Yinghua Zhu

Real-time magnetic resonance imaging and electromagnetic articulography database for speech production research (TC)

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.

GOCART: GOlden-angle CArtesian randomized time-resolved 3D MRI

PURPOSE To develop and evaluate a novel 3D Cartesian sampling scheme which is well suited for time-resolved 3D MRI using parallel imaging and compressed sensing. METHODS The proposed sampling scheme, termed GOlden-angle CArtesian Randomized Time-resolved (GOCART) 3D MRI, is based on golden angle (GA) Cartesian sampling, with random sampling of the ky-kz phase encode locations along each Cartesian radial spoke. This method was evaluated in conjunction with constrained reconstruction of retrospectively and prospectively undersampled in-vivo dynamic contrast enhanced (DCE) MRI data and simulated phantom data. RESULTS In in-vivo retrospective studies and phantom simulations, images reconstructed from phase encodes defined by GOCART were equal to or superior to those with Poisson disc or GA sampling schemes. Typical GOCART sampling tables were generated in <100ms. GOCART has also been successfully utilized prospectively to produce clinically valuable whole-brain DCE-MRI images. CONCLUSION GOCART is a practical and efficient sampling scheme for time-resolved 3D MRI. It shows great potential for highly accelerated DCE-MRI and is well suited to modern reconstruction methods such as parallel imaging and compressed sensing.

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

The aim of this work was to develop and evaluate an MRI‐based system for study of dynamic vocal tract shaping during speech production, which provides high spatial and temporal resolution.

Dynamic 3-D Visualization of Vocal Tract Shaping During Speech

Noninvasive imaging is widely used in speech research as a means to investigate the shaping and dynamics of the vocal tract during speech production. 3-D dynamic MRI would be a major advance, as it would provide 3-D dynamic visualization of the entire vocal tract. We present a novel method for the creation of 3-D dynamic movies of vocal tract shaping based on the acquisition of 2-D dynamic data from parallel slices and temporal alignment of the image sequences using audio information. Multiple sagittal 2-D real-time movies with synchronized audio recordings are acquired for English vowel-consonant-vowel stimuli /ala/, /ara/, /asa/, and /a∫a/. Audio data are aligned using mel-frequency cepstral coefficients (MFCC) extracted from windowed intervals of the speech signal. Sagittal image sequences acquired from all slices are then aligned using dynamic time warping (DTW). The aligned image sequences enable dynamic 3-D visualization by creating synthesized movies of the moving airway in the coronal planes, visualizing desired tissue surfaces and tube-shaped vocal tract airway after manual segmentation of targeted articulators and smoothing. The resulting volumes allow for dynamic 3-D visualization of salient aspects of lingual articulation, including the formation of tongue grooves and sublingual cavities, with a temporal resolution of 78 ms.

High-resolution whole-brain DCE-MRI using constrained reconstruction: Prospective clinical evaluation in brain tumor patients

PURPOSE To clinically evaluate a highly accelerated T1-weighted dynamic contrast-enhanced (DCE) MRI technique that provides high spatial resolution and whole-brain coverage via undersampling and constrained reconstruction with multiple sparsity constraints. METHODS Conventional (rate-2 SENSE) and experimental DCE-MRI (rate-30) scans were performed 20 minutes apart in 15 brain tumor patients. The conventional clinical DCE-MRI had voxel dimensions 0.9 × 1.3 × 7.0 mm(3), FOV 22 × 22 × 4.2 cm(3), and the experimental DCE-MRI had voxel dimensions 0.9 × 0.9 × 1.9 mm(3), and broader coverage 22 × 22 × 19 cm(3). Temporal resolution was 5 s for both protocols. Time-resolved images and blood-brain barrier permeability maps were qualitatively evaluated by two radiologists. RESULTS The experimental DCE-MRI scans showed no loss of qualitative information in any of the cases, while achieving substantially higher spatial resolution and whole-brain spatial coverage. Average qualitative scores (from 0 to 3) were 2.1 for the experimental scans and 1.1 for the conventional clinical scans. CONCLUSIONS The proposed DCE-MRI approach provides clinically superior image quality with higher spatial resolution and coverage than currently available approaches. These advantages may allow comprehensive permeability mapping in the brain, which is especially valuable in the setting of large lesions or multiple lesions spread throughout the brain.

Direct estimation of tracer-kinetic parameter maps from highly undersampled brain dynamic contrast enhanced MRI.

The purpose of this work was to develop and evaluate a T1‐weighted dynamic contrast enhanced (DCE) MRI methodology where tracer‐kinetic (TK) parameter maps are directly estimated from undersampled (k,t)‐space data.

State-of-the-Art MRI Protocol for Comprehensive Assessment of Vocal Tract Structure and Function.

Magnetic Resonance Imaging (MRI) provides a safe and flexible means to study the vocal tract, and is increasingly used in speech production research. This work details a state-ofthe-art MRI protocol for comprehensive assessment of vocal tract structure and function, and presents results from representative speakers. The system incorporates (a) custom upper airway coils that are maximally sensitive to vocal tract tissues, (b) graphical user interface for 2D real-time MRI that provides on-the-fly reconstruction for interactive localization, and correction of imaging artifacts, (c) off-line constrained reconstruction for generating high spatio-temporal resolution dynamic images at (83 frames per sec, 2.4 mm), (d) 3D static imaging of sounds sustained for 7 sec with full vocal tract coverage and isotropic resolution (resolution: 1.25 mm), (e) T2-weighted high-resolution, high-contrast depiction of soft-tissue boundaries of the full vocal tract (axial, coronal, sagittal sweeps with resolution: 0.58 x 0.58 x 3 mm), and (f) simultaneous audio recording with off-line noise cancellation and temporal alignment of audio with 2D real-time MRI. A stimuli set was designed to capture efficiently salient, static and dynamic, articulatory and morphological aspects of speech production in 90minute data acquisition sessions.

Feasibility of through‐time spiral generalized autocalibrating partial parallel acquisition for low latency accelerated real‐time MRI of speech

To evaluate the feasibility of through‐time spiral generalized autocalibrating partial parallel acquisition (GRAPPA) for low‐latency accelerated real‐time MRI of speech.

Joint arterial input function and tracker kinetic parameter estimation from undersampled dynamic contrast-enhanced MRI using a model consistency constraint

To develop and evaluate a model‐based reconstruction framework for joint arterial input function (AIF) and kinetic parameter estimation from undersampled brain tumor dynamic contrast‐enhanced MRI (DCE‐MRI) data.