MRI Technology

Real-time and interactive MRI requires entirely new imaging infrastructure that supports real-time reconstruction and display, as well as real-time operator controls (such as scan plane and image contrast). Our acquisition pulse sequences are implemented using the RTHawk real-time imaging system developed at Stanford. We are developing accelerated 2D and 3D imaging techniques tailored to the upper airway, and to the accurate depiction of air-tissue interfaces during vocal production. In addition, we are involved in the development and validation of new targeted phased array coils for imaging the upper airway.

Related references:

YC Kim, S Narayanan, KS Nayak. (2009). Accelerated 3D upper airway MRI using compressed sensing. Magnetic Resonance in Medicine, vol. 61, pp. 1434-1440. [pdf]

E. Bresch, Y. -C. Kim, K. Nayak, D. Byrd, S. Narayanan. (2008). Seeing Speech: Capturing Vocal Tract Shaping using Real-time Magnetic Resonance Imaging. IEEE Signal Processing Magazine, 123, May 2008. [pdf]

JM Santos, GA Wright, JM Pauly, Flexible Real-Time Magnetic Resonance Imaging Framework Proc., IEEE EMBS, 26th Annual Meeting, San Francisco, 2004. [pdf]

S. Narayanan, K. Nayak, S. Lee, A. Sethy & D. Byrd (2004s) An approach to real-time magnetic resonance imaging for speech production. Journal of the Acoustical Society of America, 115, 1771-1776. [pdf]

KS Nayak, CH Cunningham, JM Santos, JM Pauly. Real-Time Cardiac Imaging at 3 Tesla. Magnetic Resonance in Medicine. 2004:51(4):655-660. April 2004. [pdf]

Audio Technology

We have developed a data acquisition setup for recording, and processing, running speech from a person in a magnetic resonance imaging (MRI) scanner. The main focus is on ensuring synchronicity between image and audio acquisition, and in obtaining good signal to noise ratio to facilitate further speech analysis and modeling. A field-programmable gate array based hardware design for synchronizing the scanner image acquisition to other external data such as audio is described. The audio setup itself features two fiber optical microphones and a noise-canceling filter. We use a novel approach to noise cancellation employing a pulse sequence specific model of the gradient noise of the MRI scanner. The setup is useful for scientific speech production studies.

Related references:

Erik Bresch, Jon-Fredrik Nielsen, Krishna Nayak, Shri Narayanan. (2005). Synchronized audio recording and real-time MR imaging of fluent speech. Journal of the Acoustical Society of America, 120 (4), 1791-1794. [pdf]