Dynamic magnetic resonance imaging in the study of vocal tract configuration.

Studies of vocal tract configuration using magnetic resonance imaging (MRI) techniques have relied on static images. These images fail to identify transient movements and are subject to distortion from motion artifact limiting research application to stable motor events. This paper describes a dynamic MRI technique that permits study of transient movements within the vocal tract during speech and nonspeech tasks. Following description of the technique, results of two preliminary studies are presented. The initial study evaluated issues of measurement error and reliability. Results indicated that distance and area measurements obtained from this technique are accurate in reference to a calibration referent and reliable both within and among judges. The second study compared two aspects of vocal tract configuration in patients with adductor spasmodic dysphonia before and following treatment with Botox injection. Changes in vocal tract configuration are discussed in reference to prior observations of patients with spasmodic dysphonia. These preliminary investigations suggest that dynamic MRI has promise as a useful technique in the study of vocal tract configuration.