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PubMedDate not supplied

Three-dimensional echocardiography in congenital heart disease: a continuum of unfulfilled promises? No. A presently clinically applicable technology with an important future? Yes.

Three-dimensional echocardiography has important clinical applications to congenital heart disease. Such applications include assessment of ventricular volumes, and unique imaging planes and projections of septae and atrio-ventricular and semi-lunar valves. Advances in ultrasound and computer technology will improve the process of three-dimensional echocardiography to continue to bring it to everyday clinical utility application.

Artificial Intelligence↗
PubMed1996

New ultrasound contrast agents and technological innovations.

Further development of clinical diagnostic procedures, as well as new diagnostic techniques, requires ultrasound specific contrast agents as well as technological innovations. This paper reviews contrast agents developed in the last decade, which are all based on free gas or encapsulated gas bubbles.

Animals↗
PubMed1993

Investigation of roe deer--criteria for use as a bioindicator in specimen banking.

Some results are given for a 5-year study to establish standard operation procedures for roe deer (Capreolus capreolus). The criteria for bioindication of roe deer are listed for three forestry districts in the east of Lower Saxony (Braunschweig, Fallersleben, Lappwald). The organs investigated for use are liver, kidney, kidney fat, brain and were collected from animals with an intact abdomen and were packed in Teflon bags after being shot. The fresh samples are kept at +4 degrees C and prepared in a laboratory within 24 h. The organs were investigated for 20 organic and 15 inorganic constituents. Twenty-two detectable contaminants from different collections are evaluated by using a personal computer (PC) with a Statistical Package of Social Science (SPSS) program. The results show that liver is a good accumulating organ; organ size and the regular distribution of the contaminants throughout the organ are an advantage. Significant variations in concentrations of contaminants are observed in May until August; levels stabilize in September to November. Animals < 18 months of age should be selected from rather narrow and uniform biotopes for specimen banking during the periods of autumn to winter or May. Pooling of the samples is not recommended.

Adipose Tissue↗
PubMed1996

Evolutionary strategies of stochastic learning automata in the prisoner's dilemma.

Stochastic learning automata (SLA) model stimulus-response species which receive feedback from the environment and adjust their mixed strategies in a Prisoner's Dilemma. A large heterogeneous population consists of SLA applying different strategies (i.e. different learning parameters) and other players applying deterministic strategies, Tit-For-Tat (TFT) or Always-Defect (ALLD). The predicted equilibria determine the payoffs within a generation for applying particular strategies and these equilibria are confirmed by simulation. The resultant population dynamics over many generations show that SLA with insensitive penalty responses strongly favor defection and dominate in subsequent generations over SLA with sensitive penalty responses. The SLA strategies are not evolutionarily stable as they can be invaded by TFT or ALLD. With the introduction of memory in the stimulus-response model, SLA learn to cooperate with TFT players.

Computer Simulation↗
PubMed1994

Electrical impedance tomography: a review of current literature.

Electrical impedance tomography (EIT) is a relatively new imaging technique that has been developed during the past decade. The electrical properties of tissues are imaged by injecting small currents and measuring the resultant voltages. These voltages are then converted into a tomographic image using a reconstructing algorithm. The method has no known hazards and is relatively inexpensive. There are many possible clinical applications of this technique but apart from gastric emptying, most are still at the research stage as there are various technical and practical problems to be overcome. This paper describes the basic principles of EIT and reviews the English literature to try to assess its potential in clinical imaging.

Algorithms↗
PubMed1996

Neural Network Exploration Using Optimal Experiment Design.

I consider the question "How should one act when the only goal is to learn as much as possible?". Building on the theoretical results of Fedorov (1972, Theory of Optimal Experiments, Academic Press) and MacKay (1992, Neural Computation, 4, 590-604), I apply techniques from optimal experiment design (OED) to guide the query/action selection of a neural network learner. I demonstrate that these techniques allow the learner to minimize its generalization error by exploring its domain efficiently and completely. I conclude that, while not a panacea, OED-based query/action selection has much to offer, especially in domains where its high computational costs can be tolerated. Copyright 1996 Elsevier Science Ltd

Journal Article↗
PubMed1994

Emerging medical applications of virtual reality: a surgeon's perspective.

Medical applications for virtual reality (VR) technologies are just beginning to emerge. These include VR surgical simulators, telepresence surgery, complex medical database visualization, and rehabilitation. These applications are mediated through the computer interface and embody VR as an integral part of a paradigm shift in the field of medicine. The Green Telepresence Surgery System consists of two components, the surgical workstation and the remote worksite. At the remote site there is a 3-D camera system and responsive manipulators with sensory input. At the workstation there is a 3-D monitor and dexterous handles with force feedback. The VR surgical simulator is a stylized recreation of the human abdomen with several essential organs. Using a head-mounted display and DataGlove, a person can learn anatomy from a new perspective by 'flying' inside and around the organs, or can practice surgical procedures with a scalpel and clamps. Database visualization creates 3-D images of complex medical data for new perspectives in analysis. VR applications in rehabilitation medicine permit impaired individuals to perform tasks not otherwise available to them, allow accurate assessment and therapy for their disabilities, and help architects understand their critical needs in public or personal space. And to support these advanced technologies, the operating room and hospital of the future will be first designed and tested in virtual reality, bringing together the full power of the digital physician.

Computer Graphics↗
PubMed1994

A resource guide to VR in medicine.

This guide provides a bibliography of many of the most noteworthy contributions to the emerging literature about virtual reality in medicine, along with listings of the most relevant conferences and resources for researchers. This is an abridged version of a continuously updated comprehensive document which is available on-line to the research community.

