Fig. 3.

Schematic for OCT-NIRS catheter. Inside the catheter, a single-mode fiber (SMF) delivered and collected OCT light to/from tissue and a multi-mode fiber (MMF) collected NIRS light. The two fibers were combined into a double-clad fiber (DCF) using a commercial power combiner such that the OCT light transceived through the core of the SMF and DCF, while NIRS light coupled to the cladding of the DCF. At the distal end (insets), the SM and MM fibers were terminated by two angle-cleaved ball lenses for efficient delivery/collection of OCT and NIRS light to/from tissue. In order to spin the catheter for cross-sectional dual-modality imaging, all optical fibers, optical power combiner, and distal optics were housed in a 2.4-Fr driveshaft and stainless steel tubing.