PROBLEM TO BE SOLVED: To implement a technique for distinguishing between arteries and veins.SOLUTION: Regions of interest thought to be a blood vessel wall of an artery are set in a B mode image and tracking processing is carried out for each of the regions of interest. Then a maximum position speed Vu in a positive direction and a maximum displacement speed Vd in a negative direction are determined as peak values of the displacement speed of the blood vessel wall. If a first peak ratio (Vu/Vd), based on the determined maximum position speed Vu in the positive direction and maximum displacement speed Vd in the negative direction, of a region of interest corresponding to a front wall is equal to or more than a predetermined first feature threshold value (e.g., 2.0), the region of interest is determined to be an artery.【課題】動脈と静脈を識別するための技術の実現。【解決手段】Ｂモード画像内に動脈の血管壁と思われる関心領域を設定し、関心領域毎にトラッキング処理を行う。そして、血管壁の変位速度のピーク値として正方向の最大位置速度Ｖｕと負方向の最大変位速度Ｖｄとを求める。そして、求めた正方向の最大位置速度Ｖｕと負方向の最大変位速度Ｖｄとを用いて、前壁に相当する関心領域の第１ピーク比（Ｖｕ／Ｖｄ）が所定の第１特徴閾値（例えば、２．０）以上であれば、当該関心領域を動脈と判定する。【選択図】図３
