Ultrasound modulated imaging of luminescence generated within a scattering medium.

Ultrasound modulated optical tomography modulates scattered light within tissue by deterministically altering the optical properties of the sample with the ultrasonic pressure. This allows the light to be "tagged" and the degradation in spatial resolution associated with light scattering to be reduced. To our knowledge, this is the first demonstration of ultrasound modulated imaging of light generated within a scattering medium without an external light source. The technique has the potential to improve the spatial resolution of chemi- or bioluminescence imaging of tissue. Experimental results show that ultrasound modulated luminescence imaging can resolve two chemiluminescent objects separated by 5 mm at a 7 mm depth within a tissue phantom with a scattering coefficient of 30 cm-1. The lateral resolution is estimated to be 3 mm. Monte Carlo simulations indicate that, with the current system signal to noise ratio, it is feasible to apply the approach to bioluminescence imaging when the concentration of bacteria in the animal organ is above 3.4×105/μL.