Ultrasound-enhanced optical coherence tomography: improved penetration and resolution.

Increasing penetration remains one of the most important issues in optical coherence tomography (OCT) research, which we achieved with a parallel ultrasound beam. In addition to qualitative improvements of tissue imaging, quantitative improvements in resolution of up to 28%+/-2% was noted. At lower frequencies and energies the improvement occurred primarily by altering the detection of multiply scattered light (photon-phonon interaction), which was substantially greater in solids than in liquids (even though the liquid had the higher scattering coefficient). In conclusion, the use of an ultrasound beam with OCT appears the most effective means to date for increasing imaging penetration.