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PubMedDate not supplied

Anatomical macroelements in the study of craniofacial rat growth.

In order to avoid the arbitrary division of biological structures, rational polynomial interpolants are utilized to study growth. The major advantage of this method is the elimination of artificial internal element boundaries through anatomical structures. Since the boundary element methodology is employed in the finite element setting, other benefits, without additional computer coding, include the ability to use elements with any number of sides and reference frame invariance. Longitudinal landmark coordinates from midsagittal X-ray tracings of 22 albino female rat skulls of various ages were averaged. The skull was partitioned into three macroelements: a neural skull and two functionally distinct portions of the facial skull--olfactory and respiratory. The digital computer programming was carried out in the computer mathematics environment of Mathematica. Maximum elongation ratios were calculated for approximately 400 interior points. The elongation ratios in the neural skull compared well with previously documented growth behavior of internal brain structures. The calculated ratios from the facial skull were used to analyze the behavior of macroelement interpolation close to common anatomical boundaries.

Animals↗
PubMedDate not supplied

New diagnostic approach to brain lesions in nuclear medicine. Differential diagnosis of brain lesions with a computed brain scan diagnosis by the likelihood method.

Using 240 true positive brain scans, a computer system for the differential diagnosis of brain lesions has been evaluated. Eighty-six parameters were extracted from brain scan findings without relationship to neurological signs and symptoms, and the likelihood method was adopted as an example of mathematical logic. The results of our experiment indicated that the overall accuracy was 77 per cent for the maximum likelihood method. The digital computer gave satisfactory results, particularly for diseases such as infarct, meningioma, acoustic neurinoma, and subdural hematoma. In spite of several problems to be solved, this method could provide invaluable help in differential diagnosis of brain lesions.

Arteriovenous Malformations↗
PubMed1999

Digital dental radiographic identification in the pediatric, mixed and permanent dentitions.

The purpose of this paper is to investigate the utility of digital dental radiographic superimposition in the various stages of development of the human dentition. Digital, computer assisted dental identification is a means of identification which allows the spatial relationships of the root and support structures of the teeth to be compared one to the other. The technique has not been tested in patients with developing dentitions. Dental radiographs from patients in the pediatric, mixed and permanent dentition stages of development, simulating "antemortem" and "postmortem" radiographs, were digitized using a flat field radiograph scanner. Anatomic features were used as points of comparison utilizing image editing software whereby anatomic sections were digitally cut from the antemortem image and compared to the same anatomic locations on the postmortem image to assess for points of concordance. The technique was applied to 25 cases within the primary dentition, 25 cases within the mixed dentition and 25 cases within the permanent dentition. Results showed that this was a viable technique within both the pediatric and permanent dentition although it was of little value within the mixed dentition.

Adult↗
PubMedDate not supplied

Automated myocardial edge detection on MR images: accuracy in consecutive subjects.

The authors previously demonstrated the feasibility of graph-searching-based automated edge detection in cardiac magnetic resonance (MR) imaging. To further assess the clinical utility of this method, unselected images from 11 consecutive subjects undergoing clinically indicated (except for one healthy volunteer) short-axis spin-echo MR imaging were analyzed. A total of 142 images from the 11 subjects, encompassing the left ventricle from apex to outflow tract, were analyzed. The computer algorithm correctly identified complete endocardial and epicardial contours in 121 of 142 images (85%). Correlations between observer-traced and computer-derived epicardial areas for all images were good (r = .71 for epicardium, r = .83 for endocardium); they improved for a subset of higher-quality images (r = .82 for epicardium, r = .92 for endocardium). The authors conclude that the current data further support the usefulness of computer digital image processing in geometric analysis of cardiac MR image data.

Adolescent↗
PubMedDate not supplied

Accuracy and precision of computer-simulated tissue temperatures in individual human intracranial tumours treated with interstitial hyperthermia.

