Significance: Reducing the bit depth is an effective approach to lower the cost of an optical coherence tomography (OCT) imaging device and increase the transmission efficiency in data acquisition and telemedicine. However, a low bit depth will lead to the degradation of the detection sensitivity, thus reducing the signal-to-noise ratio (SNR) of OCT images.
Aim: We propose using deep learning to reconstruct high SNR OCT images from low bit-depth acquisition.
Approach: The feasibility of our approach is evaluated by applying this approach to the quantized 3- to 8-bit data from native 12-bit interference fringes. We employ a pixel-to-pixel generative adversarial network (pix2pixGAN) architecture in the low-to-high bit-depth OCT image transition.
Results: Extensively, qualitative and quantitative results show our method could significantly improve the SNR of the low bit-depth OCT images. The adopted pix2pixGAN is superior to other possible deep learning and compressed sensing solutions.
Conclusions: Our work demonstrates that the proper integration of OCT and deep learning could benefit the development of healthcare in low-resource settings.
Using optical coherence tomography angiography, we measured blood flow from the vessels in the lateral wall in the mouse cochlea directly through bone in mice with and without sympathetic neuronal function. We present in vivo imaging of blood flow and mechanical vibration in mice subjected to 30 min of loud sound. Loud sound caused blood flow reduction. In mice with superior cervical ganglion ablation, the loud sound-induced reduction in blood flow was partially ameliorated. These results demonstrate that sympathetic innervation likely plays a role in the pathological decrease in blood flow observed in the lateral wall vessels in response to loud sound.
Using a commercial available 200K swept source laser, we demonstrated high resolution wide field angiographic imaging of human retinal. 8mm by 8mm and 10mm by 6mm retina areas were imaged in a single scan within 4 seconds. By montaging four 10 x 6mm scan, 10 x 20mm wide field OCT angiography images were demonstrated.
We propose a three-dimensional (3-D) registration method to correct motion artifacts and construct the volume structure for angiographic and structural optical coherence tomography (OCT). This algorithm is particularly suitable for the nonorthogonal wide-field OCT scan acquired by a ultrahigh-speed swept-source system (>200 kHz A-scan rate). First, the transverse motion artifacts are corrected by the between-frame registration based on en face OCT angiography (OCTA). After A-scan transverse translation between B-frames, the axial motions are corrected based on the rebuilt boundary of inner limiting membrane. Finally, a within-frame registration is performed for local optimization based on cross-sectional OCTA. We evaluated this algorithm on retinal volumes of six normal subjects. The results showed significantly improved retinal smoothness in 3-D-registered structural OCT and image contrast on en face OCTA.
A microfluidic chip with microchannels ranging from 8 to 96 μm was used to mimic blood vessels down to the capillary level. Blood flow within the microfluidic channels was analyzed with split-spectrum amplitude-decorrelation angiography (SSADA)-based optical coherence tomography (OCT) angiography. It was found that the SSADA decorrelation value was related to both blood flow speed and channel width. SSADA could differentiate nonflowing blood inside the microfluidic channels from static paper. The SSADA decorrelation value was approximately linear with blood flow velocity up to a threshold Vsat of 5.83±1.33 mm/s (mean±standard deviation over the range of channel widths). Beyond this threshold, it approached a saturation value Dsat. Dsat was higher for wider channels, and approached a maximum value Dsm as the channel width became much larger than the beam focal spot diameter. These results indicate that decorrelation values (flow signal) in capillary networks would be proportional to both flow velocity and vessel caliber but would be capped at a saturation value in larger blood vessels. These findings are useful for interpretation and quantification of clinical OCT angiography results.
