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Computer simulation study of Siemens star x-ray image artifacts.

In the Siemens star image, exact determination of the first disappearance frequency, which is used to measure the focal spot size, is difficult since the disappearance band has a finite width and the image also has other artifacts. The origin of these artifacts and their appearance was studied by Siemens star image simulation on a digital computer. The simulated images were manipulated by using many different modulation and phase transfer functions. It is shown that the bending of spokes is not related to zero contrast; exact triplet splitting can occur only at the disappearance frequency, and therefore splitting is a valuable indicator of that frequency.

Computers↗

The effect of levonorgestrel-releasing intrauterine device (20 micrograms/day) (LNG-IUD-20) on the morphological structure of human endometrium: a study of the endometrial factor VIII activity in the women before and after insertion of LNG-IUD-20 by the digital image analysis.

The specimens of endometria were obtained from 18 women using an intrauterine device releasing levonorgestrel at 20 micrograms/day (LNG-IUD-20). An immunoperoxidase reaction, PAP method, with the antiserum of Factor VIII as the primary antibody, was carried out in the endometrial biopsies to detect the Factor VIII activity in the endometrial endothelium before and after insertion of LNG-IUD-20. The immunoperoxidase activity was quantitatively assessed by a computer digital image analyser. The results revealed that there were a lower Factor VIII activity in the endometrial endothelial cells after insertion of LNG-IUD-20 (p < 0.001) when compared with the control. From the results of the present study, it is suggested that the synthesis and release of endometrial endothelial Factor VIII might be inhibited by the insertion of LNG-IUD20.

Adult↗

Relevance of the electronic computer to hospital medical records.

During the past 30 years an "information explosion" has completely changed patterns of illness. Unit files of individual patients have become so large that they are increasingly difficult both to store physically and to assimilate mentally. We have reached a communications barriers which poses a major threat to the efficient practice of clinical medicine.At the same time a new kind of machine, the electronic digital computer, which was invented only 26 years ago, has already come to dominate large areas of military, scientific, commercial, and industrial activity. Its supremacy rests on its ability to perform any data procedure automatically and incredibly quickly.Computers are being employed in clinical medicine in hospitals for various purposes. They can act as arithmetic calculators, they can process and analyse output from recording devices, and they can make possible the automation of various machine systems.However, in the field of case records their role is much less well defined, for here the organization of data as a preliminary to computer input is the real stumbling-block. Data banks of retrospective selected clinical information have been in operation in some centres for a number of years. Attempts are now being made to design computerized "total information systems" to replace conventional paper records, and the possibility of automated diagnosis is being seriously discussed.In my view, however, the medical profession is in danger of being dazzled by optimistic claims about the usefulness of computers in case record processing. The solution to the present problems of record storage and handling is very simple, and does not involve computerization.

Computers↗

[Computer simulation of cell renewal systems].

This paper deals with a block diagram which describes the structure of the control of erythropoiesis by negative feedback loops. The model is transformed into an adequate simulation program using a special block-oriented programming language called ASIM (Analoge SIMulation). For both normal and diseased states of the blood forming process the dynamic responses of the erythrocytes and reticulocytes are simulated by a digital computer analysis. The computer simulation includes different forms of anemia caused by parameter variations as well as by structural alterations. Rising oscillations are obtained too in multiloop control systems containing complex paths with minor loops, which for example take into account the erythrocytic chalones. The described model shows that rising oscillations, that are unstable control loops, can be produced by changing the control-loop structure as well as by parameter changes. In case of malignant disorders such failures becoming effective in oscillations are discussed as parts of disturbed homoeostasis. The results of these studies obtained by simulation should especially stimulate scientists working in the fields of biology and medicine to new test series to verify the proposed hypothesis.

Anemia↗

Computer analysis in clinical electromyography.

Electromyographic findings are traditionally evaluated in terms of the duration, amplitude and shape of the myoelectric potentials as well as the pattern of discharge. Unfortunately, the evaluation is frequently dependent on the examiner's subjective observations with the result that mild, early cases or variations in the typical symptoms of the disease may be missed. To overcome these deficiencies, various approaches employing either analog or digital computer techniques have been explored. Programs have ranged from recognition and measurement of motor unit potentials to quantification of the interference pattern. Studies have also compared completely automatic analysis with operator-computer interaction and measurements performed manually. It is evident that the general format is still in the developmental stage. The prime need at the present time, however, is not only for quantification of the electromyogram but for innovative approaches which will expand our knowledge and increase diagnostic accuracy.

Action Potentials↗

Analyzing stochastic events in multi-channel patch clamp data.

