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The fetal imaging workstation demonstration project.

Congenital birth defects are a leading cause of infant mortality. Early detection of fetal anomalies by prenatal ultrasound may improve clinical outcome in selected cases. However, many training programs are hindered by curriculum weaknesses which include: (1) limited physician exposure to ultrasound anomalies; (2) inadequate postnatal correlation with prenatal findings; (3) constraints imposed by static images for ultrasound training; and (4) difficulty with understanding complex three-dimensional anatomy. The Fetal Imaging Workstation Demonstration Project addresses these problems by illustrating how computers can supplement traditional prenatal ultrasound training through interactive multimedia. The project uses a laserdisc library of ultrasound video images as source material for a variety of interactive software tutorials. An educational testing module has been developed that can evaluate diagnostic skills through simulated ultrasound studies provided by the laserdisc library. An interactive three-dimensional fetal heart model also provides a new way for physicians to better understand their two-dimensional ultrasound studies. A survey suggests that this prototype has been widely accepted by housestaff physicians and that there is a perceived need for this supplementary training. Future work will address the educational effectiveness of these materials and will consider cost-effective ways to disseminate the software for other institutions. However, future development must be implemented against a background of rapidly emerging technologies involving faster computers, digital video, and virtual reality applications.

Computer Systems↗

How to convert a traditional electron microscopy laboratory to digital imaging: follow the 'middle road'.

Today, electron microscopy (EM) is increasingly confronted by the revolution in image-processing technology provoked by modern computers. Digital cameras are fast replacing film-based cameras in EM, as elsewhere, and the procedures for digital image-archiving, image-analysis, and image publication are rapidly evolving. To take advantage of these advances, we have chosen for the moment a 'middle road', in which film remains our basic recording medium in the electron microscope, but immediately thereafter, all film-based images are converted to digital files for further analysis and processing. The rationale behind this approach is that film still offers far greater sensitivity and resolution (providing an image equivalent to > 10,000 pixels per inch in a 1-s exposure), and film is still far easier to organize and archive than digital images of comparable resolution. However, digital manipulation of EM images has become mandatory. Hence, we explain here, in some detail, how we convert from film to digital.

Animals↗

Uptake ratio of (19-1311) cholesterol by adrenal glands as observed by a scintigraphic method.

The adrenal scintigram was performed after administration of [19-131I] cholesterol. A high/low ratio of both adrenal glands was calculated to evaluate whether there is a difference between the left and right sides in adrenal diseases. During scanning, information was stored in a 64 X 64 matrix and then punched out on a computer compatible paper tape. This paper tape was processed with a small digital computer. The areas of interest were selected over adrenal glands. The computer decided mean counts per unit area. After subtraction of background counts, a high/low ratio of adrenal gland was calculated. In five patients with Cushing's syndrome due to bilateral hyperplasia, a high/low ratio ranged from 1.0 to 2.0. In four patients with primary aldosteronism due to adenoma, a high/low ratio ranged from 1.33 to 4.0. This method may be useful to differentiate bilateral hyperplasia from unilateral adrenocortical adenoma.

Adenoma↗

[Reliability of the ECG analyzer EAK-2 in screening tests].

In the last years the number of derivated electrocardiograms with several approaches to the problem has permanently increased. Therefore, the computer analysis seems to be obvious. The reliability of the analogo-digital-computer Express Analyzer Cardiograph EAC-2, Medexport Moscow, was for the employment for occupational medical examinations investigated on 252 experimental persons and compared with the independent manual analysis, which was carried out by two physicians. 80 per cent of the available ECGs were automatically correctly arranged into groups and all the inconspicuous electrocardiograms were sorted out, since it occurs on no account that an electrocardiogram which was recognized as pathological by means of manual analyses, was analysed as falsely normal by the computer EAC-2. Consequently, EAC-2 at low technical interference susceptibility may be very useful for the ECG-diagnosis by means of the computer during the screening investigations.

Arrhythmias, Cardiac↗

Differences in action potentials and accommodation of sensory and motor myelinated nerve fibres as computed on the basis of voltage clamp data.

1. Voltage clamp experiments were performed on sensory and motor nerve fibres of the frog using a digital computer for automatic experiment control and data recording. 2. Rates of rise and maximum amplitudes of potassium currents were determined in both sensory and motor fibres, so that comparative values of n infinity and tau-n could be obtained. 3. The results indicate that the n infinity-V curve for sensory fibres is displaced from the curve for motor fibres in a depolarising direction. The potassium kinetics are similar in both for voltage steps up to about - 20 m V, beyond which tau-n becomes progressively smaller for sensory than for motor fibres. 4. These comparative values of n affinity and tau-n have been used to calculate alpha-n and beta-n values for a model "motor" action potential by considering the Frankenhaeuser-Huxley computed action potential to be "sensory". This modification of the potassium system, together with some alteration to the sodium inactivation system produces a satisfactory model "motor" action potential. 5. The model sensory and motor action potentials behave quite similarly to their experimentally recorded counterparts with respect to action potential shape and relative duration, repetitive firing, accomodation and the simulated action of T.E.A.

Action Potentials↗

Single-exposure conventional and computed radiography image acquisition.

