Research of correcting distorted X-ray images based on least squares and biharmonic spline surface

Owing to the geometric distortions of the X-ray images, C-arm CT (computed tomography) imaging system usually suffers from adverse effects. To overcome the difficulties, an integrated approach has been put forward to correct distorted X-ray images in the paper. The approach firstly uses OTSU algorithm and morphological open operation to extract the control points coordinates in the distorted X-ray images. To obtain more coordinates and improve the correction precision, least squares is used to fit the polynomial passing by the extracted points. More coordinates are calculated by using the fitted polynomial. Then, a biharmonic spline surface is interpolated by the extracted and calculated coordinates. Finally, the distorted X-ray images are corrected by using the interpolated biharmonic spline surface. Experiment on the acquired distorted X-ray images demonstrates that the proposed approach can effectively correct the distorted X-ray images. A comparison with classical approaches further shows that the approach proposed in the paper performs better in visual effects and correction accuracy.