| Diffuse correlation spectroscopy/ tomography(DCS/DCT),developed recently,quantifies the motion of red blood cells by calculating the temporal autocorrelation function.Then the blood flow information of microcirculation tissue is estimated to realize the spatial imaging of blood flow in microcirculation tissue.The data acquisition method and image reconstruction algorithm will directly affect the speed and quality of blood flow imaging.Currently,spatial scanning and the use of optical switches can share light sources and detectors,and it is an ideal way to achieve low cost DCT imaging.Since it takes only 0.1s for the optical switch to switch between different S-D positions on the tissue surface,this method greatly reduces the data acquisition time compared with the spatial scanning of linear probes.However,when the optical fiber array with M light sources and J detectors distributed around each light source is used,the optical switch needs to be switched M times to complete the complete data acquisition of the M*J array.Therefore,if the blood flow image is reconstructed from the complete DCT signals,there will be a certain amount of time for data acquisition,and dynamic blood flow imaging cannot be realized.To solve the above problems,The following work is done in this paper:(1)In terms of data acquisition,this paper changes the traditional data acquisition method,that is,manually click the switch button of the next channel to switch optical path after the data acquisition of the upper light source is finished.Using Visual Basic to write the corresponding program,under the same clock(timer),by judging the frame parameter,control the light path switching of different light sources,realize the automatic acquisition of the original signal,greatly shorten the signal data acquisition time.After the data collection of each light source is finished,file storage control is triggered.Through the MKdir function,file storage path is preset and data folder is automatically generated to realize the automatic collection and saving of blood flow signals.(2)In terms of imaging algorithms,a rapid blood flow imaging algorithm WA-ART(weight adjustment and algebraic iterative reconstruction technique)was proposed in this paper.Weight judgment was combined with algebra reconstruction technique to find the increment of blood flow change after each optical switch.The number of voxel units to be reconstructed is reduced to realize the updating of blood flow image at the sampling rate of 5s.Through this innovative algorithm,the data acquisition method is improved to realize the dynamic acquisition of microcirculation tissue blood flow image at faster time sampling rate by using near infrared diffuse light.Computer simulation experiments,phantom experiments and human physiological experiments fully prove that this algorithm can not only improve the contrast of blood flow imaging,but also greatly improve the real-time computational efficiency of blood flow imaging,and realize the continuous and dynamic 3D image reconstruction of microvascular blood flow. |
