Sweep Frequency Tympanometryに関する研究

周波数音圧曲線,周波数位相差曲線のパラメータ主成分分析による診断法

抄録

A sweep-frequency tympanometer has been developed to diagnose auditory ossicular lesions more precisely. This device measures acoustic middle ear features by changing the probe tone frequency continuously. The oscillator sweeps frequency of the probe tone from 200 to 2, 500Hz in 1.5 seconds. A microphone picks up the changes in the acoustic pressure and the phase in the external auditory meatus during the frequency change of the probe tone. These measurements are performed under pressures at -200 and 0 dapa, and differences of both the acoustic pressure and the phase between these two pressures are graphically displayed using a microcomputer. This device can also measure and digitally display the frequency (BHz) and the sound pressure (BdB) at the minimum point (B) of the sound pressure curve, the frequency (ZHz) at 0 crossing point (Z) of the sound pressure curve, and the frequency (PHz) and the phase difference (Pdeg) at the maximum point (P) of the phase curve.
Normal ranges of these five values were obtained to establish diagnostic criteria from 200 normal ears. The normal values were as follows : BHz, 480 to 1, 070Hz ; BdB, -6.0 to -1.8dB ; ZHz, 1, 100 to 1, 860Hz ; PHz, 910 to 1, 820Hz ; and Pdeg, 16.3 to 47.9°. Eight cases of ossicular dislocation and 14 cases of ossicular fixation, all of which had normal external auditory meati and tympanic membrance, were evaluated based on these values. All the cases with ossicular dislocation and 12 cases out of 14 with ossicular fixation were correctly diagnosed.
Principal component analysis was performed on the data from 200 normal ears to calculate the primary principal component (PCA 1) and secondary principal component (PCA 2) in order to display these data on a two dimensional figure. Then this analysis was also performed on pathological ears. The results showed that the normal cases concentrated in the cross of the coordinate and abscissa, and cases of dislocation and of fixation were plotted on the right side and left upper side, respectively. As a conclusion, the sweep-frequency tympanometry is useful for the diagnosis of auditory ossicular lesions, and the numerical and two dimensional expression of the test result is a practical way as the diagnosis could be done based on the location of points in a PCA 1(X)-PCA 2(Y) figure.