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At least 1,693 records · Page 94Linked to original sources
PubMed1996

Perception of detail and greyscale range in X-ray fluoroscopy images captured with a personal computer and frame-grabber.

OBJECTIVE: To assess the dynamic range of radiological images captured with a personal computer frame-grabbing system coupled to an X-ray fluoroscopy machine. METHODS: A 386DX-40 MHz, IBM compatible, computer with an SVGA monochrome graphics subsystem and a 387 co-processor, installed with a Screen Machine frame-grabber and controlled by a program specially written was used. Various systems were examined and the observer's perceptions of the results assessed. RESULTS: The dynamic range available to an ordinary X-ray fluoroscopy system was found to be restricted to about 750 mV. Similar measurements showed that the dynamic range was always restricted to 3/4-1/2 of the full available signal because of a high value of the dark voltage of the TV camera's target on all seven systems measured. The dynamic range of the computer-frame grabber system was found to be significantly wider than the Image Intensifier-TV camera chain but, surprisingly, it was affected by the type of file format used for image storing on disk. Clinical images from a barium meal examination as well as CT images captured after optimisation of the frame-grabber were found to contain large quantities of noise in the first two least significant bit planes making them redundant and limiting the grey levels needed for image display to less than 64. This number was also less than the 80 grey levels that could be discriminated by the human eye on the computer monitor. CONCLUSIONS: It was concluded that 6 bit digitisation would have been sufficient for image capture. The advantages of the wider dynamic range of the frame-grabber and the processing capabilities of the computer were tested for the possibility of improving the perception of detail. However, the results were negative. The limiting spatial resolution measured with a variable density bar pattern at all magnifications was about 0.4 lp/mm lower from that measured directly on the fluoroscopic screen. A detail perception test had the same result. The perception success was significantly lower with the digital images at all but the highest of the exposure rates and despite the use of image processing filters.

Artifacts↗
PubMed1999

The dynamics of vortex-like reentry wave filaments in three-dimensional computer models.

Recent studies using computer simulation and biological studies in 2-dimensional excitable media have suggested that spiral wave reentrant activation and its core dynamics are important elements in the mechanism of functional reentrant tachyarrhythmias, such as atrial and ventricular fibrillation. However, vortex-like reentry has been observed in homogeneous 3-dimensional excitable media, and the dynamics of the related "filaments," which have 3-dimensionally connected "cores" in 2 dimensions, have not been clarified. In order to determine whether the filaments of vortex-like reentry waves can be observed in 3-dimensional media using a mathematical ionic current heart model and whether the abnormal ionic currents in myocardium affect the complexity of the filaments, we studied the qualitative features of vortex-like reentry dynamics using mathematical models in computer simulations. We employed the Luo-Rudy Phase I and the FitzHugh-Nagumo models for our heart media, which were cubic and ventricular shaped, and consisted of 8,000,000 and 5,636,654 myocardial units, respectively. Functional reentry, in the form of vortex waves, was induced in the media by the S1-S2 method. The vortex-like reentry waves and their filaments were displayed by computer graphics. Computations were performed on an NEC SX-4 supercomputer (NEC, Tokyo, Japan) using programs written in C language. Computer simulation studies have shown that the filament dynamics of vortex-like reentry in the original Luo-Rudy model is considerably more complex than that in the FitzHugh-Nagumo model. However, when we mathematically modified the L-type calcium current and shortened the action potential duration, just as occurs with sustained rapid ventricular pacing, the dynamics of the vortex-like reentrant wave fronts and the filaments were similar in both models. Our results suggested that the original character of myocardium causes drastic changes in filament shape and location, resulting in intricate functional reentrant waves, and that if the L-type calcium current is depressed, the complexity of the dynamics of the filaments are decreased to some degree.

Calcium↗
PubMed2000

Computer-aided detection and diagnosis of breast cancer.

The limitations of radiologists when interpreting mammogram examinations provides a reasonable, if not compelling, basis for application of computer techniques that have the potential to improve diagnostic performance. Computer algorithms, at their present state of development, show great promise for clinical use. It can be expected that such use will only improve as computer technology and computer methods continue to become more formidable. The eventual role of computers in mammographic detection and diagnosis has not been fully defined, but their effect on practice may one day be very significant.

Algorithms↗
PubMed1998

Computer and information technology: hardware.

