US Patent 6846288 Photoacoustic assay and imaging system

A method for assaying a component of a localized region of interest in a body comprising: illuminating the region with at least one pulse of radiation having a wavelength at which the radiation is absorbed by the component to generate a change in an acoustic property of the region; transmitting ultrasound so that it is incident on the region; measuring at least one effect of the change on the incident ultrasound; using the measured at least one effect to determine an absorption coefficient for the radiation in the region; and using the determined absorption coefficient to determine concentration of the component in the region.