High-resolution imaging in a deep turbid medium based on an ultrasound-switchable fluorescence technique.

The spatial resolution of fluorescence imaging techniques in deep optically turbid media such as tissues is limited by photon diffusion. To break the diffusion limit and achieve high-resolution and deep-tissue fluorescence imaging, a fundamentally different method was demonstrated based on a concept of ultrasound-switchable fluorescence. The results showed that a small fluorescent tube with a diameter of ∼180 μm at a depth of ∼20 mm in an optical scattering medium ([Formula: see text] and [Formula: see text] cm(-1)) can be clearly imaged with a size of ∼260 μm. The depth-to-resolution ratio is shown to be about one order of magnitude better than other deep-tissue fluorescence imaging techniques.