A custom-built dynamic-focus swept-source optical coherence tomography (SS-OCT) system with a central wavelength of 1310 nm was used to image the anterior eye from the cornea to the lens. An electrically tunable lens was utilized to dynamically control the positions of focusing planes over the imaging range of 10 mm. The B-scan images were acquired consecutively at the same position but with different focus settings. The B-scan images were then registered and averaged after filtering the out-of-focus regions using a Gaussian window. By fusing images obtained at different depth focus locations, high-resolution and high signal-strength images were obtained over the entire imaging depth. In vivo imaging of human anterior segment was demonstrated. The performance of the system was compared with two commercial OCT systems. The human eye ciliary body was better visualized with the dynamic-focusing SS-OCT system than using the commercial 840 and 1310 nm OCT systems. The sulcus-to-sulcus distance was measured, and the result agreed with that acquired with ultrasound biomicroscopy.
An automated algorithm was developed for total retinal blood flow (TRBF) using 70-kHz spectral optical coherence tomography (OCT). The OCT was calibrated for the transformation from Doppler shift to speed based on a flow phantom. The TRBF scan pattern contained five repeated volume scans (2×2 mm) obtained in 3 s and centered on central retinal vessels in the optic disc. The TRBF was calculated using an en face Doppler technique. For each retinal vein, blood flow was measured at an optimal plane where the calculated flow was maximized. The TRBF was calculated by summing flow in all veins. The algorithm tracked vascular branching so that either root or branch veins are summed, but never both. The TRBF in five repeated volumes were averaged to reduce variation due to cardiac cycle pulsation. Finally, the TRBF was corrected for eye length variation. Twelve healthy eyes and 12 glaucomatous eyes were enrolled to test the algorithm. The TRBF was 45.4±6.7 μl/min for healthy control and 34.7±7.6 μl/min for glaucomatous participants (p-value=0.01). The intravisit repeatability was 8.6% for healthy controls and 8.4% for glaucoma participants. The proposed automated method provided repeatable TRBF measurement.
Alzheimer’s disease (AD) and cerebrovascular disease are often comorbid conditions, but the relationship between amyloid-β and in vivo vascular pathophysiology is poorly understood. We utilized a multimodal, multiscale optical imaging approach, including spatial frequency domain imaging, Doppler optical coherence tomography, and confocal microscopy, to quantify AD-dependent changes in a triple transgenic mouse model (3xTg-AD) and age-matched controls. From three months of age (naïve) to 20 months (severe AD), the brain tissue concentration of total and oxy-hemoglobin (Total Hb, ctO2Hb) decreased 50 and 70%, respectively, in 3xTg-AD mice. Compared to age-matched controls, significant differences in brain hemoglobin concentrations occurred as early as eight months (Total Hb: 126±5 μM versus 108±4 μM; ctO2Hb: 86±5 μM versus 70±3 μM; for control and AD, respectively). These changes were linked to a 29% vascular volume fraction decrease and 35% vessel density reduction in the 20-month-old 3xTg-AD versus age-matched controls. Vascular reduction coincided with increased brain concentration of amyloid-β protein, vascular endothelial growth factor (VEGF), and endothelial nitric oxide synthase (eNOS) at eight and 20 months compared to the three-month baseline. Our results suggest that amyloid-β blocks the normally reparative effects of upregulated VEGF and eNOS, and may accelerate in vivo vascular pathophysiology in AD.
Optical coherence tomography (OCT) is an emerging noninvasive imaging technique, which is based on low-coherence interferometry. OCT images suffer from speckle noise, which reduces image contrast. A shrinkage filter based on wave atoms transform is proposed for speckle reduction in OCT images. Wave atoms transform is a new multiscale geometric analysis tool that offers sparser expansion and better representation for images containing oscillatory patterns and textures than other traditional transforms, such as wavelet and curvelet transforms. Cycle spinning-based technology is introduced to avoid visual artifacts, such as Gibbs-like phenomenon, and to develop a translation invariant wave atoms denoising scheme. The speckle suppression degree in the denoised images is controlled by an adjustable parameter that determines the threshold in the wave atoms domain. The experimental results show that the proposed method can effectively remove the speckle noise and improve the OCT image quality. The signal-to-noise ratio, contrast-to-noise ratio, average equivalent number of looks, and cross-correlation (XCOR) values are obtained, and the results are also compared with the wavelet and curvelet thresholding techniques.
