A 50.4 kHz swept source laser (SSOCT-1310, Axsun Technologies Inc., Billerica, Massachusetts) with a polarized output power of 20 mW centered at wavelength and a bandwidth of (full width half maximum) was coupled 90% sample/10% reference into a single-mode Mach–Zehnder OCT interferometer. The sample arm was connected using a fiber-optic rotary joint (MJP-SAPB, Princetel Inc., Pennington, New Jersey) to a 0.9 mm diameter, rotationally driven, side-looking fiber optic probe (C7 Dragonfly Imaging Catheter, St. Jude Medical Inc., St. Paul, Minnesota). Light exits the probe at approximately 64 deg relative to the tip of the fiber optic probe (i.e., slightly forward looking). For in vivo lung imaging, the open-ended probe was inserted into a closed-ended 1.5 mm diameter sheath to prevent direct probe-patient contact and was guided to the imaging location using a bronchoscope. The probe was driven using a custom built motor capable of rotational speeds up to 100 Hz and pullbacks up to 50 mm in length. In this study, the probe was spun at speeds of 6.25 Hz (8064 A-lines/frame) and 12.5 Hz (4032 A-lines/frame). The interference signal was detected using a pair of 75 MHz balanced detectors (PDB420C, Thorlabs-Inc., Newton, New Jersey) using a polarization diversity detection scheme. A high speed digitizer (ATS9350, Alazar Technologies Inc., Pointe-Claire, Quebec) in “k-clock” acquisition mode collected the data. The data was processed to provide live-streaming 2-D structural OCT and CDOCT imaging using custom written data acquisition software. This study was approved by the Research Ethics Board of the University of British Columbia and the British Columbia Cancer Agency. All subjects gave written, informed consent.