Research On Cone-beam CT Reconstruction Technology Based On Flat Panel Detector

Cone-beam CT outperform 2D parallel-beam and fan-beam CT in the aspects ofacquisition data speed, spatial resolution and ray utilization rate, which are very significant formedical diagnosis and industrial non-destructive testing. Large-areas amorphous siliconflat-panel detector becomes more and more popular in the field of industry ray imaging. Inthis paper, 3D cone-beam CT image reconstruction method is researched systematically,according to the characteristics of the cone-beam projection data based on the flat-paneldetector. The main contents of the paper include the following:According to the transformation relationship between Cartesian coordinates and polarcoordinates, this paper proposes a fast reconstruction algorithm for the back-projectionalgorithm of the polar coordinates for fan-beam collinear equispaced CT based on the featuresof sine and cosine function. The experimental results show that, compared with the traditionalfiltered back-projection algorithm, this method can improve the reconstruction speed by morethan 4 times, and will not bring new reconstruction error. This method has been successfullyapplied to the reconstruction of 3D cone-beam.The 3D cone-beam FDK reconstruction algorithm is discussed and the characteristics ofthis algorithm are analyzed. The numerical calculation method of the computer realization isalso derived in this paper. Moreover, the FDK optimization algorithm is proposed accordingto the characteristics of the reconstruction steps. The experimental results show that theproposed optimization algorithm can effectively shorten the reconstruction time and it issuperior to the standard FDK reconstruction algorithm in the reconstruction image quality.On the basis of discussing several common filter functions and analyzing thecharacteristics of the sample sequence for each filter function, a mixed filter functioncombining with the R-L and Cosine filer function is proposed in this paper. And the proposed filter integrates with the advantages of R-L and Cosine filter function. While this filter canguarantee the image spatial resolution, it relatively increases the density. This filter makes agood compromise between the high and low frequency information. The experimental resultsshow that the error of the reconstructed image by the proposed filter is relatively small. At thesame time, it smoothed the image.This paper also focuses on the study of the projection data rebinning algorithm namedF-FDK based on flat panel detector. This algorithm which refers to the idea of P-PDKalgorithm and absorbs the advantages of T-FDK algorithm, rearranges the cone-beam datainto fan-beam data in the vertical plane, then reconstructs image by the principle of theparallel-beam. This algorithm truly achieves the data rebinning by converting projection datain both directions of m and n. The experimental results show that F-FDK algorithm reducedthe artifact which caused by the cone angle increasing, and the reconstruction image qualitycan be obviously improved.