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An introduction to hybrid computers and their application to optimization problems.

The author, who is Secretary of the Analog Section of the British Computer Society, describes the way in which some of the logic components of a parallel logic analog computer function, and goes on to discuss the use of such a computer in optimization problems, as for instance in finding the best estimates of the parameters on compartmentation analysis of isotopic tracer experiments. The increased power which is gained when an analog computer is coupled to (hybridized with) a general purpose digital computer is then discussed, as shown for example in the increased speed of random-search optimization techniques when an analog computer is used to integrate the differential equations, or the improvement in steepest ascent methods when the parallel logic can be used to keep the hill-climb path continuously on the line of steepest ascent. Finally, the use of a hybrid computer in solving partial differential equations is briefly outlined.

Journal Article↗

[Experimental model of bronchial asthma (author's transl)].

Allergic asthma-like attacks were induced in guinea pigs by intraperitoneal injections of Ovalbumin and following inhalation of Ovalbumin aerosol. The animals were narcotized, tracheotomized and a small catheter was placed in mid-oesophagus. The quantities: oesophageal pressure, respiratory flow and tidal volume were measured and recorded on magnetic tape during spontaneous breathing. A technique was applied for automated computation of the parameters of respiratory mechanics using a digital computer. The parameters compliance, resistance, work of breathing and power of breathing showed typical pathological variances and characteristic response-curves in the experimental phases during and after the asthma attacks. These parameters became normal after the injection of Alupent.

Animals↗

An adjustable zoom-made gain control for computerized gamma-camera systems.

Many nuclear medicine departments use a digital computer to process scintillation-camera images. For optimal use of the computer, there should be a means to amplify the position signals of each scintillation event by an appropriate amount before their conversion to digital form. What is needed is a series of calibrated gains from which the best value may be chosen. Many systems now in use do not provide such a selection. The circuitry described here provides an inexpensive solution to this problem. It may be inserted between the camera and the computer's analog-to-digital converters to provide the desired amplification. No internal modification of the computer or the camera is required.

Computers↗

Computer analysis of rapid eye movements.

Simulation of the saccadic eye movement mechanism and, more recently, diagnosis of neuromuscular disorders associated with saccades rely on accurate recording and analysis of saccade characteristics. Traditionally, eye movements are monitored objectively by registering a transduced voltage correlate of eye position on a pen or cathode ray oscillograph. Analysis of the record obtained is tedious and often inaccurate. The advent of small digital computers with analog-to-digital capability permits more efficient recording. However, computer programs reviewed are limited to the analysis of specific saccade parameters or partly depend on manual operations. The computer program described stores the entire saccadic event of each eye between pre-defined limits including the pre- and post-saccade intervals. Preliminary operations including artifact identification, location of onset, elimination of RC decay, DC offset and amplitude scaling prepare the data for display and subsequent analysis. The program also includes a subroutine to derive the mean and standard deviation of successive saccades.

Computers↗

Computer-based interviewing system dealing with nonverbal behavior as well as keyboard responses.

A digital computer has been programmed to conduct a medical interview while simultaneously monitoring the heart rate and keyboard response latency of the respondent for each question frame. The program can branch to new frames contingent upon the heart rate and response latency values, as well as the keyboard responses, and thus alter the course of the interview on the basis of this nonverbal information. The program is presented as a technique for studying the use of nonverbal respondent behavior in automated, clinical interviews.

Computers↗

Use of computers in dysmorphology.

As a consequence of the increasing power and decreasing cost of digital computers, dysmorphologists have begun to explore a wide variety of computerised applications in clinical genetics. Of considerable interest are developments in the areas of syndrome databases, expert systems, literature searches, image processing, and pattern recognition. Each of these areas is reviewed from the perspective of the underlying computer principles, existing applications, and the potential for future developments. Particular emphasis is placed on the analysis of the tasks performed by the dysmorphologist and the design of appropriate tools to facilitate these tasks. In this context the computer and associated software are considered paradigmatically as tools for the dysmorphologist and should be designed accordingly. Continuing improvements in the ability of computers to manipulate vast amounts of data rapidly makes the development of increasingly powerful tools for the dysmorphologist highly probable.

