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Biomedical Engineering, IEEE Transactions on

Issue 5 • Date May 1995

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Displaying Results 1 - 11 of 11
  • Design, fabrication, and in vitro evaluation of an in vivo ultrasonic Doppler wall shear rate measuring device

    Publication Year: 1995 , Page(s): 433 - 441
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (957 KB)  

    In vivo wall shear rates have been obtained based on estimates from either volume flow rate or single-point velocity measurements along with the wall no slip assumption and a simple linear regression. Recent results (R.S. Fatemi and S.E. Rittgers, 1994) have shown that, under pulsatile flow conditions, wall shear rates are more accurately predicted by using up to four velocity points and a second- or third-order polynomial curve fit. The authors evaluate the accuracy of a new, in vivo transducer capable of determining wall shear rates nonintrusively from velocities at three points along a line perpendicular to the vessel wall. Three 20-MHz ultrasound crystals were embedded in an elastomer at distances of 1.5 and 2.1 mm with beam angles of 30°, 15°, and 60° to the horizontal plane. Microscopic examination showed that intercrystal spacings were within 1.5% of the design and the crystal angles were placed within 2.0%. In vitro calibration was performed under steady and pulsatile flow conditions with average shear rates being within 4.3±17.3% and 0.2±0.6.0% respectively, of the theoretically predicted values. Furthermore, peak and oscillatory shear rates were within -5.6±2.2% and -2.4±5.7% accuracy, respectively. Results from this study show this device to be capable of providing accurate wall shear rates in vivo. View full abstract»

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  • Real time frequency domain fiberoptic temperature sensor

    Publication Year: 1995 , Page(s): 471 - 476
    Cited by:  Papers (4)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    The excited state phosphorescence lifetime of alexandrite crystals is used to monitor temperature in the physiological range from 15-45°C with precision and accuracy of 0.2°C. A 500-μm cubic alexandrite crystal bounded to the distal end of an optical fiber of similar core dimensions is excited with pulsed Ne-He laser light. This apparatus uses a sampler for data acquisition and frequency domain methods for data fitting. The instrument amplifies the AC components of the detector output and band limits the signal to 12.5 kHz. The fundamental frequency of the excitation is set to 195.13 Hz to obtain 64 harmonics. This band limited signal is sampled and averaged over few hundred cycles in the time domain. The frequency domain representation of the data is obtained by employing fast Fourier transform algorithms. The phase delay and the modulation ratio of each sampled harmonic are then computed. Five to 50 values of the phase and modulations are averaged before computing the sensor lifetime. The instrument is capable of measuring precise and accurate excited state lifetimes from subpicowatt luminescent signals in plastic optical fibers. A least squares fit yields the lifetimes of single exponentials. A component of zero lifetime is introduced to account for the backscatter excitation seen by the photodetector leaking through optical interference filters. The phosphorescence lifetimes measured reproducibly to about three parts in a thousand are used to monitor physiological temperature. Temperatures are computed employing empirical polynomials. The system drift is negligible over 15 h of continuous operation. The instrumentation and methods allow 1.3-s update times and 30-s full response times View full abstract»

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  • An instrument to measure the dimensions of skin wounds

    Publication Year: 1995 , Page(s): 464 - 470
    Cited by:  Papers (12)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (696 KB)  

    A new instrument based on the principle of color-coded structured light has been developed to measure the area, volume, and color of skin ulcers and pressure sores. A set of parallel stripes of alternating colors is projected onto the ulcerated skin and recorded by a CCD camera. The color, width, distance, and coding of the stripes have been adjusted to maximize the precision of the instrument. Algorithms have been developed to extract the stripes and determine their centers to better than 0.1 mm, even under circumstances where the skin reflectivity varies widely over short distances. A depth map for the ulcerated skin is calculated by triangulation. The volume of the ulcer is that sandwiched between the base of the lesion and the original healthy skin, which is simulated by a cubic spline interpolation between the surrounding areas of healthy skin. The instrument measures the ulcer's volume with a precision of about 5% provided the ratio of the ulcer's volume to area is greater than 0.4 cm. The technique has been used in hospital clinics for a wide variety of wounds View full abstract»

