Abstract
Motion of the sample arm fiber in optical coherence tomography (OCT) systems can dynamically alter the polarization state of light incident on tissue during imaging, with consequences for both conventional and polarization-sensitive (PS-)OCT. Endoscopic OCT is particularly susceptible to polarization-related effects, since in most cases, the transverse scanning mechanism involves motion of the sample arm optical fiber to create an image. We investigated the effects of a scanning sample arm fiber on the polarization state of light in an OCT system, and demonstrate that by referencing the state backscattered from within a sample to the measured state at the surface, changes in polarization state due to sample fiber motion can be isolated. The technique is demonstrated by high-speed PS-OCT imaging at 1 frame per second, with both linear and rotary scanning fiber-optic probes. Measurements were made on a calibrated wave plate, and endoscopic PS-OCT images of ex-vivo human tissues are also presented, allowing comparison with features in histologic sections.
Highlights
Fiber-optic probes compatible with medical endoscopes and catheters have enabled optical coherence tomography (OCT) imaging of previously inaccessible regions within the human body [1,2]
Fiber-based PS-OCT systems have typically been used in the laboratory with a stationary sample arm and transverse scanning at the distal end, or in the clinic with only minimal fiber motion during acquisition of each A-line [27,28,29]
Using an average surface state reduces the error in determining the initial Stokes vector, with a corresponding improvement in determination of sample retardation and optic axis orientation. This averaging method is valid when the incident state is not changing, which is a reasonable assumption for most reported fiber-based PS-OCT systems
Summary
Fiber-optic probes compatible with medical endoscopes and catheters have enabled optical coherence tomography (OCT) imaging of previously inaccessible regions within the human body [1,2]. These fibers and optics are incorporated within and affixed to a wound cable, capable of transducing proximal motion from outside the body to distal motion at the catheter or endoscope tip. Proximal linear or circumferential scanning of the wound cable and associated optics produces a similar motion of the focused beam at the sample, thereby enabling formation of the OCT image [3,4,5,6,7]. In larger-lumen channels such as the gastrointestinal tract, circumferential scanning may result in distant surfaces appearing out of focus due to the limited depth of focus of the probe For such situations, linear scanning devices were developed [5], producing OCT images in the familiar transverse geometry. While a few investigators have developed probes that incorporate miniature scanning mechanisms at the distal tip [8,9,10], transduction of proximal motion to the distal optics by means of a wound cable remains the most convenient method for transverse scanning in endoscopic and catheter-based OCT, especially when the probe diameter is constrained
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