Computer Graphics↗
PubMed2006

From vagueness in medical thought to the foundations of fuzzy reasoning in medical diagnosis.

OBJECTIVE: This article delineates a relatively unknown path in the history of medical philosophy and medical diagnosis. It is concerned with the phenomenon of vagueness in the physician's "style of thinking" and with the use of fuzzy sets, systems, and relations with a view to create a model of such reasoning when physicians make a diagnosis. It represents specific features of medical ways of thinking that were mentioned by the Polish physician and philosopher Ludwik Fleck in 1926. The paper links Lotfi Zadeh's work on system theory before the age of fuzzy sets with system-theory concepts in medical philosophy that were introduced by the philosopher Mario Bunge, and with the fuzzy-theoretical analysis of the notions of health, illness, and disease by the Iranian-German physician and philosopher Kazem Sadegh-Zadeh. MATERIAL: Some proposals to apply fuzzy sets in medicine were based on a suggestion made by Zadeh: symptoms and diseases are fuzzy in nature and fuzzy sets are feasible to represent these entity classes of medical knowledge. Yet other attempts to use fuzzy sets in medicine were self-contained. The use of this approach contributed to medical decision-making and the development of computer-assisted diagnosis in medicine. CONCLUSION: With regard to medical philosophy, decision-making, and diagnosis; the framework of fuzzy sets, systems, and relations is very useful to deal with the absence of sharp boundaries of the sets of symptoms, diagnoses, and phenomena of diseases. The foundations of reasoning and computer assistance in medicine were the result of a rapid accumulation of data from medical research. This explosion of knowledge in medicine gave rise to the speculation that computers could be used for the medical diagnosis. Medicine became, to a certain extent, a quantitative science. In the second half of the 20th century medical knowledge started to be stored in computer systems. To assist physicians in medical decision-making and patient care, medical expert systems using the theory of fuzzy sets and relations (such as the Viennese "fuzzy version" of the Computer-Assisted Diagnostic System, CADIAG, which was developed at the end of the 1970s) were constructed. The development of fuzzy relations in medicine and their application in computer-assisted diagnosis show that this fuzzy approach is a framework to deal with the "fuzzy mode of thinking" in medicine.

Diagnosis↗
PubMed2006

Attention in natural scenes: Neurophysiological and computational bases.

How does attention operate in natural scenes? We show that the receptive fields of inferior temporal cortex neurons that implement object representations become small and located at the fovea in complex natural scenes. This facilitates the readout of information about an object that may be reward or punishment associated, and may be the target for action. Top-down biased competition to implement attention has a much weaker effect in complex natural scenes than in otherwise blank scenes with two objects. Part of the solution to the binding problem is thus that competition and the foveal cortical magnification factor emphasize what is present at the fovea, and limit the binding problem. Part of the solution to the binding problem is that neurons respond to combinations of features present in the correct relative spatial positions. Stimulus-dependent neuronal synchrony does not appear to be quantitatively important in feature binding, and in attention, in natural visual scenes, at least in the inferior temporal visual cortex, as shown by information theoretic analyses. The perception of multiple objects in a scene is facilitated by the fact that inferior temporal visual cortex neurons have asymmetrical receptive fields with respect to the fovea in complex scenes. Computational models of this processing are described.

Action Potentials↗
PubMed1998

Advances in ophthalmic ultrasound.

New ultrasound technologies, including three-dimensional imaging, tissue characterization, and very high frequency (50 MHz) ultrasound, have become available recently. We demonstrate how these technologies can be used alone and together to improve the use of ultrasound for diagnosis of ocular pathology.

Eye↗
PubMed1999

Cigarette smoking among native and foreign-born African Americans.

PURPOSE: To examine differences in current smoking status and the number of cigarettes consumed daily between foreign and native-born African Americans, and the impact of demographic and socioeconomic status (SES) factors on smoking behavior. METHODS: Data were obtained from combining the 1990-1994 National Health Interview Surveys and consisted of 16,738 U.S. born and foreign-born African Americans between 18 and 64 years of age. The statistical analysis included cross-tabulations and weighted multiple logistic regression (MLR) using the Statistical Packages for the Social Sciences (SPSS) and the Survey Data Analysis (SUDAAN) computer programs. RESULTS: Adjusted MLR analysis revealed that native-born African Americans were more likely (odds ratio (OR) = 2.7, p < 0.001) to be current smokers than foreign-born blacks. Within the native-born group, smoking prevalence decreased with increasing education and income, but these associations were not found for foreign-born blacks. Women in both groups were less likely than men to be current smokers. Statistically significant differences were not found between the two groups in the number of cigarettes smoked per day. CONCLUSIONS: This analysis of nativity and smoking behavior further demonstrates the social diversity among African Americans and suggests the differential impact of social and cultural factors on smoking behavior within racially classified social groups. In areas where there are substantial numbers of foreign-born blacks, researchers should consider differentiating smoking status by nativity. Though differences in smoking prevalence were apparent for native and foreign-born American Americans, prevention and cessation programs are needed for both groups.

Adolescent↗
PubMed1999

Chemoinformatics--a new name for an old problem?

Library chemistry and high-throughput screening require greater use of chemoinformatics to increase their effectiveness. Recent advances in chemoinformatics include new molecular descriptors and pharmacophore techniques, statistical tools and their applications. Visualisation methods and hardware development are also opening new opportunities. The advent of a chemically aware web language and cross-platform working is ensuring that chemoinformatics methods are becoming available to all chemists in a more appropriate manner. Much time will continue to be wasted with incompatible file types without internationally agreed standards.

Chemical Phenomena↗