Research On Laser Speckle Blood Flow Imaging System For Clinical Application

Blood flow is considered as an important parameter to reflect biological hemodynamics, so measurement of it has significance for basic life research and clinical diagnosis and treatment. Compared with other exiting methods for measuring blood flow, laser speckle blood flow imaging has the advantages of real time, full field and high spatio-temporal resolution, and it can realize quantitive analysis of the change in blood flow. Hence, the design and application of laser speckle blood flow imaging system are getting increasing attention and have great prospect. However, there still lacks comprehensive analysis of the influencing factors for laser speckle blood flow imaging system, and now the applications are limited in laboratory experiments research. Therefore, this thesis analyzes comprehensivly multi-factors which influence the performance of the system through numerical simulation and phantom experiments. On this basis, we design and set up coaxial laser speckle blood flow imaging system for large field of view use and the system has been applied clinically to monitor the blood flow of different skin diseases. Moreover, we analyze the problems in illuminating and imaging of endoscopic laser speckle blood flow imaging system, which is for realizing blood flow imaging in cavity and deep tissue.The main results of this thesis include:(1) Analyze comprehensivly multi-factors which influence the performance of the laser speckle imaging system through numerical simulation and phantom experiments and find out:the intensity of light source has little influence in laser speckle contrast when satisfying the specified signal to noise ratio, but if the degree of the coherence and polarization of the laser decrease, the system factorβ will be increased; the system factorβ is also influenceced by the magnification and F-number of the imaging system through adjusting the speckle size, to satisfy the Nyquist Sampling Law, the speckle size should be at least twice the pixel size, but the spatial resolution and statistical accuracy will be reduced with the increase of speckle size; the system factor β will be increased if the noise level of the camera increases, and the exposure time of the camera will change the linear velocity response range; in practical application, the difference of system factor β between different imaging systems or the same imaging system with different parametes should be taken into consideration to realize the comparison of the measurement results. The above conclusionss will guide the design and application of the system.(2) Design and set up the coaxial laser speckle imaging system for large filed of view use, and analyze the influence of different application conditions on analysis of relative change of velocity:the working distance has little influence on it, but the linear velocity response range will move forward high velocity if the working distance is increased; the exposure time has little influence on it, and for this system it is not proper to set a very small exposure time; the observing angle will not influence analysis of relative change of velocity but if it is set to be large, it will reduce the comparability between different regions in one blood flow image; the intensity has little influcne on it when satisfying the specified signal to noise ratio. Moreover, the system has been applied in clinical blood flow imaging of skin diseases, and has offered important and useful information for locating and classifying the lesion, assessing the treatment and adjusting the treatment plan in time.(3) Combine the laser speckle blood flow imaging with fiberic endoscopy to realize blood flow imaing in cavity and deep tissue; present a nLSSCA method to correct the detrimental effects of spatial discontinuous sampling of a imaging fiber on laser speckle spatial statistics, and this method has higher temporal resolution and statistical accuracy than LSTCA; through phantom experiments and animal experiments, verify that there is a good linear relationship between the measurments and actual velocity when the object is illuminated by the fiberic laser which is a process of'speckled speckle'.