Sequential images play a significant role in reconstruction of 3D images for computeraided surgery and radio-therapy. The most important problem we must solve is to realize optimal and automatic boundary detection with feasible computational coat. In this paper

we develop a dynamic programing（DP）-based method with the aid of "band" and introduces a novel searching strategy to achivethis goal. Experimenal results in ultrasonic image sequences of normal and abnormal cardiac vessels prove this method to be practicable.