Phased-array surface coil MR of the orbits and optic nerves

Abstract

Purpose: To devise a practical technique for high-resolution evaluation of the anterior optic apparatus using a phased-array surface coil system, and to evaluate this system in patients with suspected optic pathway abnormalities.

Methods: A four-element phased-array coil pair was placed on each side of the head, and signal-to-noise measurements were obtained using a head phantom. Comparison between the phased-array coil, the quadrature coil, and a single-turn 12.7-cm (5-in) surface coil was done. T1 spin-echo and T2 fast spin-echo sequences were obtained in the oblique axial and oblique sagittal planes, to approximate the long axis of the optic nerves and the nonoblique coronal plane.

Results: The phantom signal-to-noise measurements at simulated locations of the optic nerve head, optic canal, and optic chiasm revealed an improvement of at least 30% using the phased-array system. Of 24 imaged cases, 9 had trauma, 5 had suspected neoplasms, and 2 had optic neuritis. In 3 patients, an unexpected diagnosis of optic pathway contusion or infarction was made. The remaining 8 patients had various suspected visual pathway lesions.

Conclusion: Phased-array surface coils allow rapid, thin-section imaging of the entire anterior optic pathway, with improved signal-to-noise ratio. This may improve evaluation of optic pathway lesions over conventional techniques.