An adaptive MR-compatible lens

Introduction We present an MR-compatible adaptive membrane lens, which is integrated into a wide-angle objective to form part of an optical tracking system. This work is motivated by the need for optical head tracking devices for use in prospective motion correction [1], but an alternative application could be high-resolution eye tracking for fMRI. The challenge for in-bore cameras is the limited focal depth and small field of view, which this approach addresses. We have previously described the fabrication process of the lens [2] and elements of its design and characterization [3, 4]. The aim of this work was to construct an MR-compatible objective incorporating the lens, and to verify the performance and compatibility of the adaptive lens during MR imaging.