| Since the birth of computer tomography(CT)technology,it has made great contributions to the progress of human society.With the continuous progress of technology,theimage acquisition method of CT system has been developed into the popular cone beam with flat panel detector from the beginning of the pencil beam and fan beam with a small detector.Scanning speed grows into faster and faster and the resolution is getting higher and higher.At present,CT system can not avoid the impact of artifacts on imaging so the artifact correction has been a major direction to improve the image quality for long.Based on the artifact correction,the paper has studied the following four directions.(1)The development process of CT system has been investigated,and it makes a brief introduction to the working principle and development direction of CT system.This paper analyzes the causes of hardening and scattering artifacts common to CT systems,and classifies the common correction methods of hardening and scattering artifacts in the published articles,which lays the foundation for the subsequent micro-nano CT artifact correction(2)The intensity changes of the detection signal in the micro-nano CT system under different filter,ray source current,and source voltage are tested.In the micro-nano CT,the attenuation ratio of the beam increases with the thickness of the filter plate.Under the same filter condition,the attenuation ratio is not obvious with the voltage change while with the current change obviously.A simple experimental test was made on the hardening artifacts at a source voltage of 120 kV and a source electric current of 200 μA.In this case,the filter sheet has a large effect on the low energy ray less than half the total energy of the ray,and has little effect on the high energy ray.After the reconstruction of the uniform material,the corrected gradation of the slices was better than that the non-corrected,which achieves a good hardening correction effect in micro-nano CT.(3)This paper analyzes the application principle,key details and operation flow of two kinds of single scattering correction schemes,such as Beam Stop Array(BSA)and Beam Hole Array(BHA).A Beam Stop Grid(BSG)correction scheme is proposed to optimize the defects of the traditional BSA scheme.The correction scheme adopted in the paper can be applied to the micro-nano CT reconstruction of complex workpiece.The results analysis is not only limited to the discrete scattering signal,but also achieved the analysis of discrete point images,digital radiography(DR)images and reconstructed images in BSA,BHA,BSG program,which improves the practicality and reliability of scattering correction program.In the case of a source voltage of 120 kV and a source electric current of 200 μA,the paper uses the circuit board and different types of industrial aluminum for scattering correction.The results show that the design of BSA,BHA,BSG correction schemes have achieved better correction effect for the scattering correction on micro-nano CT imaging.(4)Combining single hardening correction and single scattering correction scheme,three hybrid correction schemes considering the hardening correction and scattering correction are proposed: Filter-Beam Stop Array(FBSA),Filter-Beam Hole Array(FBHA)and Filter-Beam Stop Grid(FBSG).In the case of a source voltage of 120 kV and a source electric current of 200 μA,the paper uses the circuit board and different types of industrial aluminum for hardening and scattering mixed correction.In a variety of evaluation system,the paper gives the uncorrected,single hardening correction,single scattering correction,mixed correction in the same workpiece under the quantitative results and intuitive results.The results show that the three correction schemes of FBSA,FBHA and FBSG can effectively correct the hardening and scattering artifacts of micro-nano CT imaging in one experiment.The correction results are better than single hardening correction and single scattering correction,which provides an effective means for hardening and scattering artifact correction in micro-nano CT system. |
