VESGEN Analysis of Generational Branching Patterns in Arteries and Veins for Investigating Diabetic Retinopathy by Spectralis^® Angiographic Imaging

Abstract

Purpose: We hypothesize that site-specific patterning within branching generations of arterial and venous trees in the human retina can be mapped and quantified by VESsel GENeration Analysis (VESGEN) software. Using images acquired by 30° Spectralis^® fluorescein angiography (FA), we demonstrate that the methodology may be useful for analysis of longitudinal progression of diabetic retinopathy (DR).

Methods: The retina of a patient diagnosed with mild nonproliferative DR was photographed at 12.5μm/pixel with 30° Heidelberg Spectralis^® imaging following fluorescein injection. Binary (black/white) vascular patterns of branching arterial and venous trees were extracted from the grayscale photograph (768✕768 pixels) as described previously for 50° FA (IOVS 2010, 51:498). The resulting arterial and venous images served as sole inputs to the VESGEN software. The vascular patterns were automatically mapped by VESGEN to generate vessel branching generations (G_x) and to quantitatively analyze them by computing numerous vascular parameters, including the densities of vessel length (L_v), area (A_v), number (N_v), and the fractal dimension (D_f). Results for the branching generations were further assigned by VESGEN into two groups of large (G_1-3) and small (G_≥4) vessels.

Results: L_v1-3 and A_v1-3 were 5.02E-4 μm/μm² and 4.50E-2 μm²/μm² for large arteries, and 5.42E-4 μm/μm² and 4.85E-2 μm²/μm² for large veins. For small arteries, L_v≥4 and A_v≥4 were 9.26E-4 μm/μm² and 3.37E-2 μm²/μm², compared to 1.10E-3 μm/μm² and 4.41E-2 μm²/μm² for small veins. Trends for A_v and L_v were confirmed by D_f and N_v. Agreement among these several key parameters reveal that the density of small veins was greater than that of small arteries.

Conclusions: Our study supports the future feasibility of VESGEN analysis for highly sensitive mapping and quantification of remodeling of retinal arterial and venous trees from clinical images obtained by 30° Spectralis^® fluorescein angiography. The VESGEN mapping methodology will support evidence-based conclusions for ongoing longitudinal studies on how and where site-specific remodeling occurs and progresses within the human retina.