Hand-held arthroscopic optical coherence tomography for in vivo high-resolution imaging of articular cartilage.
We describe a novel hand-held polarization optical coherence tomographic (OCT) probe that can be inserted into mammalian joints to permit real-time cross-sectional imaging of articular cartilage. The transverse and axial resolutions of the arthroscopic OCT device are roughly 17 and 10 microm, respectively. Two-dimensional cross-sectional images of cartilage tissue with 500 x 1000 pixels covering an area 6 mm in length and 2.8 mm in depth can be acquired at nearly five frames/s and with over 100 dB of dynamic range. Design of an OCT as a hand-held device capable of providing such an optical biopsy of articular cartilage allows eventual in vivo detection of microstructural changes in articular cartilage that are not apparent using conventional arthroscopic cameras. The OCT probe can be easily incorporated in a conventional arthroscope for cartilage site guidance. The optical arrangement in the OCT scope minimizes specular back-reflection of the probe end face and absorption of body fluid in the path and ensures in-focus OCT imaging when it is in contact with the cartilage specimen to be examined. Successful application of in vivo arthroscopy to porcine articular cartilage demonstrates sufficient resolution and practicality for use in human joints.