In the preceding article, the measurement of an index of echogenicity has been described. In this article, we present the mean value and standard deviation of this index in normal thyroid and pathological cases. It appears that the index is very significantly lowered in Hashimoto's disease compared to its value in normal thyroids and simple goiters. The advantage of this index in other cases such as Graves' disease, subacute thyroiditis, and thyroid nodules is discussed.

The technique reported here uses a simple electronic system adaptable to a standard manual echograph with the aim of obtaining a numerical index of echogenicity. The index is the ratio of the average echo amplitude within a gated portion of tissue at a given depth to the average echo amplitude within the same gated portion measured under the same conditions on a phantom filled with a "tissue-mimicking" material. A theoretical analysis shows that the index depends not only on the attenuation coefficient and the backscattering coefficient of the tissue but also on the depth of the measurement. It is demonstrated that it is feasible to measure the attenuation coefficient using the current system, and the reproducibility of the index measurement is evaluated on a normal thyroid.