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Engineering in Medicine and Biology Magazine, IEEE

Issue 1 • Date Jan.-Feb. 1996

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Displaying Results 1 - 17 of 17
  • Bioengineering Grad Tells of Life in the Real World [Student's Corner]

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    Freely Available from IEEE
  • From the Guest Editor

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    Freely Available from IEEE
  • Biological applications of near-field optical microscopy

    Page(s): 51 - 58
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    Presents several biological applications of near field optical microscopy, in combination with force microscopy. Aperture near field scanning optical microscopy (NSOM) with fluorescence detection gives (bio)chemical specificity and orientational information, in addition to the simultaneously acquired force image. This technique has large potential for DNA sequencing, molecular organization in monolayers, and study of the role of the cytoskeleton in cellular mobility in cell growth, cell migration, formation of protrusions, etc. Fluorescence NSOM gives high resolution on flat, not too deep surfaces. Fluorescence NSOM induces virtually no bleaching, as opposed to confocal fluorescence microscopy. Bright field NSOM in transmission generally yields a complicated contrast, caused by a mixture of dielectric and topographic contributions. Shear force feedback is essential in aperture NSOM operation with fibers, and operates on soft surfaces of cells and chromosomes. Ultimately, aperture NSOM is limited by low efficiency with a source brightness of typically 100 pW to 10 nW. Thus, in spectroscopic applications (fluorescence, Raman, etc.) photon noise will be a fundamental limit in the speed of imaging. Photon tunneling in combination with force microscopy allows routine scanning with a high optical lateral resolution. However, interference effects can be dominant on surfaces which display extensive scattering. As such, the application potential of PSTM to biological surfaces is rather limited. Clearly, the virtues of optics, non-invasiveness, high spectral resolution, and high time resolution all apply to the near field optical domain with its high spatial resolution, which adds extensively to the potential of scanning probe microscopy. View full abstract»

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  • An improved electric pulp tester

    Page(s): 112 - 115
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    The vitality of dental pulp is for important routine diagnosis and for treatment of tooth inflammation and necrosis. To determine the pulp vitality of a tooth, many techniques have been adopted by clinicians, such as radiographic examination, tooth plethysmography, and electric pulp testing (EPT). With regard to cost, effectiveness, and degrees of invasiveness, EPT has become the most useful and important diagnostic aid for evaluating pulp vitality. In this study, the authors investigated a commercial EPT system, to which feedback control was applied. The modified system, using a notebook computer to derive the feedback function, improved the operation of the commercial pulp tester. This system allowed the authors to re-evaluate the effectiveness of the pulp tester, and allowed them to determine how the system becomes more robust to threshold current. View full abstract»

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  • FISH image analysis

    Page(s): 67 - 75
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    Fluorescence in situ hybridization (FISH) is a rapidly expanding imaging technique in medical research and clinical diagnosis. Both researchers and clinicians find it helpful to employ quantitative digital imaging techniques with FISH images. This technique is of particular interest for multi-probe mixtures and for the automated analysis of large numbers of specimens. In the preparation of FISH specimens, multiple probes, each tagged with a different fluorophore, are often used in combination. This permits simultaneous visualization of several different molecular components of the cell. Usually, the relative positions of these components within the specimen are of scientific or clinical interest. The authors discuss these techniques and their applications. FISH dot counting is increasingly used in research and clinical studies. Research procedures and clinical tests using FISH almost certainly have an increasingly significant role to play in the future of biology and medicine. In much the same way as cytogenetics has adopted digital imaging, the techniques described here, and similar ones, will become a routine part of research and clinical practice as the use of FISH techniques expand. As in radiology, one can expect digital image processing to become an indispensable part of the activity View full abstract»

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  • Characterizing biostructures and cellular events in 2D/3D [using wide-field and confocal optical sectioning microscopy]

    Page(s): 92 - 100
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    Cellular structures are made up of a very interesting puzzle of components, whose changes in molecular distribution are believed to underlie a wide range of cellular functions. For example, the cell cycle of mammalian cells is characterised by a series of ordered biochemical events. The availability of several specific probes has led to a renewed interest in optical microscopy as a very powerful tool in cell and molecular biology. This has led to the development of methods for studying the relationship between the 3D structure of specific cellular constituents and the cell function. Within this framework, several methods have been developed and applied. In the authors' study, wide-field optical sectioning microscopy and confocal scanning laser microscopy have been utilised, demonstrating the feasibility of a 3D reconstruction of biostructures imaged by an optical microscope View full abstract»

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  • Characterizing biological tissue using scanning laser acoustic microscopy

    Page(s): 42 - 45
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    The scanning laser acoustic microscopy (SLAM) technique offers high resolution for determining the properties of individual layers. To introduce the SLAM technique as a method for measuring the speed of sound in tubular layered organs, and possibly distinguish between the layers by this measure, the authors chose the guinea-pig urethra, due to its relatively simple layered structure. To obtain more data of the acoustic properties of tissue, the attenuation coefficient was determined for the wall in toto View full abstract»

