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.
Highlights
Optical imaging catheter devices have had a longstanding clinical impact in the endoscopic imaging of luminal organs such as the gastrointestinal (GI) tract, with optical coherence tomography (OCT) [1,2,3] and confocal microscopy [4,5]
Proximal scan actuation was known to result in nonuniform rotational distortion (NURD) and longitudinal distortion [8,9,10]
Studies proposed the use of a micromotor to perform rotary scanning at the distal end [11,12], which was recently revisited by multiple groups [13,14,15,16,17]. These studies still relied on a proximal motorized actuation for the slow pullback scan, and the micromotor still exhibited NURD [18]. 2D scanning with purely distal mechanisms has been largely limited to forward viewing probes, using microelectromechanical systems (MEMS) [19] or piezoelectric actuators [20,21,22,23]
Summary
Optical imaging catheter devices have had a longstanding clinical impact in the endoscopic imaging of luminal organs such as the gastrointestinal (GI) tract, with optical coherence tomography (OCT) [1,2,3] and confocal microscopy [4,5]. Side-viewing optical probes, such as for three-dimensional (3D) OCT imaging, were traditionally scanned with rotary and pullback mechanisms at the proximal end [6,7]. Studies proposed the use of a micromotor to perform rotary scanning at the distal end [11,12], which was recently revisited by multiple groups [13,14,15,16,17]. These studies still relied on a proximal motorized actuation for the slow pullback scan, and the micromotor still exhibited NURD [18]. Forward viewing piezoelectric probes for OCT and other scanning microscopies have been typically limited to small fields [25] of
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