Dynamic Imaging of the Eye, Optic Nerve, and Extraocular Muscles With Golden Angle Radial MRI

Abstract

PurposeThe eye and its accessory structures, the optic nerve and the extraocular muscles, form a complex dynamic system. In vivo magnetic resonance imaging (MRI) of this system in motion can have substantial benefits in understanding oculomotor functioning in health and disease, but has been restricted to date to imaging of static gazes only. The purpose of this work was to develop a technique to image the eye and its accessory visual structures in motion.MethodsDynamic imaging of the eye was developed on a 3-Tesla MRI scanner, based on a golden angle radial sequence that allows freely selectable frame-rate and temporal-span image reconstructions from the same acquired data set. Retrospective image reconstructions at a chosen frame rate of 57 ms per image yielded high-quality in vivo movies of various eye motion tasks performed in the scanner. Motion analysis was performed for a left–right version task where motion paths, lengths, and strains/globe angle of the medial and lateral extraocular muscles and the optic nerves were estimated.ResultsOffline image reconstructions resulted in dynamic images of bilateral visual structures of healthy adults in only ∼15-s imaging time. Qualitative and quantitative analyses of the motion enabled estimation of trajectories, lengths, and strains on the optic nerves and extraocular muscles at very high frame rates of ∼18 frames/s.ConclusionsThis work presents an MRI technique that enables high-frame-rate dynamic imaging of the eyes and orbital structures. The presented sequence has the potential to be used in furthering the understanding of oculomotor mechanics in vivo, both in health and disease.

Real-Time MRI Reveals Unique Insight into the Full Kinematics of Eye Movements

“…Dynamic MR eye imaging allows observation of the entire eyeball in full anatomic detail ( Berg et al, 2012 ; Sengupta et al, 2017 ; Franceschiello et al, 2020 ) and can therefore circumvent the aforementioned limitations. Measuring eye movements during blinks, which typically last only 100–300 ms, or saccades (which last only a few dozen milliseconds) requires a spatial and temporal resolution beyond that of classical MRI.…”

Influence of eye movement on lens dose and optic nerve target coverage during craniospinal irradiation

“…MRI is a validated method to explore movement of the separate eye components [17] , [18] , [19] . For lenses and optic discs, the latter considered as the most peripheral part of the optic nerve, mean movement amplitudes of all 10 volunteers in our study ranged between±3 mm to±7 mm, with overall largest amplitudes, of even > 9 mm, in the caudal gaze direction.…”

“…During treatment, eye movements will be less extreme than registered here, and smaller PRV lenses may be applicable. Further study in patients is recommended to evaluate this, in which natural eye movements may be captured comfortably with fast-MRI instead of static MRI [19] .…”

Role of Structural, Metabolic, and Functional MRI in Monitoring Visual System Impairment and Recovery

“…However, since involuntary eye and optic nerve motion may provide valuable information about oculomotor function in health and disease, dynamic imaging of the eye using a golden angle radial sequence has shown promise. 57 This sequence was found to be not only motion-robust, but also temporally advantageous, with an ~15-second acquisition time. On the other hand, accurate diffusion measures of the optic pathway often suffer from low SNR and long scan times due to the application of strong gradients at high resolutions in many encoding directions.…”