The ability of optical coherence tomography (OCT) to rapidly image millimeters of tissue with micron resolution has proven incredibly useful in ophthalmology, where it can provide non-destructive in-vivo 3D visualization of various retinal layers. A growing number of studies using side and circumferential viewing endoscopes have demonstrated utility in cardiology and gastroenterology. However, a forward viewing geometry would be most easily adapted as a general surgical OCT endoscope, but such systems have been generally far fewer in number.
In this paper, the authors present a fully packaged MEMS endoscopic catheter for forward imaging optical coherence tomography (OCT). Their current imaging catheter has external dimensions of 7 x 7 x 28 mm, with much of the diameter required only to house a 5 mm objective lens. The actual MEMS scanners are only 2.7 mm wide, leaving room for future miniaturization of the housing, and have resonance frequencies of 236 and 293 Hz in the two lateral directions using a Lissajous pattern. The endoscope has a 15 mm working distance and a scanning range of 2 x 2 mm, with a transverse resolution of 7.7 µm.
They demonstrate the remarkable capabilities of their endoscope through spectral-domain OCT imaging of a mouse ear. A three-dimensional reconstruction of data acquired at high speeds using the endoscope demonstrates the ability to accurately reconstruct a high-quality volume through mapping of a Lissajous scanning pattern.
While individual aspects of this work are not entirely new, this paper presents a novel combination of MEMS-based resonant scanning for a forward viewing OCT endoscope that will provide new directions for guided surgical procedures.
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