Novel focused OCT-LIF endoscope

Colon phantoms with cancer lesions for endoscopic characterization with optical coherence tomography

Optical coherence tomography (OCT) is a growing imaging technique for real-time early diagnosis of digestive system diseases. As with other well-established medical imaging modalities, OCT requires validated imaging performance and standardized test methods for performance assessment. A major limitation in the development and testing of new imaging technologies is the lack of models for simultaneous clinical procedure emulation and characterization of healthy and diseased tissues. Currently, the former can be tested in large animal models and the latter can be tested in small animal disease models or excised human biopsy samples. In this study, a 23 cm by 23 cm optical phantom was developed to mimic the thickness and near-infrared optical properties of each anatomical layer of a human colon, as well as the surface topography of colorectal polyps and visual appearance compatible with white light endoscopy.

Gabor domain optical coherence microscopy combined with laser scanning confocal fluorescence microscopy

We report on the development of fluorescence Gabor domain optical coherence microscopy (Fluo GD-OCM), a combination of GD-OCM with laser scanning confocal fluorescence microscopy (LSCFM) for synchronous micro-structural and fluorescence imaging. The dynamic focusing capability of GD-OCM provided the adaptive illumination environment for both modalities without any mechanical movement. Using Fluo GD-OCM, we imaged ex vivo DsRed-expressing cells in the brain of a transgenic mouse, as well as Cy3-labeled ganglion cells and Cy3-labeled astrocytes from a mouse retina. The self-registration of images taken by the two different imaging modalities showed the potential for a correlative study of subjects and double identification of the target.

In vivo endoscopic Doppler optical coherence tomography imaging of the colon

BACKGROUND AND OBJECTIVE

Colorectal cancer (CRC) remains the second deadliest cancer in the United States. Several screening methods exist; however, detection of small polyps remains a challenge. Optical coherence tomography (OCT) has been demonstrated to be capable of detecting lesions as small as 1 mm in the mouse colon, but detection is based on measuring a doubling of the mucosa thickness. The colon microvasculature may be an attractive biomarker of early tumor development because tumor vessels are characterized by irregular structure and dysfunction. Our goal was to develop an endoscopic method of detecting and segmenting colon vessels using Doppler OCT to enable future studies for improving early detection and development of novel chemopreventive agents.

METHOD

We conducted in vivo colon imaging in an azoxymethane (AOM)-treated mouse model of colorectal cancer using a miniature endoscope and a swept-source OCT system at 1,040 nm with a 16 kHz sweep rate. We applied the Kasai autocorrelation algorithm to laterally oversampled OCT B-scans to resolve vascular flow in the mucosa and submucosa. Vessels were segmented by applying a series of image processing steps: (i) intensity thresholding; (ii) two-dimensional matched filtering; and (iii) histogram segmentation.

RESULTS

We observed differences in the vessels sizes and spatial distribution in a mature adenoma compared to surrounding undiseased tissue and compared the results with histology. We also imaged flow in four young mice (two AOM-treated and two control) showing no significant differences, which is expected so early after carcinogen exposure. We also present flow images of adenoma in a living mouse and a euthanized mouse to demonstrate that no flow is detected after euthanasia.

CONCLUSION

We present, to the best of our knowledge, the first Doppler OCT images of in vivo mouse colon collected with a fiber-based endoscope. We also describe a fast and robust image processing method for segmenting vessels in the colon. These results suggest that Doppler OCT is a promising imaging modality for vascular imaging in the colon that requires no exogenous contrast agents. Lasers Surg. Med. 49:249-257, 2017. © 2016 Wiley Periodicals, Inc.

A high-efficiency fiber-based imaging system for co-registered autofluorescence and optical coherence tomography

We present a power-efficient fiber-based imaging system capable of co-registered autofluorescence imaging and optical coherence tomography (AF/OCT). The system employs a custom fiber optic rotary joint (FORJ) with an embedded dichroic mirror to efficiently combine the OCT and AF pathways. This three-port wavelength multiplexing FORJ setup has a throughput of more than 83% for collected AF emission, significantly more efficient compared to previously reported fiber-based methods. A custom 900 µm diameter catheter ‒ consisting of a rotating lens assembly, double-clad fiber (DCF), and torque cable in a stationary plastic tube ‒ was fabricated to allow AF/OCT imaging of small airways in vivo. We demonstrate the performance of this system ex vivo in resected porcine airway specimens and in vivo in human on fingers, in the oral cavity, and in peripheral airways.

Coregistered autofluorescence-optical coherence tomography imaging of human lung sections

Autofluorescence (AF) imaging can provide valuable information about the structural and metabolic state of tissue that can be useful for elucidating physiological and pathological processes. Optical coherence tomography (OCT) provides high resolution detailed information about tissue morphology. We present coregistered AF-OCT imaging of human lung sections. Adjacent hematoxylin and eosin stained histological sections are used to identify tissue structures observed in the OCT images. Segmentation of these structures in the OCT images allowed determination of relative AF intensities of human lung components. Since the AF imaging was performed on tissue sections perpendicular to the airway axis, the results show the AF signal originating from the airway wall components free from the effects of scattering and absorption by overlying layers as is the case during endoscopic imaging. Cartilage and dense connective tissue (DCT) are found to be the dominant fluorescing components with the average cartilage AF intensity about four times greater than that of DCT. The epithelium, lamina propria, and loose connective tissue near basement membrane generate an order of magnitude smaller AF signal than the cartilage fluorescence.