Rotating orthogonal polarization imaging

Zhu, Qun (2009) Rotating orthogonal polarization imaging. PhD thesis, University of Nottingham.

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Abstract

Non-invasively characterizing the polarization properties of tissues has potential for in vivo clinical applications such as monitoring the healing state of wounds and burns. Conventional methods, which measure the polarization difference of a tissue and usually involve a co-polarized detection, are either restricted by a sample's surface reflections or can only be performed in off-axial systems with the use of matching fluid and a glass plate applied to the sample's surface. In this thesis a new technique called rotating orthogonal polarization imaging (ROPI) is presented.

The technique involves illumination in a single polarization state and detection in the orthogonal polarization state in a coaxial system. Synchronously rotating both the illumination and orthogonal detection states can provide a polarization difference image that is free from surface reflections and sensitive to the polarization property of a target embedded within a scattering medium.

The basic theoretical principle of the technique is demonstrated using Mueller calculus. Monte Carlo (MC) simulations are used to simulate the ideal performance when detecting a polarizing target embedded in a scattering medium at different depths. Tissue phantom experiments also investigate the imaging of a polarizing target embedded within a scattering medium at different depths using manual rotation of polarisers and liquid crystal tunable filters.

ROPI is far more effective than conventional polarization difference imaging due to the significant reduction in surface reflections. The technique is sensitive to polarizing targets embedded at depths of up to 17 mean free paths within the medium. Accurate quantification of dichroism is difficult due to scattering that occurs between the target and the exit surface of the medium.

In addition, preliminary measurements of the linear dichroism of different real tissues (bovine tendon, lamb tendon, chicken breast and human skin) and a tissue engineered tendon orientated at two orthogonal directions are demonstrated.

It should be noted that the majority of simulation and tissue phantom results that are presented in this thesis are for performing ROPI for polarizing targets embedded in a scattering solution. Much further work is required before the technique can be taken into clinical practice. Issues such as image alignment and the inversion of the data to produce clinically useful images still need to be addressed.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Crowe, J.A.
Morgan, S.
Stockford, I.
Keywords: Optics, polarizers (Light), diagnostic imaging, research
Subjects: Q Science > QC Physics
Faculties/Schools: UK Campuses > Faculty of Engineering > Department of Electrical and Electronic Engineering
Item ID: 13518
Depositing User: EP, Services
Date Deposited: 12 Aug 2013 11:37
Last Modified: 13 Sep 2016 23:20
URI: http://eprints.nottingham.ac.uk/id/eprint/13518

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