Endoscopically guided spectral-domain OCT with double-balloon catheters.

Fourier-domain optical coherence tomography (OCT) and balloon-based catheters have furthered the potential of OCT as a real-time surveillance tool for Barrett's esophagus (BE). However, a balloon catheter, which expands the esophagus and centers the catheter, applies direct pressure on the esophagus. This may affect the tissue appearance and the ability to detect dysplasia in BE. To study this effect, we propose a double-balloon catheter to allow imaging with and without balloon-tissue contact. A system design based on a spectral-domain OCT platform is reported and validated by acquisition of high quality, volumetric images of swine esophagus in vivo.

Image analysis for classification of dysplasia in Barrett's esophagus using endoscopic optical coherence tomography.

Barrett's esophagus (BE) and associated adenocarcinoma have emerged as a major health care problem. Endoscopic optical coherence tomography is a microscopic sub-surface imaging technology that has been shown to differentiate tissue layers of the gastrointestinal wall and identify dysplasia in the mucosa, and is proposed as a surveillance tool to aid in management of BE. In this work a computer-aided diagnosis (CAD) system has been demonstrated for classification of dysplasia in Barrett's esophagus using EOCT. The system is composed of four modules: region of interest segmentation, dysplasia-related image feature extraction, feature selection, and site classification and validation. Multiple feature extraction and classification methods were evaluated and the process of developing the CAD system is described in detail. Use of multiple EOCT images to classify a single site was also investigated. A total of 96 EOCT image-biopsy pairs (63 non-dysplastic, 26 low-grade and 7 high-grade dysplastic biopsy sites) from a previously described clinical study were analyzed using the CAD system, yielding an accuracy of 84% for classification of non-dysplastic vs. dysplastic BE tissue. The results motivate continued development of CAD to potentially enable EOCT surveillance of large surface areas of Barrett's mucosa to identify dysplasia.

Extending the effective imaging range of Fourier-domain optical coherence tomography using a fiber optic switch.

The effective imaging range of Fourier-domain optical coherence tomography is limited by falloff. We present a very simple method to extend the effective imaging range with dual reference arms and a high-speed fiber optic switch. The effective imaging range was increased by 1.8 with two reference arms compared with a single reference arm. Ex vivo tissue images show significantly improved sensitivity over a large imaging range. Further extension of the imaging range is feasible with multiple reference arms. The tradeoff between image acquisition rate and imaging range is discussed.

Automated quantification of colonic crypt morphology using integrated microscopy and optical coherence tomography.

Colonic crypt morphological patterns have shown a close correlation with histopathological diagnosis. Imaging technologies such as high-magnification chromoendoscopy and endoscopic optical coherence tomography (OCT) are capable of visualizing crypt morphology in vivo. We have imaged colonic tissue in vitro to simulate high-magnification chromoendoscopy and endoscopic OCT and demonstrate quantification of morphological features of colonic crypts using automated image analysis. 2-D microscopic images with methylene blue staining and correlated 3-D OCT volumes were segmented using marker-based watershed segmentation. 2-D and 3-D crypt morphological features were quantified. The accuracy of segmentation was validated, and measured features are in agreement with known crypt morphology. This work can enable studies to determine the clinical utility of high-magnification chromoendoscopy and endoscopic OCT, as well as studies to evaluate crypt morphology as a biomarker for colonic disease progression.

Analytical model of spectrometer-based two-beam spectral interferometry.

We report an analytical model of signal formation in spectrometer-based two-beam spectral interferometry. Considering the pixel size, the optical resolution and the spectral resolution of the spectrometer, and dispersion, the model represents the signal recorded by a spectrometer based on a diffraction grating and linear detector array. The model is general, but degenerates to more familiar forms with simplifying assumptions. The model is validated by comparison with experimental measurements, where it is shown that the model can accurately predict both signal fall-off and axial resolution for Fourier-domain optical coherence tomography imaging. The model may be useful for determining design specifications and expected performance parameters for spectrometers for spectral interferometry.