A diagram of the SMC-OCT system is shown in Fig. 1. The optical paths of each modality are separated proximally, but combined distally in the sample arm. The fluorescence-based SMC proximal subsystem contains the excitation light source, optics for coupling this excitation light into the fiber bundle, filtering out the emission light, and imaging onto a charge coupled device (CCD) camera. Dichroic and emission filters are optimized to the emission peak of the methylene blue contrast agent and the use of a 638-nm laser diode source (Fibertec II, Blue Sky Research, Milpitas, CA).14 The laser source was coupled into the system via a single-mode fiber with a numerical aperture (NA) of 0.11. Light exiting this laser source fiber was collected with an 25-mm focal length lens, reflected off of a long-wave pass (LWP) filter centered at (HQ655LP, Chroma Technology Corp., Bellows Falls, VT), and focused at the entrance pupil of a , 0.40 NA microscope objective (PLN 20X, Olympus America, Center Valley, PA). This arrangement allowed for Kohler illumination of a coherent imaging fiber bundle (IGN-, Sumitomo Electric USA, Torrance, CA), which relayed light to the distal endoscopic optics (discussed below). Laser power on the sample was 8 mW. Emission light collected by the distal optics was relayed back to the proximal optics via the same fiber bundle. The proximal face of the fiber was imaged onto the CCD camera (PIXIS 1024, Princeton Instruments, Trenton, NJ). The emission light transmits through the dichroic filter, and excitation light is further suppressed by a long pass emission filter (ZQ633RDC, Chroma Technology Corp., Bellows Falls, VT) placed directly in front of the CCD. SMC images were acquired with integration times between , with a readout time of 250 ms.