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S. M. Warden, J. B. Christoforidis, P. A. Caruso, M. Romano, F. Scotti, D. J. D'Amico; Computed Tomography and Magnetic Resonance Imaging of Anecortave Acetate After Posterior Juxtascleral Injection in the Rabbit. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5819.
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Anecortave acetate is an anti-angiogenic steroid derivative that is used for the treatment of choroidal neovascularization. It is administered as a periocular posterior juxtascleral depot (PJD) using a specially designed curved cannula. Anecortave acetate cannot be directly visualized within the posterior sub-Tenon’s space after delivery. The focus of this study was to determine if anecortave acetate could be detected radiographically using magnetic resonance imaging (MRI) or computed tomography (CT) after posterior juxtascleral injection in a small animal model, and to test whether either technique could be used to follow the drug over time.
A Dutch-belted rabbit was anesthetized and 300 microliters of 3% anecortave acetate suspension was injected as a PJD in the left eye, and a mixture of 200 microliters of anecortave acetate suspension and 100 microliters of diluted gadolinium contrast agent was injected as a PJD in the right eye. Orbital MRI and CT were performed on the rabbit prior to injection, immediately after injection, and 5 days after injection. MRI and CT imaging of a vial containing anecortave acetate was also performed.
Anecortave acetate demonstrated a houndsfield attenuation of 30 units on CT, and demonstrated intermediate to high signal compared to water on MRI. Orbital CT imaging of the left eye immediately after injection did not detect the anecortave acetate in the posterior sub-Tenon’s space. However, orbital MRI imaging of the left eye revealed high signal within the sup-Tenon’s space that was thought to represent anecortave acetate. Both CT and MRI of the right eye containing the mixture of anecortave acetate and gadolinium contrast agent revealed detectable signal immediately after injection. There was no detectable signal of either eye 5 days after injection.
This study demonstrates that anecortave acetate can be visualized in the appropriate anatomical location immediately after PJD delivery in a rabbit animal model using MRI. Neither CT nor MRI can detect the drug 5 days after delivery. We postulate that as the anecortave acetate becomes dehydrated the residual substance becomes isointense to the surrounding ocular tissue.
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