Determination of the volume of the thyroid gland by a high resolutional ultrasonic scanner.

We developed a new ultrasonic scanner for the thyroid and, in this study, the estimated volumes of the thyroids by this scanner were compared with the weights of those obtained at operation. In this ultrasonic scanner, an annular array transducer was employed instead of the conventional single element concave transducer. The distance of the focused area by this transducer was as long as 5 cm compared to 1 cm by the conventional transducer; therefore, the image obtained by the new scanner was so clear that it was not difficult to draw accurately the outlines of the thyroids. The volumes of the thyroids were calculated by a computerized digitizer. The estimated volumes of the thyroids by the ultrasonic scanner were closely correlated with their weights calculated by adding the actual weights of the thyroids removed to the estimates of the thyroids left at operation. Their correlation coefficients were as high as 0.99. This suggests that this new ultrasonic scanner is very useful in the determination of the volumes of the thyroids, since the measurement is very accurate, simple, and reproducible.