Third International Conference on Spoken Language Processing (ICSLP 94)

Yokohama, Japan
September 18-22, 1994

Measurement of 3D shapes of Vocal Tract, Dental Crown and Nasal Cavity Using MRI: Vowels and Fricatives

Masafumi Matsumura (1), Takuya Nukawa (1), Koji Shimizu (2), Yasuji Hashimoto (2), Tatsuya Morita (3)

(1) Department of Applied Electronics, Faculty of Engineering, Osaka Electro-Communication University, Neyagawa, Japan
(2) Medical Systems Division, SHIMADZU Corporation, Kyoto, Japan
(3) Department of Electrical Engineering, Faculty of Engineering, Osaka University, Suita, Japan

This paper deals with the measurement of three dimensional shapes of vocal tract, dental crown and nasal cavity using magnetic resonance imaging (MRI). 3D MR images of the vocal tract and nasal cavity of 3 adult males were obtained in the steady state productions of Japanese vowels and fricatives. MR images of the dental crown that contain a small amount of water were obtained using a dental crown plate that is shaped so as to tightly attach to the subject's dental crown by thermoforming and that contain a contrast medium for MR imaging. The measurement time was 186 second for 28 transverse sections from the larynx to the nasal cavity at a 6 mm interval, and was 186 second for 32 coronal sections from the tip of the nose to the atlas at a 4 mm interval. A computer algorithm for air-tissue boundary tracing of arbitrary sections of the vocal tract and nasal cavity from the 3D MR image was proposed. The algorithm is based on the gray level interpolation and the threshold operation. Images of arbitrary sections of the vocal tract and nasal cavity from 3D MR image were reconstructed using the gray level interpolation based on the sampling theorem. Thresholds of the gray level were computed from gray levels at air-tissue border points. Shapes of arbitrary sections of the vocal tract and nasal cavity were obtained using the present algorithm. The boundary tracing error of the dental crown from the 3D MR image was less than 5.7%, The 3D shape and area function of vocal tract during the productions of fricatives /s/ were obtained. The 3D shapes of sinus frontails, sinus spenoidalis and sinus maxillaris were observed.

Full Paper

Bibliographic reference.  Matsumura, Masafumi / Nukawa, Takuya / Shimizu, Koji / Hashimoto, Yasuji / Morita, Tatsuya (1994): "Measurement of 3d shapes of vocal tract, dental crown and nasal cavity using MRI: vowels and fricatives", In ICSLP-1994, 619-622.