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PubMed1987

A microprocessor system for the digital synthesis of pulsed and continuous discharges of electric fish (or animal vocalizations).

Traditionally, the sensitivity of electric fish to electric stimuli has been investigated using a variety of electronically generated signal functions, for example sine, square, and sawtooth waves (both continuous and pulsed). None of these resemble the species- or sex-specific electric organ discharges (EODs) of fish. Therefore, EODs recorded on magnetic tape were used in open-loop playback experiments. However, as shown in the present paper, the waveforms of EODs reproduced from magnetic tape are distorted, and cannot be manipulated with speed and accuracy as to frequency or pulse repetition rate by feedback from the experiment. Good EOD imitations are generated by our microprocessor-based system for the digital synthesis of EODs which is controlled by a small 'personal computer'. Digitized EOD samples edited by computer are output by the fast digital-to-analogue converter of the microprocessor system. This system was devised for the synthesis of pulse-type (discontinuous) and wave type (continuous) EODs with continuous, on-line frequency and amplitude control. The rate of digital synthesis is 500 kHz in pulse-type EODs, and 250-500 kHz in wave type EODs at 0.06-0.24 Hz frequency resolution, depending on the repetition frequency of the synthesized wave EOD. The present paper describes the steps in EOD synthesis, and indicates some applications which benefit from the playback of high-fidelity imitations of natural EODs at amplitudes and frequencies selected by the experimenter, or automatically controlled by feedback from the experiment in closed-loop applications.

Analog-Digital Conversion↗
PubMed1999

Linear circuits for neural networks and affective computing.

Biological phenomena are often modeled with software on digital computers, even though the events may be analog in nature. The author describes the use of linear circuitry in two areas of biological simulation: artificial neural networks and affective computing. The operational amplifier, with the assistance of some new analog chips and simple digital microcontrollers, is featured prominently in these linear designs.

Computer Simulation↗
PubMed1991

Imaging of a parapharyngeal hemangiopericytoma. Radioimmunoscintigraphy (SPECT) with indium-111-labeled anti-CEA antibody, and comparison to digital subtraction angiography, computed tomography, and immunohistochemistry.

A 27-year-old male patient with a parapharyngeal hemangiopericytoma was investigated radiologically with orthopantomography, computed tomography, and digital subtraction angiography before the operation. Because a malignancy was suspected, the patient was imaged with gamma camera using radiolabeled monoclonal anticarcinoembryonal antigen antibody including single photon emission computed tomography. The radioantibody accumulated strongly into the neoplasm. Tumor to background ratio was 2.2. Samples of the excised tumor were stained immunohistochemically for desmin, vimentin, muscle actin, cytokeratin, CEA (carcinoembryonic antigen), and factor VIII. They showed that the antibody uptake was of unspecific nature and not due to CEA expression in the tumor.

Adult↗
PubMed1975

Analysis of motor conduction velocity in the human median nerve by computer simulation of compound muscle action potentials.

A digital computer was used to reconstruct compound muscle action potentials recorded from the human thenar eminence after stimulation of the median nerve. The programme allowed the following parameters to be varied: (1) the dimensions of a representative single motor unit potential; (2) the number of motor units in the muscle and the range and distribution of conduction velocities in their nerve fibres; and (3) the distance along the nerve from the point of stimulation to the muscle. The reconstructed compound muscle action potentials were similar to real compound potentials recorded from normal subjects. The number of single motor units and the range of conduction velocities required for the reconstruction correlated with quantitative histologic studies of the recurrent branch of the median nerve to the thenar muscles. By altering the distribution of conduction velocities it was possible to study the effect of abnormal patterns of nerve conduction on the configuration of the simulated compound muscle action potentials. It was found that abnormally slow conduction caused an increased discrepancy between the main parameters of compound potentials corresponding to stimulation of the nerve at proximal and distal sites. These observations suggest that a careful analysis of the differences between pairs of compound muscle action potentials may provide a method for more detailed assessment of conduction velocity in clinical studies of peripheral nerve disorders.

Action Potentials↗
PubMed1969

Construction of biochemical computer models.