Computers open the door to an ever-expanding arena of knowledge and technology. Most nurses practicing in perianesthesia setting were educated before the computer era, and many fear computers and the associated technology. Frequently, the greatest difficulty is finding the resources and knowing what questions to ask. The following is the first in a series of articles on computers and information technology. This article discusses computer hardware to get the novice started or the experienced user upgraded to access new technologies and the Internet. Future articles will discuss start up and usual software applications, getting up to speed on the information superhighway, and other technologies that will broaden our knowledge and expand our personal and professional world.

Computer Communication Networks↗
PubMed2003

Perspectives on computer aiding in cognitive work domains: toward predictions of effectiveness and use.

A two-stage process is proposed for evaluating computer aiding in cognitive work domains. The first stage relies on a taxonomic framework that facilitates assessments regarding the relative strengths and weaknesses of humans and computers for different computer-aiding schemes. The second stage introduces the construct of tension, which addresses the potential implications of the interplay between computer aiding constraints and human tendencies. This approach is intended to provide designers, analysts and managers with greater insight into the nature of computer aiding and ultimately to enhance their ability to predict its effectiveness as well as its prospects for being used.

Attitude to Computers↗
PubMed2005

IMRT planning on adaptive volume structures--a decisive reduction in computational complexity.

The objective of radiotherapy planning is to find a compromise between the contradictive goals of delivering a sufficiently high dose to the target volume while widely sparing critical structures. The search for such a compromise requires the computation of several plans, which mathematically means solving several optimization problems. In the case of intensity modulated radiotherapy (IMRT) these problems are large-scale, hence the accumulated computational expense is very high. The adaptive clustering method presented in this paper overcomes this difficulty. The main idea is to use a preprocessed hierarchy of aggregated dose-volume information as a basis for individually adapted approximations of the original optimization problems. This leads to a decisively reduced computational expense: numerical experiments on several sets of real clinical data typically show computation times decreased by a factor of about 10. In contrast to earlier work in this field, this reduction in computational complexity will not lead to a loss in accuracy: the adaptive clustering method produces the optimum of the original optimization problem.

Algorithms↗
PubMed1999

Surgical planning of computer-assisted repositioning osteotomies.

Repositioning osteotomies are frequently used in orthopedic surgery and traumatology to correct malpositions. Computed tomography (CT), stereolithographic models, and x-rays are used in planning. However, the precision achieved in the planning phase is usually not translated to patients. The Surgical Segment Navigator (SSN) is a navigation system that allows computer-assisted correction of malpositions. It consists of an infrared positioning device, two dynamic reference frames (DRF), an infrared pointer, and an infrared camera. All data are displayed numerically and graphically on the monitor of the SSN workstation. The Laboratory Unit for Computer-Assisted Surgery (LUCAS) is used for planning surgery in the laboratory. LUCAS requires only a native CT scan. A preparatory operation to implant bone markers that will be visible in x-rays and a further planning CT scan showing the bone markers, which were necessary with previous systems, are not required for the LUCAS and SSN system. This significantly reduces the radiation exposure of the patient and the costs of surgical planning. Measuring anatomical landmarks in the surgical site, which is time-consuming and reduces accuracy, is not required with the SSN system because the position of the infrared transmitters is known during surgical planning on the LUCAS workstation. This makes the surgical approach faster and much more precise. The surgical planning data are transferred to the surgical site using a data file and an individual surface pattern that fits the surface of the navigated bone segment. The data file is exported from the LUCAS-workstation to the SSN workstation. The planned spatial displacement of the infrared transmitters is saved in this file. The individual surface pattern carries the infrared transmitters. This pattern is the mechanical interface between infrared transmitters and navigated bone segment. The individual surface pattern can be polymerized directly on a small stereolithographic model of the navigated bone segment. The surface pattern can also be generated as negative form from a CT data set using a computer-assisted design/manufacture system. In summary, LUCAS and SSN allow for the computer-assisted correction of malpositions and positioning of artificial joints and implants. In principle, the systems can be used in all fields of surgery.

Biomechanical Phenomena↗
PubMed2003

Will the digital computer transform classical mathematics?

Mathematics and machines have influenced each other for millennia. The advent of the digital computer introduced a powerfully new element that promises to transform the relation between them. This paper outlines the thesis that the effect of the digital computer on mathematics, already widespread, is likely to be radical and far-reaching. To articulate this claim, an abstract model of doing mathematics is introduced based on a triad of actors of which one, the 'agent', corresponds to the function performed by the computer. The model is used to frame two sorts of transformation. The first is pragmatic and involves the alterations and progressive colonization of the content and methods of enquiry of various mathematical fields brought about by digital methods. The second is conceptual and concerns a fundamental antagonism between the infinity enshrined in classical mathematics and physics (continuity, real numbers, asymptotic definitions) and the inherently real and material limit of processes associated with digital computation. An example which lies in the intersection of classical mathematics and computer science, the P=NP problem, is analysed in the light of this latter issue.