Accurate knowledge of tissue temperature is necessary for effective delivery of clinical hyperthermia in the treatment of malignant tumours. This report compares computer-predicted versus measured intratumoral temperatures in 11 human subjects with intracranial tumours, treated with a conceptually simple 'conductive' interstitial hyperthermia system. Interstitial hyperthermia was achieved by the use of parallel arrays of implanted, electrically heated catheters. The tissue was warmed by thermal conduction and blood convection. Simulation of intratumoral temperatures was achieved by solving a modified bioheat transfer equation on a digital computer using a finite difference method. Comparison of intratumoral temperatures from simulations and measured values differed by about +/- 0.75 degrees C. Further analysis of computed temperature distributions between catheters revealed a rapidly computable relationship between the local minimum tumour temperature and nearby catheter power and temperature that accounts for effects of varying blood flow. These findings suggest that 'on-line' prediction and control of local minimum tumour temperatures are feasible with the conductive interstitial technique.

Adult↗
PubMed1997

A Neural Approach to the Underdetermined-Order Recursive Least-Squares Adaptive Filtering.

The incorporation of the neural architectures in adaptive filtering applications has been addressed in detail. In particular, the Underdetermined-Order Recursive Least-Squares (URLS) algorithm, which lies between the well-known Normalized Least Mean Square and Recursive Least Squares algorithms, is reformulated via a neural architecture. The response of the neural network is seen to be identical to that of the algorithmic approach. Together with the advantage of simple circuit realization, this neural network avoids the drawbacks of digital computation such as error propagation and matrix inversion, which is ill-conditioned in most cases. It is numerically attractive because the quadratic optimization problem performs an implicit matrix inversion. Also, the neural network offers the flexibility of easy alteration of the prediction order of the URLS algorithm which may be crucial in some applications. It is rather difficult to achieve in the digital implementation, as one would have to use Levinson recursions. The neural network can easily be integrated into a digital system through appropriate digital-to-analog and analog-to-digital converters.

Journal Article↗
PubMed1993

Computer algorithm offers a comprehensive view of quantitative bacteriuria.

Using improved microscopy of urine sediment, the consistent finding of bacteria, usually gram-positive cocci at low counts, free or even in casts, in the sediment of carefully collected urines from patients with systemic illnesses has led to the need to reconsider their exclusion by the customary criteria for 'significance' of bacteria in urine. Since 'significance' is currently based upon mathematical assumptions limited to high counts (> 10(5) colony-forming units/ml) for the prediction of clinical pyelonephritis alone, a digital computer program was created to predict the full spectrum of the expected concentration of bacteria in bladder urine versus time for a very wide range of possible bacterial division times, bladder kinetics and urine flow rates. Curves generated resulted in the discovery of very simple rules based on an easily calculated discriminant, the host's critical division time (CDT) for any bacterial species in his urine. (1) If the division time in the urine of a species entering the urinary tract is shorter than the CDT, the bacteria will proliferate to > 10(5) cfu/ml. Published data on growth in human urine show that very few bacterial species can divide so fast in urine, and those are the ones currently considered 'significant'. Except for some enterococci, streptococci cannot. (2) With a division time only marginally longer than the CDT, any bacterium would wash out unless continuously supplemented via the kidney or from the bladder wall. (3) With a continued supplement and the longer division time, the concentration would fall to a low plateau, and that plateau is diagnostic of a continued supplement. The cocci observed by microscopy are fastidious or dead. They grow poorly if at all in urine, and thus are not likely to ascend the urinary tract. Their appearance corresponds to the earlier studies of bacteriuria and to the known excretion of blood-borne bacteria in natural disease, whether or not there are anatomical changes in the kidney. It is suggested that the low-level coccal bacteriuria found is a marker for scent bacteremia in many systemic diseases for which a bacterial provocation has been sought.

Algorithms↗
PubMed1998

Hip joint fluid: detection and distribution at MR imaging and US with cadaveric correlation.

