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Engineering in Medicine and Biology Magazine, IEEE

Issue 5 • Date Sept.-Oct. 1997

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Displaying Results 1 - 18 of 18
  • New Trends In Cardiovascular Dynamics

    Page(s): 63
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    First Page of the Article
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  • Investigating baroreflex control of circulation using signal processing techniques

    Page(s): 86 - 95
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    The authors examine recent approaches for the assessment of baroreflex control of circulation. The application of these techniques has provided them with new insights into cardiovascular regulation including: 1) a comprehensive description of the effects of the arterial baroreflex on different components of blood pressure variability and heart rate variability; and 2) a description of the dynamic modulation of the spontaneous baroreflex gain, which occurs in the laboratory environment and in daily life activities. Given the recent evidence that information on baroreflex cardiovascular control may have prognostic value in a variety of pathological conditions, the clinical application of the above techniques may offer new perspectives for the routine evaluation of patients with cardiovascular diseases. View full abstract»

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  • Linear and nonlinear system identification of autonomic heart-rate modulation

    Page(s): 96 - 105
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    The authors' findings show that system identification provides a useful, noninvasive, and quantitative means for evaluating cardiovascular regulatory mechanisms. With combinations of linear and nonlinear identification, new insights about the cardiovascular regulatory dynamics were obtained. System identification provides a new way of studying and monitoring cardiovascular function. Instead of just studying the signals generated by the cardiovascular regulatory system, the signals are analyzed to characterize quantitatively the mechanisms that generate them. System identification is a type of "inverse modeling"in which the physiologic signals are used to create a model of cardiovascular regulation for the specific individual from whom the data are obtained. As such, system identification would appear to be a desirable means for evaluating effects of physiologic alterations resulting from pharmacological interventions, changes in environment such as changes in gravitational field, physiologic stresses such as hypoxia and exercise, and disease processes. System identification may also prove to be an attractive means to study closed-loop regulation in other physiologic systems, ranging in size from biochemical pathways to intact multi-organ systems. View full abstract»

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  • Classical but effective techniques for estimating cardiovascular dynamics

    Page(s): 106 - 112
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    This article first describes the effectiveness and the limitations of classical approaches based on linear models for the cardiovascular system. The authors then introduce their own work on less-invasive and real-time estimation of cardiac output flow and pump function in the clinical setting. It is shown that system identification techniques using linear models can yield unexpectedly accurate results useful for patient care. View full abstract»

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  • Short-term analysis of heart-rate variability of adapted wavelet transforms

    Page(s): 113 - 118
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    The purpose of this study is to characterize the heart rate variability (HRV) signal in the frequency domain by using wavelet and cosine packets. Here, the authors introduce the adapted wavelet transform methods to analyze heart-rate fluctuations. These methods were chosen because the components in the signals can be analyzed and quantified at different scales, e.g., long windows can be used for the low-frequency component while short-time windows can be used for high-frequency components. In this study, adaptive wavelet transform methods are applied to the HRV obtained from normal subjects. A comparison is made on the same data base with results based on the short-term Fourier transform method. View full abstract»

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  • Time-frequency analysis of heart-rate variability

    Page(s): 119 - 126
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    We present the results of a study that shows the viability of a new technique for the diagnosis and monitoring of myocardial ischemia that is based on the utilization of heart-rate variability (HRV) information. Ischemia is understood as being the lack of oxygen supply to the heart, a situation that in an extreme and irreversible case results in acute myocardial infarction (AMI), a reason for which early detection and treatment is of great interest. The treatment of ischemia can be approached via the evolution of the ECG, and especially from one of the parameters extracted from it-the ST segment (ECG signal between S and T waves) deviation. The utility of this measure is found in its capacity for detecting abnormalities in the conduction of the cardiac impulse that are associated with the presence of ischemia. View full abstract»

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  • The relationship between cardiac contraction and intramyocardial hemodynamics

