The Research Of Multibeam Of Multiplexed Imaging X-ray Control System

In the modern society, breast cancer has become one of the major disease threaten to women’s health. To diagnose and therapy the disease, the DBT (Digital Breast Tomosynthesis, DBT) breeds. Digital Breast Tomosynthesis Scanner is the most effective of the existing tool for early detection and diagnosis of breast cancer, and has made great contributions to reduce the mortality rate of breast cancer. SDBT (Stationary Digital Breast Tomosynthesis, SDBT) uses X-ray sources, which is made of carbon nanotubes, and X-ray emission mode is based on multibeam field emission.Field emission of X-ray source has the advantages of small volume, high density of emission current, no delay and power consumption of the cathode, and high integration, make its application prospect much better than other X-ray source. Recent years, with the continuous research and development of the theory and technology about carbon nanotube, it has been used as field emissionof X-ray source’s cathode. Used as multibeam field emission of X-ray source’s cathode material in X-ray control system, electron emission will be controlled, and there is no delay time in the process of emissin.Carbon nanotube’s excellent properties of field emission needs ultra-high voltage to activate the carbon nanotube cathode, and the timing sequence of cathode electron emission should be controlled. As a result, when the control system needs level to KV voltage as the activation voltage of carbon nanotube cathode, and must be provided high frequency pulse signal, make the timing sequence controlled of cathode electron emission.Because the time of CT’s traditional imaging mode is long, and the image is affected by the mechanical action of CT scanning system itself, rotary speed and X-ray source peak voltage, the CT projection image reconstruction is complicated.To solve the problems provided above, this paper proposes a SDBT system based on the multiplex in the imaging of multibeam of X-ray sources’field emission control system. The decrease in imaging time, simplify system design and research the SDBT’s potentiality of improving image quality compared with the traditional way of DBT imaging mode. Choose FPGA as the microprocessor and Insulated Gate Bipolar Transistor (IGBT) as the core device of the switch circuit between each X-ray source. The IGBT emitter is connected to the amplify circuit, and the sampling resistor’s voltage is amplified 10 times, then through the analog-to-digital conversion circuit. Using USB transfers data to the workstation. Then workstation will calculate sampling resistance current value, and according to the preset X-ray emission current value, automatic compensating voltage to keep the X-ray emission current being default.Choose FPGA chip, EP4CE10E22C8N belonging to Cyclone IV, which is producted by Altera corporation, as the microprocessor of the field emission of multibeam X-ray sources’ control system. Taking the full advantages of FPGA’s logic resources and user’s 10 to complete the control system hardware module, including RS-232 protocol, square wave signal, analog-digital conversion, LED lights and modulus conversion module.To solve the problems caused by the images reconstruction, this paper provides a control system based on multibeam X-ray sources field emission, and explores the orthogonal frequency division multiplexing technology in the field of communication on the SDBT system’s application prospect.Use the ideas of orthogonal frequency division multiplexing in the field of communication on the SDBT, which requires the emission frequency of the SDBT’s X-ray sources different. The frequency of multiplexing imaging technology increases 0.1 Hz between each X-ray source in turn. Orthogonal Frequency Division Multiplexing (Orthogonal Frequency Division Multiplexing, OFDM), is a branch of multi-carrier modulation technology, and its essence is to high speed data signal into several parallel low speed of data flow channel, the low speed modulation to each child child data flow channel for transmission.Proved by the experiment, Compareing with the traditional technique of CT imaging technology, the multiplex imaging technology’s scanning time will be shortened to the traditional N/2 times, and the image resolution is high after the MATLAB decodes the multiplexing projection image.