Advancements in Optical Coherence Tomography: Innovations and Applications for Ophthalmology and Dermatology

Abstract

Optical coherence tomography (OCT) is a well-established imaging modality widely used in ophthalmology and is emerging as a valuable clinical tool in dermatology. OCT angiography (OCTA), an advanced extension of OCT, utilizes intrinsic blood flow movement to generate angiographic images beneath the tissue surface, eliminating the need for contrast agents. This thesis demonstrates the capabilities of OCT in high-resolution imaging of 3D structures and microvasculature in the human eye and skin under diverse conditions. The opening chapter of this thesis serves as an introduction to OCT technology, providing a foundation for the subsequent chapters. In Chapter 2, we delve into novel algorithms and methods developed for OCT imaging. We begin with a straightforward yet highly effective approach for estimating the optical attenuation coefficient (OAC) from OCT images. OAC not only enhances OCT imaging contrast but also serves as a valuable physical parameter for assessing tissue properties, as alterations in tissue morphology and content can impact OAC. Building on this, we leverage the OAC to enhance OCT imaging contrast, leading to the development of algorithms for more precise and efficient segmentation of epidermal thickness in the OCT imaging of skin tissue, and retinal pigment epithelium (RPE) and calcified drusen in the imaging of retina tissue. Additionally, we introduce TransUnet, an innovative deep learning-based method developed for accurate segmentation of the outer retinal layer (ORL). Through this progressive exploration of OCT technology and advanced algorithms, our research significantly improves imaging segmentation and analysis in OCT clinical applications.

Building on this foundation, Chapter 3 showcases the remarkable capabilities and potentials of OCT in clinical ophthalmology. Firstly, we investigate the symmetry of interocular choroidal thickness and vascularity index measurements in normal eyes using SS-OCT, finding choroidal differences between normal fellow eyes in adults without obvious pathology. This study aids clinicians and researchers in distinguishing expected asymmetric changes in normal eyes from changes associated with diseases. Secondly, we examine variations in the ORL thickness among different stages of age-related macular degeneration (AMD), revealing significant differences in ORL thickness measurements among various AMD stages, indicating the potential of ORL thickness as an independent biomarker for predicting AMD progression.

Lastly, in Chapter 4, we discuss the clinical applications of OCT for dermatology. Firstly, we integrate pressure sensors with a handheld probe to facilitate imaging of micro vasculature, addressing the challenge of uncontrollable mechanical stress during contact mode imaging of the skin. This handheld scanning probe with built-in pressure sensors provides real-time feedback to control the mechanical stress, enabling repeatable and reliable OCTA images for a more accurate investigation of skin conditions. Secondly, we employ a clinical-prototype OCT system to image severe burn wounds at multiple scan sites across two time points. Quantitative analysis of vascular area density and surface roughness offers key insights into the pathophysiological mechanisms responsible for wound healing, potentially serving as critical biological indicators in future clinical evaluation and monitoring of wound healing. Lastly, we demonstrate the potential of OCT alongside OCTA to non-invasively image and monitor human skin graft health and integration over time, providing valuable insights for wound healing monitoring after skin graft surgery.

In conclusion, this thesis contributes to the advancement of OCT technology through the development of novel algorithms and its applications in clinical ophthalmology and dermatology. The research presented here significantly enhances imaging segmentation and analysis in OCT and offers valuable insights for disease diagnosis and monitoring in ophthalmology and wound healing evaluation in dermatology.