This paper described methods for constructing (digital) computer models of biochemical systems when the main object is to investigate the system itself, and not to fit experimental data (e.g., from tracer kinetics) to a set of equations. The author describes model-building as an art which is difficult to communicate, but nevertheless gives valuable tips on the conceptual and practical aspects, from his own considerable experience.

Journal Article↗
PubMed1992

Personal computer equipment for dental digital subtraction radiography vs. industrial computer equipment and conventional radiography.

A "low-cost" personal computer (PC) system used to digitize dental radiographs was tested by assessing the accuracy of its subtraction images versus those of "high-cost" industrial equipment and conventional radiography. Subtraction images were made of artificial lesions in human femur bone and subsequently evaluated by students and teachers. The observations were analyzed in terms of true positive and false positive reports. "Low-cost" and "high-cost" subtraction images revealed only small differences in diagnostic accuracy. Compared to conventional radiography, the diagnostic accuracy of the subtraction images with the "low-cost" PC system was significantly higher for all observers. The interexaminer variance was similar for the subtraction and the conventional images for both students and teachers, except for a significantly reduced interexaminer variance for the teachers concerning the true positive reports with the "low-cost" PC subtraction technique.

Bone and Bones↗
PubMed1997

The use of digital images in pathology.

Digital images are routinely used by the publishing industry, but most diagnostic pathologists are unfamiliar with the technology and its possibilities. This review aims to explain the basic principles of digital image acquisition, storage, manipulation and use, and the possibilities provided not only in research, but also in teaching and in routine diagnostic pathology. Images of natural objects are usually expressed digitally as 'bitmaps'--rectilinear arrays of small dots. The size of each dot can vary, but so can its information content in terms, for example, of colour, greyscale or opacity. Various file formats and compression algorithms are available. Video cameras connected to microscopes are familiar to most pathologists; video images can be converted directly to a digital form by a suitably equipped computer. Digital cameras and scanners are alternative acquisition tools of relevance to pathologists. Once acquired, a digital image can easily be subjected to the digital equivalent of any conventional darkroom manipulation and modern software allows much more flexibility, to such an extent that a new tool for scientific fraud has been created. For research, image enhancement and analysis is an increasingly powerful and affordable tool. Morphometric measurements are, after many predictions, at last beginning to be part of the toolkit of the diagnostic pathologist. In teaching, the potential to create dramatic yet informative presentations is demonstrated daily by the publishing industry; such methods are readily applicable to the classroom. The combination of digital images and the Internet raises many possibilities; for example, instead of seeking one expert diagnostic opinion, one could simultaneously seek the opinion of many, all around the globe. It is inevitable that in the coming years the use of digital images will spread from the laboratory to the medical curriculum and to the whole of diagnostic pathology.

Humans↗
PubMed1999

The promise of computer aided detection in digital mammography.

Computer-aided detection (CAD) is a new technology now being implemented in many clinics to reduce the false negative rate in mammography screening. A large clinical study has been completed which shows that a substantial false negative (miss) rate exists in screening mammography, a significant fraction of the missed cancers are not subtle, and CAD has high sensitivity to these missed cancers. Full field digital mammography is now coming on the scene, but has not yet been proven in clinical practice. The authors believe that full acceptance of the new digital technology depends not merely on demonstrations of 'substantial equivalence' to film-screen technology, but rather on more complete exploitation of the unique advantages of digital technology, and that CAD can play a key role. These advantages derive from CAD's ability to quickly (in near real-time) perform analytical computations on digital information that is not readily available to the radiologist until after the cost of film-processing has occurred.

Breast Neoplasms↗
PubMed1999

The Visible Human Project: a resource for education.

Throughout recorded history, the relationships between biological structure and function have been central to the understanding of health and disease. For many centuries, the anatomy illustrations originally created during the medieval period formed the basis for the study of medicine. But learning and understanding anatomic structures is limited by the fundamentally two-dimensional images traditionally used to teach them. The digital computer now allows scientists to acquire, store, manipulate, and display complex images. In 1989, the National Library of Medicine (NLM) began a project to use computer technologies to build a prototype digital image library of data representing a complete normal adult human male and female. In this paper, the author describes the beginnings of this project, the Visible Human Project (VHP), the digital images currently available in the VHP database, ongoing research and development, and plans for the future of the VHP.

