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A system for the analysis of long-term electrocardiographic studies in clinical research and training.

A computer system has been developed for the analysis of data from long-term electrocardiographic studies in the context of an institution committed to clinical research and training. The major characteristics required of such a system are intelligence, flexibility, friendliness, and maintainability. These attributes are achieved by a user interface which consists of menus and interactive graphics, and by the use of highly modular software developed in a high-level programming language. The system has been used in studies of the effects of drugs on cardiac arrhythmias and has been easy to learn and convenient to use.

Academies and Institutes

An algorithm to manage variable-length records for highly portable clinical data base systems.

An algorithm to archive patient data at free size in disk storage is presented. A record, assumed to be a character string such as an ASCII-coded text, is compressed and divided into fixed-length blocks. One block consists of a data field and a pointer field, and the blocks comprising a record are chained with pointers forwardly. A head pointer of each record is sequentially saved on a separate file. The data compression is performed as follows: if the same character code appears more than twice in succession, we count the number of the repetitions and save it with initial two characters. The algorithms for fetching, re-saving, and purging a record are also presented. These were implemented in FORTRAN77 and tested for performance using a practical patient data file. As the algorithm allows highly flexible record manipulation and can easily be implemented in conventional programming languages, it will make a useful tool for constructing a portable data base management system.

Evaluation Studies as Topic

Managing research data with self-documenting files.

Processing biomedical research data is frequently complex due to the evolutionary nature of experiments and the requisite modification of analysis software. For the past several years we have been evolving a set of software tools designed to improve our ability to respond to evolving experimental designs. These tools allow the investigator to easily manipulate the research data and specify desired data transformations at run time. Coupling of analysis software to research data files is dependent on data files that are commented in a manner similar to that used in programming languages. The resulting annotated data files are self-documenting, and their use facilitates visual interpretation of displayed data as well as automatic processing of subsets of data. Here we present a formal description of a self-documenting file and describe several software tools that facilitate processing of biomedical research data.

Electronic Data Processing

The dynamics of HIV spread: a computer simulation model.

Mathematical modeling of the AIDS pandemic has been limited by the difficulty of satisfactorily representing the marked behavioral heterogeneity that characterizes the various populations at risk. We propose an approach which models the spread of infection as a discrete-event simulation using SIMSCRIPT, a powerful simulation language. The program developed provides sufficient flexibility to adequately represent and study a wide range of risk-group dynamics. Using this tool we have verified the May-Anderson prediction relating contact rate heterogeneity to the rate of HIV spread. We have also been able to assess the sensitivity of the model to the particular choice of distribution for contact rates, disease stage durations, and intercontact intervals. It is thought that this approach will permit the empirical testing of hypotheses which do not lend themselves to a purely mathematical treatment.

Acquired Immunodeficiency Syndrome

Derivation of rule-based knowledge from established medical outlines.

The purpose of this paper is to describe the derivation of a rule base for an expert system from an existing medical auditing method called a criteria map. The criteria map represents the physician's logic in the specialty involved. The system described, EMERGE, is written in the standard Pascal programming language, operates on a microcomputer, and provides a convenient user-interface. All medical knowledge in EMERGE is contained in an independent set of production rules, which are derived from the criteria map.

Diagnosis, Computer-Assisted

EGTA.

A method is described to compute the free calcium concentration in a solution buffered by EGTA. The effects of solution pH and [Mg] are fully taken into account. A sample program in the C programming language is described.

Calcium

Software control of sensing and stimulation for cardiac electrophysiological study.

A software-controlled cardiac stimulator for clinical investigations is described. The stimulator is programmed by the user at a keyboard, while current status and values of parameters are presented on a visual display screen. A menu of predefined cardiac electrophysiological tests is available for user selection. Validity checks on data keyed in by the user and internal checks on safe pacing limits are incorporated in case of malfunction or user error. The system consists of a separate relatively simple isolated sensing and stimulation unit which communicates, via a standard digital input output interface, with a controlling microcomputer. All timing and control functions are performed in software by the computer. The use of high-level FORTRAN as the main programming language provides the system with a high degree of adaptability.

Computers

Design of an automated temperature mapping system for ultrasound or microwave hyperthermia.

