Research On Key Technologies Of Laser Doppler Blood Flow Velocity System

Blood and human health are inseparable,by studying the blood microcirculation system can get the body tissue lesions,such as burns,fundus diseases.The traditional method of detecting blood flow velocity is mainly ultrasonic wave,but the ultrasonic transverse resolution is insufficient,can only measure the arterial and thick vein blood flow,can not detect the vein microcirculation system.The use of laser Doppler blood flow measurement,to meet the blood microcirculation system transverse resolution detection requirements,but also noninvasive,simple operation,etc.,has a wide range of applications in clinical medicine,so researchers have much attention on laser Doppler blood flow measurement in the domestic and foreign medical equipment.Through the study of a variety of laser Doppler blood flow system,this research abandons the single point and scanning blood flow method,and choose the current representative of the laser wide field Doppler imaging blood flow technology(LDI)as the main research object of this paper.The main research contents are as follows:Firstly,optical heterodyne interference theory,blood perfusion imaging theory,and laser Doppler blood flow detection system characteristics are introduced,the light source,image sensor and other key devices are selected.Based on the comprehensive analysis of the existing experimental system structure,a new type of optical system is designed.Secondly,the hardware circuit design of high frame rate image acquisition system is completed,including CMOS image sensor control circuit,FPGA interactive circuit,SDRAM control circuit,STC51 interface circuit and CY7C68013 A peripheral circuit.In the PCB design stage,the crosstalk simulation and reflection simulation are carried out to determine the rules such as device trace topology,termination method and board structure.The PCB board is drawed,and then the circuit system design is completed.Thirdly,laser wide field Doppler blood flow system software design,including: clock management program design,image sensor control program design,SDRAM read and write program design,CY7C68013 A read and write program design,CY7C68013 A firmware program and USB 2.0 host computer control program design.When designing the FPGA logic module,each module uses a state machine to perform the loop operation.The modules are designed in a combination of pseudo-sequence operation and parallel operation,and each logic module is simulated by Modelsim-Altera.Next,the host computer interface production is completed by using Labview VISA control function,and establish communication with high frame rate image acquisition device.Finally,experimental system of the LDI presented by this article is established by using the self-designed high frame rate image acquisition device to get the living skin tissue microcirculation system perfusion imaging.The experimental system sampling frequency is 8kfps,get tissue microcirculation perfusion imaging chart maximum resolution of 64x64,and can clearly see the blood flow changes.The effects of noise on blood flow imaging are eliminated through further experimental study of whiteboard,and the influencing factors of blood perfusion imaging is analyzed.