The purpose of this study was to develop a dynamic tunable focal distance graded-refractive-index lens rod-based high-speed 3-D swept-source (SS) optical coherence tomography (OCT) endoscopic system and demonstrate real-time in vivo, high-resolution (10-µm) imaging of pleural-based malignancies in an animal model. The GRIN lens-based 3-D SS OCT system, which images at 39 fps with 512 A-lines per frame, was able to capture images of and detect abnormalities during thoracoscopy in the thoracic cavity, including the pleura, chest wall, pericardium, and the lungs. The abnormalities were confirmed by histological evaluation and compared to OCT findings. The dynamic tunable focal distance range and rapid speed of the probe and SS prototype OCT system enabled this first-reported application of in vivo 3-D thoracoscopic imaging of pleural-based malignancies. The imaging probe of the system was found to be easily adaptable to various sites within the thoracic cavity and can be readily adapted to other sites, including rigid airway endoscopic examinations.
A multiphoton endoscopy system has been developed using a two-axis microelectromechanical systems (MEMS) mirror and double-cladding photonic crystal fiber (DCPCF). The MEMS mirror has a 2-mm-diam, 20-deg optical scanning angle, and 1.26-kHz and 780-Hz resonance frequencies on the x and y axes. The maximum number of resolvable focal spots of the MEMS scanner is 720×720 on the x and y axes, which indicates that the MEMS scanner can potentially support high-resolution multiphoton imaging. The DCPCF is compared with standard single-mode fiber and hollow-core photonic bandgap fiber on the basis of dispersion, attenuation, and coupling efficiency properties. The DCPCF has high collection efficiency, and its dispersion can be compensated by grating pairs. Three configurations of probe design are investigated, and their imaging quality and field of view are compared. A two-lens configuration with a collimation and a focusing lens provides the optimum imaging performance and packaging flexibility. The endoscope is applied to image fluorescent microspheres and bovine knee joint cartilage.
We present a kind of rotational two photon mciroendoscopy for 1μm fiber
femtosecond laser. The fiber laser provide ultrashort femto-second pulses with center
wavelength at 1.034μm and repetition rate of 50MH. The rotational probe is based on
double cladding photonic crystal fiber (CD PCF) fiber, Grin lens, microprism and
rotational MEMS motor. The MEMS motor has diameter of 2.2mm and can provide
360 degree full view rotation. We experimentally show that the DC PCF fiber works
for 1μm fiber laser two photon system. Second harmonic generation (SHG) singnal
line profile of rat tail tendon and fish scale was taken with the endoscopy system.
KEYWORDS: Optical coherence tomography, GRIN lenses, In vivo imaging, Endoscopy, 3D image processing, Signal to noise ratio, Mirrors, Tissues, Lung, 3D image reconstruction
In this manuscript, we report a fast speed swept source endoscopic OCT system utilizing a 4.5mm
diameter rigid GRIN lens rod probe. The rigid probe has a tunable working distance with tuning
range 0~7mm. The system could take front scanning images with speed of 40frames per second
(512 A line per frame). The probe can work in contact and non contact mode. Fast speed contact
and non-contact imaging was demonstrated.
To understand the influence of topographical variations in collagen fibril orientation of articular cartilage on optical phase images of polarization-sensitive optical coherence tomography (PS-OCT), we use polarized light microscopy (PLM) to quantify the orientation and phase retardation of the collagen architecture in cartilage at the same locations imaged by PS-OCT. The PS-OCT experiments demonstrate that articular cartilage has normal variations in polarization sensitivity at different locations over an intact bovine tibial plateau. Articular cartilage is not polarization sensitive along the vertical axis on the medial edge and central areas of the joint surface, but becomes polarization sensitive on the lateral edge of the tibia. This difference in optical phase retardation, as demonstrated by PS-OCT, is verified by PLM to be caused by differences in collagen fibril orientation at different locations of the tibial plateau. This study demonstrates that normal topographical variations in the collagen architecture of articular cartilage within a joint have a profound influence on the optical phase retardation detected by PS-OCT imaging, and therefore must be understood and mapped for specific joints before PS-OCT imaging can be used for the evaluation of the health status of individual joint surfaces.
In this paper, a GRIN lens rod based dynamic focusing spectral domain optical coherence tomography (OCT) system with 2D scanners is presented and is used to investigate a fresh bovine joint in vitro by 3D OCT with lateral and axial resolutions of 10 μm at the speed of 8 frames/s. The experimental results demonstrate the 3D image can more efficiency and accurate to evaluate articular cartilage joint disease. It shows great potential for use in extremely compact OCT endoscopes to combine with arthroscope to image articular cartilage in vivo for diagnosis of early DJDs and simultaneously perform both 3D imaging and surface imaging in the same channel.
The practical limitation of in vivo multiphoton excitation microscopy (MPM) is the lack of a compact and flexible probe.
