Development of Retinal Vascular Imaging Platform using total body irradiation of New Zealand Rabbit model

Abstract

Purpose : We hypothesize a decrease in retinal density post-irradiation. This work will prepare future studies to hypothesize that retinal vascular imaging can allow reproducible non-invasive, serial mapping of structural changes in the vascular network, which will also map to systemic vasculopathy in other organs/tissues.

Methods : We utilized fluorescein angiography to measure radiation-induced retinal microvascular changes in three cohorts of three New Zealand White Rabbits (NZWR, n = 9). All animals underwent baseline fluorescein angiography imaging in one eye prior to irradiation. Rabbits were whole-body irradiated with 7.25 Gy and subsequently underwent fluorescein angiography on days 1, 5, 10, 15, 20, 25, and 30 following radiation or until euthanasia criteria were met. The vessels were segmented manually, and angiograms were binarized. Large vessels (> 80 microns) were identified and analyzed separately from small vessel density (Figure 1). Vessel density was defined as the proportion of pixels occupied by binarized vessels in an image. The total and percent change in vessel density after irradiation was calculated at day 5 and day 10 as other dates have incomplete data or rabbits were euthanized. Skeletonized images were also used to calculate vessel densities (Figure 2).

Results : At baseline the average large vessel density was 0.0922±0.0136, and the average small vessel density was 0.1812±0.0814. The average large vessel density was not significantly different at day 5 or day 10 after irradiation. Small vessel density was not significantly different at day 5 but was significantly decreased by 12.7% at day 10 (0.183+0.041, p < 0.01). For skeletonized images, average large vessel density at baseline was 0.0096±0.0019, and the average small vessel density was 0.0519±0.0085. The average small vessel density was not significantly different at day 5 but was significantly decreased by 19.1% at day 10 (0.0251±0.0315, p=0.005). The average large vessel density did not significantly change at any point post-irradiation.

Conclusions : Retinal large vessel density is unchanged by whole body irradiation at 5 and 10 days whereas there is reduced small vessel retinal density 10 days post-irradiation in the NZWRs.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Figure 1. Workflow showing retinal image (left), binarized larger vessels (middle) and all binarized vessels (right).

 

Figure 2. Skeletonized image of final binarized vessels.