Many diseases involve changes in the biomechanical properties of tissue, and there is a close correlation between tissue elasticity and pathology. We report on the development of a phase-resolved acoustic radiation force optical coherence elastography method (ARF-OCE) to evaluate the elastic properties of tissue. This method utilizes chirped acoustic radiation force to produce excitation along the sample's axial direction, and it uses phase-resolved optical coherence tomography (OCT) to measure the vibration of the sample. Under 500-Hz square wave modulated ARF signal excitation, phase change maps of tissue mimicking phantoms are generated by the ARF-OCE method, and the resulting Young's modulus ratio is correlated with a standard compression test. The results verify that this technique could efficiently measure sample elastic properties accurately and quantitatively. Furthermore, a three-dimensional ARF-OCE image of the human atherosclerotic coronary artery is obtained. The result indicates that our dynamic phase-resolved ARF-OCE method can delineate tissues with different mechanical properties.
We developed a multimodality fluorescence and optical coherence tomography probe based on a double-clad fiber (DCF) combiner. The probe is composed of a DCF combiner, grin lens, and micromotor in the distal end. An integrated swept-source optical coherence tomography and fluorescence intensity imaging system was developed based on the combined probe for the early diagnoses of atherosclerosis. This system is capable of real-time data acquisition and processing as well as image display. For fluorescence imaging, the inflammation of atherosclerosis and necrotic core formed with the annexin V-conjugated Cy5.5 were imaged. Ex vivo imaging of New Zealand white rabbit arteries demonstrated the capability of the combined system.
Coronary heart disease (like myocardial infarction) is caused by atherosclerosis. It cause over 30% of all deaths in North
America and are the most common cause of death in European men under 65 years of age and the second most common
cause in women. To diagnose this atherosclerosis before it gets rupture is the most effect way to increase the chance of
survival for patients who suffer from this disease. The crucial tusk is how to find out vulnerable plaques. In resent years
optical coherence tomography (OCT) has become a very useful tool for intravascular imaging, since it has high axial and
transverse resolution. OCT can tell the detail structure inside the plaque like the thickness of plaque cap which is an
important factor to identify vulnerable plaques. But we still need to find out the biochemical characteristics that is unique
for vulnerable plaques (like inflammation). Fluorescence molecular imaging is a standard way to exam the biochemical
property of biological samples. So we integrate these two techniques together into one probe. Our probe is comprised of
a double-clad fiber (DCF) and a grin lens, and rotates with a micro mirror in front. The single-mode inner core of the
DCF transmits both OCT and fluorescence excitation light, and the multimode inner cladding is used to detect
fluorescence signal. In vitro result shows that this is a possible way for more accurate diagnose of vulnerable plaques.
Traditional phase-resolve Doppler method demonstrates great success for in-vivo imaging of blood flow and blood vessel. However,
the phase-resolved methods always require high phase stability of the system. During phase instable situations, the performance of the phase-resolved
methods will be degraded. We propose a modified Doppler variance algorithm that is based on the intensity or amplitude value.
Performances of the proposed algorithm are compared with traditional phase-resolved Doppler variance and color Doppler methods for two
phase instability systems. The proposed algorithm demonstrates good performances without phase instability induced artifacts.
A fiber-based multimodal imaging system that combines multiphoton microscopy (MPM) with Fourier domain optical coherence microscopy (OCM) is reported. The system uses a fiber-based femtosecond laser, a fiber coupler, and a double-clad fiber (DCF) device. The fiber laser has a central wavelength of 1.04 μm and bandwidth of 29 nm. Longer excitation wavelength is used to increase penetration depth and increase the excitation efficiency for dyes, such as red fluorescent dyes. A single mode fiber coupler is used to replace the free-space beam splitter and one arm of the coupler is fused with a double-clad fiber device. The MPM and OCM share the same excitation light path in the core of a double-clad fiber, while the OCM and MPM signals were collected by the core and clad of the double-clad fiber, respectively. The performance of the introduced double-clad device is analyzed. The device can confine all the excitation light in the core and has a collection efficiency of 20% for the MPM signal. The efficiency can be further increased by fusing more multimode fibers with the DCF. Simultaneous optical coherence microscopic imaging, second harmonic generation imaging, and two-photon excitation fluorescence imaging are demonstrated in biological samples.