Most MPM depends on the bench-top microscope, which prohibits expansion of in vivo application. In this study, we
introduced a miniaturized MPM probe using a microelectromechanical system (MEMS) scanning mirror and a doubleclad
photonic crystal fiber (DCPCF). Benefits from both a MEMS mirror and a DCPCF overcome current obstacles for
probe development, such as size reduction, rapid scanning, efficient delivery of short pulses, and high collection rate of
fluorescent signals. In this study, the completed probe was 1 cm in outer diameter and 14 cm in length. The probe was
then integrated to the MPM system and used to image fluorescent beads, paper and biological specimens.
In this study, PS-OCT is used to image fresh bovine joints to investigate the orientation of collagen fibrils in relation to
optical phase retardation to better understand the distribution of normal matrix orientation and articular cartilage
birefringence in different regions of a whole joint. Understanding and mapping variations in matrix organization and
orientation within the normal joint is an important issue in potential applications of PS-OCT for evaluation and diagnosis
of degenerative joint disease (DJD). The experimental results demonstrate that articular cartilage is not polarization
sensitive on the edge of the medial, but polarization sensitive on the lateral edge of the tibial plateau. The collagen
orientation on the edge of the joint is different from the central areas of the joint. Normal articular cartilage demonstrates
regional polarization sensitivity within joints that is important to understand in order to accurately assess cartilage health
by PS-OCT.
The directional polarization sensitivity of articular cartilage and meniscus is investigated by use of polarization-sensitive optical coherence tomography (PS-OCT) by varying the angle of incident illumination. Experimental results show that when the incident light is perpendicular to the tissue surface, normal articular cartilage demonstrates little polarization sensitivity, while meniscus demonstrates strong polarization sensitivity. Differences in optical phase retardation produced by articular cartilage and meniscus are observed when the incident angle of the scanning light beam is adjusted between 0 and 90 deg relative to the tissue surface. Directional polarization sensitivity of articular cartilage and meniscus as obtained by PS-OCT imaging using variations in the angle of incident illumination can be used to assess the orientation and organization of the collagen matrix of these tissues. The polarization sensitivity as evidenced by the Stokes vector and optical phase retardation images can be explained by the orientation of the angle of illumination relative to the unique structural organization of the collagen fibrils and fibers of articular cartilage and meniscus.
In this paper, the polarization sensitivity of articular cartilage was investigated by using polarization sensitivity optical coherence tomography (PS-OCT) obtained by varying the angel of incident illumination. Experimental results show that when the incident light is perpendicular to the tissue surface, normal articular cartilage demonstrates little polarization sensitivity. Significant variations in birefringence of articular cartilage observed when the angle of incident light was adjusted between 0° and 90° relative to the tissue surface. Directional polarization sensitivity of articular cartilage as obtained by PS-OCT imaging using variations in the angle of incident illumination can be used to access the orientation and organization of the collagen matrix of these tissues. The polarization sensitivity and the birefringence images obtained can be explained by the angle of illumination relative to the unique microstructure and orientation of the collagen fibrils and fibers of articular cartilage.
Menisci are frequently injured. A small meniscus tear may progress to a deeper tear if not treated. We will present the capability of diagnosis of meniscus injuries with OCT and PSOCT and the performance improvement of OCT that benefits from both local birefringence imaging and 3-dimensional reconstructions.
In this paper, the conventional and polarization sensitive optical coherence tomography (PS-OCT) were used to image bovine articular cartilage and diagnose degenerative joint disease. The results showed that these 2D cross-sectional OCT images that can cover an area of 6×2.8mm2 (limited by scope size) with a traverse resolution of 12 μm and an axial resolution of 10 μm could assess the microstructure of articular cartilage and differentiate the abnormalities in structure. The results were confirmed by their histology. Compared to conventional OCT, PS-OCT could provide depth-resolved strokes parameter images, which reflect tissue birefringence. Both conventional and PS-OCT have high efficiency and sensitivity of osteoarthritis and cartilage injury and disease diagnosis.
This paper summarizes the engineering development of our lab for endoscopic optical coherence tomography toward the ultimate goal to image bladder micro architecture and to diagnose bladder cancers. To test the utility and potential limitations of OCT setups for bladder tumor diagnosis, we used a rat bladder cancer model to track the morphological changes following tumor growth. Image results are presented, suggesting that OCT is able to differentiate cancerous lesions from inflammatory lesions based on OCT characterizations of epithelial thickness and backscattering changes of bladder tissue.
In this paper, a fiber OCT system illumined by a superluminescent diode in the 940 nm wavelength region is reported. To test the 940nm OCT system, ex-vivo rabbit bladder, porcine bladder and rat bladder with tumor were imaged and compared with 1320nm OCT. The results demonstrate that the 940nm OCT system provides higher axial resolution up to 5 μm and less speckle noise, but the experimental results showed that the image depth for bladder samples in the 940 nm OCT system is slightly lower than the 1300nm OCT due to water absorption. During experiments, it was found that the fiber caused more dispersion at the wavelength of 940 nm than 1320 nm.
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