Observation of the cricothyroid joint by high-resolution MRI

Abstract

Magnetic resonance imaging (MRI) excels at three-dimensional visualization of the living body and is used for functional analysis of speech organs. Despite MRI's many advantages, however, this technique has several problems with respect to laryngeal observation: image resolution and signal-to-noise ratio are insufficient because of the small size of the larynx, and respiratory effort results in motion artifacts in the images. In this study, two attempts were made to solve these problems: a custom larynx coil was built by modifying the antenna of a small circular coil, and a phonation-synchronized imaging method was devised to avoid motion artifacts. Applying these techniques in combination, we obtained laryngeal images from a male subject during repetitions of the vowel /i/ at normal voice pitch (120 Hz) and high pitch (180 Hz). The images were of sufficient quality for visualizing the cartilages, which allowed us to measure movements of the cricothyroid joint. Our findings in this case indicated that the cricothyroid joint demonstrates a rotation of 5 degrees and a translation of 1 mm between the two pitch levels.