The main goal of this project is to develop new technology to measure tissue elasticity by deforming it with acoustic radiation force applied to femtosecond laser produced microbubbles. First we will study physical functional relationships by measuring bubble motion in gelatin phantoms with known elastic and viscoelastic properties. Bubbles will be placed in these specimens with photodisruption from a femtosecond pulsed laser so that bubble size and position can be controlled. The bubble is displaced by acoustic radiation force from a high amplitude tone burst originating from one ultrasonic transducer and tracked by a broadband, low amplitude signal from a secondary high-frequency (50-100 MHz) transducer. Relationships between physical parameters can be used to determine elastic and viscoelastic properties in unknown specimens. After initial development, the technique will be validated on animal and then human lenses, and then used to map the spatial variation in these tissues. Preliminary experiments for this proposal would be limited to cadaverous tissues. These results will be helpful for future research with this technique on manipulating lens elasticity by photodisrupting small areas of tissue in a loosely spaced grid. In another application, with further development of equipment, this technique could be modified to measure elasticity of structures within individual cells. It is the aim, therefore, of this proposed work to address the following issues in detail: 1) Experimentally determine the relationship between physical parameters in three main areas: elastic media, acoustics, and bubbles. 2) Develop theory and mathematical models to yield insight on experimental results and to calculate unknown viscoelastic properties of specimens from measured properties. 3) Test and refine this method by mapping the spatial distribution of elasticity in tissue with medical significance, the intraocular lens.