We demonstrate a high-speed and wide-tuning-range swept laser for optical coherence tomography (OCT) imaging.
The repetition rate of the laser is twice the speed of the polygon filter and is achieved by using two delay fibers in
a Fox-Smith cavity. The performance of the laser is the following: a scanning range of 110nm centered at 1310nm,
and the output power of 10mw at a 102.2 kHz sweeping rate.
In this paper, we analyzed the retinal and choroidal blood vasculature in the posterior segment of the human eye with
optimized color Doppler and Doppler variance optical coherence tomography. Depth-resolved structure, color Doppler
and Doppler variance images were compared. Blood vessels down to capillary level were able to be obtained with the
optimized optical coherence color Doppler and Doppler variance method. For in-vivo imaging of human eyes, bulkmotion
induced bulk phase must be identified and removed before using color Doppler method. It was found that the
Doppler variance method is not sensitive to bulk motion and the method can be used without removing the bulk phase. A
novel, simple and fast segmentation algorithm to indentify retinal pigment epithelium (RPE) was proposed and used to
segment the retinal and choroidal layer. The algorithm was based on the detected OCT signal intensity difference
between different layers. A spectrometer-based Fourier domain OCT system with a central wavelength of 890 nm and
bandwidth of 150nm was used in this study. The 3-dimensional imaging volume contained 120 sequential two
dimensional images with 2048 A-lines per image. The total imaging time was 12 seconds and the imaging area was 5x5
mm2.
We present a new low-nonlinearity fiber of mode-filtered large-core fiber for flexible beam delivery of intense pulsed
light aiming at multi-photon endoscopy application. A multimode fiber of a large core diameter (20 μm) equips a mode
filtering means in the middle of the fiber link to suppress the high-order modes selectively. A large effective core area of
~200 μm2 has been achieved at 0.8-μm and 1.0-μm bands. This is 8 times larger than the core area of a conventional
SMF used for those spectral bands. Various advantages of our large-mode area fiber will be demonstrated and discussed
in this report.
Non-invasive tumor microvasculature visualization and characterization play significant roles in the detection of tumors
and importantly, for aiding in the development of therapeutic strategies. The feasibility and effectiveness of a Doppler
variance standard deviation imaging method for tumor angiogenesis on chorioallantoic membrane were tested in vivo on
a rat glioma F98 tumor spheroid. Utilizing a high resolution Doppler Variance Optical Coherence Tomography
(DVOCT) system with A-line rate of 20 kHz, three-dimensional mapping of a tumor with a total area of 3×2.5mm2 was
completed within 15 seconds. The top-view image clearly visualized the complex vascular perfusion with the detection
of capillaries as small as approximately 10μm. The results of the current study demonstrate the capability of the Doppler
variance standard deviation imaging method as a non-invasive assessment of tumor angiogenesis, with the potential for
its use in clinical settings.
This manuscript demonstrates a multimodal imaging system which combined multiphoton
microscopy (MPM) imaging modality with Fourier domain (FD) optical coherence microscopy (OCM)
imaging modality. The system used a single fiber-based femtosecond laser as the light source for both MPM
and OCM modality. The femtosecond fiber laser has a central wavlength of 1.03 μm, a pulse width of 120 fs
and a bandwidth of 29 nm. The systems used fiber-based devices for both MPM and OCM imaging. The
MPM and OCM shared the same excitation light path. The excitation light was delivered with the core of a
dual-clad fiber. The MPM and OCM signal was collected by different parts of the dual-clad fiber. The
MPM signal was collected by the clad of the dual-clad fiber and the OCM signal was collected by the core of
the dual-clad fiber. The FD OCM used a home-built InGaAs detector array spectrometer with a maximum Aline
speed of 7.7 KHz. The multiphoton signal collection efficiency was analyzed and several imaging
modality including second harmonic generation imaging, two-photon excited fluorescence and optical
coherent microscopy imaging were demonstrated.