An automated temperature mapping system was designed to accomplish the following goals: remote control mapping; a maximum position error of 0.5 mm; mapping simultaneously on several channels; real-time screen display on a dedicated computer; to be inexpensive, and have a simple patient interface and set up. A four channel, microstepper system was fabricated for less than $1000 and controlled by an IBM-AT computer. The system utilizes direct drive of Luxtron fibre-optic probes fed through thin flexible Teflon tubing which allows for patient movement. The driving and control software were written in the programming language "C". Mapping parameters for each independent channel include start and stop positions and map increment. The software permits the user to automatically find the maximum temperature along a track in three passes of 2.0, 1.0 and 0.5 mm steps. The latter two passes take five or seven readings centred about the maximum of the previous pass. A high resolution monitor plots the temperatures in real time, overlaying the previous map in a new colour. A screen dump was written to drive a colour printer with the plot information. The computer evaluates each plot to safeguard against any shift in the maximum location. Visualization of orthogonal pullbacks provides rapid feedback and aids in the repositioning of superficial hyperthermia transducers. The time saved over the previous manual mapping methods easily justifies the additional set up time.

Animals

An automated data acquisition system for isolated tissue studies.

The automation of an isolated atria assay is described. Data acquisition, operation of the strip chart recorder, data reduction and manipulation and generation of notebook pages showing final EC50's, dose-ratios and local pA2's has been completely automated. The data are acquired via a SYM-1 (6502 CPU) 8-bit single board computer running an assembly language program stored on an EPROM chip. The data from a physiological recorder system are stored by the SYM-1 and, at the conclusion of the experiment, transmitted to a DEC MINC-11 microminicomputer running a sequence of programs in BASIC for the mathematical manipulation of the data and the automatic generation of lab notebook pages. The automated system totally eliminates hand transcription of data, manual plotting of curves and mathematical errors.

Animals

A microcomputer system designed for psychological and behavioural experiments.

This paper describes a relatively cheap MC6809-based microcomputer designed to run experiments in real-time, and to use the hardware and software facilities of a larger (HOST) computer. Each microcomputer is capable of controlling a wide range of psychological and behavioural experiments, and includes 32K RAM, 4K EPROM, 32 digital input lines, 32 digital output lines, analogue/digital converters, and programmable timers. Any programming language may be used, providing a cross-compiler generating MC6809 executable code exists for the HOST. Following over a year of use we can confirm that this system provides an effective method of running psychological and behavioural experiments.

Computers

Enhancing high-speed digitization of single-unit neuronal activity on a microcomputer using a hybrid software-hardware technique.

A new data acquisition technique allows a microcomputer simultaneously to digitize spikes at high rates, analyze spike waveforms for computer-based spike separation and manage other control tasks. The technique has two key features: a software scheduling routine written in a high-level language and a hardware analog delay of neuronal signals using simple hardware external to the computer. The technique provides an alternative for real-time data acquisition and can be used on microcomputers without requiring interrupt processing and assembly language programming.

Action Potentials

A fast, high precision and inexpensive analog to digital board for PC-AT or compatible.

We describe a simple and inexpensive circuit for analog data acquisition with high speed and high resolution, for use in an IBM PC-AT or compatible. The circuit is suitable for a wide range of applications in electrophysiology. Features of the circuit include multichannel reading, programmable sampling rate, and direct memory access controlled dual buffering for continuous recording. A program written in the C programming language for control of data acquisition is also given.

Computers

A computerized system for rapid retrieval and compilation of critical or interesting patient data.

The timely availability and presentation of critical and interesting patient data is essential to ensure quality patient care as well as ease of recognition and, secondarily, to provide material for teaching and research. The ability to accomplish these goals expeditiously in a complex and busy clinical laboratory may be difficult to acquire. An on-line, computerized system has been developed which automatically searches each patient record for up to 600 different laboratory tests, compares each result against individually established limits, and then formats pertinent test results for maximum discrimination. The report format also includes patient and specimen collection data, diagnosis, attending physician's name, and other desired associated test results. An additional feature of the system is that selected critical or interesting results for each laboratory division may be displayed on video display terminals located throughout the laboratory and at nursing stations. The system was written using the FORTRAN programming language and runs on a Control Data Cyber 18 computer.

Clinical Laboratory Techniques

SEQUAL: an interactive computer program for sequential classification of biomedical data.