A technique for simultaneously acquiring a conventional film-screen radiographic image and a digital computed radiography (CR) image with a single x-ray exposure is described. Measurements of image contrast, spatial resolution, and signal-to-noise ratios demonstrate that a modified film cassette in which the first intensifier screen has been replaced with a CR imaging plate permits dual-image, single-exposure imaging with only nominal degradation in film and CR image quality relative to the two standard image counterparts. This technique may be used to acquire matched image pairs for research or as a way to provide full-size conventional film images in the clinical environment, while retaining the advantages offered by computed radiography systems.

Humans↗

[Effect of alternating milieu changes on specific substrate consumption in microorganisms].

In technical microbiology microorganisms often undergo alternating milieu changes. For instance, this is the case in recirculation reactors. The organisms react on these changes with an increase of entropy production and in connection with this with increasing substrate consumption. This increasing substrate consumption contradicts the aim of an optimum yield from a given substrate. Thus, studies of the reaction of microbial growth to alternating milieu changes are of great importance. A simple model of the influence of alternating milieu changes on specific substrate consumption is given. In it the biological conversion of substances is built up by an irreversible consecutive reaction. After preliminary examinations on the analogue computer the reaction of the model to alternating perturbations is simulated on the digital computer. The results of the stimulations are compared with experimental data. The good agreement of experiment and model justifies the use of the simple formulation in the preparation of technical processes.

Candida albicans↗

The use of computers in pharmacokinetics.

A review of computer applications is presented, and several examples of the use of analog and digital computers are given. Special attention is given to fitting the time concentration data to the one, two or more exponential equations, for estimation of pharmacokinetic parameters, for dosage regimen of drugs and for evaluation of bioavailability.

Biological Availability↗

Computer analysis of micturition parameters and accuracy of uroflowmeter.

Several micturition parameters in healthy volunteers have been studied with digital computer analysis. The accuracy of the uroflowmeter has also been tested. Total voiding time, average flow rate, maximum flow rate, volume and time at maximum flow rate are all the function of volume voided. The first half of urinary volume is rapidly evacuated in the first one third of the total voiding time, and the rest in the remaining two thirds of the voiding period. When the constant stream hits at the center of the disk, the response of the flowmeter is fairly good. Once the urinary stream is accelerated and/or hits at the edge of the disk, the response is not reliable.

Adolescent↗

A computer analysis of serial interactions in spaced responding.

Serial dependencies in interresponse times were studied by means of a digital computer. In monkeys exposed to a DRL 20-sec schedule of reinforcement, serial interactions appeared at all stages of training. Early in training the serial effects consisted of trains of relatively long interresponse times interspersed among trains of relatively short ones. Later on, the serial effects appeared to be characterized by a tendency to drift up and down in long wavelength periods around the minimum interval required for reinforcement. After training to a point at which most interresponse times produced reinforcement, serial effects of a still more subtle nature appeared. These effects were made apparent by autocorrelation and power spectrum methods and consisted of both long-term and extremely short-term fluctuations in interresponse times.

Animals↗

Acquisition of gamma camera and physiological data by computer.

We have designed, implemented, and tested a new Research Data Acquisition System (RDAS) that permits a general purpose digital computer to acquire signals from both gamma camera sources and physiological signal sources concurrently. This system overcomes the limited multi-source, high speed data acquisition capabilities found in most clinically oriented nuclear medicine computers. The RDAS can simultaneously input signals from up to four gamma camera sources with a throughput of 200 kHz per source and from up to eight physiological signal sources with an aggregate throughput of 50 kHz. Rigorous testing has found the RDAS to exhibit acceptable linearity and timing characteristics. In addition, flood images obtained by this system were compared with flood images acquired by a commercial nuclear medicine computer system. National Electrical Manufacturers Association performance standards of the flood images were found to be comparable.

Humans↗

[Correlation between ventricular volume calculated manually and by computer].

We present here a program of ventricular volumes measurements in which an area-lenght procedure and a digital computer were used. The results were compared with those obtained by the manual method using the same formula. The correlative estatistical analysis of these results showed a high index of 0.95 when compared to the telediastolic volumes obtained by both technics, while the index reached 0.99 in reference to the telesistolic volumes and the ejection fraction.

Anthropometry↗

[Differentiation of benign from malignant pulmonary nodules with the digital analysis of computed radiography].

To differentiate benign pulmonary nodules from malignant nodules, digital analysis of computed radiography (CR) was performed retrospectively. A total of 142 histologically or clinically proved cases were studied. Digital analysis was performed using the method of gradient processing reported by Sherrier et al. Gradient number with and without background trend correction and gradient number corrected by L-value were obtained from the raw data of CR. The mean gradient of 93 malignant nodules was significantly different from that of 49 benign nodules. The analysis of gradient number without background trend correction and L-value correction was most sensitive. Seven radiologists evaluated these nodules as to benign or malignant, status, degree of calcification and homogeneity. A correlation was found between the detectability of benign nodules and degree of calcification. In conclusion, CR-gradient analysis is useful as a screening test to differentiate benign nodules from malignant ones.

