Accurate measurement of three-dimensional shapes of a vocal tract and a dental crown using magnetic resonance imaging: Japanese fricative consonants
Takuya Niikawa, M. Matsumura, Takashi Tachimura, Takeshi Wada, Kōji Shimizu, Yasuji Hashimoto · The Journal of the Acoustical Society of America · 1996
Three-dimensional MR images of the vocal tract of three adult males were obtained during steady-state production of the Japanese fricatives /s/, /sh/, and /shu/. MR images of dental crowns containing a small amount of water were obtained using a dental crown plate which was shaped so as to attach tightly to the subject’s dental crown by thermoforming which contained a contrast medium for MR imaging. A computer algorithm based on gray level interpolation and threshold operation for air–tissue boundary tracing of arbitrary sections of the vocal tract taken from axial and coronal MR images were proposed. Images of arbitrary sections of the vocal tract were reconstructed from 3-D MR images using gray level interpolation based on the sampling theorem. Gray level thresholds were computed from the gray levels at points on the air–tissue border. The boundary tracing error of the dental crowns from the 3-D MR images was less than 5.7%. The 3-D shape and area function of the vocal tract during production of the Japanese fricatives /s/, /sh/, and /shu/ were obtained.