Ultrahigh field MR - Imaging of a polymeric Injectable Local Drug Delivery System

Abstract

Purpose : In the course of open angle glaucoma, polymer-based local drug delivery (LDD) systems would overcome poor patient’s compliance and replace the necessity of eye drop application. The aim of the present study was use of ultrahigh field magnetic resonance imaging (MRI) to determine the anatomical location of LDD and tissue reaction of the injected LDD system in rabbit eyes.

Methods : The LDD system consists of hyaluronic acid sodium salt (HA) and an isocyanate functionalized 1,2-ethylene glycol bis(dilactic acid) (ELA-NCO). The HA/ELA-NCO 1/1 (v/v) mixture was injected in the subtenon space via a 27 gauge extruder system into 5 New Zealand white rabbits. Ultra high-field in vivo MRI (7 Tesla, Bruker BioSpec) was performed six months after LDD injection. T1w Flash (TE/TR: 4/546 ms) and T2-weighted RARE (TE/TR: 705180 ms) sequences were used to detect LDD induced swelling in the subtenon space.

Results : Macroscopically, a moderate swelling was observed after treatment around the injection site. This reaction was persistent for up to 3 months, but then regressed over time. The sequences showed good image quality with an in plane resolution of 200 microns. LDD quantity of the depot was visualized in cross and en-face section and it’s placement was detected in the subconjunctival as well as in the deeper tenon space. Furthermore, the anatomy of surrounding conjunctiva, eye muscles and orbital fat tissue were displayed in high resolution.

Conclusions : MRI can be used to monitor the anatomical position of a LDD system after injection in the subtenon space and is therefore serves as a valuable tool for quantifying LDD resorption during longitudinal experimental animal studies.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.