KEYWORDS: Optical coherence tomography, Microelectromechanical systems, Mirrors, Actuators, Doppler tomography, In vivo imaging, 3D image processing, Endoscopy, Ear, Cancer
Most cancers occur inside human body, so endoscopic high-resolution imaging modalities are required for early cancer
detection and surgical removal. This paper reports in vivo endoscopic 3D imaging based on optical coherence
tomography (OCT). Endoscopic imaging is enabled by integrating rapid-scanning MEMS mirror into a miniature
imaging probe. The MEMS mirror has an aperture size of 1 mm by 1 mm and a chip size of 2 mm by 2 mm. The optical
scan angle exceeds ±25 V at 6 Vdc, and thus large, constant-velocity, linear scan can be realized. The outer diameter of
the probe is only 5 mm. The axial resolution is about 10 μm and the imaging speed is 2.5 frames per second. Doppler
OCT imaging has also been demonstrated.
Optical coherence tomography (OCT) is an evolving noninvasive imaging modality and has been
used to image the human larynx during surgical endoscopy. The design of a long GRIN lens based
probe capable of capturing images of the human larynx by use of swept-source OCT during a typical
office-based laryngoscopy examination is presented. In vivo OCT imaging of the human larynx is
demonstrated with 40 fame/second. Dynamic vibration of the vocal folds is recorded to provide not
only high-resolution cross-sectional tissue structures but also vibration parameters, such as the
vibration frequency and magnitude of the vocal cord, which provide important information for
clinical diagnosis and treatment, as well as in fundamental research of the voice. Office-based OCT
is a promising imaging modality to study the larynx.
Meniscal tear is one of the most common knee injuries leading to pain and discomfort. Partial and total meniscectomies
have been widely used to treat the avascular meniscal injuries in which tears do not heal spontaneously. However, the
meniscectomies would cause an alteration of the tibiofemoral contact mechanics resulting in progressive osteoarthritis
(OA). To mitigate the progression of OA, maximal preservation of meniscal tissue is recommended. The clinical
challenge is deciding which meniscal tears are amenable to repair and which part of damaged tissues should be removed.
Current diagnosis techniques such as arthroscopy and magnetic resonance imaging can provide macrostructural
information of menisci, but the microstructural changes that occur prior to the observable meniscal tears cannot be
identified by these techniques. Serving as a nondestructive optical biopsy, optical coherence tomography (OCT), a newly
developed imaging modality, can provide high resolution, cross-sectional images of tissues and has been shown its
capabilty in arthroscopic evaulation of articular cartilage. Our research was to demonstrate the potential of using OCT
for nondestructive characterization of the histopathology of different types of meniscal tears from clinical cases in dogs,
providing a fundamental understanding of the failure mechanism of meniscal tears. First, cross-sectional images of torn
canine menisci obtained from the OCT and scanning electronic microscopy (SEM) were be compared. By studying the
organization of collegan fibrils in torn menisci from the SEM images, the feasibility of using OCT to characterize the
organization of collegan fibrils was elucidated. Moreover, the crack size of meniscal tears was quantatitively measured
from the OCT images. Changes in the crack size of the tear may be useful for understanding the failure mechanism of
meniscal tears.
Optical coherence tomography (OCT) is an evolving noninvasive imaging modality and
has been used to image the human larynx during surgical endoscopy. The design of a long GRIN
lens based probe capable of capturing images of the human larynx by use of a swept-source OCT
during a typical office-based laryngoscopy examination is presented. An optical-ballast-based 4F
optical relay system is proposed to realize variable working distance with a constant optical delay. In
vivo OCT imaging of the human larynx is demonstrated with 40 fame/second. Office-based OCT is a
promising imaging modality to study the larynx.
Optical coherence tomography (OCT) is an evolving noninvasive imaging modality that has been used to image the human larynx during surgical endoscopy. The design of a long gradient-index lens-based probe capable of capturing images of the human larynx by use of spectral domain OCT during a typical office-based laryngoscopy examination is presented. An optical-ballast-based 4f optical relay system is proposed to realize variable working distance with a constant optical delay. In-vivo OCT imaging of the human larynx is demonstrated. Office-based OCT is a promising imaging modality for early laryngeal cancer diagnosis.
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.
Smoke inhalation injury causes acute airway injury that may result in airway compromise with significant morbidity and mortality. We investigate the ability of high resolution endobronchial optical coherence tomography (OCT) to obtain real-time images for quantitatively assessing regional differences between upper tracheal versus lower tracheal and bronchial airway injury responses to smoke inhalation in vivo using a prototype spectral domain (SLD)-OCT system we constructed, and flexible fiber optic probes. 33 New Zealand White rabbits are intubated and mechanically ventilated. The treatment groups are exposed to inhaled smoke. The OCT probe is introduced through the endotracheal tube and maintained in place for 5 to 6 h. Images of airway mucosa and submucosa are obtained at baseline and at specified intervals postexposure. Starting within less than 15 min after smoke inhalation, there is significant airway thickening in the smoke-exposed animals. This is maintained over 5 h of imaging studies. The lower tracheal airway changes, correlating closely with carboxyhemoglobin levels, are much greater than upper tracheal changes. Significant differences are seen in lower trachea and bronchi after acute smoke inhalation compared to upper trachea as measured in vivo by minimally invasive OCT. OCT is capable of quantitatively detecting regional changes in airway swelling following inhalation injury.
