Purpose: To develop a real-time imaging technique that allows for simultaneous visualization of vocal tract shaping in multiple scan planes, and provides dynamic visualization of complex articulatory features.
Materials and methods: Simultaneous imaging of multiple slices was implemented using a custom real-time imaging platform. Midsagittal, coronal, and axial scan planes of the human upper airway were prescribed and imaged in real-time using a fast spiral gradient-echo pulse sequence. Two native speakers of English produced voiceless and voiced fricatives /f/-/v/, /θ/-/ð/, /s/-/z/, /∫/- in symmetrical maximally contrastive vocalic contexts /a_a/, /i_i/, and /u_u/. Vocal tract videos were synchronized with noise-cancelled audio recordings, facilitating the selection of frames associated with production of English fricatives.
Results: Coronal slices intersecting the postalveolar region of the vocal tract revealed tongue grooving to be most pronounced during fricative production in back vowel contexts, and more pronounced for sibilants /s/-/z/ than for /∫/-. The axial slice best revealed differences in dorsal and pharyngeal articulation; voiced fricatives were observed to be produced with a larger cross-sectional area in the pharyngeal airway. Partial saturation of spins provided accurate location of imaging planes with respect to each other.
Conclusion: Real-time MRI of multiple intersecting slices can provide valuable spatial and temporal information about vocal tract shaping, including details not observable from a single slice.
Copyright © 2011 Wiley Periodicals, Inc.