Dual-modality needle probe for combined fluorescence imaging and three-dimensional optical coherence tomography.

To the best of our knowledge, we present the first needle probe for combined optical coherence tomography (OCT), and fluorescence imaging. The probe uses double-clad fiber (DCF) that guides the OCT signal and fluorescence excitation light in the core and collects and guides the returning fluorescence in the large-diameter multimode inner cladding. It is interfaced to a 1310 nm swept-source OCT system that has been modified to enable simultaneous 488 nm fluorescence excitation and >500 nm emission detection by using a DCF coupler to extract the returning fluorescence signal in the inner cladding with high efficiency. We present imaging results from an excised sheep lung with fluorescein solution infused through the vasculature. We were able to identify alveoli, bronchioles, and blood vessels. The results demonstrate that the combined OCT plus fluorescence needle images provide improved tissue differentiation over OCT alone.