We report the use of spectral Doppler optical coherence tomography imaging (SDOCTI) for quantitative evaluation of dynamic blood circulation before and after a localized ischemic stroke in a mouse model. Rose Bengal photodynamic therapy (PDT) is used as a noninvasive means for inducing localized ischemia in cortical microvasculature of the mouse. Fast, repeated Doppler optical coherence tomography scans across vessels of interest are performed to record flow dynamic information with high temporal resolution. Doppler-angle-independent flow indices are used to quantify vascular conditions before and after the induced ischemia by the photocoagulation of PDT. The higher (or lower) flow resistive indices are associated with higher (or lower) resistance states that are confirmed by laser speckle flow index maps (of laser speckle imaging). Our in vivo experiments shows that SDOCTI can provide complementary quantified flow information that is an alternative to blood volume measurement, and can be used as a means for cortical microvasculature imaging well suited for small animal studies.
Optical methods have been widely used in basic neuroscience research to study the cerebral blood flow dynamics in order to overcome the low spatial resolution associated with magnetic resonance imaging and positron emission tomography. Although laser Doppler imaging and laser speckle imaging can map out en face cortical hemodynamics and
columns, depth resolution is not available. Two-photon microscopy has been used for mapping cortical activity. However, flow measurement requires fluorescent dye injection, which can be problematic. The noninvasive and high resolution tomographic capabilities of optical coherence tomography make it a promising technique for mapping depth resolved cortical blood flow. Here, we present a functional Doppler optical coherence tomography (OCT) imaging modality for quantitative evaluation of cortical blood flow in a mouse model. Fast, repeated, Doppler OCT scans across
a vessel of interest were performed to record flow dynamic information with a high temporal resolution of the cardiac
cycles. Spectral Doppler analysis of continuous Doppler images demonstrates how the velocity components and longitudinally projected flow-volume-rate change over time, thereby providing complementary temporal flow information to the spatially distributed flow information of Doppler OCT. The proposed functional Doppler OCT
imaging modality can be used to diagnose vessel stenosis/blockage or monitor blood flow changes due to pharmacological agents/neuronal activities. Non-invasive in-vivo mice experiments were performed to verify the capabilities of function Doppler OCT.
We developed a multiphoton microscope which integrates an all normal dispersion fiber laser, a double cladding photonic crystal fiber and a MEMS mirror scanner based hand-held probe. The fiber laser has a
central wavelength of 1.06μm,a repetition rate of 76MHz and maximum average output power of more than 1W. The MEMS mirror based probe is compact and Second harmonic generation and two photon excited fluorescence images of biological sample were demonstrated.
A fiber based multiphoton microscopy (MPM) system is designed and demonstrated.
An all normal dispersion fiber laser with central wavelength around 1um was used as laser
source. A double clad photonic crystal fiber (DCPCF), and galvanometer mirror scanner based
handheld probe is designed. Second harmonic generation (SHG) images and two photon excited
fluorescence (TPEF) images of biological tissue were demonstrated by the system.
KEYWORDS: Tissues, CARS tomography, Signal detection, Single mode fibers, Femtosecond phenomena, Signal generators, Picosecond phenomena, Silica, In vivo imaging, Skin
We demonstrate a fiber-based probe for maximum collection of the Coherent
anti-Stokes Raman Scattering (CARS) signal in biological tissues. We discuss the design
challenges including capturing the back-scattered forward generated CARS signal in the
sample and the effects of fiber nonlinearities on the propagating pulses. Three different
biological tissues were imaged in vitro in order to assess the performance of our fiberdelivered
probe for CARS imaging, a tool which we consider an important advance
towards label-free, in vivo probing of superficial tissues.