Artificial Intelligence↗
PubMed1992

Initial results for automated computational modeling of patient-specific electromagnetic hyperthermia.

Developments in finite-difference time-domain (FD-TD) computational modeling of Maxwell's equations, super-computer technology, and computed tomography (CT) imagery open the possibility of accurate numerical simulation of electromagnetic (EM) wave interactions with specific, complex, biological tissue structures. One application of this technology is in the area of treatment planning for EM hyperthermia. In this paper, we report the first highly automated CT image segmentation and interpolation scheme applied to model patient-specific EM hyperthermia. This novel system is based on sophisticated tools from the artificial intelligence, computer vision, and computer graphics disciplines. It permits CT-based patient-specific hyperthermia models to be constructed without tedious manual contouring on digitizing pads or CRT screens. The system permits in principle near real-time assistance in hyperthermia treatment planning. We apply this system to interpret actual patient CT data, reconstructing a 3-D model of the human thigh from a collection of 29 serial CT images at 10 mm intervals. Then, using FD-TD, we obtain 2-D and 3-D models of EM hyperthermia of this thigh due to a waveguide applicator. We find that different results are obtained from the 2-D and 3-D models, and conclude that full 3-D tissue models are required for future clinical usage.

Computer Simulation↗
PubMed2006

German dental faculty attitudes towards computer-assisted simulation systems correlated with personal and professional profiles.

BACKGROUND: Computer technology is increasingly used in practical training at universities. However, in spite of their potential, computer-assisted simulation (CAS) systems still appear to be underutilised. OBJECTIVES: To investigate the practical usage of CAS/computer-assisted learning (CAL) systems, the familiarity and level of use of CAS systems, as well as the acceptance of approved learning content and English as the language of instruction in CAS/CAL systems. METHODS: A survey was conducted in the Departments of Conservative Dentistry and Prosthetic Dentistry of all 32 dental schools in Germany. Besides investigating the usefulness of, familiarity with and level of current usage of CAS systems, the questionnaire also contained questions regarding each respondent's gender, age, academic rank, experience in academia and computer skills, all of which correlated with the responses. RESULTS: The response rate was 90% (112 out of 125). The use of CAS/CAL systems was considered 'partly' to 'very' useful for evaluating the acquisition of knowledge (83.9%), qualitative issues (73.2%) and processes (72.3%) of dental preparation exercises and complex treatment strategies. However, only about half the respondents reported that they knew of, and even fewer used, the following systems in preclinical or clinical training: EDUnet (KaVo, Germany) (46.3%/0.9 %), PREPassistant (KaVo, Germany) (50%/0.9%), or the DentSim system (DenX, Israel) (52.8%/1.9%). The virtual simulation system VRDTS-CP (Novint, USA), used by none of the respondents, was known to only 16.5%. Responders agreed at least partly to accept approved learning content (74.9%) and English as the language of instruction (82.1%) as the standards for CAS systems. CONCLUSION: The survey indicates a distinct discrepancy between a generally positive attitude towards the usefulness of computer technology for dental education, the level of familiarity with current computer systems and their actual use. However, two prerequisites for ultimately decreasing the cost and increasing the usage of CAS systems--the acceptance of approved learning content and English as the language of instruction in CAS systems--seem to be generally accepted by respondents.

Adult↗
PubMed1995

Application of high-performance computing to numerical simulation of human movement.

We have examined the feasibility of using massively-parallel and vector-processing supercomputers to solve large-scale optimization problems for human movement. Specifically, we compared the computational expense of determining the optimal controls for the single support phase of gait using a conventional serial machine (SGI Iris 4D25), a MIMD parallel machine (Intel iPSC/860), and a parallel-vector-processing machine (Cray Y-MP 8/864). With the human body modeled as a 14 degree-of-freedom linkage actuated by 46 musculotendinous units, computation of the optimal controls for gait could take up to 3 months of CPU time on the Iris. Both the Cray and the Intel are able to reduce this time to practical levels. The optimal solution for gait can be found with about 77 hours of CPU on the Cray and with about 88 hours of CPU on the Intel. Although the overall speeds of the Cray and the Intel were found to be similar, the unique capabilities of each machine are better suited to different portions of the computational algorithm used. The Intel was best suited to computing the derivatives of the performance criterion and the constraints whereas the Cray was best suited to parameter optimization of the controls. These results suggest that the ideal computer architecture for solving very large-scale optimal control problems is a hybrid system in which a vector-processing machine is integrated into the communication network of a MIMD parallel machine.

