Fluid dynamics, cavitation, and tiptotissue （流体动力学、气蚀和tiptotissue）.pdfVIP

LABORATORY SCIENCE Fluid dynamics, cavitation, and tip-to-tissue interaction of longitudinal and torsional ultrasound modes during phacoemulsification Jaime Zacharias, MD, Claus-Dieter Ohl, PhD PURPOSE: To describe the fluidic events that occur in a test chamber during phacoemulsification with longitudinal and torsional ultrasound (US) modalities. SETTING: Pasteur Ophthalmic Clinic Phacodynamics Laboratory, Santiago, Chile, and Nanyang Technological University, Singapore. DESIGN: Experimental study. METHODS: Ultra-high-speed videos of a phacoemulsifying tip were recorded while the tip operated in longitudinal and torsional US modalities using variable US power. Two high-speed video cameras were used to record videos up to 625 000 frames per second. A high-intensity spotlight source was used for illumination to engage shadowgraphy techniques. Particle image velocimetry was used to evaluate fluidic patterns while a hyperbaric environmental system allowed the evaluation of cavitation effects. Tip-to-tissue interaction at high speed was evaluated using human cataract fragments. RESULTS: Particle imaging velocimetry showed the following flow patterns for longitudinal and tor- sional modes at high US powers: forward-directed streaming with longitudinal mode and backward- directed streaming with torsional mode. The ultrasound power threshold for the appearance of cavitation was 60% for longitudinal mode and 80% for torsional mode. Cavitation was suppressed with pressure of 1.0 bar for longitudinal mode and 0.3 bar