KEYWORDS: Optical coherence tomography, Injuries, Control systems, Fiber optics, Blood, In vivo imaging, Animal model studies, Cartilage, Scanning electron microscopy, GRIN lenses
Optical coherence tomography (OCT) is a micron scale high-resolution optical technology that can provide real-time in vivo images noninvasively. The ability to detect airway mucosal and submucosal injury rapidly will be valuable for a range of pulmonary applications including assessment of acute inhalation smoke and burn injury. OCT has the potential ability to monitor the progression of airway injury changes including edema, hyperemia, and swelling, which are critical clinical components of smoke-inhalation injury. New Zealand white male rabbits exposed to cold smoke from standardized unbleached burned cotton administered during ventilation were monitored for 6 h using a 1.8-mm diameter flexible fiberoptic longitudinal probe that was inserted through the endotracheal tube. The thickness of the epithelial, mucosal, and submucosal layers of the rabbit trachea to the tracheal cartilage was measured using a prototype superluminescent diode OCT system we constructed. OCT was able to detect significant smoke-injury-induced increases in the thickness of the tracheal walls of the rabbit beginning very shortly after smoke administration. Airway wall thickness increased to an average of 120% (±33%) of baseline values by 5 h following exposure. OCT is capable of providing real-time, noninvasive images of airway injury changes following smoke exposure. These studies suggest that OCT may have the ability to provide information on potential early indicators of impending smoke-inhalation-induced airway compromise.
A preliminary study to assess noninvasive optical coherence tomography (OCT) for early detection and evaluation of chemotherapy-induced oral mucositis in five patients. In five patients receiving neoadjuvant chemotherapy for primary breast cancer, oral mucositis was assessed clinically, and imaged using noninvasive OCT. Imaging was scored using a novel imaging-based scoring system. Conventional clinical assessment using the Oral Mucositis Assessment Scale was used as the gold standard. Patients were evaluated on days 0, 2, 4, 7, and 11 after commencement of chemotherapy. OCT images were visually examined by one blinded investigator. The following events were identified using OCT: (1) change in epithelial thickness and subepithelial tissue integrity (beginning on day 2), (2) loss of surface keratinized layer continuity (beginning on day 4), (3) loss of epithelial integrity (beginning on day 4). Imaging data gave higher scores compared to clinical scores earlier in treatment, suggesting that the imaging-based diagnostic scoring was more sensitive to early mucositic change than the clinical scoring system. Once mucositis was established, imaging and clinical scores converged. Chemotherapy-induced oral changes were identified prior to their clinical manifestation using OCT, and the proposed scoring system for oral mucositis was validated for the semiquantification of mucositic change.
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.
Optical coherence tomography (OCT) is an evolving noninvasive imaging modality and has been used to image the larynx during surgical endoscopy. The design of an OCT sampling device capable of capturing images of the human larynx during a typical office based laryngoscopy examination is discussed. Both patient's and physician's movements were addressed. In vivo OCT imaging of the human larynx is demonstrated. Though the long focal length limits the lateral resolution of the image, the basement membrane can still be readily distinguished. Office-based OCT has the potential to guide surgical biopsies, direct therapy, and monitor disease. This is a promising imaging modality to study the larynx.
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.
Conventional polarization-sensitive optical coherence tomography (PS-OCT) can provide depth-resolved Stokes parameter measurements of light reflected from turbid media. A new algorithm, which takes into account changes in optical axis, is introduced to give depth-resolved birefringence and differential optical axis orientation images using fiber-based PS-OCT. Quaternion, a convenient mathematical tool, is used to represent an optical element and simplify the algorithm. Experimental results with beef tendon and rabbit tendon and muscle show that this technique has promising potential for imaging the birefringent structure of multiple-layer samples with varying optical axes.
A cladding pumped self-Q-switched Yb3+ fiber laser is described in this paper. By exploiting fiber nonlinearity -- stimulated Brillouin scattering (SBS) in the fiber laser cavity, we demonstrated a series of stable pulses with the full width at half maximum (FWHM) about 2 ns and repetition frequency about 29.4 MHz.
In this paper, a self-Q-switched Er-doped fiber (EDF) laser is reported, which employs stimulated Brillouin scattering (SBS) in single-mode (SM) fiber as a passively Q-switched mechanism. The stable nanosecond magnitude optical pulses were obtained. Pulses with peak power 800 mW, pulse width 2.2 ns and repetition rate about 64.5 MHz could be achieved, when the pumped power was 88.0 mW. A few factors that affect the pulse characters are studied.
In this paper some results of a narrow-band tunable external- cavity semiconductor laser with the Littman set-up are reported. The laser system consists of a commercial semiconductor laser at wavelength of 803 nm, a blazed grating, and an external mirror. The output power 17.9 mW and sideband suppression ratio over 20 dB were obtained. The laser is tuned conveniently in a range greater than 10 nm. The laser is single frequency, has a narrow linewidth, and is tunable over a wide range. The laser beam has good directional stability when it is tuned.
The tunable external cavity laser diode by using fiber Bragg grating, which is adhered to a cantilever beam, is reported for the firstly in our knowledge in this paper. A tuning range 7 nm is achieved. The side mode suppression ratio about 39 dB is realized. The output power dependence on the drive current and the cooling current is discussed in detail.
In this paper, the mode-hop free tuning method and its construction of external cavity laser diode are reviewed. The mode-hop free tuning range is restricted by the positioning errors of the components under the laboratory conditions, which will be analyzed in detail for first time as our knowledge. Those are the important reference to the design and the assembly of mode-hop free tuning construction.
In this letter we introduce a new nonlinear organometallic complex CdHe(SCN)4 crystal, which is used to double the frequency of the 808nm laser diodes. The blue-violet light output of 11.8 mw, and the SHG conversion efficiency of 0.60 percent are obtained.
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