We present an endomicroscopic OCT probe for in vivo examination of the mucosa in the nose based on a voice coil actuator.
The side-viewing endoscope has a tip diameter of 3 mm and a usable length of 7 cm. A graded-index (GRIN) lens optics achieve a lateral resolution of 3 µm. At an actuator frequency between 40 Hz and 100 Hz the scanning range is up to 2 mm. A supercontinuum laser based mOCT system enables an axial resolution of 1 µm at a depth range of 700 µm.
The postprocessing includes the linearization of the sinusoidal scan pattern and a registration of the time series from B-scans.
The potential of the new design was demonstrated on ex-vivo mouse trachea. Essential morphological structures such as epithelium with ciliated cells, glands, blood and lymph vessels and also mucus transport were be visualized.
Here we present a forward-looking endoscope for dynamic microscopic OCT reaching a lateral resolution of 1.3 µm and 0.8 mm field of view. Since tissue motion degrades dynamic imaging, tissue was immobilized by suction. The endoscope was placed in a 4 mm stainless-steel sheath, which was connected to a vacuum pump. In mice, the endoscope can access various inner organs using open surgery or laparoscopy. The potential of the dynamic endo-microscopic OCT was demonstrated on relevant murine tissue such as liver, spleen and kidney. Otherwise invisible cellular and subcellular structures were imaged by dynamic mOCT with high contrast.
Changes in the structure of the nasal mucosa can be a morphological biomarker and therefore helpful for diagnosis and follow-up of various pulmonary diseases such as asthma, cystic fibrosis and primary ciliary dyskinesia. In order to verify that microscopic optical coherence tomography (mOCT) is a valuable instrument for the investigation of those changes, an endoscopic OCT system with microscopic resolution (emOCT) was developed and built for clinical testing. The endoscope is based on a graded-index (GRIN) lens optic and provides a calculated lateral resolution of 0.7 μm and an axial resolution of 1.25 μm. The imaging depth was up to 500 μm in tissue; axially, a lateral range of approximate 250 μm could be covered. B-scans were acquired at 80 Hz with 512 pixels in lateral and 1024 pixels in depth-direction. The diameter of the endoscope decreases over a length of 8 cm from 8 mm at the beginning to 1.4 mm at the end and is small enough to observe the mucous membrane in the human nasal concha media and inferior down to the nasopharynx. The emOCT workstation was designed to meet German electrical, optical and biological safety standards. The applicability of the endoscope could be demonstrated in vivo. Mucus transport, glands, blood and lymphatic vessels could be visualized.
In order to fully exploit the diagnostic potential of optical coherence tomography (OCT) in contemporary restorative dentistry, an intraorally applicable OCT probe has been constructed. The probe was connected to a commercially available OCT system. The handling of the probe and the quality of the OCT images were optimized and evaluated on human extracted teeth fixed in a patient-equivalent simulation. In addition, the probe was applied intraorally to volunteers. With the intraoral OCT probe hard tooth substances, carious lesions in enamel and dentin and composite restorations could be imaged. In vivo, the probe allowed OCT imaging of all tooth surfaces except the vestibular surfaces of third molars and proximal surface areas of molars within a "blind spot" at a distance of 2.5 mm from the tooth surface. Superficial tissue structures of the marginal gingiva could also be imaged. The intraoral OCT probe is a promising tool for non-invasive imaging and monitoring of healthy and diseased hard tooth substances and tooth-colored restorations. It can be a valuable addition to established methods for caries diagnosis and restoration evaluation.
Optical coherence tomography (OCT) images scattering tissues with 5 to 15 μm resolution. This is usually not sufficient for a distinction of cellular and subcellular structures. Increasing axial and lateral resolution and compensation of artifacts caused by dispersion and aberrations is required to achieve cellular and subcellular resolution. This includes defocus which limit the usable depth of field at high lateral resolution. OCT gives access the phase of the scattered light and hence correction of dispersion and aberrations is possible by numerical algorithms. Here we present a unified dispersion/aberration correction which is based on a polynomial parameterization of the phase error and an optimization of the image quality using Shannon’s entropy. For validation, a supercontinuum light sources and a costume-made spectrometer with 400 nm bandwidth were combined with a high NA microscope objective in a setup for tissue and small animal imaging. Using this setup and computation corrections, volumetric imaging at 1.5 μm resolution is possible. Cellular and near cellular resolution is demonstrated in porcine cornea and the drosophila larva, when computational correction of dispersion and aberrations is used. Due to the excellent correction of the used microscope objective, defocus was the main contribution to the aberrations. In addition, higher aberrations caused by the sample itself were successfully corrected. Dispersion and aberrations are closely related artifacts in microscopic OCT imaging. Hence they can be corrected in the same way by optimization of the image quality. This way microscopic resolution is easily achieved in OCT imaging of static biological tissues.