Vascular Image Processing Using Recursive Directional Filters

In this paper we present a design method for a class of 2D recursive filter banks with wedge-shaped channels, based on frequency transformations. The design starts from a given analog prototype filter with specified parameters and a transfer function factorized into biquads. Applying adequate frequency transformations to these functions, the desired 2D filters are directly obtained in a factorized form. The approach is mainly analytical but also uses numerical approximations and is simple, efficient and versatile. These filter banks find applications in medical image analysis, as shown on some angiography images, for instance the detection of blood vessels with a specified orientation. A design example starting from imposed specifications and simulation results are provided.