PURPOSE: To define the magnetic resonance (MR) imaging appearance of a hip effusion. MATERIALS AND METHODS: Fifty-two asymptomatic hips in 26 volunteers aged 20-37 years and five fractured hips were imaged at 1.5 T with T2-weighting in three planes. Images were computer digitized and analyzed for hip fluid volume and visually assessed for the presence and width of fluid pockets (in millimeters) seen in the acetabular notch; recesses anterior, posterior, and lateral to the femoral head; and recesses anterior, posterior, and medial to the femoral neck. Cadaveric hips were also injected with graduated amounts of saline (1-20 mL), and sequential MR and ultrasound images were obtained. RESULTS: Computer analysis yielded an average fluid volume of 2.7 mL (range, 0.7-5.6 mL) in asymptomatic and 6.1 mL (range, 1.7-11.6 mL) in symptomatic hips. The mean difference between the right and left hips was 0.8 mL (range, 0.0-2.9 mL). Discrete fluid pockets, sometimes measuring greater than 5 mm in width, were commonly seen in asymptomatic hips. Distention of the capsule by at least 5 mm along the length of the femoral neck was almost always seen after injection of 5 mL of saline and was consistently seen after injection of 10 mL of saline into cadaveric hips. CONCLUSION: Fluid adjacent to the entire length of the femoral neck, measuring at least 5 mm in width, is compatible with a joint effusion.

Acetabulum↗
PubMed1982

Factors regulating serial dependencies in the discharge patterns of nerve cells: a computer simulation study in relation to dorsal spinocerebellar tract neurones.

This study was undertaken to investigate the factors which may contribute to the strong negative correlation between successive interspike intervals which characteristically occur in the discharge of dorsal spinocerebellar tract (DSCT) neurones. This correlation is reflected by a first-order serial correlation coefficient (R1) which is often less than --0.6(17). This strongly negative correlation would be expected to increase the rate at which the DSCT neurone transmits information from peripheral receptors. A model of a DSCT neurone has been developed and simulated on a digital computer. It was found that the discharge pattern of the model could be very similar to that of a real DSCT neurone and the value of R1 could be less than --0.6. In order for such values of R1 to be generated, a number of conditions had to occur simultaneously. These were that the discharge of the excitatory presynaptic fibres impinging on the neurone had to be fairly regular, that the overall range of firing frequencies on these fibres had to be rather small and that the mean firing rate of the neurone had to be about double that of each presynaptic fibre. Provided these 3 conditions were met, the precise properties of the model were relatively unimportant. Parameter values derived from biophysical studies of real DSCT neurones fulfilled these conditions.

Action Potentials↗
PubMed1971

Pharmacokinetic model for the successive demethylation and biliary secretion of methyl orange in the rat.

1. A one-compartment pharmacokinetic model was developed in which a drug underwent two successive metabolical reactions (for example, metabolism followed by conjugation) and free drug and both metabolites were excreted.2. Techniques were described whereby graphical estimates of the first-order rate constants may be derived from cumulative excretion data on the drug and its metabolites. Computer simulation techniques were used to show that the experimental data permit reasonably accurate estimation of the rate constants of the model by graphical and computer methods.3. Tritiated methyl orange (2 mg) was administered to five groups of six rats with biliary cannulation. The bile produced by each animal was collected at hourly intervals for 6 h and the amounts of methyl orange and its metabolites, 4'sulpho-4-methylaminoazobenzene and 4'sulpho-4-aminoazobenzene, determined by thin layer chromatography and radioactive counting techniques.4. The data were analysed graphically and with an iterative digital computer programme to yield the first-order rate constants for the successive demethylation steps in the metabolism of methyl orange. The removal of the first methyl group had a rate constant of 0.684+/-0.142 h(-1) (+/-S.D.) and the second methyl group 1.00+/-0.302 h(-1). The rate constant for biliary excretion of the free methyl orange was 0.164+/-0.042 h(-1), for the monomethyl derivative 0.672+/-0.461 h(-1), and for the demethylated metabolite 6.413+/-3.222 h(-1).

Animals↗
PubMed1980

[Atrial fibrillation process studied in clinical practice by using statistical analysis methods].

