Measurement algorithm for the size of the thyroid gland in ultrasonography (US) images has been proposed on the basis of the position of the neighboring regions in order to objectively evaluate target organs for medical screening and secondary use. The measurement algorithm extracts the operator's notion about the setting information on the basis of a drawn mark in the US images for decreasing computational costs. The measurement experiments for real US images performed in Kochi Medical School Hospital showed that the proposed algorithm detects the neighboring regions for the all target US images and that the enlarged thyroid glands evaluated by the proposed algorithm have relation with other blood test results. The proposed algorithmcan assist the evaluation of US screening and medical data analysis on the basis of the quantitative value of the US images.