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Coherent backscatter and its use in measuring the optical properties of biological tissues

Eddowes, Miles Hugh; (1995) Coherent backscatter and its use in measuring the optical properties of biological tissues. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

This thesis is concerned with the measurement of the scattering and absorption properties of biological tissues using the technique of Coherent Backscatter (also known as Coherent Enhancement or Weak Localization). The Coherent Backscatter method offers a remote sensing technique that may be superior to conventional alternatives through its applicability to in vivo measurements, its sensitivity at the relatively high values of scattering often found in biological media, the small volumes of tissue that can be interrogated, and its low equipment costs. A Monte Carlo approach is used to accurately evaluate the spatial characteristics of light that is backscattered from biological media and an important prediction is made on the likely depth to which the technique probes. The phenomenon of Coherent Backscatter is introduced in the context of tissue optics and the development of a numerical method based on the Monte Carlo results is reported that predicts the coherent enhancement peaks that are likely to be recorded from biological media. This includes accurate predictions of the effects of scattering anisotropy, refractive index mismatches, and certain illumination geometries that have not, as yet, been achieved exactly by any analytical methods. A neural network has been implemented to provide a very fast and robust method for processing an experimental reading in order to extract the reduced scattering and absorption coefficients. The experimental data presented evaluates the accuracy of the technique and demonstrates its use on a variety of media including an in vivo human hand. The technique is also used to investigate the possible dependence of the optical properties on the polarization state of the probing light and the orientations of fibres in certain media.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Coherent backscatter and its use in measuring the optical properties of biological tissues
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Pure sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10103957
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