The results of studying the electrical activity of the atria in 53 patients with cardiac fibrillation by means of a special digital computer system are discussed. On the strength of the aggregate of amplitude, rate, and morphological characteristics, three varieties of fibrillation waves are distinguished. It is shown that in the absence of cardiotropic therapy, the principal regular features in the distribution of the ff waves according to the frequency ranges are preserved in one and the same patients for a long period of time. A characteristic dynamics of changes in atrial activity during treatment with preparations of digitalis was disclosed, which may be an additional criterion of digitalization. A connection was revealed between the changes in atrial activity during treatment with digitalis preparations and the characteristic dynamics of the ventricular rhythm structure. The absence of such correlative connection may be evidence of the possible occurrence of atrioventricular block after restoration of the sinus rhythm.

Adult↗
PubMed1984

Modeling acoustic attenuation of soft tissue with a minimum-phase filter.

Soft biological tissue has been observed to exhibit an acoustic attenuation log-magnitude characteristic which increases as an approximately linear function of frequency. This paper describes the implementation of a finite-impulse-response (FIR) digital filter model for simulating this behavior on a digital computer. To insure that the filter is causal, the minimum-phase constraint is imposed. For minimum-phase filters, the log-magnitude and phase characteristics form a Hilbert Transform pair. The discrete-time Hilbert Transform of the linear log-magnitude characteristic was evaluated to determine the phase of the filter. The inverse Fourier Transform of the resulting real and imaginary components of the frequency transform produces the finite-duration unit-sample response of the digital filter model. Experimental results using plexiglas material, which has a linear-with-frequency loss characteristic, indicate that the minimum-phase model is more accurate than the linear-phase model, resulting in a rms error between predicted and observed time waveforms that is 3 times smaller. The effects of varying the sampling period and the size of the FIR filter are discussed. A FORTRAN program to calculate the minimum-phase unit-sample response from the slope of the log-magnitude characteristic is included in the Appendix.

Computers↗
PubMed1982

High resolution computerized tomography in otorhinolaryngology.

Since the initial application of CT to otorhinolaryngology in the 1970's, marked improvements in computed tomographic technology have occurred, especially in the past 2-3 years. Further improvements in density and spatial resolution have resulted in high resolution images of either soft tissue or bony structures. Faster scanning times (5-10 seconds for high resolution images) have allowed studies of areas where motion artifact previously existed. Thinner slices (1.5 mm) and extended bone windows have allowed markedly improved bone detail, especially of the temporal bone. Digital computed radiographs can offer a preliminary overview, allowing improved active radiologic monitoring. Reformatted images in axes not able to be directly scanned have also improved. These improvements have resulted in newer widespread applications of CT to study otorhinolaryngologic disease, with CT often the definitive study.

Craniocerebral Trauma↗
PubMedDate not supplied

A computer analysis of EEG-intersignal reactions during the development of motoric alimentary conditioned reflexes in dogs.

The background electrical activity of the neocortex in the interstimulus periods at the stage of generalization during the development of alimentary motor conditioned reflexes (CR) in dogs was the investigational object. It was characterized by the appearance of brief (0.1-0.3 sec) trains of high frequencies (HF), significantly exceeding the adjacent initial baseline in frequency and amplitude. The relative variance index which we had developed made it possible to distinguish this EEG phenomenon in the initial realizations of the background activity when they were inputted into a digital computer. It was not possible to evaluate the parameters of the HF chains by means of a spectral correlation analysis. Nonstandard techniques of computer analysis directed toward the decomposition of the EEG tracing into a system of oscillations and toward the obtaining of the corresponding amplitude-frequency distributions (maps) were developed by us for the purpose of accomplishing this objective. It was demonstrated that HF trains were localized in these maps in specific, quite compact regions.

Animals↗
PubMed1977

A computerized system for the evaluation of community dental programs.