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  • A triplane video-based experimental system for studying axisymmetrically inflated biomembranes

    Publication Year: 1995 , Page(s): 442 - 450
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (728 KB)  

    Uniform inflation experiments are useful for studying the multiaxial mechanical properties of thin biological soft tissues, but previous inflation studies have been limited by: (1) the lack of a theory that allows a specific form of the constitutive relation to be inferred directly from data; and (2) slow, off-line methods for the measurement and analysis of strain. Here, the authors describe a new on-line, triplane, video-based experimental system for performing new theoretically based tests on axisymmetrically inflated biomembranes. In particular, in-plane principal stretch ratios and principal curvatures can be measured continuously in multiple regions during pressure-controlled inflation tests. Data from tests on rubber membranes and fusiform aneurysms illustrate the utility of both the new theory and the experimental system View full abstract»

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  • Data transmission from an implantable biotelemeter by load-shift keying using circuit configuration modulator

    Publication Year: 1995 , Page(s): 524 - 528
    Cited by:  Papers (51)  |  Patents (93)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    Using the reflected impedance property of an inductive couple (transformer), a modulation method, load-shift keying using circuit configuration modulator (LSK-CCM), was developed to perform data transmission from an implantable telemeter. With a very simple circuit, this method utilizes a radio-frequency electromagnetic field induced with a single pair of coils to transmit power into the implant and data out of it View full abstract»

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  • Modeling and estimation for patient controlled analgesia of chronic pain

    Publication Year: 1995 , Page(s): 477 - 485
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (672 KB)  

    An existing mathematical model of the patient and the pain in patient controlled analgesia is extended to account for the potent metabolite morphine-6β-glucuronide and to characterize chronic pain. Nominal population parameters characterizing pain and analgesic effect are tuned to make the model match observed clinical behavior. The model is used to design an on-line estimator generating state estimates which should be suitable for use in a stochastic PCA algorithm delivering a self-adjusting continuous infusion View full abstract»

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  • Application of the surface harmonic expansions for modeling the human torso

    Publication Year: 1995 , Page(s): 521 - 524
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    A method is described to represent the human-torso geometry, as obtained from, e.g. MR imaging, in terms of the surface harmonic expansion. Three specific torso geometries, two male and one female, were reconstructed with the root-mean-square (rms) error <5 mm using 168 and 248 parameters, respectively. The method can be used in radiation therapy and enhances the accuracy of forward and inverse modeling in electrocardiology View full abstract»

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  • The signal-to-noise ratio of nuclear magnetic resonance surface coils and application to a lossy dielectric cylinder model. II. The case of cylindrical window coils

    Publication Year: 1995 , Page(s): 507 - 520
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1124 KB)  

    For pt. I see ibid., vol. 42, no. 5, p. 497-506 (1995). In pt. I the authors developed complete expressions for the power dissipated by and for the signal-to-noise ratio (S/N) of a coil of arbitrary geometry facing an infinite lossy dielectric cylinder. They now consider an example coil geometry, a “cylindrical window”, and demonstrate the effects of coil size and position, tissue properties, and source location on the S/N. Frequencies ranging from 1 to 170 MHz are investigated for two coil sizes, the larger having four times the surface area of the smaller. For a dipole source of strength assumed independent of frequency, the S/N is constant for frequencies up to about 10 MHz. Both coil sizes yield similar optimal S/N values when imaging structures deep within the body, the larger coil showing less dependence on the source location. For more superficial structures, the smaller coil has a better performance at all frequencies investigated while still being more sensitive to source position. Hence, when imaging superficial structures the choice of coil size should be balanced between image uniformity and the need for a higher S/N. For each coil size, there is an optimal position away from the tissues which yields the highest S/N when imaging deep. By contrast, the coil should be placed as close as possible to the body when the source is near the surface. From an electromagnetic standpoint and aside from the increased equilibrium magnetization in the tissues, the S/N of both coils is actually improved by operating at a higher frequency when imaging superficially, whereas it is degraded when imaging deep. Experimental results gathered on a saline-filled cylinder correlate very well with these simulations and show the model will also predict with good accuracy the S/N for a finite length cylinder as long as that length is at least three or four times the coil longitudinal dimension View full abstract»

