Optimization Design Of Static Digital Breast Imaging System Based On Carbon Nanotube Ray Source

Breast cancer is a major disease that threatens the health of women all over the world,effective breast imaging methods can effectively assist doctors in the early diagnosis of breast diseases,so the study of breast imaging methods has always been a research hotspot in the field of medical health.Static digital breast tomosynthesis(sDBT)is a new method of breast imaging based on digital breast tomosynthesis(DBT)by improving x-ray source to achieve static imaging.In order to improve the imaging quality of s-DBT system,optimizing the structure and electrical parameters of the electron gun of carbon nanotube x-ray source and improving the imaging control system based on s-DBT system 1.0 to improve the spatial resolution and contrast of the system imaging system.Firstly,according to the imaging principle of s-DBT system,the factors affecting the imaging quality of the system are analyzed,the method of optimizing the electron passing rate and the anode focal spot size of the carbon nanotube electron gun is determined,and the control system design of the optimized electron gun is needed.Secondly,according to the characteristics of carbon nanotube x-ray source and electron field emission theory,it is proposed to optimize the structure and electrical parameters of electron gun by adding auxiliary electrode(focusing electrode),change the electric field distribution so as to make the carbon nanotube field emission electron beam focus,increase the electron passing rate,reduce the size of anode focal spot,and finally achieve the purpose of improving the x-ray intensity and improving the imaging quality.A three-dimensional model of carbon nanotube electron gun is established by using Xenos three-dimensional electromagnetic field simulation and analysis module.Based on the electron gun model,electromagnetic field analysis is carried out,and the influence of cathode-grid spacing,grid thickness,focusing electrode voltage and other parameters on field emission current and electron beam trajectory are analyzed.The simulation analysis value of focal spot shrinkage is reduced to 1/6 of that of the original electron gun,and more than 60% simulation analysis value of electron passing rate is obtained,which provides a basis for optimizing the electron gun structure and voltage parameters of x-ray tube.Then,according to the characteristics and range of electron gun focus electrode voltage,combined with the real-time control requirements of s-DBT system,the focus electrode control system is designed by using CompactRIO embedded controller and LabVIEW development platform.Including the system software,hardware and interactive interface design.After the design is completed,the accuracy and real-time performance of the monitoring are verified.The experimental results show that the relative error of the voltage control of the high voltage power supply is less than 0.5%.Finally,the optimized system is tested by tube current and the system imaging experiment is carried out.The experimental results show that the maximum electron passing rate can be increased from less than 20% to more than 50% after optimizing the electron gun.During the experiment,the imaging quality was measured quantitatively and qualitatively by using different types of phantom,and the breast phantom image with spatial resolution of 0.133 mm was obtained.The imaging quality is compared before and after optimization.the results show that the spatial resolution and contrast are improved after optimization,and the imaging quality is optimized to some extent.