Improved imaging of lingual articulation using real‐time multislice MRI

Abstract

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 speakers of native English produced voiceless and voiced fricatives /f/-/v/, /θ/-/ð/, /s/-/z/, /ʃ/-/ʒ/ 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 Tongue grooving was observed from the coronal slice intersecting the post-alveolar region to be most pronounced during fricative production in back vowel contexts, and more pronounced for sibilants /s/-/z/ than for /ʃ/-/ʒ/. 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.

High‐frame‐rate full‐vocal‐tract 3D dynamic speech imaging

“…Significant efforts have been made to improve the speed of speech MRI, resulting in a number of promising methods, which include (a) fast-scanning methods with specialized pulse sequences (24,25) or parallel imaging (26,27), and (b) model-based methods utilizing support constraints (28,29), low-dimensional signal models (30)(31)(32)(33)(34) and sparsity constraints (35)(36)(37)(38)(39). Effective integration of these methods has also led to greater acceleration in imaging speed (23,(40)(41)(42)(43)(44)(45).…”

A fast and flexible MRI system for the study of dynamic vocal tract shaping

“…Two single slice sequences with spatial resolutions of 2.4 mm 2 and 1.76 mm 2 were realized, which respectively corresponded to 13 and 21 spiral interleaves/frame for Nyquist sampling. A flexible multi-slice time interleaved sequence (33) was also adapted to realize an arbitrary three-slice select sequence at 2.4 mm 2 . The golden angle increment for the three-slice sequence occurred every 3TR.…”

3D dynamic MRI of the vocal tract during natural speech

“…Generally, dynamic MRI techniques have been limited to one mid-sagittal imaging plane or a few 2D imaging planes. [7][8][9][10][11][12][13][14][15] This has nevertheless provided good utility to speech scientists due to the fact that important information about "place of articulation," which is critical in linguistic contrasts, can be obtained from constriction details in the mid-sagittal plane (e.g., in phonemes /p/, /t/, and /k/ with constrictions that are located at the lips, alveolar ridge, and velar region). However, vocal tract shaping during speech is enormously complex in geometry and in temporal structuring and cannot be fully understood from mid-sagittal constriction posture along the vocal tract.…”