RÉSUMÉ
Objective:To analyze the bubble dynamic characteristics of shock wave enhanced emission photoacoustic streaming(SWEEPS)technique in free water region under different temporay delays.Methods:The Er∶YAG laser tip was activated in free water model with SWEEPS mode at 150-600 μs pulse delay.The bubble dynamic process during irrigation was recorded by a high-speed camera(200 000 Hz).Matlab was used to analyze the interaction between bubble made by the dual pulses frame by frame.The distance between bubble remnants and laser tip was measured before the bubble disappeared.The experimental data were statisti-cally analyzed by SPSS 19.0.Results:In free water region,different temporal delays caused different interaction between the bub-bles activated by the SWEEPS technique with a dual pulse modality.The interactions include bubble fusion,bubble collision and bubble separation.When the temporal delay between 360-440 μs,bubble collision was the most violent,and the farthest distance between bubble remnants and laser tip was reached.Conclusion:In free water region,the dual pulse of SWEEPS technique can lead to bubble interaction which may enhance the cavitation effect of Er∶YAG laser irrigation,and improve the debridement in clinic ap-plication.