automatic lumen segmentation from intravascular optical coherence tomography (ivoct) images is an important and fundamental work for diagnosis and treatment of coronary artery disease. however, it is a very challenging task due to irregular lumen caused by unstable plaque and bifurcation vessel, guide wire shadow, and blood artifacts. to address these problems, this paper presents a novel automatic level set based segmentation algorithm which is very competent for irregular lumen challenge. before applying the level set model, a narrow image smooth filter is proposed to reduce the effect of artifacts and prevent the leakage of level set meanwhile. moreover, a divide-and-conquer strategy is proposed to deal with the guide wire shadow. with our proposed method, the influence of irregular lumen, guide wire shadow, and blood artifacts can be appreciably reduced. finally, the experimental results showed that the proposed method is robust and accurate by evaluating 880 images from 5 different patients and the average dsc value was 98.1% +/- 1.1%.