Ultrasonic diagnostic apparatus may receive to generate a received signal from the reflected ultrasonic wave from the blood vessel of the subject received by the probe and the transmission process for transmitting ultrasonic waves into the blood vessel of the subject by driving the probe an ultrasonic signal processing unit for performing processing, and a tomographic image processing unit for constructing a tomographic image from the received signal, a boundary detecting unit for detecting the tunica adventitia boundary and lumen membrane boundaries of the blood vessel from the tomographic image or the received signal , and vessel wall thickness calculating unit that calculates as vessel wall thickness value the interval of the tunica adventitia boundary and intraluminal membrane boundary within which it has been detected in the boundary detection unit, intraluminal membrane boundary within which it has been detected of the tomographic image or the received signal and determining reliability determination unit the reliability of the blood vessel wall thickness value based on the characteristics of the image information on the signal or on at the position of the tunica adventitia boundary, and the inner vessel wall thickness value based on the result of the determination of the reliability determination unit I and a control unit determining the tunica media complex thickness.本発明の超音波診断装置は、探触子を駆動し被検体の血管へ超音波を送信する送信処理及び探触子によって受信した被検体の血管からの反射超音波から受信信号を生成する受信処理を行う超音波信号処理部と、受信信号から断層像を構築する断層像処理部と、受信信号又は断層像より血管の内腔内膜境界及び中膜外膜境界を検出する境界検出部と、境界検出部で検出された内腔内膜境界及び中膜外膜境界の間隔を血管壁厚値として算出する血管壁厚算出部と、受信信号又は断層像の検出された内腔内膜境界及び中膜外膜境界の位置における信号上又は画像情報上の特徴に基づき血管壁厚値の信頼性を判定する信頼性判定部と、信頼性判定部の判定結果に基づき血管壁厚値を内中膜複合体厚と確定する制御部とを備える。
