtaining an accurate measurement of the MRCL, the minimal set of competing models should account of at least 2 different populations of cells in addition to the random or senescence destruction models.