Computers↗

Computation of physicochemical parameters, namely pH, in complex (bio)chemical systems: extension to gas-liquid systems.

The first model has been proposed to compute, in complex liquid (bio)chemical systems, a number of physicochemical parameters, namely pH, concentration of one of any chemical species, partition between acid-base forms, global charge, or ionic strength, assuming the physicochemical equilibrium state. The extension of the present model, described here, permits moreover the computation of gas-liquid distributions, specific gas volumes, or total pressures. The model solely requires the knowledge of existing thermodynamic constants and of the concentration of every chemical species other than the species under examination. The model elicits a unique equilibrium state. Computed values agreed with experimental measurements, thereby validating the model. Digital computer programs were prepared to use the proposed algorithms.

Algorithms↗

Making bootstrap statistical inferences: a tutorial.

Bootstrapping is a computer-intensive statistical technique in which extensive computational procedures are heavily dependent on modern high-speed digital computers. The payoff for such intensive computations is freedom from two major limiting factors that have dominated classical statistical theory since its beginning: the assumption that the data conform to a bell-shaped curve, and the need to focus on statistical measures whose theoretical properties can be analysed mathematically. The name "bootstrap" was derived from an old saying about pulling oneself up by one's bootstraps. In this case, bootstrapping means redrawing samples randomly from the original sample with replacement. The key idea, computations, advantages, limitations, and application potential of bootstrapping in the field of physical education and exercise science are introduced and illustrated using a set of national physical fitness testing data. Finally, an example of a bootstrapping application is provided. Through a step-by-step approach, the development and implementation of the bootstrap statistical inference are illustrated.

Data Interpretation, Statistical↗

A comparison of bone tunnel measurements made using computed tomography and digital plain radiography after anterior cruciate ligament reconstruction.

PURPOSE: The purpose of this study was to compare measurements of bone tunnel enlargement after anterior cruciate ligament (ACL) reconstruction using digital plain radiography and computed tomography (CT). TYPE OF STUDY: Within-subjects comparison of 2 imaging techniques. METHODS: Twenty-two patients who had undergone primary ACL reconstruction had anteroposterior and lateral digital plain radiographs and a CT scan of their operated knee 12 months after surgery. Using digital calipers, the sclerotic margins of each tunnel were measured at the widest point in each plane. Measurements were corrected for magnification and expressed as a percentage change in tunnel width compared with the size of the drill bit used at surgery. RESULTS: In all but 1 instance, bone tunnels seen on CT were also seen on the corresponding digital radiograph. In the single incidence in which a bone tunnel was identified on the CT scan but not on the radiograph, the tunnel had the smallest diameter of the group and had decreased since surgery by 30%. There was no difference between the group-averaged CT and radiographic measurements for the tibia, but femoral tunnel radiographic measurements were clearly larger than CT, particularly for the anteroposterior view (P < .001). Moderate discrepancy was noted between individual radiograph and CT measurements. CONCLUSIONS: Digital plain radiography appears to be satisfactory for detecting bone tunnel enlargement following ACL reconstruction. Thus it may offer a time- and cost-effective means for monitoring this phenomenon. LEVEL OF EVIDENCE: Level I.

Adult↗

Medical informatics--a catalyst for operating room transformation.

For many years, computers have supported complex clinical ancillary functions such as the laboratory, radiology, endoscopy, and others. Digital computers have been successfully incorporated into specialized clinical instruments to offer advanced digital devices such as fetal monitors, heart monitors, and imaging equipment. But these devices are often not fully integrated with clinical management and operational systems. Beyond ancillary department applications, the result of almost 30 years of trying to automate the clinical processes in healthcare is large investments in both computer systems and paper medical records that have resulted in paper-based, computer-assisted processes of care. This expensive combination of partial clinical automation and archaic paper-based support processes is a major obstacle to improvements in care delivery and management. The need to use software, informatics, and standards to help manage the operating room and perioperative processes of care is significant. The potential to reduce adverse events, cost of care, and to enhance the quality of care are real and worth attaining. This paper focuses on what medical informatics improvements are needed to support improvements in surgical care and to assist in the management of the highly complex operating room and perioperative care process, and proposes research priorities in these areas.

