A technique is provided for imaging based on localization of fluorescence in a medium. The technique includes illuminating the medium with an excitation light to excite fluorescence, scanning the medium at a plurality of locations via an ultrasonic beam, modulating a portion of the emitted light from the fluorescence via the ultrasonic beam at each of the plurality of locations, differentially detecting the modulated light at a boundary of the medium, and reconstructing an image from the detected signal.