Research And Implementation Of The Laser Speckle De-correlation Standard Deviation Algorithm

Since the biological tissue micro-vascular blood flow imaging can provide information on the tissue's blood flow in addition to its structure,the study of the fields related to microcirculation is attracting increasingly more attention.The laser speckle contrast imaging is a technology which adopts the laser of a certain wavelength to irradiate on the object to be examined.Due to the interference of the laser,the laser speckles vary in brightness with different movement states of the examined object which can be obtained according to the probability statistics of speckles.Being high-resolution and non-intrusive,the laser speckle contrast imaging technology,one of the ways to study the tissue micro-vascular blood flow imaging,has currently become a hot issue in the field.Given that the superficial vein imaging with existing traditional laser speckle contrast imaging technology is unclear and susceptible to the examined targets' conditions like respiration,heartbeat,tissue movement,etc.,the author puts forward an Laser Speckle De-correlation Standard Deviation Algorithm(LSDSDA)algorithm,explored the applicability of LSDSDA in superficial vein imaging,and conducted an experimental research on its practicality.The research mainly includes four parts as follows:(1)Since the laser speckle is affected by the object itself such as its respiration and heartbeat,this paper proposes an LSDSDA algorithm which will take bicubic interpolation algorithm,de-correlation algorithm,standard deviation calculation and image processing on the original speckle images.Finally,the blood flow images are achieved.The algorithm can effectively reduce the effect of the static speckles on the motion information of the exmained objects,enhance the signal-to-noise ratio,and strengthen the visibility of blood vessels.(2)A laser speckle flow imaging system is constructed.The semiconductor laser of 650-nanometer wavelength and the beam expander are used to achieve the laser speckles of high power density.Then through controlling the puA1600 monochrome industrial camera with OpenCV programming,the images are captured and stored in real time and displayed on the computer synchronously.(3)A "concave" microfluidic target of 300 micrometers wide and 250 micrometers deep is designed.By controlling the flow speed of the howkmed(?)injection pump,29 groups of speckle images of different flow speed between 0.0 mm/s and 10.36 mm/s(the minimum interval:0.37mm/s)is obtained.The microfluidic target experiment tests the feasibility of the designed system and meanwhile indicates that the LSDSDA can also be adopted to estimate the blood flow speed like the Laser Speckle Temporal Contrast Analysis(LSTCA)algorithm.(4)The speckle images of the nude mice's ears are collected through the designed system.Then the LSDSDA algorithm and LSTCA algorithm are carried out respectively on the pictures to get the corresponding blood flow images.The result shows that LSDSDA algorithm can effectively improve the visibility of microvessels and the signal-to-noise ratio(SNR),the vascular connectivity.In summary,an LSDSDA algorithm is proposed in this paper.And based on the algorithm,a laser speckle blood flow imaging system is designed.With this system,one can analyze the blood flow changes of microfluidic targets under different flow speeds,and meanwhile achieve clear micro-vascular blood flow images of the normal nude mice's ears which can well distinguish the ear vessels from other tissues.