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

We present a robust and fiducial-marker-free algorithm that can identify and correct stick-slip distortion caused by nonuniform rotation (or beam scanning) in distally scanned catheters for endoscopic optical coherence tomography (OCT) images. This algorithm employs spatial frequency analysis to select and remove distortions. We demonstrate the feasibility of this algorithm on images acquired from ex vivo rat colon with a distally scanned DC motor-based endoscope. The proposed algorithm can be applied to general endoscopic OCT images for correcting nonuniform rotation distortion.

An Algorithm for Increasing Tissue Contrast in Visualization of the Structure of Complex Scattering Media by Optical Coherent Tomography

A phantom of a human blood vessel is used to study the quality of structural images in endoscopic OCT. Small-angle raster scanning, averaging and multilevel filtering are used. Compression of the structural image with raster averaging increases the contrast of the structural image by reducing the level of speckle noise. File compression is part of the imaging process and is performed for each pixel. The graphical dependence of the upper lines of the A-scans of the structural image of the blood vessel phantom wall is presented. The proposed algorithm allows obtaining high-quality structural images for gastroenterology, urology, gynecology, and in vivo cardiovascular diagnostics using conventional and endoscopic OCT; characterized by high processing speed of initial data and optimal file size; reduces the requirements for the detector bandwidth of the endoscopic OCT system. For calculations, an HP Z640 Workstation with two six-core E5-2620v3c processors and a 4GB NVIDIA Quadro K4200 video card was used.

Imaging of the human tympanic membrane by endoscopic optical coherence tomography

Endoscopic optical coherence tomography is a non-invasive and contactless imaging technique based on white light interferometry. It enables high-resolution three-dimensional imaging of scattering tissue up to a depth of about 2 mm. In addition, Doppler-OCT can detect sub-resolution movements. These features can be used to examine the tympanic membrane, the surrounding tissue and nearby areas of the tympanic cavity. For this purpose, we present an endoscopic OCT system, which provides access to the tympanic membrane. The design of the endoscope is based on a gradientindex (GRIN) lens system. This allows a broad field of view and a large working distance. An additional VIS beam path allows visual imaging and orientation inside the auditory canal. Therefore, illumination fibers are attached a round the GRIN-system. The resulting endoscope has a length of 55 mm and a diameter of 3.5 mm. By attaching an earphone and a probe microphone, the oscillation of the tympanic membrane can be measured under acoustic stimulation. With the endoscopic OCT system, we provide an examination tool for the diagnosis of a broad number of diseases like conductive hearing loss.