Computer Systems↗
PubMed2001

Why British GPs use computers and hospital doctors do not.

Almost all general medical practitioners (GPs) in the UK use computers, compared with less than one in ten of hospital doctors. This paper explains how this unexpected situation came about over a thirty-year period, identifying some of the successes and failures of British medical computing along the way. Twelve separate factors are considered. The major determinants have not been technical, but rather a strong tide of political backing for general practice and leadership from the profession at the highest level, which have combined to build an appropriate regulatory framework and financial incentives that have encouraged GPs to embrace computers. Hospital computing has some difficulties not met by GPs, but the main factor preventing progress has been the lack of any real incentive positive (carrot) or negative (stick), for hospital doctors to use computers.

Attitude to Computers↗
PubMed1986

Computers in dentistry.

Traditionally, each professional school has developed its own course or department of health care informatics. We may find it more efficient and productive to establish a department of Medical Informatics to serve all health science colleges. Therefore the initial costs would be reduced and the common knowledge bank would be greatly increased. In a position paper written for the Association of Academic Health Centers lies the detailed plans for the establishment of an integrated health sciences center computer resource. The inclusion of computer courses in the curriculum can be summarized in the following action step. The chief administrative officer of the academic health center should facilitate the work of the deans of the schools of the health professions in convening faculty task forces that will address the introduction of computer literacy and computer applications in health care to the curricula. Although dental informatics is still in its infancy, we must lay a solid foundation for the controlled growth and development of this field of dental science. The problems encountered in developing a course in dental informatics are not unique to this one area. All specialties of health care are grappling with the questions posed by medical informaticians. Although each specialty has its own needs and requirements, the basic underlying principles of medical informatics remains the same. The knowledge we can gain by the exchange of experiences between all fields can greatly increase the speed and accuracy of development. The primary goal of computer literacy in dental education should be to prepare our students for the changing practice environment of the future.

Computer Literacy↗
PubMed2001

Utilization of a pediatric emergency department education computer.

OBJECTIVE: To describe the use of a computer education station placed within a pediatric emergency department. DESIGN: Prospective tracking of computer tutorial use. SETTING: A tertiary care pediatric emergency department. METHODS: A computer with two 30-minute multimedia computer tutorials was installed in the emergency department. The tutorials were designed for residents to use on a voluntary basis but were available to medical students and allied health professionals as well. Software tracked time, date, duration of use, and the user's path through each tutorial. Data were collected from July 15, 1996, through April 30, 1997. RESULTS: Twenty-eight residents interacted 71 times with the computer during the study. The mean duration of interactions was 22 minutes (SD, 18 minutes; range, 0-75 minutes), but many lasted less than 5 minutes (15 [21%] of 71). Twenty-four (34%) of the interactions led to tutorial completion. Residents were more likely to complete a tutorial during the day shift (22 [40%] of 55) compared with the evening shift (1 [7%] of 14) (P =.02). A third of the interactions were during evenings and weekends. The education station delivered 26.1 hours of instruction in total. Of 32 first-year pediatric and emergency medicine residents, 22 attempted the tutorials; 4 completed both, and 10 completed one. Allied health professionals were responsible for 28% of the total interactions. They were significantly more likely than medical trainees to have brief interactions, but they were no less likely to complete the tutorials (10 [22%] of 46 vs 31 [27%] of 115; P =.44). CONCLUSIONS: Pediatric residents are willing to use an educational computer placed in the emergency department. Choice of form and content should take into account the likelihood of short interactions and the demonstrated interest of allied health professionals.

Academic Medical Centers↗
PubMedDate not supplied

Analysis of antepartum fetal heart rate tracing by physician and computer.

