Source: https://www.osapublishing.org/oe/abstract.cfm?URI=OPEX-11-15-1817
Timestamp: 2019-04-23 16:05:55+00:00

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We describe a long-range optical coherence tomography system for size and shape measurement of large hollow organs in the human body. The system employs a frequency-domain optical delay line of a configuration that enables the combination of high-speed operation with long scan range. We compare the achievable maximum delay of several delay line configurations, and identify the configurations with the greatest delay range. We demonstrate the use of one such long-range delay line in a catheter-based optical coherence tomography system and present profiles of the human upper airway and esophagus in vivo with a radial scan range of 26 millimeters. Such quantitative upper airway profiling should prove valuable in investigating the pathophysiology of airway collapse during sleep (obstructive sleep apnea).
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Fig. 1. Schematic diagrams of the off-axis and on-axis configurations of the FDODL. SMF, single-mode fiber; L1 collimating lens; L2, focusing lens; PBS, polarizing beamsplitter; QWP, quarterwave plate; GRA, grating; GAL, galvanometer mirror; M, mirror. For simplicity, dispersion of the beam by the grating is not shown.
Fig. 2. The relative coupling efficiency of the FDODL versus delay for the configurations: (o) off-axis and off-pivot, (+) on-axis and off-pivot, and (Δ) both the off-axis and on-pivot, and on-axis and on-pivot. The heavy solid line is an experimentally measured response for the on-axis, on-pivot configuration.
Fig. 3. Schematic diagram of the endoscopic long-range OCT system. BBS, broadband source; PM, phase modulator; PC, polarization controller; M, motor.
Fig. 4. Six in vivo measurements taken of the airway (and esophagus) of a human volunteer, arranged by distance into the airway: (a) nasal cavity, (b) nasopharynx, (c) velopharynx, (d) oropharynx, (e) hypopharynx, (f) esophagus. Some anatomical features are noted: nasal septum (N), middle turbinate (MT), inferior turbinate (IT), posterior nasal spine (P), base of uvula (BU), base of tongue (BT), arytenoid cartilage (AC). The two circles at the center of the images are the reflections from the inner and outer surfaces of the catheter.
Fig. 5. (a) Measured cross-section of the in vivo hypopharynx of a human volunteer. (b) CT scan of the volunteer’s airway at a location close to where the OCT scan was performed.
Fig. 6. Three video recordings of in vivo pullback measurements in various sections of the upper airway. They are: (a) velopharynx to nasopharynx (2.41 MB), (b) nasopharynx to nasal cavity (1.67 MB), (c) nasal cavity (1.75 MB).

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