    Page(s): 127 - 132
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    Since coronary venous flow is squeezed out from the myocardial vascular bed by the extravascular compressive force of heart muscle, the coronary venous system provides a suitable model to investigate the relationship between cardiac contraction and intramyocardial hemodynamics. To investigate coronary venous flow velocity in more detail, we previously developed a laser Doppler velocimeter (LDV) with an optical fiber. Furthermore, we have recently developed a needle probe charge-coupled device (CCD) videomicroscope to visualize intramyocardial microvessels. In this article, we report I) blood flow velocity waveforms in the epicardial small veins of the left ventricle and 2) subendocardial venular diameter changes during a cardiac cycle. View full abstract»

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  • Principles and applications of the Laplacian electrocardiogram

    Page(s): 133 - 138
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    The Laplacian ECG provides enhanced lateral spatial resolution in relating the body surface ECG recordings to the underlying myocardial electrical sources. This article reviews recent research activities associated with theoretical and experimental investigations of Laplacian ECGs. The emphasis is put on theoretical interpretation and recording techniques of this new ECG measurement, with representative examples illustrating the potential applications of the Laplacian ECG. View full abstract»

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  • Identifying coronary stenosis using an image-recognition neural network

    Page(s): 139 - 144
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    The present study represents an attempt to improve the separation of specific high-risk coronary stenosis from lower-risk conditions by employing an image-recognition neural network. The system mimics the visual reading of scintigraphs from raw digitized data, with the added benefit of a computerized classification system. It models the human retina as the sensing organ that processes the image signals and forwards them to the brain, where the outputs from each visual segment are processed to produce a recognition code. In the application described here, the recognition code classifies a scintigraphic image as demonstrating normal myocardial perfusion, or a perfusion pattern consistent with single-vessel, multiple-vessel, or left-anterior descending coronary artery stenosis. The input images are from clinically performed postexercise planar myocardial perfusion scintigraphs as produced in many clinical laboratories. View full abstract»

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  • Nonautologous gene therapy with implantable devices

    Page(s): 145 - 150
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    Treatment of human diseases with gene therapy is a technological break through that has been touted to be the "ultimate medicine". A potentially more cost-effective method of gene therapy is to use universal cell lines engineered to secrete therapeutic products that are suitable for implantation in all patients requiring the same product replacement. To avoid immune rejection, these nonautologous donor cells can be protected within immuno-isolation devices such as alginate-fabricated microcapsules. This article documents the early development and current status of nonautologous somatic gene therapy, combining biomaterial with genetic engineering to develop a new direction of research. Topics covered include: questions in gene therapy; nonautologous somatic gene therapeutics; the expression of recombinant gene products in immuno-isolation devices; the delivery of recombinant gene products with encapsulated cells in vivo; and animal models of human genetic diseases. View full abstract»

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  • An oriented control system for dental implant surgery

    Page(s): 151 - 154
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    An oriented control system is proposed that is very useful for monitoring the orientation of the dental drill and the patient's head during dental implant surgery. The system incorporates an angular sensor for improved accuracy. Correct orientation assures an accurate implant and provides for the recovery of normal dental function, which include esthetics, speech, chewing, and comfort. View full abstract»

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  • Extracting evoked potentials with the singularity detection technique

    Page(s): 155 - 161
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    For a better and faster method of extracting EPs, we study the difference between the EP signal singularities and the EEG noise singularities. The ensemble-averaging operation is based on the fact that the EEG can be looked upon as white noise. The singularity detection (SD) technique that we discuss can adequately remove white noise from the signal. We found that there was a very large difference between the EP signal singularities and the EEG noise singularities. The local maxima of the wavelet-transform modulus provide enough information to analyze these singularities. We can extract the EP signal components from the EEG noise by selecting the wavelet-transform modulus maxima that correspond to the EP signal singularities. After removing the modulus maxima of the EEG noise fluctuations, we are able to reconstruct a denoised EP signal. View full abstract»

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  • Tracking the historical development of biomedical engineering: the 1960s and 1970s