OBJECTIVE: To compare the interpretation of fetal heart rate (FHR) tracings by three obstetricians with that of a computer analysis program. METHODS: Our study population consisted of high-risk pregnant women referred as outpatients for antepartum FHR monitoring. A total of 121 FHR tracings, from a series of 54 consecutive women, were interpreted by three physicians and a computer program (Oxford Sonicaid System 8000, Oxford Sonicaid Ltd., Chichester, UK). The physicians used a modified FHR scoring system to interpret the tracings. Total scores were categorized as 0-4: abnormal, 5-7: questionable, and 8-10: normal. The computer program used overall variation, categorized as normal: longer than 30 ms, abnormal: shorter than 20 ms, and questionable: 20-30 ms. RESULTS: Significant differences were found among the physicians and between the physicians and the computer analysis for the individual elements of FHR tracings. There was very good agreement between two physicians and the computer in the assessment of the FHR baseline. When physicians used a FHR scoring system to classify the tracings as normal, questionable, or abnormal, the agreement was poor (kappa values ranged from -0.037 to 0.28). The computerized analysis identified two FHR tracings as questionable but both were classified as normal by all three physicians. CONCLUSIONS: The level of agreement in the interpretation of FHR tracings was poor among physicians and between physicians and the computer analysis. A FHR scoring system did not improve the level of agreement between physicians.

Adolescent↗
PubMed2001

Laboratory instruction in histology at the University at Buffalo: recent replacement of microscope exercises with computer applications.

Histology is a morphologic science in which the structure of the cells, tissues, and organs of the body are examined with a microscope. In the laboratory courses in histology at the School of Medicine of the University at Buffalo, histologic specimens had been used since the late 19th century to teach the principles of cell, tissue, and organ structure. Students also had to learn how to analyze or "read" slides with a microscope. Learning histology in this way, i.e., by direct examination of actual specimens, is time consuming and viewed by some as unnecessary. As a result of recent curricular reform at the School of Medicine that reduced contact time in histology, half of all laboratory exercises that would have been performed with a microscope were performed instead with interactive computer applications. By replacing some microscope exercises with more efficient computer applications, the histology course accommodated curricular change by both reducing contact time and continuing to offer valuable microscope laboratories for most of the organ systems of the body. To provide a basis for comparing traditional microscope exercises with computer-assisted instruction in histology, the nature of the laboratory experience between 1846 and 1998 is briefly reviewed. The instructional strategy behind the use of computers is presented, along with the nature of the computer applications and the means by which the computer applications were incorporated into the school's laboratory course in histology.

Computer-Assisted Instruction↗
PubMed1995

Microscopic computation in human brain evolution.

When human psychological performance is viewed in terms of cognitive modules, our species displays remarkable differences in computational power. Algorithmically simple computations are generally difficult to perform, whereas optimal routing or "Traveling Salesman" Problems (TSP) of far greater complexity are solved on an everyday basis. It is argued that even "simple" instances of TSP are not purely Euclidian problems in human computations, but involve emotional, autonomic, and cognitive constraints. They therefore require a level of parallel processing not possible in a macroscopic system to complete the algorithm within a brief period of time. A microscopic neurobiological model emphasizing the computational power of excited atoms within the neuronal membrane is presented as an alternative to classical connectionist approaches. The evolution of the system is viewed in terms of specific natural selection pressures driving satisfying computations toward global optimization. The relationship of microscopic computation to the nature of consciousness is examined, and possible mathematical models as a basis for simulation studies are briefly discussed.

Algorithms↗
PubMed1997

Is computer interpretation of the exercise electrocardiogram a reasonable surrogate for visual reading? Veterans Affairs ACME Investigators.

BACKGROUND: Interpretation of exercise tests as positive or negative is primarily based upon exercise-induced ST segment changes. Consistently accurate measurements are difficult to obtain during exercise. HYPOTHESIS: This study compared on-line computer-generated electrocardiographic (ECG) analysis with visual interpretation. The goals were to document the extent of agreement, establish reasons for disagreements, characterize ST-segment depression (extent, onset, duration), and determine the sensitivity and ability to localize coronary artery disease for each method. METHODS: Comparisons were made in 120 patients at eight Veterans Affairs Medical Centers. An exercise test was considered positive if > 1.0 mm horizontal or downsloping ST-segment depression was detected 0.08 s after the J point during exercise or recovery. The ST-segment depression had to be present on at least two successive ECG recordings 15 s apart. Computer interpretation was based on median averaged beats. RESULTS: There was an 88% agreement of visual and computer interpretations [106/120 (both positive, n = 62; both negative, n = 44)]. The disagreements involved visual negative, computer positive in 10 cases and visual positive, computer negative in 4 cases. Correlation was excellent between methods for characterization of ST-segment depression (p < 0.0001). Sensitivity for detecting and the ability to localize coronary artery disease (> or = 70% stenosis) were similar for both methods. CONCLUSION: This computer algorithm using median averaged beats is a reasonable surrogate for visual interpretation of the exercise ECG, making it a valuable source of confirmation of physician readings in large research trials and in clinical settings.

Algorithms↗