传统的基于梯度向量流的活动轮廓模型只能产生静止不变的外力场，外力场中普遍存在“平衡问题”，导致轮廓曲线难以收敛到长凹形边界． 为此，文中提出了一种动态的梯度向量流模型． 该模型首先利用与演化轮廓曲线相关的示性函数对边缘梯度图进行加权并扩散生成一个动态力场，然后利用边界停止函数控制演化轮廓曲线的收敛． 该模型充分利用了演化轮廓曲线的信息，避免了静态外力场因“平衡问题”导致的过早收敛问题，能够驱使轮廓曲线收敛到凹形边界． 仿真实验结果表明，相比于传统的模型，文中模型能成功地分割出目标的长凹形边界，并且对复杂目标边界也有较好的分割效果．

Traditional active contour models based on the gradient vector flow can only produce static force field，in
which the equilibrium problem often occurs and it causes a difficulty in the convergence of the contour curve to a long concave boundary． In order to solve this problem，a dynamic gradient vector flow model is proposed in this paper． In the model，first，a dynamic force field is generated by adopting an indicative function relevant to the evolving contour curve to weigh the edge gradient map． Then，the edge stopping function is employed to control the convergence of the evolving contour curve． The proposed model makes full use of the information of the evolving contour curve，and thus it avoids the premature convergence caused by the equilibrium problem of static external force field and pushes the contour to evolve to the concavity boundary． Simulation results show that，in comparison with the traditional models，the proposed model can segment the long concave boundary of the object successfully and achieves better segmentation results in extracting the complex boundary of the object．