KEYWORDS: Optical coherence tomography, Signal to noise ratio, Calibration, Image filtering, Digital filtering, Tomography, Optical filters, Adaptive optics, Data acquisition, Data analysis
Empirical mode decomposition (EMD) is a new adaptive data analysis method in which the analyzed data is decomposed into a limited number of intrinsic mode functions (IMFs) through a sifting
process. One problem with EMD is mode mixing, which has been solved by Wu et al using ensemble EMD (EEMD). In this paper, we applied the EEMD method to data acquired from optical coherence
tomography (OCT) to improve the image quality. First, the original OCT fringe data is converted from linear wavelength to linear frequency through a calibration process. Second, the calibrated data is decomposed into different IMFs by EEMD. Third, the physical meaning of different IMFs was analyzed.
Fourth, IMFs that represented noise were removed from the calibrated fringe data. The noise removed
fringe data was then Fourier transformed to get depth information. EEMD was found to be able to separate
different frequency noise into different IMFs. The signal to noise ratio of OCT image was improved by
removing the IMFs that represent noise from the acquired fringe data.
KEYWORDS: Optical coherence tomography, Imaging systems, Wavelength division multiplexing, Mode locking, Data acquisition, Tissues, Data processing, Signal processing, Signal to noise ratio, Laser sources
A high-speed, ultra-broad band wavelength swept source based on Fourier domain mode-locking (FDML) technique was
demonstrated. Two semiconductor optical amplifiers were used as the gain media. The laser is capable of FWHM
tuning range of more than 180 nm and the edge-to-edge scanning range of more than 220 nm at 100 kHz sweeping rate.
With the built swept source, an ultra high resolution high speed FDOCT system was developed which can achieve axial
resolution of 3 μm in tissue. Imaging of rabbit trachea was demonstrated with the FDOCT system.
We present a combined optical Doppler tomography/spectral Doppler imaging modality to quantitatively evaluate the
dynamic blood circulation and the artery blockage before and after a localized ischemic stroke in a mouse model. Optical
Doppler Tomography (ODT) combines the Doppler principle with optical coherence tomography for noninvasive
localization and measurement of particle flow velocity in highly scattering media with micrometer scale spatial
resolution. Spectral Doppler imaging (SDI) provides complementary temporal flow information to the spatially
distributed flow information of Doppler imaging. Fast, repeated, ODT scans across an entire vessel were performed to
record flow dynamic information with high temporal resolution of cardiac cycles. Spectral Doppler analysis of
continuous Doppler images demonstrates how the velocity components and longitudinally projected flow-volume-rate
change over time for scatters within the imaging volume using spectral Doppler waveforms. Furthermore, vascular
conditions can be quantified with various Doppler-angle-independent flow indices. Non-invasive in-vivo mice
experiments were performed to evaluate microvascular blood circulation of a localized ischemic stroke mouse model.
KEYWORDS: Optical coherence tomography, Injuries, Image processing, 3D image processing, Microelectromechanical systems, Reconstruction algorithms, In vivo imaging, 3D modeling, 3D image reconstruction, Endoscopes
We report on the feasibility of rapid, high resolution, 3-dimensional swept source optical coherence tomography (3D
SSOCT) to detect early airway injury changes following smoke inhalation exposure in a rabbit model. The SSOCT
system obtains 3-D helical scanning using a microelectromechanical system (MEMS) motor based endoscope. Real-time
2-D data processing and image display at the speed of 20 frames per second are achieved by adopting the technique of
shared-memory parallel computing. Longitudinal images are reconstructed via an image processing algorithm to remove
motion artifacts caused by ventilation and pulse. We demonstrate the ability of the SSOCT system to detect increases in
tracheal and bronchial airway thickness that occurs shortly after smoke exposure.