Humans↗

Computer technique for digital radiographic images correction based on the digitizer characteristic curve.

This article presents a computer correction technique for radiographic digital images based on digitization process inaccuracy in pixel gray levels relative to the respective image optical densities. The technique consists of determining the digitizer characteristic curve by digitizing a step-wedge radiographic image with known optical densities. Calibration is done by determining the mathematical function that automatically adjusts the pixel gray levels to the expected values according to the manufacturer. Two laser film digitizers were investigated for which discrepancies between measured and expected pixel values were reported. For these cases, the proposed algorithm automatically adjusted the pixel gray levels of the digitized images. Using this method, the digital images show more accurate values of gray levels compared to the original radiographic image. In addition, it allows the development of uniform images databases.

Image Processing, Computer-Assisted↗

Computation of physiochemical parameters, inter alia, pH, in complex (bio)chemical systems.

Generic equations and algorithms are derived to compute, in complex (bio)chemical systems at equilibrium, the following physicochemical parameters: pH (or the concentration of any chemical species), partitions between acid and base forms, global charge, molar mean charges, ionic strength, and molar mean contributions to ionic strength. The model only requires the knowledge of existing thermodynamic constants and of the composition of the system in chemical species as the sum of the different forms other than the species under examination. It takes ionic strength aspects into consideration. Several innovations simplify the computation process: use of polyacidity constants, generalized expression of molar parameters, computation of global parameters from molar mean contributions, simplified corrections for activity, and easy iterative process for pH determination. The model always elicits a unique equilibrium state, namely, it always yields a unique pH value. Computed values always agreed with experimental measurements, thereby validating the model. Digital computer programs were prepared to use the proposed algorithms, which are also a very simple and easy way, compared to the available mathematical descriptions, to solve the problem "manually" without computer facilities.

Biochemistry↗

VECTAN II: A computer program for the spatial analysis of the vectorcardiogram.

This paper presents the operation of a digital computer program, VECTAN II, for the spatial analysis of the vectorcardiogram (VCG). The program incorporates a unique waveform recognition algorithm based on the spatial vector length which has been shown to perform better than previous algorithms. The waveform analysis employed by the program considers the vectorcardiogram as a three dimensional entity rather than as scalar or planar representations. VECTAN II is designed chiefly to measure and quantify the VCG response of normal subjects to a controlled stress by analyzing one VCG complex every five seconds throughout a long experiment. The program has been used to analyzeom the NASA Johnson Space Center Cardiovascular Laboratory, from the pre- and postflight medical examinations of the Apollo 15, 16 and 17 crewmen, and from onboard Skylab experiments.

Aerospace Medicine↗

Computing and the cultures of proving.

This article discusses the relationship between mathematical proof and the digital computer from the viewpoint of the 'sociology of proof': that is, an understanding of what kinds of procedures and arguments count for whom, under what circumstances, as proofs. After describing briefly the first instance of litigation focusing on the nature of mathematical proof, the article describes a variety of 'cultures of proving' that are distinguished by whether the proofs they conduct and prefer are (i) mechanized or non-mechanized and (ii) formal proofs or 'rigorous arguments'. Although these 'cultures' mostly coexist peacefully, the occasional attacks from within one on another are of interest in respect to what they reveal about presuppositions and preferences. A variety of factors underpinning the diverse cultures of proving are discussed.

Algorithms↗

Accuracy of linear temporomandibular joint measurements with cone beam computed tomography and digital cephalometric radiography.

