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Louie, Daniel Christopher

University of British Columbia

The design challenge of improving melanoma care stems from two factors: its incidence which continues to increase, and its lethality if not detected and treated early. In the search for tools that can benefit rather than exacerbate the effort to implement widespread and accessible detection of melanoma, this dissertation embarks on a research program to design a lightweight optical probing technology to quantifiably measure cellular malignancy. Probing skin tissue with a laser generates polarization speckle, a stochastic interference pattern containing both polarization and coherence information, from which tissue morphology metrics such as surface roughness can be extracted. A simple optical probe was developed to investigate polarimetry for rapid melanoma detection, while incorporating considerations for the generation of speckle in its design. This probe was tested in a pilot clinical study on a variety of skin lesions in vivo, where it was found that the mean degree of polarization (DOP±sterr) for melanoma (0.46 ± 0.09) was greater than that of benign nevus (0.31 ± 0.06) and all nonmelanoma lesions (0.28 ± 0.01). This result was expanded upon in an exploration of a new metric called polarization memory rate (PMR). Polarization memory rate is a ratio of circular to linear degrees of polarization, which is based on the scattering and depolarization differences between benign and malignant cells due to their differing optical refractive index. This metric (PMR±sterr) as measured by the probe was able to further separate melanoma (0.97 ± 0.11) from nevus (0.58 ± 0.07) and separate cancerous lesions from benign lesions with p < 0.05. Further work is done on design refinements for polarization speckle technology. Experiments were done to validate the miniaturization of speckle devices through reducing illumination to a low cost laser diode, and generating an experimental calibration curve that matches speckle contrast to surface roughness. Finally, a robust Stokes vector speckle system was constructed, employing two pixel polarizer cameras. This system was designed, constructed, and calibrated to measure the complete polarization state map of speckle. Each of these innovations furthers technological development towards a lightweight optical probing technology to quantifiably measure cellular malignancy.

Text

2023-04-21

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/84412

Biomedical Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/