The Study Of The Reconstruction Algorithm On The Region Of Interest In Cone-Beam CT

With the rapid development of CT technology, it has also been widely used in engineeringand medicine. In many cases, it does not require a complete global CT imaging, only toobtain the region of interest of the objects in many engineering applications and the medicalfield. So the local reconstruction for the region of interest (ROI) is becoming one of theimportant studies in image reconstruction. This paper mainly studies the reconstructionalgorithm on the region of interest in three dimensional cone beam CT. The main contentsinclude:1. The paper learns and achieves the classical FDK algorithm,the helical FDK algorithmand the Katsevich exact reconstruction algorithm.The impact of the cone angle on imagequality is analyzed in the classical FDK algorithm. Cone-beam helical CT is complexand time-consuming in reconstruction algorithm for the moment. So the thesis researcheson reconstruction speed from the coordinate symmetry of trigonometric functions toreduce the computational complexity in procedure. Computer simulation experimentsabout the helical FDK reconstruction algorithm express that the method can efficientlyimprove the speed of image reconstruction.2. The improvement of the reconstructed image based on truncated projection data.Reconstructing the local image by using the direct projection data(the truncatedprojection data) generates the gray shift artifact in the reconstructed ROI image. For theartifact, this paper puts forward the method that combines the new filter function and thedata marginal extension to effectively improve the quality of the reconstructed ROIimage.3. The new method of the region reconstruction based on the new objective function.Theidea of Pesudo local tomography local reconstruction algorithm is to intercept a part of Hilbert transform as the objective function for the local area reconstruction. Based on theidea, the paper proposes the new objective function to reconstruct the region of interest.The method is to lock the position and size of the region of interest according thecoordinate system and consider the region of interest as the new objective function toreplace the original density function.The numerical experiment results and real objectexperiments verify that the method effectively achieves the local image reconstruction.