Quantitative Evaluation For Photodynamic Vascular Damage Using Laser Speckle Imaging

Laser speckle imaging(LSI)is a full-field,quantitative and real-time optical technique that has been widely utilized for motoring dynamic blood flow.Vascular targeted photodynamic therapy(V-PDT)is used to treat vascular related diseases through sealing blood vessel selectively.The changes of blood flow and diameter are important to evaluate V-PDT treatment outcomes.In this study,we use LSI and microscope to study the relationship of irradiances and the blood vessel response induced by V-PDT.The mice dorsal skinfold window chamber model was investigated when photosensitizer Rose Bengal(RB)is injected via tail vein injection at a dose of 25 mg/Kg body weight.Four various laser irradiances(50,75,100 and 200 mW/cm2)is provided by 532 nm laser.In addition,the custom-built fluorescence detection system is also used to monitor the photosensitizer fluorescence and photobleaching during V-PDT.The result suggests that the irradiance is positively correlated to V-PDT blood vessel damage,the quantative data shows that the blood flow decrease immediately after V-PDT treatment(50 mW/cm2:91.52±3.89%;75 mW/cm2:75.23±11.29%;100 mW/cm2:72.51 ±17.33%;200 mW/cm2:57.94±4.39%),the blood flow recovers a lot after 1 hour(50 mW/cm2:62.20± 12.38%;75 mW/cm2:48.50±6.31%;100 mW/cm2:42.73±8.37%;200 mW/cm2:37.01 ±6.79%).Significant difference in blood vessel damage was found between the lower irradiances(50,75 and 100 mW/cm2)and higher irradiance(200 mW/cm2).Furthermore,complete arteriole vasoconstriction occurred in all the four groups immediately and 1h after V-PDT,while the venules have partial response.The blood flow image indicate that the blood vessel damage induced by V-PDT is positively correlated with irradiance,and the better vessel response is achieved when the lower irradiance is performed for the treatment..