Adult↗
PubMed1988

Relative contributions of the nasal septum and airways to total nasal capsule volume in normal and cleft lip and palate fetal specimens.

The present study examines the relative contributions of the nasal septum and airway volumes to the total volume of the fetal nasal capsule. For comparative purposes, 29 human fetal specimens (20 "normal" and 9 with cleft lip and palate (CLP] were celloidin embedded, sectioned, and stained with hemotoxylin and eosin. The specimens ranged from 8 to 21 weeks in postmenstrual age. Photomicrographs of the serial sections allowed selected anatomic structures to be computer digitized, reconstructed as three-dimensional computer representations, and quantified. Various nasal capsule component measurements were compared with overall nasal capsule size values, producing relative size indices. Significant differences (p less than 0.05) were noted between the "normal" and CLP fetal samples in the relative sizes of the nasal capsule, airways, and septum. Relative mean CLP nasal capsule volume was 14% smaller than normal, relative mean CLP airway volume was approximately 43% smaller than that of the normal specimens, whereas relative mean CLP septum volume was approximately 45% larger. Aspect ratios (i.e., height:width ratios) were utilized for shape analysis of the nasal septal cartilage and indicated that the CLP septal shape was one of increased width relative to height compared with normal specimens. Results were consonant with clinical impressions of nasal capsule deficiency in the CLP nasal capsule and revealed some new structural associations in the fetal nasal capsule.

Airway Obstruction↗
PubMed1980

Computer recognition of cardiac arrhythmias.

The current status of systems for computer recognition of cardiac arrhythmias for routine clinical electrocardiography and for rhythm monitoring has been presented. The goal is to approach the pattern recognition capabilities of the human observer and to add the advantages of the computational prowess and indefatigability of the digital computer. The accuracy of the methods obviously depends on the population studied; excellent results in screening of normals contrast with poorer achievement in patients with complex arrhythmias. The other factors involved include high quality (noise-free) ECG recordings, parameter measurement accuracy, the degree of program sophistication, and the role of human intervention in the various systems. The future looks extremely promising for both computer applications for ECG arrhythmia analysis. The important factors to be considered have been presented at the Tenth Bethesda Conference on "Optimal Electrocardiography" in April 1977. The establishment of "gold standard" tapes for both routine and monitored ECG recordings will provide vital data for evaluation of all systems. There is an ongoing, constant upgrading of recording and computer equipment, data transmission methods, and program sophistication together with continual cost reduction. With this rapid progress, computer analysis of cardiac arrhythmias can be expected to achieve routine application in our cardiologic diagnostic armamentarium.

Arrhythmias, Cardiac↗
PubMed1993

Phosphor plate computed radiography: response to variation in mAs at fixed kVp in an animal model. Potential role in neonatal imaging.

Computed digital radiography offers a number of potential advantages over conventional film-screen imaging. To determine the applicability of these to portable neonatal examinations we performed a controlled prospective study comparing conventional 200 speed film-screen with a computed radiography unit in an animal model. Images acceptable for diagnostic purposes were obtained on the digital system over an exposure range many orders of magnitude greater than was possible on the film-screen system. Digital imaging offers potential for elimination of repeat examinations due to suboptimal exposure factors, and for reduction in radiation dose to the patient. We believe that computed digital radiography should be particularly suited to portable neonatal imaging.

Animals↗
PubMed1994

Computer vision and artificial intelligence in mammography.

The revolution in digital computer technology that has made possible new and sophisticated imaging techniques may next influence the interpretation of radiologic images. In mammography, computer vision and artificial intelligence techniques have been used successfully to detect or to characterize abnormalities on digital images. Radiologists supplied with this information often perform better at mammographic detection or characterization tasks in observer studies than do unaided radiologists. This technology therefore could decrease errors in mammographic interpretation that continue to plague human observers.

Artificial Intelligence↗
PubMed2005

A comparative study of rectal dose histograms in prostate brachytherapy: some analytic and numerical results.