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  • Comparing maximum likelihood estimation and constrained Tikhonov-Miller restoration

    Page(s): 76 - 83
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    The authors have compared the performance of the EM-MLE and ICTM restorations applied to confocal images. Both methods greatly reduce diffraction-induced distortions of confocal images. Due to their nonlinearity, both are able (partially) to restore data of missing frequencies. From the authors' experiments, it is clear that for their test objects, the EM-MLE algorithm performs much better than ICTM. The EM-MLE algorithm produces better results under all the conditions the authors tested, and with respect to all 3 performance measures (I-Divergence, MSE, GDT) the authors used. Only for high SNR conditions, the MSE performance of ICTM approaches the EM-MLE results. It must be noted that this conclusion is only valid for the type of objects the authors used in their experiments (sparse objects); it may well be that for more dense objects, the situation is different. The poor ICTM performance shows that its functional is not well suited for images distorted with Poisson noise. The authors did not find artifacts such as ringing in the results of either algorithm. The restoration results on the cylindrical objects show, however, that the EM-MLE algorithm has a tendency to reconstruct an image that is sharper and smaller than the original object. This aspect of EM-MLE should be investigated thoroughly. Greander's method of Sieves (1991) seems promising for regularizing the EM-MLE algorithm. Finally, to reduce the computational burden of ICTM and EM-MLE, methods to speed up these algorithms should be investigated more fully View full abstract»

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  • The retrospectroscope: electrocorticography

    Page(s): 101 - 103
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    Recording the electrical activity of the exposed brain, known as an electrocorticogram (ECoG), has had a long history. Multichannel recordings from the exposed brain cortex of conscious human patients as a diagnostic procedure to localize epileptic foci began in the early 1940s. Two centers, one at McGill University and the other at Harvard University launched this new field. Relatively unrecognized at that time were the severe requirements for recording microvolt signals in the electrically hostile environment of the operating room. Not only did the electrodes have to be electrically stable initially, but they had to be stable and noise-free after steam sterilization. In 1945, one of the authors (LAG) joined the staff of the Montreal Neurological institute and the Department of Electrical Engineering, both of McGill University, and became deeply involved with the development of ECoG equipment for permanent installation in Wilder Penfield's operating room. The design goal was that the ECoG and electrodes would function on command. Because it required less than one half hour to steam sterilize the electrodes, a surgical procedure could be scheduled at any time, providing the ECoG and electrodes would perform on command View full abstract»

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  • Unsupervised color image segmentation: with application to skin tumor borders

    Page(s): 104 - 111
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    The images used in this research were digitized from 35mm color photographic slides obtained from a private dermatology practice and from New York University. The authors compared 6 color segmentation methods and their effectiveness as part of an overall border-finding algorithm. The PCT/median cut and adaptive thresholding algorithms provided the lowest average error and show the most promise for further individual algorithm development. Combining the different methods resulted in further improvement in the number of correctly identified tumor borders, and by incorporating additional heuristics in merging the segmented object information, one could potentially further increase the success rate. The algorithm is broad-based and suggests several areas for further research. One possible area of exploration is to incorporate an intelligent decision making process as to the number of colors that should be used for segmentation in the PCT/median cut and adaptive thresholding algorithms. For comparison purposes, the number of colors was kept constant at three in the authors' application. Other areas that can be explored are noise removal and object classification to determine the correct tumor object View full abstract»

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  • Coherent methods in confocal microscopy

    Page(s): 84 - 91
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    The authors review the use of 2 kinds of coherent imaging methods in confocal microscopy: interferometry and the use of optical fibres. In both cases, the emphasis is concerned with detecting both the confocal field amplitude and its phase. It is usual in confocal systems to detect only the image intensity and so to loose all phase information. In order to detect the phase with an incoherent photodetector, it is necessary to use some form of interferometry. In the classical interferometer, the authors show that by detecting the phase and amplitude in a conventional interference microscope employing a large area detector it is possible to obtain confocal imaging. Indeed, the interference term images in conventional and confocal interference microscopes are found to be identical. An optical fibre-based confocal interference microscope is shown to have some practical advantages over a conventional, noncommon path implementation. The question of resolution in phase imaging is discussed and it is shown that due to the inherent nonlinearity of the process, great care should be taken in interpreting these images. The introduction of optical fibres instead of pinholes is shown to lead to simplification in system design. However, the introduction of 2-mode fibres makes the system more versatile. In essence, the fundamental mode detects the image amplitude and the first order mode detects the differential of the image amplitude. These modes then propagate along the fibre with different speeds and, hence, emerge from the fibre with a relative phase difference determined by the length of the fibre. These 2 modes are finally allowed to interfere. In this way, it is possible to obtain both confocal differential amplitude contrast, and differential phase contrast images simultaneously, without any other alteration to the optical system View full abstract»

