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1869 results in Biomedical engineering

Page 14 of 94

X-ray Microscopy
  • Chris Jacobsen
  • Published online:
    28 October 2019
    Print publication:
    19 December 2019
  • Written by a pioneer in the field, this text provides a complete introduction to X-ray microscopy, providing all of the technical background required to use, understand and even develop X-ray microscopes. Starting from the basics of X-ray physics and focusing optics, it goes on to cover imaging theory, tomography, chemical and elemental analysis, lensless imaging, computational methods, instrumentation, radiation damage, and cryomicroscopy, and includes a survey of recent scientific applications. Designed as a 'one-stop' text, it provides a unified notation, and shows how computational methods in different areas are linked with one another. Including numerous derivations, and illustrated with dozens of examples throughout, this is an essential text for academics and practitioners across engineering, the physical sciences and the life sciences who use X-ray microscopy to analyze their specimens, as well as those taking courses in X-ray microscopy.

Principles of Biomedical Instrumentation
  • Andrew G. Webb
  • Published online:
    11 August 2019
    Print publication:
    11 January 2018
  • This accessible yet in-depth textbook describes the step-by-step processes involved in biomedical device design. Integrating microfabrication techniques, sensors and digital signal processing with key clinical applications, it covers: the measurement, amplification and digitization of physiological signals, and the removal of interfering signals; the transmission of signals from implanted sensors through the body, and the issues surrounding the powering of these sensors; networks for transferring sensitive patient data to hospitals for continuous home-monitoring systems; tests for ensuring patient safety; the cost-benefit and technological trade-offs involved in device design; and current challenges in biomedical device design. With dedicated chapters on electrocardiography, digital hearing aids and mobile health, and including numerous end-of-chapter homework problems, online solutions and additional references for extended learning, it is the ideal resource for senior undergraduate students taking courses in biomedical instrumentation and clinical technology.

  • 5 - Transmission Matrix Approach to Light Control in Complex Media

  • from Part III - Focusing Light through Turbid Media Using the Scattering Matrix
  • Edited by Joel Kubby, University of California, Santa Cruz, Sylvain Gigan, Meng Cui, Purdue University, Indiana
  • Book:
    Wavefront Shaping for Biomedical Imaging
    Published online:
    10 June 2019
    Print publication:
    20 June 2019, pp 121-137

  • Summary

    While transmission and scattering matrices have been a convenient way to describe wave propagation in complex media in mesoscopic physics, being able to describe important quantities such as total transmission, intensity statistics, etc. it has mainly been studied in this domain from a statistical point of view, i.e. to extract average quantities. Extracting the exact matrix of a given system was never even considered. In this chapter, we will describe how, leveraging on spatial light modulator technologies and the new possibilities offered by digital holography, it is possible to experimentally measure this quantity in the optical domain, not in a statistical sense, but for a particular realization of disorder, i.e. a given system, which will be for most of the experiments described in this chapter an ideal multiply scattering medium, essentially a layer of white paint, but could in principle be biological tissues. Once this information is known, the problem of recovering an image is not bound to be carried using ballistic photons. Indeed, even in the diffusive regime, the result of the propagation of a field can be deterministically predicted for scattered light. In particular, the optimal wavefront that will generate a focus on one or several output modes can be easily extracted from the matrix. We will discuss the various initial implementations of this concept, and its applications for focusing and imaging. Recent developments have shown different ways of either simplifying the procedure, or expanding its capabilities to new domains, for instance the spectral domain.

  • 8 - Feedback-Based Wavefront Shaping

  • from Part IV - Focusing Light through Turbid Media Using Feedback Optimization
  • Edited by Joel Kubby, University of California, Santa Cruz, Sylvain Gigan, Meng Cui, Purdue University, Indiana
  • Book:
    Wavefront Shaping for Biomedical Imaging
    Published online:
    10 June 2019
    Print publication:
    20 June 2019, pp 189-216

  • Summary

    In this chapter, I will first introduce the concept of feedback-based wavefront shaping and some of the fundamental properties of this technique. Then, I will review the different algorithms that can be used for finding the wavefront, and discuss different options for obtaining a feedback signal in the first place. After that, I touch on some of the wave correlations that play a role in wavefront shaping, and briefly link to related research fields. This chapter is concluded with an outlook of future applications.

  • 7 - Imaging and Controlling Light Propagation Deep within Scattering Media Using a Time-Resolved Reflection Matrix

  • from Part III - Focusing Light through Turbid Media Using the Scattering Matrix
  • Edited by Joel Kubby, University of California, Santa Cruz, Sylvain Gigan, Meng Cui, Purdue University, Indiana
  • Book:
    Wavefront Shaping for Biomedical Imaging
    Published online:
    10 June 2019
    Print publication:
    20 June 2019, pp 161-186

  • Summary

    In this chapter, we introduce two noteworthy methods for exploring the use of the so-called time-resolved reflection matrix (TRRM) of the scattering medium. TRRM is made of the amplitude and phase maps of reflected waves taken at specific arrival time and for various angles or positions of illumination. It provides us with unprecedented amount of information covering both spatial input-output correlation and temporal response. With the vast amount of information at hand, studies have been conducted to relieve the limitations of imaging depth and energy delivery that the multiple light scattering imposes. In section 2, we describe a time-domain approach for measuring TRRM and its application for dramatically improving imaging depth that maintains diffraction-limited spatial resolution. Spectral-domain approach of measuring TRRM is introduced in section 3 along with its application for enhancing energy delivery to the target depth by the implementation of time-dependent eigenchannels.

  • 14 - Light Sheet Microscopy with Wavefront-Shaped Beams: Looking Deeper into Objects and Increasing Image Contrast

  • from Part VI - Shaped Beams for Light Sheet Microscopy
  • Edited by Joel Kubby, University of California, Santa Cruz, Sylvain Gigan, Meng Cui, Purdue University, Indiana
  • Book:
    Wavefront Shaping for Biomedical Imaging
    Published online:
    10 June 2019
    Print publication:
    20 June 2019, pp 331-357

  • Summary

    Light propagation through inhomogeneous, disordered materials is still an enigmatic problem with unpredictable output, since complex multi-particle light scattering results in uncountable phase delays from scattered or absorbed photons. In coherent optics, strong intensity modulations arise from the interference of ballistic and diffusive photons and thus generate deterministic chaotic intensity distributions after some dozens of microns of propagation through scattering materials such as biological tissue. This circumstance is detrimental to the quality of an image p(x,y,z) in light-sheet based microscopy (LSBM), where a thin plane within the sample is illuminated by a sheet of light. In the ideal, but unrealistic case the light-sheet consists of purely ballistic photons, which do not interact with the various scatterers inside the sample to be imaged. However, only recently it has been shown that the relative number of ballistic photons could be increased by holographically shaping the phase of the incident laser beam. This effect leads not only to enhanced penetration depths, but consequently also reduces diffusive photons or beam deflections by scattering objects.

Page 14 of 94