High-speed, ultrahigh-resolution distal scanning OCT endoscopy at 800 nm for in vivo imaging of colon tumorigenesis on murine models

Abstract

We present the first, most compact, ultrahigh-resolution, high-speed, distal scanning optical coherence tomography (OCT) endoscope operating at 800 nm. Achieving high speed imaging while maintaining an ultrahigh axial resolution is one of the most significant challenges with endoscopic OCT at 800 nm. Maintaining an ultrahigh axial resolution requires preservation of the broad spectral bandwidth of the light source throughout the OCT system. To overcome this critical limitation we implemented a distal scanning endoscope with diffractive optics to minimize loss in spectral throughput. In this paper, we employed a customized miniature 900 µm diameter DC micromotor fitted with a micro reflector to scan the imaging beam. We integrated a customized diffractive microlens into the imaging optics to reduce chromatic focal shift over the broad spectral bandwidth of the Ti:Sapphire laser of an approximately 150 nm 3dB bandwidth, affording a measured axial resolution of 2.4 µm (in air). The imaging capability of this high-speed, ultrahigh-resolution distal scanning endoscope was validated by performing 3D volumetric imaging of mouse colon in vivo at 50 frames-per-second (limited only by the A-scan rate of linear CCD array in the spectral-domain OCT system and sampling requirements). The results demonstrated that fine microstructures of colon could be clearly visualized, including the boundary between the absorptive cell layer and colonic mucosa as well the crypt patterns. Furthermore, this endoscope was employed to visualize morphological changes in an enterotoxigenic Bacteriodes fragilis (ETBF) induced colon tumor model. We present the results of our feasibility studies and suggest the potential of this system for visualizing time dependent morphological changes associated with tumorigenesis on murine models in vivo.

Stick-slip nonuniform rotation distortion correction in distal scanning optical coherence tomography catheters

“…This SD-OCT system incorporated a distal scanning endoscope. 8 The distal-end scanning endoscope employed a 1.9 mm diameter DC micromotor along with a micromirror to perform circumferential beam scanning. The micromotor was capable of rotating up to 300 rotations/second.…”

“…Distal scanning endoscopes with miniature micromotors are an alternative for performing circumferential beam scanning that can avoid the aforementioned resistance-based image distortions. [2][3][4][5][6][7][8][9] Due to size constraints, micromotors incorporated in distal scanning endoscopes often lack feedback mechanisms such as encoders, making it difficult to maintain the rotational velocity. Distal scanning catheters can also exhibit NURD due to an imbalanced load on the motor shaft, or simply due to mechanical instabilities at higher speeds.…”

Low-cost, ultracompact handheld optical coherence tomography probe for in vivo oral maxillofacial tissue imaging

“…Further, the reflection mirror can be rotated with a high-speed miniature DC motor to scan the beam in a helical fashion to form an extended FOV. 42,43 The 500-μm working distance of the current design is optimized for mucosa penetration, and the penetration depth in teeth can reach as deep as ∼2 mm. Dynamic focus tuning through a solid tunable lens [44][45][46] or shape memory alloy 47 can also be implemented in future designs to better accommodate different imaging setups.…”

Real-time colorectal cancer diagnosis using PR-OCT with deep learning

“…Clinical translation of PR-OCT requires integration of the probe into the colonoscope for "optical biopsy" in real time during endoscopic evaluation. Several studies have demonstrated the feasibility of endoscopic OCT in both rodent and human models [17][18][19]26,27], especially, cameraguided endoscopic OCT [24,25]. Current screening methods for colorectal tissue rely on histologic evaluation of biopsy specimens, which take days to receive.…”

“…In prior work, several research groups have demonstrated promising results that suggest OCT, an established high resolution imaging modality [9][10][11][12][13], may address the shortcomings of traditional camera endoscopy in the upper gastrointestinal tract [14][15][16] or large intestine [17][18][19]. OCT has been shown to accurately differentiate abnormal from normal tissue in multiple organs as an "optical biopsy" tool [20][21][22][23] in both murine and human colorectal models [24][25][26][27]. However, clinical application of the technology is complicated by the large volume of data generated and the subtle qualitative differences between normal and abnormal tissue.…”