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Title: Developments of magnetomotive optical coherence tomography and polarization-sensitive optical coherence tomography for clinical applications
Author: Li, Wei
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2020
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There are two main aims in this project: (1) develop a contrast agent which can be tracked by our in-house phase-sensitive spectral domain (SD) OCT and commercial confocal fluorescence microscopy (CFM) simultaneously; (2) apply our in-house polarization-sensitive (PS) OCT to investigate birefringence and collagen alignment in the human cervix and assess its potential to characterise changes in extracellular matrix structure during pregnancy. To realize the first aim, the SD-OCT was optimized to recover/improve its performance at first. Before the optimization, the SD-OCT had poor performance due to the shifting alignment resulted from the movements of its optical components by vibration and gravity. The optimized SD-OCT has a sensitivity of 81.4 dB and an axial and lateral resolution of 3.4 ?m and 6.2 ?m respectively. Then, the optimized SD-OCT system was adapted to magnetomotive OCT (MMOCT) to track magnetically labelled cells. A contrast agent, magnetic graphene quantum dot (MGQD), was synthesized by hydrothermally reducing and cutting graphene oxide-iron oxide sheet. The MGQD showed significant tuneable blue fluorescence and superparamagnetism, hence it can be used as a dual-modality tracer for CFM and MMOCT. 3T3 cells were labelled by the MGQD, and the MGQD labelled cells have been successfully localized and imaged by a commercial CFM and our in-house MMOCT system. As CFM and MMOCT are provide intracellular details and anatomical information respectively, hence a more comprehensive diagnosis can be achieved through the application of MGQD for cell tracking. For the second aim, 20 cervical cross-sections from non-gravid women were interrogated by our in-house PS-OCT. Several algorithms have been applied to process and map the images of sample's intensity, phase retardance, birefringence and depolarization using the data obtained from the PS-OCT. The physical information obtained from the PS-OCT is able to identify cervical epithelium, measure epithelial thickness and image the distribution of cervical collagen. Three-dimension orientation of collagen fibres in cervical samples was estimated by a conical beam scan protocol. Previous observation by X-ray diffraction was confirmed by our study which suggests that in the human cervix, collagen fibres adjacent to the endocervical canal and in the outermost area are mostly arranged longitudinally but in the middle area, fibres are predominantly circumferential with significant higher birefringence (p<0.05) than other areas. A significant increase in apparent birefringence of the middle area with age was identified, which is consistent with a study result by second harmonic generation and indicates a physiological re-modelling in the cervical collagen fibres as the reproductive function of the cervix diminishes. PS-OCT holds the potential to help us better understand cervical remodelling prior to birth pending the development of an in vivo probe.
Supervisor: Matcher, Stephen ; Chen, Biqiong Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available