Diagnosis, Differential↗

An economical, semi-automatic system for measuring cellular tree structures in three dimensions, with special emphasis on Golgi-impregnated neurons.

The hardware and software of a semi-automatic system are described for the measurement of cellular tree structures in thick microscopical sections such as the process of Golgi-impregnated neurons. With this system, the morphologist--viewing the neuron directly through the microscope--measures the tree structures using three cartesian coordinates of characteristic points, e.g. centre of cell, origin of processes, bifurcation points, end points, deflection points, etc. The system requires an on-line computer, but does not demand a dedicated computer since a joy-stick generator usually drives the microscopical stage during cell tracking. A digital computer is utilized for acquisition of data, and, when needed, to return the stage to a required position. The microscope stage is coupled to three stepping motors with 0.5 micron as the smallest step. The stepping motor for movement of the stage parallel to the optical axis (z-direction) is coupled directly to a spindle mechanism, replacing the original cog wheel mechanism. This construction shows no measurable backlash. The practical advantages of this new measuring system in relation to the existing digital systems currently in use, its accuracy and its costs, are discussed.

Animals↗

Digitally reconstructed fluoroscopy and other interactive volume visualizations in 3-D treatment planning.

PURPOSE: Add radiographic context to the beam's-eye-view used in 3-dimensional treatment planning. Improve methods for interactive visualization of anatomy and dose distributions. METHODS AND MATERIALS: Most 3-dimensional treatment planning systems feature a beam's-eye view that includes only graphical representations of patient anatomy. With input devices such as a mouse or trackball, the user interactively shapes the treatment field using the graphical models to provide geometric information. Radiographic context provides additional geometric information important for determining field shape. We have implemented digitally reconstructed fluoroscopy in the beam's-eye view by increasing the efficiency for computing digitally reconstructed radiographs. In addition we have improved algorithms for real-time surface and volume rendering for anatomy and doses using an experimental graphics supercomputer. RESULTS: Without radiographic context in the beam's-eye-view, field shapes were sometimes changed after simulation or portal images were obtained. Digitally reconstructed fluoroscopy has essentially eliminated these changes. Higher quality interactive three-dimensional displays improve the comprehension, confidence and efficiency of the user. Our improvements have already been implemented on one model of a new generation of commercial graphics workstations. CONCLUSION: Addition of radiographic context to the beam's-eye-view is recommended. Incorporation of higher quality interactive graphics is rapidly becoming practical and is encouraged.

Computer Simulation↗

A flexible signal-averaging system for cardiac waveforms.

The repetitive nature of cardiac waveforms renders them suitable for processing by signal averaging. A flexible system is described, based on a general-purpose digital computer, capable of averaging a variety of cardiac signals in excess of 0.5 microV containing frequency components below a theoretical Nyquist limit of 5 kHz. Important features of the system include real-time processing capability at a high level of interactive control, and the facility to trigger the averaging process accurately from any part of either the data or a synchronous reference waveform. Application of the system to electrocardiographic and phonocardiographic signals at conventional gain has enabled clinically useful records to be obtained in the face of obtrusive environmental noise. The averaging of signals of a similar nature after considerably increased amplification has revealed cardiac activity unseen in conventional records in a total of 81 subjects.

Analog-Digital Conversion↗

Towards computing with proteins.

Can proteins be used as computational devices to address difficult computational problems? In recent years there has been much interest in biological computing, that is, building a general purpose computer from biological molecules. Most of the current efforts are based on DNA because of its ability to self-hybridize. The exquisite selectivity and specificity of complex protein-based networks motivated us to suggest that similar principles can be used to devise biological systems that will be able to directly implement any logical circuit as a parallel asynchronous computation. Such devices, powered by ATP molecules, would be able to perform, for medical applications, digital computation with natural interface to biological input conditions. We discuss how to design protein molecules that would serve as the basic computational element by functioning as a NAND logical gate, utilizing DNA tags for recognition, and phosphorylation and exonuclease reactions for information processing. A solution of these elements could carry out effective computation. Finally, the model and its robustness to errors were tested in a computer simulation.

Adenosine Triphosphate↗

Ventilatory and gas exchange dynamics in response to sinusoidal work.

The dynamic relationships between ventilation and gas exchange variables during exercise were determined utilizing frequency analysis techniques. Five subjects exercised on a cycle ergometer for 30 min at work rates which fluctuated sinusoidally between 25 W and 80% of the anaerobic threshold at sinusoidal periods of 0.7, 1,2,4,6, and 10 min. VE, VCO2, VO2, and HR were computed and displayed breath-by-breath. From these and steady-state response data, digital computer routines extracted amplitude and phase relations between each variable and the perturbing work load. These response characteristics were well described by first-order linear dynamics with time constants for VE, VCO2, VO2, and HR averaging 1.4, 1.2, 0.8, and 0.8 min, respectively. The time constants of VE and VCO2 were strongly correlated among subjects (r = 0.97). Further, there was no evidence that neural afferents from the exercising limbs induced fast components in the ventilatory response to these forcings. These results are consistent with the hypothesis that exercise hyperpnea is linked to metabolism via carbon dioxide production.

Adult↗