The Study Of Algorithm For On Variable Voltage X-ray CT Reconstruction

X-ray CT has been widely applied in industrial, medical and other fields as anadvanced nondestructive detection technology. However, The current structurecomponent has some characteristics of irregular shape, complex structure, bigthickness difference and multi-materials with the development of science andtechnology. And the projection data in conventional imaging mode of fixationvoltage easily appears the phenomenon of overexposed in high energy andunderexposed in low energy because of the fixed energy and the limit of the dynamicrange of imaging system. The projection information of structure component is loss.This will impact the quality of CT reconstruction seriously. In order to obtain all thestructure information of current structure, variable voltage CT reconstruction hasbeen put forward based on the conventional CT theory. It obtains a series ofprojection sequences matched with the thickness by changing the voltages andrealizes the CT imaging for the complicated structural component.Based on the conventional CT imaging, the paper analyzes the limitations offixed voltage imaging model and put forward the theory of variable voltage CTfusion imaging. The methods fuses the effective information extracted by the bestgray zone and obtains an complete, high dynamic projection data of complicatedstructural component. Experiment shows that the result using TV-ART algorithm issuperior to the fixed voltage CT imaging.Then, the paper put forward the weight algorithm of variable voltage CTrefering to the high dynamic imaging technology. In the process of reconstruction,the reconstructive image of the low voltage is used as a initial value of the effectiveprojective reconstruction of the adjacent high voltage，get the reconstructive imageof the adjacent high voltage,and so on until to the highest voltage according to the gray weighted algorithm. And the virtual experiment has proved that the method isfeasible in variable voltage CT imaging. Due to all the projective informationincluding to the low quality image are involved in the reconstruction process, it notonly caused the discontinuous structure edge of the final result, also reduces the rateof convergence.For the above problem, the paper put forward the weight algorithm of thevariable voltage CT based on the effective area. Their difference is only effectivearea. The paper put forward the improved method of negative logarithm transformaccording to beer theorem. It can compress all the image gray display range, reducethe noise influence effectively and improve the quality of CT details. Experimentsshow that this improved method can achieve effective imaging of complexcomponents.