A computer program for sequential bayesian classification of patterns defined by integer and real-valued data is described. Classified patterns from a training sample are used to estimate the non-parametric (kernel) probability density functions and the a-priori class probabilities necessary to implement the bayesian classification. For each pattern and at each step in the sequential program, the 'best' feature to be measured at the next step is computed on the basis of the estimated misallocation error rate. The user can actually use the proposed feature or any other one; once the chosen feature has been measured, its value is used to allocate the pattern into the class with the highest conditional a-posteriori probability, according to the Bayes formula. The main feature of the program consists in the computation of the 'probability of reversal' at each step of the sequential procedure. The probability of reversal represents the probability that at the next step the pattern will be classified into a class different from the present one. The probability of reversal can be used as a stopping criterion, which is more efficient than other commonly used stopping rules, such as the a-posteriori Bayes probability or the estimated misallocation error rate. The program, available in FORTRAN 77 for a VAX/VMS machine, has been tested both on simulated and real data collected from patients suffering from various forms of hepatic disease.

Bayes Theorem

A new combined integral-light and slit-scan data analysis system (DAS) for flow cytometry.

Flow cytometry using list mode parameters such as fluorescence emission, light scatter and size on one hand and different slit-scan parameters on the other hand needs a fast, flexible, efficient and easy-to-use data analysis software. A new software package (data analysis system, DAS) has been developed that integrates data analysis for conventional (integral-light) flow cytometry and for slit-scan flow cytometry. The requirements, design and some examples are discussed and an implementation for IBM-compatible computers is presented. Special attention is directed to the handling of different data types from one-parameter histograms to multiparameter slit-scan data files. The package can be used as an interpreting programming language or as an interactive menu-driven command line interpreter with a large number of graphic, mathematical and statistical functions. DAS is not limited to use in flow cytometry only, but multidimensional data analysis, from astronomy to economics, can be done as well.

Data Display

X window system based user interface in radiology.

A teleradiology system was designed for image transfer between two hospitals. One of the main challenges of the work was the user interface, which was to be easy to operate and to learn, and was equipped with useful functions for image manipulation and diagnosing. The software tools used were the Unix operating system (HP-UX v.7.0), C programming language and the X Window System (or simply X). The graphical user interface (GUI) was based on OSF-Motif standard, and it was developed by using the HP-Interface Architect. Both OSF-Motif and HP-Interface Architect are based on X. The results of the development project were installed for clinical use in the Turku University Central Hospital. The work demonstrates, that the X Window System has useful and advantageous features for radiology department's computer network environment.

Computer Communication Networks

How to improve a neural network for early detection of hepatic cancer.

Radiologists perform differential diagnoses of hepatic (liver) masses using ultrasonography (US), computed tomography (CT), magnetic resonance imaging (MRI), and laboratory tests, but interpretation is often difficult. In our earlier research, a backpropagation neural network was designed to diagnose five classifications of hepatic masses: metastatic carcinoma, hepatoma, cavernous hemangioma, abscess, and cirrhosis. After being trained using ultrasonographic data and laboratory tests, the network classified hepatic masses correctly in 51 of 72 cases. That accuracy of 71% is higher than the 50% scored by the average radiology resident in training but lower than the 90% scored by the typical board-certified radiologist. What do we need to do to increase that accuracy and make the network friendly enough that radiologists will use it in their diagnoses? We have reviewed the literature, discussed alternatives and developed a plan to improve the diagnostic accuracy of the networks. That plan consists of: (i) get many more patient cases and more data variables, including MRI and CT data, so the network can be more highly trained. A shortage of enough patient cases to properly train the network is the key problem; (ii) use genetic algorithms and other techniques to preprocess the data; (iii) the network should have an optical interface to read images directly; and (iv) build a user-friendly interface using the C programming language on a 486 microcomputer. Continued research along the guidelines in this study should provide a sophisticated neural network for early detection of hepatic cancer that hopefully will exceed the diagnostic abilities of most radiologists.

Carcinoma, Hepatocellular

The portable virtual simulator.

The Virtual Simulator is a software tool for support and management of the geometric component of 3-dimensional radiotherapy treatment design. The Virtual Simulator is a software implementation of a physical simulator with additional functionality not currently available on physical simulators. Treatment of a virtual patient, derived from CT or other source, is simulated using the Virtual Simulator in the same way a physical simulator would be used. The intent of this approach is to provide the user with a familiar working environment for radiotherapy treatment design. Key features include an effective and efficient user interface, and the use of computing techniques and software standards which enhance portability to a variety of computer workstations. The Virtual Simulator is implemented in the C programming language using the X Window System, and has been written with the generic UNIX workstation in mind. It has been demonstrated that it can be installed and run without modification on workstations from a number of vendors.

Computer Simulation