Quantification of Longitudinal Changes in Retinal Vasculature from Wide-Field Fluorescein Angiography via a Novel Registration and Change Detection Approach

Li Ding, Ajay Kuriyan, Rajeev S. Ramchandran, Gaurav Sharma

Abstract: Wide-field fluorescein angiography (FA) images are commonly used in ophthalmology to assess longitudinal changes in retinal vasculature, specifically, non-perfusion. Current practice relies on manual qualitative comparisons between images taken at successive clinic visits, a few months apart. Objective quantitative assessments, although desirable for evaluating disease progression and treatment, are impractical to perform manually and challenging for image analysis because of the changes in the capture viewpoints and temporal imaging variations seen as the FA dye injection perfuses the retina. We propose a methodology for quantifying retinal non-perfusion by automated analysis of the FA images captured during successive clinical visits. Blood vessels are first detected in the image from each visit. The vascular networks in FA images are then precisely registered to obtain a co-aligned pair via parametric chamfer matching under polynomial transformation, a process that explicitly allows for increase or decrease in perfusion. Changes in perfusion are then quantified by identifying the common and distinct regions in co-aligned image pairs. The proposed framework is tested on FA images that are manually annotated by an ophthalmologist to provide ground truth binary vessel masks and to identify vasculature changes. Results indicate that the proposed method provides assessments of vasculature changes that are in good agreement with the ophthalmologist-provided annotations.