A cumulative dose histogram is the graph of an integral function integrated over a domain VCR3 and is dubbed the dose-volume histogram (DVH), the dose-surface histogram (DSH) or the dose-wall histogram (DWH), depending on the dimension and structure of the region V. This paper presents a comparative study of the three rectal dose histograms for sixty patients as well as for a cylindrical model of the rectum; in particular, the DSH and DVH for the cylindrical model with one point source are computed analytically in terms of elliptic integrals. The difference among the three relative dose histograms, averaged over the sixty patients, is less than 5%, whereas that between DVH and DWH for various wall-thickness can be as large as 3-12 cm3 in the range 60-100 Gy. The paper also contains an error analysis using two simple models of the rectum, for which the true DSH and DWH can be computed via numerical integration, to evaluate the effect of digitization. The digitized computation agrees quite well with the pre-digitization numerical integration, within 1% or 0.2 cm3, because of the low dose-gradient effect near the rectum in prostate brachytherapy.

Body Burden↗
PubMed1998

Computer anxiety: a comparison of pen-based personal digital assistants, conventional computer and paper assessment of mood and performance.

The recent growth of pen-based devices, such as the Personal Digital Assistant (PDA), offer mobility and a more natural interface than that of a conventional computer. The feasibility and application of the PDA for mood and cognitive assessment were investigated by examining possible interactions of individual characteristics and administration medium. Previous studies have provided evidence that individual characteristics of 'computer anxiety' and 'private self-consciousness' divergently covaried with mood scores measured by computer and paper methods. To investigate the relationship between individual characteristics and medium effects, 136 paid participants were allocated to and completed mood assessment tasks and a short battery of cognitive tasks by either the computer, PDA or the paper method. Self-ratings of mood measured by these three modalities covaried divergently with measures of computer anxiety and private self-consciousness. In addition, computer anxiety covaried with reaction time on the visual search task obtained on computers, but there was no such relationship when measured by a PDA. These results show that computer anxiety can affect the results of assessments of cognitive function as well as of mood ratings, and suggest that pen-based systems may have advantages over conventional computers in this respect.

Adolescent↗
PubMed1981

Progress in computer analysis of the exercise electrocardiogram.

The potential advantages of digital computer processing of exercise electrocardiographic data include reduction of noise, compression of data, improved precision and application of optimal criteria. Most prior approaches to such processing required equipment that was both expensive and inconvenient. With the revolution in instrumentation brought about by the development of microcomputers, powerful dedicated computers can now be afforded by many exercise laboratories. There are many approaches to computerized management of exercise electrocardiographic data and various criteria for ischemia. Studies are necessary to validate computer algorithms so that these devices can be used diagnostically to best advantage. Cardiologists need some understanding of this field so that they can be discriminating users of computer systems. In addition, the results of studies correlating electrocardiographic changes with radionuclide methods of assessing myocardial perfusion and function should enable such assessments to be made from the electrocardiographic signals alone, particularly when aided by computer analysis of spatial shifts.

Angina Pectoris↗
PubMed1981

Efficient computer subroutines for interconversion of oxygen tension and saturation.

Two digital computer subroutines are described. NORSAT computes human hemoglobin saturation from oxygen tension data; NORINV performs the inverse computation. Each subroutine is based on an algorithm that is a direct mathematical inverse of the other. The effects of nonstandard conditions of temperature, pH, and CO2 tension on the saturation curve can be computed. The relative efficiency of these subroutines is compared to that of published subroutines having similar function. The new subroutines use computer time more efficiently with no loss of accuracy. The subroutines are provided in FORTRAN in a form suitable for direct inclusion in a number of user-specified programs.

Computers↗
PubMedDate not supplied

1978 memorial award paper: a computer-aided technique for overlaying cerebral angiograms onto computed tomograms.

We have developed a method which uses a digital computer to combine angiographic images of the cerebral vasculature with a computed tomogram of the brain. The procedure is simple and could be implemented in any radiology department equipped with both a CT scanner and a bi-plane angiography suite. We have performed the entire process in prototype on phantoms and on a patient and have produced images that appear accurate and informative.

Brain↗