Abstract
Optical coherence tomography angiography (OCTA) is a non-invasive optical technique for imaging the microvasculature, available commercially and used clinically and in research. Various imaging protocols, image processing methodologies, and quantitative metrics that can serve as biomarkers for different diseases have been demonstrated. However, standardised quantification methods that can generate metrics and have a significant test-retest repeatability need to be put forward. Due to this absence, studies and results published so far cannot be readily compared with each other. Preliminary studies have shown that capillaries, arterioles, and venules, collectively referred to as microvasculature, may be the indicators of various diseases. Changes in microvasculature can indicate and help in the diagnosis of various age-related cardiovascular diseases and diabetes. To drive OCTA from research to the clinic, approved reference values for the quantitative biomarkers affected by diseases need to be set. Standard values and ranges of these metrics that define the microvasculature for healthy and diseased populations need to be established to distinguish between the two. Also, investigation of image acquisition settings and imaging protocols is needed to acquire good quality images that can generate relevant, consistent, and accurate results. This research project demonstrates the effects of using various imaging protocols and settings to acquire good quality images. The images are then subjected to quantification using open-source OCTAVA software designed in our group to assess the effects of these settings and protocols which helped in defining the optimal values for them. Data analysis that helped in defining the parameters for OCTAVA, which is a step towards standardisation of OCTA metrics, is also carried out and explained in this thesis. A further study was carried out to investigate the age-related differences in microvasculature metrics from healthy and diabetic people. 52 healthy and 11 diabetic people were imaged for this study. Data analysis was done based on the results generated by OCTAVA in which these participants were divided into age dependent groups and analysed. Results from this study defining ranges for nine metrics based on age groups are reported in the thesis. This thesis concerns the potential of OCTA and its application in diagnosis of disease. The studies reported in this thesis represent a step forward in implementing OCTA as a standard diagnostic tool in clinics and point to the growing significance of utilising the microvasculature architecture in defining various health conditions.