This paper reports on a relatively uncomplicated and inexpensive computerized system for prospective evaluation of clinical dental programs from the point of view of effectiveness and efficiency. Availability of this system does away with some high start-up costs. Three forms of input data, new case information, examination findings and operative procedure information, are regularly collected on data sheets and specially designed Port-a-punch IBM cards. Easily interpreted output tables are generated monthly on such variables as completed cases according to treatment series and clinician, number of various procedures performed by clinicians, etc. Productivity is measured, in part, by application of monetary constants to procedure data. This paper describes the computer programs used, the cost of setting up and operating the system (which is within the budgetary constraints of most small, publicly funded programs) and the benefits that can be derived from the use of such a system. The system provides prompt feedback of relevant administrative data, thus allowing for relatively quick response to problems. Use of the system reduces clerical needs to a minimum and the program can easily be implemented on any except the very smallest digital computer.

Community Dentistry↗
PubMed1981

A new adrenal computer imaging technique using dual-radioisotopes.

Computer processed adrenal imaging using dual-radioisotopes, 6 beta-iodomethyl-19-nor-cholest-5(10)-en-3 beta-ol-131I and 99mTc-phytate was performed in 12 patients with primary aldosteronism and 4 with Cushing's syndrome due to adrenocortical tumor. Adreno-photoscanning and hepato-photoscanning were performed in the same position 2-4 days following intravenous administration of radiocholesterol. The scintigraphic information was stored on cassettes and scan subtraction and a digital-computer method for data smoothing were performed on an oscilloscope. The tumor site could be determined in all cases until day 4 by this computer processed image.

Adosterol↗
PubMed1994

Computer determined compliance of the respiratory system (Crs) in ventilated newborn infants.

We describe a simple, low cost technique for computerized measurements of compliance of the respiratory system (Crs) by airway occlusion technique in intubated newborn infants. Tidal volumes of 5, 7.5, and 10 mL/kg were injected from a calibrated syringe into the endotracheal tube via a three-way stop cock and a t-piece. Airway pressure was measured by means of a differential pressure transducer. The analog pressure signal was fed into an optically isolated signal conditioning termination panel and an analog input board which was connected to the PC bus. The signal was amplified and A/D converted by the input board and processed by the digital computer. Crs was determined as the ratio of the injected tidal volume to the difference between the endexpiratory pressure and the pressure at airway occlusion. The software is written in Turbo Pascal (Borland Int.) and includes a patient data base and facilities for system configuration, calibration of transducers, data acquisition, handling, calculation of Crs, reporting and archive storage. Data sampling frequency may be individually set at 60 to 200 Hz. Synchronous measurements in 10 newborn infants using analog pressure amplification and polygraphic recording showed that pressures were correctly determined by the computer and that amplitude and frequency response of the pressure recordings were adequate.

Airway Resistance↗
PubMed1999

Discontinuities in recurrent neural networks.

This article studies the computational power of various discontinuous real computational models that are based on the classical analog recurrent neural network (ARNN). This ARNN consists of finite number of neurons; each neuron computes a polynomial net function and a sigmoid-like continuous activation function. We introduce arithmetic networks as ARNN augmented with a few simple discontinuous (e.g., threshold or zero test) neurons. We argue that even with weights restricted to polynomial time computable reals, arithmetic networks are able to compute arbitrarily complex recursive functions. We identify many types of neural networks that are at least as powerful as arithmetic nets, some of which are not in fact discontinuous, but they boost other arithmetic operations in the net function (e.g., neurons that can use divisions and polynomial net functions inside sigmoid-like continuous activation functions). These arithmetic networks are equivalent to the Blum-Shub-Smale model, when the latter is restricted to a bounded number of registers. With respect to implementation on digital computers, we show that arithmetic networks with rational weights can be simulated with exponential precision, but even with polynomial-time computable real weights, arithmetic networks are not subject to any fixed precision bounds. This is in contrast with the ARNN that are known to demand precision that is linear in the computation time. When nontrivial periodic functions (e.g., fractional part, sine, tangent) are added to arithmetic networks, the resulting networks are computationally equivalent to a massively parallel machine. Thus, these highly discontinuous networks can solve the presumably intractable class of PSPACE-complete problems in polynomial time.

Algorithms↗