snake和lbf模型是活动轮廓的主要模型，利用水平集原理，在处理医学图像上具有很好的效果，可以自适应拓扑结构的变化(The snake and LBF model is the main active contour model, using the level set principle, has the very good effect on treatment of medical image, can be adaptive topology changes)

基于梯度的图像分割，可以精准定位，效果较一般的阈值，速度较快(Gradient based image segmentation can be precise positioning, the effect is more than the general threshold, faster)