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  • The signal-to-noise ratio of nuclear magnetic resonance surface coils and application to a lossy dielectric cylinder model. I. Theory

    Publication Year: 1995 , Page(s): 497 - 506
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (760 KB)  

    Surface coils are used in magnetic resonance imaging (MRI) for their high signal-to-noise ratio (S/N) when placed near the-region to be imaged. However, their optimization for high field MRI systems is hampered by the lack of understanding of the electromagnetic effects taking place at high frequencies when a coil is placed near the human body. The aim of this work was to calculate the S/N of surface coils using complete solutions to Maxwell's equations and also to study the high frequency effects and parameters determining the S/N. Here the authors present a general approach to the computation of the S/N of surface coils using the reciprocity principal and the complex Poynting vector for arbitrary coil and body geometries. This approach is then applied to the case of the human body modeled as an infinitely long homogeneous dielectric cylinder exhibiting both conductive and dielectric losses. The S/N of a coil of unspecified geometry facing the cylinder is derived using a dyadic Green's function. Complete solutions for the fields of a dipolar source arbitrarily located in the cylinder are first derived, and applying the reciprocity principle, the authors deduce the fields created at the dipole position by a coil excited with a unit radiofrequency current. These yield the expressions for the power dissipated in the cylinder, for its reciprocal the noise picked up by the coil, and also for the signal received. Any coil geometry and any coil or source position can be evaluated with this infinite cylinder model. It is valid at all frequencies and for any tissue parameter. The general approach to the computation of the S/N of MRI coils can be applied to other body geometries as well View full abstract»

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  • An optical multiple indicator dilution technique to measure lung permeability-surface area: calibration and baseline measurement

    Publication Year: 1995 , Page(s): 451 - 463
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1132 KB)  

    A device was designed to measure the change in optical density (ΔOD) of blood at selected wavelengths as a function of the concentration of optically absorbing multiple indicator dilution (MID) tracers. The optical MID (OMID) tracers selected for this measurement device and their corresponding wavelengths are the following: indocyanine green(ICG)-bound albumin measured at 820 nm, sulfhemoglobinated erythrocytes (Shb-RBC's) measured at 620 nm, and 1,2-propanediol measured at 9.55 μm. Arterial blood from cannulated anesthetized dogs was circulated through an extracorporeal flow-through circuit which included this ΔOD measurement device. Calibration of the 820 nm and 620 nm channels produced r2 of greater than 0.95 for the optical density-tracer mass regressions. The propanediol measurement channel (9.55 μm) was also linearly calibrated. An in vivo optical MID study was performed and compared to a radioisotope MID study. Lung vascular permeability-surface area (PS) values calculated using the two methods were 5.76 and 5.73 mL/s. It is concluded that this OMID technique is an acceptable alternative to radioisotope MID studies View full abstract»

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  • Neural network models in EMG diagnosis

    Publication Year: 1995 , Page(s): 486 - 496
    Cited by:  Papers (22)  |  Patents (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1000 KB)  

    In previous years, several computer-aided quantitative motor unit action potential (MUAP) techniques were reported. It is now possible to add to these techniques the capability of automated medical diagnosis so that all data can be processed in an integrated environment. In this study, the parametric pattern recognition (PPR) algorithm that facilitates automatic MUAP feature extraction and Artificial Neural Network (ANN) models are combined for providing an integrated system for the diagnosis of neuromuscular disorders. Two paradigms of learning for training ANN models were investigated, supervised, and unsupervised. For supervised learning, the back-propagation algorithm and for unsupervised learning, the Kohonen's self-organizing feature maps algorithm were used. The diagnostic yield for models trained with both procedures was similar and on the order of 80%. However, back propagation models required considerably more computational effort compared to the Kohonen's self-organizing feature map models. Poorer diagnostic performance was obtained when the K-means nearest neighbor clustering algorithm was applied on the same set of data View full abstract»

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Aims & Scope

IEEE Transactions on Biomedical Engineering contains basic and applied papers dealing with biomedical engineering. Papers range from engineering development in methods and techniques with biomedical applications to experimental and clinical investigations with engineering contributions.

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Meet Our Editors

Editor-in-Chief
Bin He
Department of Biomedical Engineering