Measurement Of Microvascular Physiological Parameters Based On Microscopic Imaging And Monte-Carlo Optical Simulation Of In Biological Tissues

The cardiovascular system plays a crucial role in the human body,and cardiovascular disease is one of the most common diseases,which seriously threatens human life and health.The main function of the cardiovascular system is to complete the exchange of substances between the body and the outside world and maintain the metabolic balance in the body.As an important part of the cardiovascular system,the blood oxygen saturation,red blood cell flow rate and oxygen metabolism rate of microcirculation are important physiological parameters to indicate the health of microcirculation.The current microvascular physiological devices can only measure the physiological parameters of one kind of capillary,and has specific requirements for the measurement environment.For example,laser Doppler flowmeter mainly measures microvascular red blood cell flow velocity,while common pulse wave oximeter only measures arterial oxygen saturation.In addition,infrared light is commonly used for the measurement of microvascular physiological parameters,but it has a heating effect that may interfere with physiological measurements.In order to overcome the limitations of the measurement environment and to realize the measurement of multiple physiological parameters in a single imaging method,this study using a nailfold microcirculation microscope as a microvascular imaging device to measure microvascular physiological parameters.This microscope uses visible light as an illumination source,can clearly observe capillaries and red blood cells.This approach has the advantage of a closer approximation to daily illumination methods and can reduce the limitation of the measurement environment for microvascular imaging.In this study,the Monte Carlo method was used to simulate the propagation of visible light in microvascular physiological tissues under varying blood oxygen saturation conditions,and the simulation results were used to establish the relationship between RGB color space intensity and blood oxygen saturation.There was a good correlation between blood oxygen saturation and the ratio of R channel and B channel intensity in the measurement range(r2 = 0.571,P = 0.039),which proved the possibility of measuring blood oxygen saturation through RGB color space.The study also collected and preprocessed microvascular images using the nailfold microcirculation microscope.The images were calibrated using a pulse wave oximeter,and the relationship between color channel intensity and blood oxygen saturation was determined by fitting,and the accuracy of the relationship was verified by Bland-Altman plot.The arteriolar to venule oxygen saturation was measured,and the results showed a continuous decrease from arterial oxygen saturation to 80%,consistent with the oxygen delivery process to tissues by red cells in microvasculature.Finally,the study measured the red blood cell flow velocity and metabolic rate of oxygen in capillary.in capillaries using the nailfold microcirculation microscope.The flow velocity of red blood cells in arterioles(1000-2000 μm/s)was found to be faster than that in venules(700-1200 μm/s).The metabolic rate of oxygen at the nailfold [2.0-3.5(1/s)] was found to be 2-3 folds higher than that in the flanking regions [0.3-2.0(1/s)],indicating the tip of the nailfold as the primary region for oxygen exchange.In conclusion,this study proposes a novel approach for measuring multiple microvascular physiological parameters using visible light illumination and a nailfold microcirculation microscope.This approach has the potential to reduce the measurement environment’s limitation and enable the measurement of multiple physiological parameters in a single imaging method.This can aid in the early screening of cardiovascular diseases and the development of effective treatment strategies.