Ｕｌｔｒａｓｏｕｎｄ ＬａｒｙｎｇｏｇｒａｐｈｙとＰｈｏｔｏｅｌｅｃｔｒｏｇｌｏｔｔｏｇｒａｐｈｙによる声帯振動の観察

Abstract

A newly developed ultrasonic laryngeal imaging system, ultrasound laryngography (ULG), can record vocal cord vibrations by the simultaneous use of high-speed M-mode, ultrasonic pulse transmissions, and the other methods. The purpose of this study was to compare normal male vocal cord vibrations simultaneously recorded by ULG at several pitches and loudness with those obtained by photoelectroglottography (PGG). The open quotient (OQ), speed quotient (SQ), and speed index (SI) were measured by these two methods. While only relative glottal area can be obtained by PGG, exact glottal width can be obtained by ULG. So the mean opening/closing velocity as well as the mean opening/closing steepness of the vocal cord vibration plot were measured by ULG. The results are summarized as follows: 1) The OQ, SQ, and SI values measured by these two methods were very similar. There was a trend for greater mean values in these parameters as measured by ULG compared with those determined by PGG. 2) This difference was presumed to be due to (1) vocal cord phase differences in horizontal and vertical components, (2) the location of the light source and that of photosensor from the glottis, and (3) ULG beam width in relation to vertical movements of the vocal cords. 3) Glottal width curve obtained by ULG was asymmetrical triangular wave because closing phase was shorter. By ULG observation, as voice loudness increased, opening/closing steepness became greater and closed phase longer, while closing phase shorter. The waveform obtained by ULG was presumed to be relatively similar to glottal flow waveform because there was a trend of more asymmetrical triangular waveform obtained by ULG than those obtained by PGG. In conclusion, ULG is the only method to be able to obtain exact glottal width compared with the other glottography, and this method is considered to be useful for the investigation of the vocal cord vibrations.