    Page(s): 164 - 173
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    Biomedical engineering has evolved with unique multidisciplinary characteristics. In its lifespan this discipline has grown to encompass an ever-widening array of clinical, scientific, and engineering areas. This field offers a picture of an engineering science that has matured in an alternative direction from other scientific areas in the 20th century. This article proposes a historic research overview or matrix (3D) of biomedical engineering in the 1960s and 1970s. A derivative methodology is presented that was utilized to create this matrix. The immediate goals are to see what practitioners of that time were defining as biomedical engineering and the nature of its expansion. The primary concern of this preliminary assessment is to determine the general direction of research for the early community. The disciplinary or institutional organization of this body of knowledge is also an important key. While other questions about the dynamics of the community are also important, the first step is to understand the types of problems that were focused on. View full abstract»

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  • Litigating fear: electrical and magnetic fields (EMF) and the law

    Page(s): 176 - 178
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    A large number of persons in the United States and Europe believe that EMF causes human illness. These illnesses include childhood leukemia, other cancers, high blood pressure, the aggravation of other diseases, and electrical sensitivity syndrome. EMF has become a legal issue as people seek compensation for alleged injuries and try to have power lines relocated away from their homes. This column discusses the problem of making good legal decisions about complex scientific problems such as EMF. Topics discussed include: the history; the Denver study; fear and the law; proving negatives and the law; economic consequences of fear; and fear and the public utility consequences. The author concludes that so far, the courts and most state public-utility regulatory commissions have acted reasonably when dealing with EMF. They have recognized that the potential risk is very small, if there is any risk at all, and that the potential harm from regulation is very high. This is a precarious balance, however, and it could easily be upset by either trial judges allowing EMF cases to be litigated or a state public-utility commission giving in to public pressure and declaring EMF a threat to health. Scientists and others who understand these problems should speak out and try to shape public opinion to diminish the suffering that comes from irrational fears and the social dislocations that follow bad policy choices. View full abstract»

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  • Flow-dependent Regulation of Vascular Function [Book Reviews]

    Page(s): 179 - 180
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    Freely Available from IEEE
  • Contemporary Perspectives In Three-dimensional Biomedical Imaging [Book Reviews]

    Page(s): 179 - 181
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    Freely Available from IEEE
  • Continuous monitoring of the sympatho-vagal balance through spectral analysis

    Page(s): 64 - 73
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    The activity of the autonomic nervous system is noninvasively studied by means of autoregressive (AR) frequency analysis of the heart-rate variability (HRV) signal. Some methods of noise rejection and robustness for AR recursive identification are presented that make on-line frequency analysis of the heart-rate variability signal more reliable. The performance of the algorithms is first tested through simulations, and then results obtained on real data during ischemic episodes are presented View full abstract»

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  • Model dependency of multivariate autoregressive spectral analysis

    Page(s): 74 - 85
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    A combination of simulations and experimental data analysis has been used to demonstrate that, because cardiovascular control represents a complex linking of input and output parameters, interpreting the variability of individual parameters such as heart rate and arterial pressure virtually requires the use of techniques that quantify control by relating these inputs and outputs. Transfer functions represent appropriate techniques for this purpose. Further, despite the complexities of in vivo physiological control, many of the control elements can be well characterized by only taking into account single inputs and outputs and using a bivariate AR model. However, occasionally when two control systems have a strong and simultaneous influence on a single output parameter, such as arterial pressure and respiratory activity on RR interval, an expansion of the model to the general multivariate case may be required for a complete interpretation. Finally, although not fully demonstrated here, because of the closed-loop nature of cardiovascular control it is likely that algorithms that include causality to account for this characteristic, such as the AR formulation, will most accurately identify the transfer relations View full abstract»

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Aims & Scope

IEEE Engineering in Medicine and Biology Magazine contains articles on current technologies and methods used in biomedical and clinical engineering.

 

This Magazine ceased publication in 2010. The current retitled publication is IEEE Pulse.

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