In an effort to understand the gating properties of ionic channels in biological membranes, an efficient method was developed to estimate the kinetic constants from opening-closing events of the channels. Our method is suitable to single channel patch-clamp recordings that contain several ionic channels functioning simultaneously. It is different from the maximum likelihood method previous developed by Horn and Lange, in that our method is a continuum approach and makes uses of analytic expressions of the probability density functions of the event times. Combinatorial analysis was necessary to correctly include more typical multi-channel recordings. This yields computationally quicker results than the method of Horn and Lange, which uses a discretized time series. Model-dependent portions of the code are minimal and easily modified. To illustrate the goodness of our method, we have generated the open-close processes of the patch-clamp records on a digital computer using the exponential random number generators. For multi-channel patches, we have introduced a few plausible approximations to make our algorithm more efficient. The soundness of the our approximations were tested with such measures as the fraction of the open state at time t, Popen (t), and frequencies of the number of openings per run. A copy of the computer code implementing this algorithm can be obtained from the authors.

Computer Simulation↗

Spatial filtering of electron micrographs of negatively stained alpha-amylase crystals.

Images of the alpha-amylase molecule from pig pancreas have been obtained in two projections by the application of spatial filtering techniques to electron micrographs of negatively stained microcrystals of the enzyme. The Fourier filtering was performed on a PPD 11/40 digital computer after microdensitometry on an Optronics P-1000 photoscan system. The set of procedures and programs we employed are described herein. We compared these images with equivalent images obtained by three-dimensional X-ray diffraction analysis using conventional isomorphous replacement at approximately twice the resolution. We find that there is quite good agreement between the two kinds of images, and that a number of gross structural features compare quite well. We conclude that the combination of electron microscopy with digital spatial filtering when applied to protein microcrystals yields very respectable results.

Amylases↗

Mathematical modeling and computer simulation of isoelectric focusing with electrochemically defined ampholytes.

A mathematical model of isoelectric focusing at the steady state has been developed for an M-component system of electrochemically defined ampholytes. The model is formulated from fundamental principles describing the components' chemical equilibria, mass transfer resulting from diffusion and electromigration, and electroneutrality. The model consists of ordinary differential equations coupled with a system of algebraic equations. The model is implemented on a digital computer using FORTRAN-based simulation software. Computer simulation data are presented for several two-component systems showing the effects of varying the isoelectric points and dissociation constants of the constituents.

Journal Article↗

Single photon emission computed tomography of the lung: preliminary results.

Single photon emission computed tomography (SPECT) of the lung was performed, in addition to conventional camera scintigraphy, in 41 patients with pulmonary disorders as well as with regular pulmonary perfusion. For SPECT investigation a rotating gamma camera (Gammatome) was used consisting of a system with a high-resolution parallel-hole collimator interfaced with a digital computer. In 6 of 41 patients the diagnostic accuracy of pulmonary scintigraphy was improved by SPECT. Topographic identification of segmental perfusion defects in pulmonary embolism seems to be particularly promising. Special abnormalities that cannot be assessed by conventional lung imaging are mediastinal hernia and recessus retrotrachealis as a normal variant. For a detailed evaluation of this method a large number of patients must be investigated.

Humans↗

Dynamic-range compression in surface-coil MRI.

The large dynamic range in signal intensity present in MR surface-coil images makes proper windowing and photography difficult. By removing the low-spatial frequency information caused by variations in surface-coil field intensity from the high-spatial frequency information containing the image data, a considerable compression of this dynamic range of signal intensity is possible. To accomplish this, a technique was implemented on a digital computer for use with MR surface-coil image data. The compression was done as a postprocessing option after the patient scan had been completed and therefore did not alter actual scan times. Although the image signal-to-noise was not altered, the ease of photography for most images was improved. Thus, digital dynamic-range compression is a practical technique to aid in surface-coil MRI studies.

Adenocarcinoma↗

[Automated recognition and identification of soft tissue landmarks in cephalematric analysis]

OBJECTIVE: To establish the automatic x-ray cephalometric analysis system to provide the convenient and reliable method for clinical cephalometric analysis. METHODS The graphics, image processing techniques and artificial intelligence was usedand the computer digital image processing and pattern recognition such as median filtering, histogram equalization, Laplacian and Canny edge detection were introduced. To provide the templates of the variable anatomical structures, which could automatically outline the contour lines of the hard and soft tissues. Thirty five cases were measured and analysied with the system. RESULTS: The computer measurements had the same consistency with hand measurements. The system could calculate more precisely and save more time and energy than other systems. CONCLUSION: The system can supply a more convenient and precise measurement for cephalometry.

Journal Article↗

A model that accounts for the interdependence of extent and severity in the automatic evaluation of myocardial defects.

BACKGROUND: The extent and severity are two important parameters when describing a regional defect in myocardial single-photon emission computed tomography (SPECT) perfusion imaging. Intuitively, these two parameters should be independent of each other, but we have shown in a previous study that there is an interdependence. This interdependence has been investigated in two commercially available analysis programs (AutoQUANT and 4D-MSPECT) using Monte Carlo-simulated SPECT data. METHODS: An anthropomorphic digital computer phantom and a Monte Carlo program were used to generate SPECT data. Several defects of different volumes and lesion activity uptake reductions were simulated and evaluated. Comparison of the measures of extent and severity with their corresponding known values led to the development of a correction model based on least-squares parameter estimation. This model was then applied to a test group consisting of 10 different computer-simulated patients. RESULTS: Our results showed that the interdependence was reduced significantly for most of our test cases after applying the correction method. The application of the correction model to the test group demonstrated that the model was robust with respect to different patient geometries. A further test with projections that simulated a perfect SPECT system revealed that the interdependence between the extent and severity was not caused by the limited spatial resolution of the SPECT system, but rather the inherent design of the algorithms of the analysis programs. CONCLUSIONS: A model has been developed to take into account the interdependence of the extent and severity.

