Research On The Laser Speckle Temporal Contrast Imaging

Monitoring cerebral blood flow is important to understand the mechanisms of neurovascular coupling and regulation in normal and diseased brain. However, conventional methods used to measure blood flow suffer from the low spatial resolution and temporal resolution. Laser speckle imaging technique is a non-scanning imaging technique which can improve the measurements of the regional blood flow with high spatial and temporal resolution. Thus this method is becoming more and more popular.Based on the characteristics of laser speckle imaging, the mechanism as well as application of laser speckle spatial contrast analysis and laser speckle temporal contrast analysis is introduced. Then systematic analysis is carried out on the laser speckle temporal contrast analysis which based on time statistic of time-integrated speckle. The main contents and conclusions are listed as follows:(1) The effect of laser speckle spatial contrast analysis and laser speckle temporal contrast analysis to reduce static speckle is compared through theoretical analysis, model experiment and animal experiment. The result shows that, the laser speckle temporal contrast analysis has more advantages in restraining static speckle than laser speckle spatial contrast analysis.(2) Based on the self-built active noise reduction laser speckle system, we compared the active noise reduction and passive noise reduction system using laser speckle temporal contrast analysis. Facts are verified by model experiments that: active noise reduction system has favorable noise-reduction ability and the noise of contrast scales with the frame N of independent speckle as 1/N^1/2 . When the sample has certain dynamic characteristics, independent speckle images can also be acquired by passive noise reduction system, and get similar noise-reduction ability as active noise reduction system. The noise level can be downed to 10% when the independent speckle images N>100. (3) By analyzing the principle of speckle quasi-confocal system based on time statistic of time-integrated speckle, the performance of system is evaluated. The result of model experiment and the animal experiment shows that the system has favorable resolution under the illumination of statistically independent. The axel resolution is about 8μm.