Real-time magnetic resonance imaging of velopharyngeal activities with simultaneous speech recordings.

OBJECTIVE: To examine the relationships between acoustic and physiologic aspects of the velopharyngeal mechanism during acoustically nasalized segments of speech in normal individuals by combining fast magnetic resonance imaging (MRI) with simultaneous speech recordings and subsequent acoustic analyses.
DESIGN: Ten normal Caucasian adult individuals participated in the study. Midsagittal dynamic magnetic resonance imaging (MRI) and simultaneous speech recordings were performed while participants were producing repetitions of two rate-controlled nonsense syllables including /zanaza/ and /zunuzu/. Acoustic features of nasalization represented as the peak amplitude and the bandwidth of the first resonant frequency (F1) were derived from speech at the rate of 30 sets per second. Physiologic information was based on velar and tongue positional changes measured from the dynamic MRI data, which were acquired at a rate of 21.4 images per second and resampled with a corresponding rate of 30 images per second. Each acoustic feature of nasalization was regressed on gender, vowel context, and velar and tongue positional variables.
RESULTS: Acoustic features of nasalization represented by F1 peak amplitude and bandwidth changes were significantly influenced by the vowel context surrounding the nasal consonant, velar elevated position, and tongue height at the tip.
CONCLUSIONS: Fast MRI combined with acoustic analysis was successfully applied to the investigation of acoustic-physiologic relationships of the velopharyngeal mechanism with the type of speech samples employed in the present study. Future applications are feasible to examine how anatomic and physiologic deviations of the velopharyngeal mechanism would be acoustically manifested in individuals with velopharyngeal incompetence.