Attenuation coefficient measurement in the thyroid

To assess the feasibility of a novel method of measuring the attenuation coefficient in the thyroid, which offers less variability of results than the conventional method. Methods. In our new method, the attenuation coefficient was evaluated on the basis of the following equation with sound field correction: alpha = -1/4[f(c)(z) - epsilon(z)] (.) d/dz [log(M-0(z)) - tau(z)]. In our system, the attenuation coefficient was also evaluated by the spectral shift central frequency method at the same time. In this study, we used 32 cases of normal thyroid, 26 cases of Graves disease, and 11 cases of Hashimoto thyroiditis in the system. Results. With this novel method, attenuation coefficient values of the thyroid (mean +/- SD) were 1.50 +/- 0.26 dB (.) cm(-1) (.) MHz(-1) in the normal group, 0.91 +/- 0.23 dB (.) cm(-1) (.) MHz(-1) in the Graves disease group, and 1.10 +/- 0.27 dB (.) cm(-1) (.) MHz(-1) in the Hashimoto thyroiditis group. The novel method recorded a statistically significant difference between normal and diseased thyroids (P < .0001) and between Graves disease and Hashimoto thyroiditis groups (P = .0035). Statistical variation of the attenuation coefficient values obtained using the novel method was much smaller than that of those obtained by the spectral shift central frequency method in every group. Conclusions. This new method is considered usable for evaluating the attenuation coefficient of the thyroid in vivo.