基于分数阶微分的TV-L^1光流模型的图像配准方法研究

Research on TV-L^1 Optical Flow Model for Image Registration Based on Fractional-order Differentiation

图像的非刚性配准在计算机视觉和医学图像分析中有着重要的作用.TV-L^1(全变分L^1范数、Total variation-L^1)光流模型是解决非刚性配准问题的有效方法,但TV-L^1光流模型的正则项是一阶导数,会导致纹理特征等具有弱导数性质的信息模糊.针对该问题,将G-L(Grünwald-Letnikov)分数阶引入TV-L^1光流模型,提出基于G-L分数阶微分的TV-L^1光流模型,并应用原始–对偶算法求解该模型.新的模型用G-L分数阶微分代替正则项中的一阶导数,由于分数阶微分比整数阶微分具有更好的细节描述能力,并能有效地、非线性地保留具有弱导数性质的纹理特征,从而提高图像的配准精度.另外,通过实验给出了配准精度与G-L分数阶模板参数之间的关系,从而为模板最佳参数的选取提供了依据.尽管不同类型的图像其最佳参数是不同的,但是其最佳配准阶次一般在1～2之间.理论分析和实验结果均表明,提出的新模型能够有效地提高图像配准的精度,适合于包含较多弱纹理和弱边缘信息的医学图像配准,该模型是TV-L^1光流模型的重要延伸和推广.

In computer vision and medical image analysis, non-rigid image registration is a challenging task. TV-L^1 （Total variation-L^1） optical flow model has been proved to be an effective method in the field of non-rigid image registration. It can solve the problem of fuzzy edge caused by smooth displacement fields of Horn-Schunck, but its first-order derivative in regularization term leads to fuzzy texture information with weak derivative property. Aiming at the problem, this paper introduces G-L （Griinwald-Letnikov） fractional differentiation to TV-L1 optical flow model, and proposes a new TV-L^1 optical flow model based on fractional differentiation, and then finds the solution of the model using primal-dual algorithm. In this paper we use Griinwald-Letnikov fractional order differential instead of the first-order derivative in the regularization term for its better ability of detail description than first-orderls. Then we purposefully control to retain or inhibit the texture information with weak derivative nature, thus improving the registration accuracy. Experimental results show that the proposed method has a better registration accuracy in registration of texture information with weak derivative, and that it can be considered an important extension and generalization of TV-L^1 optical flow modes.