Non-invasive in vivo studies of cochlear fluid motion may increa knowledge of the normal hearing process and may also provide useful diagnostic information in patients with sensorineural hearing loss. The goal of the proposed study is to verify, that high resolution steady state gradient echo M images can be used to observe and characterize fluid motion in the cochlea in-vivo. First, phantom models with known fluid motion patterns will be imaged t evaluate and calibrate the MRI techniques. Next, a physiological more realist model will be tested that is similar to models used in previous studies of cochlear mechanics. Finally, initial studies of healthy subjects will be conducted while their cochleas are stimulated with pure tones and composite sounds. MR images will be acquired with two types of steady state sequences, GRASS and SIMCAST using a range of suitable parameters. The GRASS sequence is very sensitive to motion and thereby expected to produce images with signal lo patterns characteristic for motion. The SIMCAST sequence, on the other hand, has little motion sensitivity, thereby producing images with uniform high signal. In the first study with known fluid motion, the steady state MR signa will be computed and compared with signal intensities measured from images. This theoretical model will then be used to characterize the complex motion patterns in the realistic cochlea model and in the in-vivo studies. In addition, the size, shape and orientation of the cochlea will be determined fr the high resolution SIMCAST images.
