Purpose To develop and evaluate a MRI-based system for study of dynamic vocal tract shaping during speech production, which provides high spatial and temporal resolution. Methods The proposed system utilizes (a) custom eight-channel upper airway coils that have high sensitivity to upper airway regions of interest, (b) 2D golden angle spiral gradient echo acquisition, (c) on-the-fly view-sharing reconstruction, and (d) off-line temporal finite difference constrained reconstruction. The system also provides simultaneous noise-cancelled and temporally aligned audio. The system is evaluated in three healthy volunteers, and one tongue cancer patient, with a broad range of speech tasks. Results We report spatio-temporal resolutions of 2.4×2.4 mm2 every 12ms for single-slice imaging, and 2.4×2.4 mm2 every 36 ms for three-slice imaging, which reflects roughly 7-fold acceleration over Nyquist sampling. This system demonstrates improved temporal fidelity in capturing rapid vocal tract shaping for tasks such as producing consonant clusters in speech, and beat-boxing sounds. Novel acoustic-articulatory analysis was also demonstrated. Conclusions A synergistic combination of custom coils, spiral acquisitions, and constrained reconstruction enables visualization of rapid speech with high spatio-temporal resolution in multiple-planes.

USC-TIMIT is an extensive database of multimodal speech production data, developed to complement existing resources available to the speech research community and with the intention of being continuously refined and augmented. The database currently includes real-time magnetic resonance imaging data from five male and five female speakers of American English. Electromagnetic articulography data have also been presently collected from four of these speakers. The two modalities were recorded in two independent sessions while the subjects produced the same 460 sentence corpus used previously in the MOCHA-TIMIT database. In both cases the audio signal was recorded and synchronized with the articulatory data. The database and companion software are freely available to the research community.

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Stretchable device systems with suspended SnO2 nanowires (NWs) as channel materials: Oxygen plasma is used to remove the underlying polymer to float the NWs. These suspended NW field‐effect transistors exhibit high electrical performance. By adopting a neutral mechanical plane and curved interconnection, electrical performance of the suspended NW field‐effect transistors is maintained under stretching up to approximately 40%.

In speech production research using real-time magnetic resonance imaging (MRI), the analysis of articulatory dynamics is performed retrospectively. A flexible selection of temporal resolution is highly desirable because of natural variations in speech rate and variations in the speed of different articulators. The purpose of the study is to demonstrate a first application of golden-ratio spiral temporal view order to real-time speech MRI and investigate its performance by comparison with conventional bit-reversed temporal view order. Goldenratio view order proved to be more effective at capturing the dynamics of rapid tongue tip motion. A method for automated blockwise selection of temporal resolution is presented that enables the synthesis of a single video from multiple temporal resolution videos and potentially facilitates subsequent vocal tract shape analysis. Magn Reson Med 65:1365-1371, 2011. V C 2010 Wiley-Liss, Inc.

Purpose: To develop a method that automatically corrects ghosting artifacts due to echo-misalignment in interleaved gradient-echo echo-planar imaging (EPI) in arbitrary oblique or double-oblique scan planes. Materials and Methods:An automatic ghosting correction technique was developed based on an alternating EPI acquisition and the phased-array ghost elimination (PAGE) reconstruction method. The direction of k-space traversal is alternated at every temporal frame, enabling lower temporal-resolution ghost-free coil sensitivity maps to be dynamically estimated. The proposed method was compared with conventional one-dimensional (1D) phase correction in axial, oblique, and double-oblique scan planes in phantom and cardiac in vivo studies. The proposed method was also used in conjunction with two-fold acceleration. Results:The proposed method with nonaccelerated acquisition provided excellent suppression of ghosting artifacts in all scan planes, and was substantially more effective than conventional 1D phase correction in oblique and double-oblique scan planes. The feasibility of real-time reconstruction using the proposed technique was demonstrated in a scan protocol with 3.1-mm spatial and 60-msec temporal resolution. Conclusion:The proposed technique with nonaccelerated acquisition provides excellent ghost suppression in arbitrary scan orientations without a calibration scan, and can be useful for real-time interactive imaging, in which scan planes are frequently changed with arbitrary oblique orientations.

In speech-production research, 3D MRI of the upper airway has provided insights into vocal tract shaping and data for its modeling. Small movements of articulators can lead to large changes in the produced sound, therefore improving the resolution of these datasets, within the constraints of a sustained speech sound (6-12 seconds), is an important area for investigation. The purpose of the study is to provide a first application of compressed sensing (CS) to high-resolution 3D upper airway MRI using spatial finite difference as the sparsifying transform, and to experimentally determine the benefit of applying constraints on image phase. Estimates of image phase are incorporated into the CS reconstruction to improve the sparsity of the finite difference of the solution. In a retrospective sub-sampling experiment with no sound production, 5x and 4x were the highest acceleration factors that produced acceptable image quality when using a phase constraint and when not using a phase constraint, respectively. The prospective use of a 5x undersampled acquisition and phase-constrained CS reconstruction enabled 3D vocal tract MRI during sustained sound production of English consonants /s/, /∫/, /l/, and /r/ with 1.5 × 1.5 × 2.0 mm3 spatial resolution and 7 seconds of scan time.

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.