Medical image elastic registration is an important subject in medical image processing. Previous work has concentrated on selecting the corresponding landmarks manually and then using thin plate spline interpolating to gain the elastic transformation. However

the landmarks extraction is always prone to error

which will influence the registration results. Localizing the landmarks manually is also difficult and time consuming. In order to solve these problems

a novel method is proposed in this paper. By smoothing the thin plate spline interpolation functions

the influence of the landmarks error can be decreased effectively. And basing on the process

a semi automatic method is used to extract the landmarks

which can simplify the selection for points. Combining these two steps

an exact

fast and robust registration approach is obtained. The approach is composed of two steps. First

it searches the contours and makes them discrete to gain the corresponding landmarks. Then by interpolating images with the smooth thin plate spline

the registration images are obtained. To validate the effect

series experiments are implemented. The experiments show that the novel method can reduce the influence of the landmarks error and gain the satisfactory registration results. In this approach

the smooth parameter is an important factor

which must be selected carefully. The principle for determining the parameter is presented in the end of this paper.