A side-viewing, 2.3-mm diameter oblique incidence reflectometry endoscope has been designed to obtain optical property measurements of turbid samples. Light from a single-mode fiber is relayed obliquely onto the tissue with a gradient index lens-based distal optics assembly and the resulting diffuse reflectance profile is imaged and collected with a 30,000 element, 0.72 mm clear aperture fiber bundle. Sampling the diffuse reflectance in two-dimensions allows for fitting of the reflected intensity profile to a well-known theoretical model, permitting the extraction of both absorption and reduced scattering coefficients of the tissue sample. Models and measurements of the endoscopic imaging system are presented in tissue phantoms and in vivo mouse colon, verifying the endoscope’s capabilities to accurately measure effective attenuation coefficient and differentiate diseased from normal colon.
The accepted model of colorectal cancer assumes the paradigm that aberrant crypt foci (ACF) are the earliest events in tumorigenesis and develop into adenoma, which further develop into adenocarcinoma. Under this assumption, basic research and drug studies have been performed using ACF as substitute markers for fully developed carcinoma. While studies have shown a correlation between the number of ACF present and the presence of adenoma/adenocarcinoma, a causal relationship has yet to be determined. The mouse has shown to be an excellent model for colorectal cancer; however, the outcomes of such experiments require sacrifice and histologic examination of ex vivo tissue. To better utilize the mouse model to study ACF and adenoma development, an endoscope was constructed for non-destructive in vivo surface visualization, molecular imaging and cross-sectional imaging of the colon. Our system combines surface magnifying chromoendoscopy (SMC) and optical coherence tomography (OCT) to image colon microstructure. Sixteen mice, treated with the carcinogen azoxymethane, were imaged at 2 week intervals, to visualize carcinogenesis events. With this dual-modality system we are able to visualize crypt structure alteration over time as well as adenoma development over time.
A side-viewing, 2.3-mm diameter, surface magnifying chromoendoscopy-optical coherence tomography (SMC-OCT) endoscope has been designed for simultaneous, nondestructive surface fluorescence visualization and cross-sectional imaging. We apply this endoscope to in vivo examination of the mouse colon. A 30,000 element fiber bundle is combined with single mode fibers, for SMC and OCT imaging, respectively. The distal optics consist of a gradient-index lens and spacer to provide a 1× magnification at a working distance of 1.58 mm in air, necessary to image the sample through a 0.23-mm thick outer glass envelope, and an aluminized right-angle prism fixed to the distal end of the gradient-index lens assembly. The resulting 1∶1 imaging system is capable of 3.9-µm lateral and 2.3-µm axial resolution in the OCT channel, and 125-lp/mm resolution across a 0.70-mm field of view in the SMC channel. The endoscope can perform high contrast crypt visualization, molecular imaging, and cross-sectional imaging of colon microstructure.
A side-viewing, 2 mm diameter, surface magnifying chromoendoscopy (SMC)-optical coherence tomography (OCT)
endoscope has been designed for simultaneous, non-destructive surface fluorescence visualization and cross-sectional
imaging. We apply this endoscope to in vivo examination of mouse colon. A 30,000 element fiber bundle is combined
with single mode fibers. The distal optics consist of a gradient-index lens and spacer to provide a magnification of 1 at a
working distance of 1.58 mm in air, necessary to image the sample through a 0.23 mm thick outer glass envelope, and an
aluminized right-angle prism fixed to the distal end of the GRIN lens assembly. The resulting 1:1 imaging system is
capable of 3.9 μm lateral and 2.3 μm axial resolution in the OCT channel, and 125 lp/mm resolution across a 0.70 mm
field of view in the SMC channel. The endoscope can perform high contrast crypt visualization, molecular imaging, and
cross-sectional imaging of colon microstructure.
Optical coherence tomography (OCT) is a minimally-invasive imaging modality capable of tracking the development of
individual colonic adenomas. As such, OCT can be used to evaluate the mechanisms and effectiveness of
chemopreventive and chemotherapeutic agents in colorectal cancer models. The data presented here represent part of a
larger study evaluating α-difluoromethylornithine (DFMO) and Sulindac as chemopreventive and chemotherapeutic
agents using mice treated with the carcinogen azoxymethane (AOM). 27 A/J mice were included in the chemoprevention
study, subdivided into four treatment groups (No Drug, DFMO, Sulindac, DFMO/Sulindac). 30 mm lateral images of
each colon at eight different rotations were obtained at five different time points using a 2 mm diameter spectral domain
OCT endoscopy system centered at 890 nm with 3.5 μm axial resolution in air and 5 μm lateral resolution. Images were
visually analyzed to determine number and size of adenomas. Gross photos of the excised colons and histology provided
gold standard confirmation of the final imaging time point. Preliminary results show that 100% of mice in the No Drug
group developed adenomas over the course of the chemoprevention study. Incidence was reduced to 71.43% in mice
given DFMO, 85.71% for Sulindac and 0% for DFMO/Sulindac. Discrete adenoma size did not vary significantly
between experimental groups. Additional experiments are currently under way to verify these results and evaluate
DFMO and Sulindac for chemotherapeutic applications.
A new focused OCT-LIF endoscope has been constructed for high resolution imaging between 325 nm and 1300 nm.
This endoscope is 2 mm in diameter for non-destructive imaging in vivo. A reflective design ball lens is employed that
eliminates the difficulty of operating achromatically over a large range, while taking advantage of TIR at two faces and
coating a third mirror face internally to focus the beams downwards. It is a 1:1 imaging system that obtains a theoretical
diffraction-limited resolution for both the OCT (800-1300 nm) and LIF (greater than 325 nm) channels.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.