INTRODUCTION: Cone beam computed tomography (CBCT) is making headway into imaging for orthodontics. The purpose of this study was to define CBCT multi-planar reformatted projections for temporomandibular joint (TMJ) examination and compare the accuracy of linear measurements of the TMJ and related structures from these projections with similar measurements made with conventional cephalograms and with the anatomic truth. METHODS: Linear dimensions between 11 anatomical sites were measured with a digital caliper to assess the anatomic truth for 25 dry human skulls. The skulls were imaged with iCAT (Xoran Technologies, Ann Arbor, Mich/Imaging Sciences International, Hatfield, Pa) CBCT, and cephalograms were made in all 3 orthogonal planes (lateral cephalometric [LC], posteroanterior [PA], and submentovertex [SMV]) acquired with photostimulable phosphor plates. Linear measurements were made on 7 custom CBCT reconstructions and the digital cephalograms. Modality means and the natural log of the standard deviations were compared post hoc against the actual dimensions by using analysis of variance with the Dunnett t test. Significance was set at P < .05. RESULTS: All CBCT measurements were accurate; however, 3 of 5 LC measurements, 4 of 5 PA measurements, and 4 of 6 SMV measurements varied significantly from the truth. Intraobserver CBCT measurements were highly reliable compared with anatomic truth and significantly more reliable than measurements made from LC, PA, and SMV images. CONCLUSIONS: Custom oblique multi-planar reformatted reconstructions with iCAT CBCT provide accurate and reliable linear measurements of mandibular and TMJ dimensions.

Analysis of Variance↗

Image management in dentistry.

Dentistry has seen a significant increase in the number of digital imaging technologies that have become commercially available during the past year. Computers, digital still cameras, scanners, intraoral cameras, digital X-ray systems, and their associated imaging software are all positioned at the top of the list of technologies that dentists plan to purchase within the next 12 months. This article provides an overview of the principles of image management in the dental office with an emphasis on hardware and software requirements as well as practical applications that a properly implemented image management system can afford the modern dental office.

Computer Storage Devices↗

Computer-assisted image classification: use of neural networks in anatomic pathology.

Artificial neural networks (ANN) implemented on digital computers have received much attention for interpretation of images in pathology and cytology. Most such images are too complex for current ANN to interpret directly; instead, ANN usually classify the images according to numeric features extracted from them. In experiments on three distinct image classification problems, ANN classifiers performed as well or better than multivariate linear discriminant analysis (a traditional parametric statistical classifier). ANN empirically define non-linear multivariate decision boundaries, and can combine non-contiguous feature areas in mapping a classification. However, many training cases are required in order to map complex area boundaries precisely and with a low risk of 'overtraining.' Careful problem selection and attention to data dimensionality and format are important for efficient ANN use.

Adenocarcinoma↗

An experimental comparison of detector performance for computed radiography systems.

The intrinsic resolution, noise, and signal-to-noise transfer characteristics of five commercial digital computed radiography (CR) systems were compared using identical experimental methods. The reader/screen combinations evaluated were Agfa ADC-Compact/MD-10, Agfa ADC-Compact/MD-30, Agfa ADC-Solo/MD-10, Agfa ADC-Solo/MD-30, Lumisys CR-2000/MD-10, Fuji FCR-9501 (HQ)/ST-Va, Kodak CR-400/GP-25, and Kodak CR-400/HR. Measurements were made at 70 and 115 kVp with 19 mm added aluminum filtration. The presampled modulation transfer functions (MTFs) of the systems were measured using an edge method. The noise power spectra (NPS) were determined by 2D Fourier analysis of uniformly exposed radiographs. The frequency-dependent detective quantum efficiencies (DQEs) were computed from the MTF, NPS, exposure measurements, and computational estimates of the ideal signal-to-noise ratios. Using 70 kVp and 0.1-0.12 mm pixel sizes, spatial frequencies of 2.1, 2.0, 2.2, 1.9, 2.0, 2.0, 2.3, 2.3, and 3.5 cycles/mm were measured at 0.2 MTF for the eight reader/screen combinations, respectively. Using 70 kVp, 7.74 x 10(-8) C/kg (0.3 mR), and 0.1-0.12 mm pixel sizes, DQE(0.15) values of 20.3%, 22.9%, 24.6%, 28.6%, 22.2%, 30.0%, 29.5%, and 17.3% were obtained for the eight combinations, respectively. The corresponding values at 115 kVp were 15.9%, 18.5%, 21.5%, 21.8%, 15.3%, 23.1%, 22.3%, and 13.8%, respectively. The findings of the study demonstrate the pixel size, orientation, beam quality, screen, and reader dependencies of image quality in CR systems. The physical performance of the systems having standard-resolution screens demonstrated similar resolution performance but more notable variations in DQE. The one high-resolution screen tested had reduced DQE and increased MTF at high frequencies.

Evaluation Studies as Topic↗