Algorithms↗

Computer simulation of after-inhibition in crayfish slowly adapting stretch receptor neuron.

A theoretical model is described which is able to mimic the responses of slowly adapting stretch receptor neurons of crayfish to applied currents. Its principal feature is postspike inhibition, in which each nerve impulses produces a small inhibitory current that decays with a simple exponential time-course that is long compared with normal interspike intervals. The model was simulated with both an analogue and a digital computer. Parameters for particular model neurons were determined both by an analysis of experimental data obtained from adaptation to constant injected currents, and by matching computer output to the data. Parameter values estimated by the two techniques agreed within +/-10%. Model parameters determined from adaptation data successfully predicted the magnitude and time-course of posttetanic hyperpolarization (PTH) in the stretch receptor neuron. In addition, model neurons were able to reproduce posttetanic depression (PTD) as seen in stretch receptor cells.

Animals↗

Spectral analysis of Doppler ultrasonic flow signals by a personal computer.

This paper describes a method of performing spectral analysis on Doppler acoustical signals from peripheral blood vessels with the use of an Apple II plus personal computer. Digitization is accomplished with a commercially available analog-to-digital converter. The data are transformed with a fast Fourier technique, and the resultant information is plotted by an inexpensive X-Y plotter and/or on a television receiver.

Blood Vessels↗

A fuzzy model of the helmsman performing a course-keeping task.

The development of a model that describes the control characteristics of a helmsman whilst course-keeping is reported herein. The basic element of the helmsman model is a fuzzy role-based course-keeping algorithm. The model is used in digital computer simulations to control the non-linear yaw dynamics of a Royal Navy warship model which is subjected to sea state disturbances. For comparison purposes, another helmsman model is developed using linear systems theory. Validation of both models is made by comparing real-time analogue simulation results produced by actual helmsmen with those obtained digitally. Both helmsman models are found to reproduce acceptable yaw response predictions, whilst the fuzzy model more closely approximates the control input of a helmsman.

Journal Article↗

Image editing and computer assisted bitemark analysis: a case report.

Bitemark evidence in a homicide usually involves a perpetrator biting the victim prior to or around the time of death. This paper presents a case in which a homicide victim bit his assailant. A suspect taken into custody was found to have what appeared to be a human bitemark on the proximal phalanx of his right thumb. Scale photographs of this injury were obtained and compared to the dentition of the decreased using digitized computer images for superimposition. Three different approaches for comparison with the bitemark photograph were utilized: comparison with radiographs of amalgam-filled impressions of dental casts, a transparent overlay technique and comparison with photographs of a simulated bitemark inked onto the hand of a volunteer. A review of these techniques as they apply to computerized bitemark analysis is presented.

Adult↗

A computer-oriented system for high-speed recording of operant behavior.

A method is described by which large quantities of data, generated at high and variable rates from a large number of test boxes, are recorded on a single eight-channel punched paper tape. The data, which include a record of the occurrence time of each event in 1/10-sec units, are in a compact form, suitable for conversion to standard Hollerith punched card codes and for decoding and summarizing by a large digital computer. Experience with the system has demonstrated a high degree of accuracy and reliability, and low operating cost.

Animals↗

Computer analysis of normal and basal cell carcinoma mast cells.

BACKGROUND: Basal cell carcinoma (BCC) is the most frequently observed neoplasm of the human skin. Mast cells are regarded as important cellular elements of all organs and tissues of the human body. They are involved in many physiological and pathological processes, including inflammation and fibrotic changes observed in BCC. The aim of our study was to characterise in detail mast cells observed in BCC and normal skin on the basis of computer analysis techniques. MATERIAL AND METHODS: Series of photographs obtained from histopathological biopsies of basal cell carcinomas from 18 patients, stained specifically for mast cells with Astra blue and nuclear red, were employed for the study. Control group consisted of series of photographs from normal skin obtained from 18 persons who underwent plastic surgery operations. All the photographs underwent digital computer analysis by means of a number of subroutines written in Delphi developed at the Technical University of Łódź. RESULTS: Specific staining allowed for thresholding the image and subsequently mast cells were visualised as black objects on a white background. Those objects were then analysed in detail i.e. their geometrical features (area, perimeter, maximal diameter) were calculated. The employed image analysis techniques allowed for the differentiation and detailed characteristics of mast cells stained with Astra blue and nuclear red. CONCLUSIONS: We observed that mast cells in BCC gathered mainly in fibrous stroma and were more numerous, had considerably larger area, longer perimeter and maximal diameter than normal skin mast cells.

Basal Cell Carcinoma↗