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  • Scanning tunneling microscopy of DNA

    Page(s): 46 - 50
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    The systematic removal or destruction of DNA by the scanning tunneling microscope (STM) stems from the low conductivity of the molecule. Imaging DNA at exceedingly low currents and high voltages prevents damaging contact in humid conditions. The STM images of DNA on mica are evidence that the STM could be used to study genomic structure on a nanometer scale. Thus, the STM may join the scanning force microscope as a powerful imaging tool for DNA studies because: 1) Such resolution is adequate for observing the curvature of DNA and DNA-protein complexes, and also the gross structure of DNA-protein complexes. 2) Both microscopes may be operated in solution to examine DNA molecules in physiological conditions. However, Lindsay et al. (1990) have encountered the above mentioned difficulties using the STM. 3) While the STM is sensitive to the electronic states of adsorbed molecules, the scanning force microscope can detect chemical parameters such as adhesion. Information in addition to topography enhances one's ability to interpret images. Undoubtedly, the scanning tunneling microscope is a very important tool with which to study conductive surfaces. For poorly conducting molecules adsorbed on substrates, hybrid microscopes with which to examine the surface by alterative methods may neatly facilitate systematic investigations View full abstract»

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  • Quantitative microscopy

    Page(s): 59 - 66
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    While light microscopy is almost 400 years old, developments of the past decade have offered a variety of new mechanisms for examination of biological and material samples. These developments include exploitation of techniques such as confocal microscopy, scanning near field microscopy, standing wave microscopy, fluorescence lifetime microscopy, and two-photon microscopy. In biology, advances in molecular biology and biochemistry have made it possible to selectively tag (and thus make visible) specific parts of cells, such as actin molecules, or sequences of DNA of 1000 base pairs or longer. In sensor technology, modern charge-coupled device (CCD) cameras are capable of achieving high spatial resolution and high sensitivity measurements of signals in the optical microscope. Modern CCD camera systems are limited by the fundamental quantum fluctuations of photons, which cannot be eliminated by “better” design. Further, proper choice of the sampling density involves not only an understanding of classic linear system theory-the Nyquist theorem-but also the equally stringent requirements of digital measurement theory. Experimental procedures that rely on the CV can be used to evaluate the quality of one's quantitative microscope systems and to identify which components are the “weakest link”. Typical values of relatively straightforward parameters such as size can easily be measured to CVs around 1% View full abstract»

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  • Japan's commercial development of the electron microscope

    Page(s): 31 - 34
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    Americans have a picture of Japan as a country which, in the years after the Second World War, was able to produce only inexpensive and shoddy goods. This picture is not, however, entirely accurate. For example, the first electronic product exported from Japan to America after the war was not, as most suppose, the transistor radio but a highly complex research tool, the electron microscope. Today, Japan manufacturers the majority of the world's electron microscopes. How could a country cut off from the West's scientific research establishment in 1939 and in economic ruin in 1945 be competitive as early as the 1950's in producing such complex technology? This short article, based largely on an interview with two of the founders of one important Japanese microscope manufacturer (JEOL) gives a few clues. Rather than present a detailed history of the company, the author identifies seventeen factors that contributed to the company's success View full abstract»

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  • Engineering and the law. Public policy and the preemption of state tort claims against medical device manufacturers

    Page(s): 121 - 124, 128
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    As the settlement of breast implant cases illustrate, the dynamics of the tort system are such that safe products can still be driven from the market by emotional pleas to juries. Given the importance of medical devices in modern medicine, it is critical that the legal system limit tort claims against medical device manufacturers. While it may ultimately be necessary for Congress to create a statutory compensation system for medical device injuries, the best short-term chance for relief of the pre-emption of tort claims is found in the MDA View full abstract»

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  • Sonography and quantitative measurements

    Page(s): 35 - 41
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    A preliminary study of coronary artery wall topography and mechanical properties is presented. The aim of this study was to give a brief demonstration of scanning acoustic microscopy (SAM) as a sonographic technique, and to apply the time-resolved SAM (TR-SAM) technique for quantification of coronary artery wall mechanical properties under passive conditions ex-vivo, and compare the data for the tunica externa and tunica media of the wall. The authors chose the diagonal branches of the left anterior descending coronary artery (LADCA) of young healthy pigs for measurements. It is concluded that SAM is well suited for sonography at the micrometer level, and TR-SAM provides a refined tool for biorheological quantification ex-vivo, provided that a number of physical factors influencing measurements and tissue properties are considered and dealt with. With time and effort, SAM may also become a valuable tool for recognizing important relations of composition and structure to function. For future SAM studies of arteries, more detailed analyses of layer interfaces and better models of biorheology should be applied to describe the anisotropy and nonlinear viscoelasticity of the wall 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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