Research Of Cone-beam CT Geometric Calibration

Micro-computed tomography (Micro-Computed Tomography, Micro-CT) as anondestructive testing technology, can well meet the needs of high-resolution imaging inanimal models, which provide fine structure information and attenuation correctionparameters for multi-modal molecular imaging devices (PET/SPECT/CT). Cone-beam CT(CBCT) with the characteristics of higher spatial resolution, higher utilization of radiation,shorter time of scanning, etc., become the new hot spot and new directions in the field ofMicro-CT.FDK algorithm is widely used in cone-beam CT system as an approximation algorithm,but the effect of FDK algorithm for cone-beam CT system is very sensitive to the geometricparameters. It requires the position of X-ray source, detector and rotary table to be in an idealstate, namely the ray source center ray vertical into the center of detector, and the axis ofrotation and the center ray are coplanar and orthogonal. After manual installation, it isdifficult for Cone-beam CT to meet the accuracy requirements of the ideal state. Thegeometric model of the actual system will be deviated from the geometry model required byideal FDK reconstruction algorithm. The deviation caused by artifact is geometric artifacts.Geometric artifacts seriously affected the effects of CT imaging reconstruction and the fusionsof other modality imaging。So, how to calibrate Cone-beam CT system conveniently andeffectively is important for achieving high-quality CT imaging reconstruction.This paper provides a set of calibration system and calibration method for Cone-beamCT system. The method based on a geometric calibration p hantom scanned, and then extractthe geometric information of CT system from different angle of projection data. According tothe geometrical information, the method could complete the geometric calibration of Cone-beam CT system. Finally, it assesses the effect of geometric calibration for geometriccalibration phantom contrast before and after calibration.