Cycloid scanning for wide field optical coherence tomography endomicroscopy and angiography in vivo

Abstract

Devices that perform wide field-of-view (FOV) precision optical scanning are important for endoscopic assessment and diagnosis of luminal organ disease such as in gastroenterology. Optical scanning for in vivo endoscopic imaging has traditionally relied on one or more proximal mechanical actuators, limiting scan accuracy and imaging speed. There is a need for rapid and precise two-dimensional (2D) microscanning technologies to enable the translation of benchtop scanning microscopies to in vivo endoscopic imaging. We demonstrate a new cycloid scanner in a tethered capsule for ultrahigh speed, side-viewing optical coherence tomography (OCT) endomicroscopy in vivo. The cycloid capsule incorporates two scanners: a piezoelectrically actuated resonant fiber scanner to perform a precision, small FOV, fast scan and a micromotor scanner to perform a wide FOV, slow scan. Together these scanners distally scan the beam circumferentially in a 2D cycloid pattern, generating an unwrapped 1 mm × 38 mm strip FOV. Sequential strip volumes can be acquired with proximal pullback to image centimeter-long regions. Using ultrahigh speed 1.3 μm wavelength swept-source OCT at a 1.17 MHz axial scan rate, we imaged the human rectum at 3 volumes/s. Each OCT strip volume had 166 × 2322 axial scans with 8.5 μm axial and 30 μm transverse resolution. We further demonstrate OCT angiography at 0.5 volumes/s, producing volumetric images of vasculature. In addition to OCT applications, cycloid scanning promises to enable precision 2D optical scanning for other imaging modalities, including fluorescence confocal and nonlinear microscopy.

Single capillary oximetry and tissue ultrastructural sensing by dual-band dual-scan inverse spectroscopic optical coherence tomography

“…In the brain D2-ISOCT may allow researchers to probe the functional vascular changes that occur during organ development or disease progression 33 , 34 . In the clinic, integrating D2-ISOCT into endoscope measurements might further enrich the contrast for OCT endoscopic imaging 35 – 38 . For example, in the colon, it has been shown that the D2-ISOCT metrics D and the vessel organization can be used in evaluating colorectal cancer risk 39 , 40 .…”

Application of OCT in the Gastrointestinal Tract

“…However, small diameter probes sacrifice FOV for transverse resolution, which is a potential drawback of en face capsule technology [124]. In 2017, a study involving Harvard Medical School and MIT demonstrated a cycloid scanner with a tethered capsule for ultrahigh speed side-viewing OCT in vivo and also produced volumetric images of vasculature [132].…”

Depth-multiplexed optical coherence tomography dual-beam manually-actuated distortion-corrected imaging (DMDI) with a micromotor catheter

“…Numerous fiber optic two-dimensional scanning catheters have been developed for endoscopic optical imaging [1,2]. Side-looking rotary-pullback catheters using proximal or distal rotary motors are ideal for examining luminal organs and several research groups have demonstrated exquisite imaging in fields such as cardiology [3,4], gastroenterology [5][6][7], and respirology [8,9]. However, rotary-pullback catheters require that there is no relative motion between the subject and catheter sheath to provide high-fidelity imaging, a constraint that may be difficult to achieve in clinical settings.…”