A framework for modeling ocular drug transport and flow through the eye using micro-CT

Abstract

This study uses micro-computed tomography (micro-CT) imaging for assessment of concentration and transport mechanisms of ocular drug surrogates following intravitreal injection. Injections of an iodinated contrast agent were administered to enucleated porcine eyes prior to scanning over 192 min. Image analysis was performed using signal profiles and regions of interest that corresponded to specific iodine concentrations. Diffusion coefficients of the injected iodine solutions were calculated using nonlinear regression analysis with a diffusion model. There was a predominantly diffusive component in the movement of the contrast to the back of the eye in the horizontal (sagittal & coronal) directions, with ultimate retinal fate observed after 120 min. The diffusion coefficients were found to have a mean of 4.87 × 10−4 mm2 s−1 and standard deviation of 8.39 × 10−5 mm2 s−1 for 150 mg ml−1 iodine concentration and 6.13 × 10−4 ± 1.83 × 10−4 mm2 s−1 for 37.5 mg ml−1 concentration. However, it should be noted that these coefficients were time dependent and were found to decay as the diffusion front interacted with the retinal wall. A real-time, accurate, non-invasive method of tracking a bolus and its concentration is achieved using a high spatial resolution and fast scanning speed micro-CT system.