Magnetic resonance imaging of the cochlea, spiral ganglia and eighth nerve of the guinea pig

Abstract

The membranous labyrinth of the guinea pig cochlea and retrocochlear neural structures were investigated by magnetic resonance imaging (MRI) using an experimental system with a field strength of 4.7T and a single turn surface coil 25 mm in diameter, or standard resonators of 34 or 70 mm in diameter and gradient field strengths of 950 mTm and 200 mTm. High-resolution 2-D and 3-D images of 0.3-1.0 mm slice thickness were acquired by a rapid acquisition with relaxation enhancement (RARE) sequence and a standard multi-echo technique. Structural and dimensional aspects of the cochlea were resolved in vitro and in vivo down to <50 microm, showing the scala vestibule, scala media, scala tympani, spiral ganglia and the cochlear (eighth) nerve. In vivo perfusions with the gadodiamide (GdDTPA-BMA) chelate-bound paramagnetic gadolinium ion resulted in dynamic temporal enhancement of the scala vestibule and scala tympani, but did not penetrate the scala media.