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 (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 a rate of 40 frames per 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 cords, which provides important information for clinical diagnosis and treatment, as well as fundamental research of the voice itself. Office-based OCT is a promising imaging modality to study the larynx for physicians in otolaryngology.
We report on the feasibility of rapid, high-resolution, 3-D swept-source optical coherence tomography (SSOCT) to detect early airway injury changes following smoke inhalation exposure in a rabbit model. The SSOCT system obtains 3-D helical scanning using a microelectromechanical system motor-based endoscope. Real-time 2-D data processing and image display at the speed of 20 frames/s are achieved by adopting the technique of parallel computing. Longitudinal images are reconstructed via an image processing algorithm to remove motion artifacts caused by ventilation and pulse. Quantitative analyses of tracheal airway thickness as well as thickness distribution along tracheal circumference are also performed based on the comprehensive 3-D volumetric data.
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.
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.
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.
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.
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.
Digital holographic microscopy allows determination of dynamic changes in the optical thickness
profile of a transparent object with sub-wavelength accuracy. Here, we report a quantitative phase
laser microsurgery system, which takes advantage of the precise optical manipulation by the laser
microbeam and quantitative phase imaging by digital holographic microscopy with high spatial and
temporal resolution. This system would enable absolute quantitation of localized alteration/damage
to transparent phase objects, such as the cell membrane or intra-cellular structures, being exposed to
the laser microbeam, which was not possible using conventional phase-contrast microscopy.
The ability to inject exogenous material as well as to alter subcellular structures in a minimally invasive manner using a laser microbeam has been useful for cell biologists to study the structure-function relationship in complex biological systems. We describe a quantitative phase laser microsurgery system, which takes advantage of the combination of laser microirradiation and short-coherence interference microscopy. Using this method, quantitative phase images and the dynamic changes of phase during the process of laser microsurgery of red blood cells (RBCs) can be evaluated in real time. This system would enable absolute quantitation of localized alteration/damage to transparent phase objects, such as the cell membrane or intracellular structures, being exposed to the laser microbeam. Such quantitation was not possible using conventional phase-contrast microscopy.
A novel image fusion method based on an expectation maximization (EM) algorithm and the discrete wavelet frame (DWF) transform is proposed. The registered images are first decomposed using the DWF transform, which is both aliasing-free and translation-invariant. The DWF decomposes the image signal into a multiresolution representation with both low-frequency coarse information and high-frequency detail information. The EM algorithm is used to fuse the low-frequency coarse information of the registered images. The informative importance measure is applied to fuse the high-frequency detail information of the registered images. The final fused image is obtained by taking the inverse transform of the composite multiresolution representations. Simulation results show that the proposed method outperforms the conventional image fusion methods.
In this paper, a novel image enhancement technique suitable for infrared image, dualistic sub-image enhancement based on two-dimensional histogram analysis and histogram equalization, is put forward. Firstly, the infrared image is segmented to two sub-images according to the correlation between the neighboring pixels, which is based on the two-dimensional histogram analysis. Then each sub-image is enhanced based on histogram equalization. At last, we get the result after the processed sub-images are composed into one image. The experiment result indicates that the algorithm can not only enhance image information effectively but also keep the fine part of original infrared image well. And this algorithm eliminates the drawback of traditional histogram equalization that the fine part is not easy to control and protect.
KEYWORDS: Voltage controlled current source, Current controlled current source, Switching, Directional couplers, Waveguides, Nonlinear optics, Optical engineering, Modulation, Lithium, Physics
Based on unbalanced Mach-Zehnder interferometers, a novel electrooptical waveguide tunable filter is proposed and designed. By coupled-mode equations method and beam propagation method, the variation of the output light intensity versus applied voltage and frequency is analyzed for a single filter. Then several filters are combined to filtrate and route one of several frequencies, and a good result is obtained.
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