Grimwood, A.; (2012) Imaging elastographic contrast in optical coherence tomography for applications in dermatology and oncology. Doctoral thesis , UCL (University College London).

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Abstract

Skin cancer diagnosis often requires invasive biopsies. These can be time-consuming and cause discomfort to the patient. Optical coherence tomography is a non-invasive tool capable of imaging skin on the micron scale. However, the modality’s contrast sensitivity limits its ability to distinguish between healthy and diseased tissue in some non-melanoma skin cancers. In this thesis, optical coherence elastography is explored as a means of contrast enhancement through the analysis of a sample’s mechanical, rather than optical, properties. An analysis of OCT imaging performance is used to design a suitable elastography phantom. Experimental measurements are also used to optimise the image tracking software. A well-defined, controlled actuation is applied to a tissue phantom and imaged using optical coherence elastography. A stiff inclusion is subsequently discerned from the surrounding material, even though conventional image contrast is low. Elastographic detail is also depicted in tissue. Finally, enhancements in axial displacement sensitivity are acquired through the acquisition of phase data and alternative actuation techniques are explored. The optical coherence elastography technique was sensitive to a Young’s modulus ratio of 7 from a 56 μm actuation. The possibility of detecting smaller changes in mechanical properties was also investigated. Axial phase displacement sensitivity was 50 nm, with an order of magnitude increase in strain sensitivity. This demonstrates the technique’s potential usefulness in discriminating between cancerous and healthy tissues.

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