Abstract 17437: Ultra Fast Brightfield and Fluorescence Imaging of Micron Size Objects for Research in Microbubble-Ultrasound Mediated Therapeutics

Abstract

Background: Ultrasound (US)-assisted therapies such as US-induced microbubble (MB) destruction have potential to enhance thrombolysis and drug or gene delivery for cardiovascular disease. Visualization of US-MB-cell interactions, which occur in nano-second time scale due to the physics of US, should yield insights into therapeutically relevant MB dynamics, and improve design of US-MB-mediated therapies. We present a high speed brightfield and fluorescence imaging system that allows unique in vitro and in vivo microscopic observations of MB acoustic behavior. Methods: Our integrated system includes a custom multi-frame camera and software control (Cordin Co), customized modular microscope and laser system, US generator, and combined US and optical imaging chamber for in vitro and in vivo MB observations. The camera system, based on a rotating mirror design, contains 64 digital CCD cameras (1392 x 1040 pixels) and acquires 128 image frames. A strobe light triggered from the timing board is used for the brightfield light source. A fast pulse capable Cyan-488 optically pumped semiconductor laser system is used for fluorescence imaging. A custom fiber optics alignment system delivers laser light through the microscope. Results: The system images at up to 25 million frames per second (Mfps). Fig 1A shows selected frames of fluorescent beads (1, 2, 4 um), proving the concept of ultra-fast fluorescent imaging, and demonstrating the potential for in vivo intravital microscopy of vibrating fluorescent MB in the microcirculation. Fig 1B shows selected brightfield frames of US-induced MB vibration, fluid jets, and invagination of thrombus (block arrow). Conclusion: We have developed a high speed camera system for fluorescence and brightfield imaging at 25 Mfps. This system should enable unique visualization of interactions between US, MB, and cells in vitro and in vivo, and ultimately help to optimize novel US-MB mediated therapies for cardiac disease.