In the measurement of tissues using Fourier-domain optical coherence tomography (FD-OCT), speckle patterns from dynamic and static components often exhibit distinct characteristics: the former can be reduced through incoherent averaging, while the latter cannot. However, in the conventional Monte Carlo (MC) based simulations of FD-OCT, the speckle patterns of dynamic medium and static regions cannot be distinguished due to the random spatial distribution of scattering events across the entire simulated phantom. To tackle this issue, we propose a hybrid phantom model for MC-based realistic simulation of speckles in FD-OCT. In the simulation using the proposed model, static tissue within the 3D structure is modeled as a swarm of fixed particles loosely packed in the background medium. Once a photon is emitted into the static tissue model, it keeps moving until encountering a fixed particle and undergoing scattering. On the other hand, the spatial distribution of scattering points in the dynamic medium is still assumed random, which makes the photon’s step size sampled based on the wavelength-dependent scattering coefficient. Compared to conventional MC simulations, speckles simulated with the proposed model at different time points exhibit a higher spatial correlation in the static structures, which allows them to remain after incoherent averaging. In contrast, speckles in the dynamic component manifest de-correlation across multiple simulations. Future works involve leveraging this method to simulate dynamic OCT and linking structural information with speckle patterns to solve inverse problems.
In previous Monte Carlo (MC) studies of modeling Fourier-domain optical coherence tomography (FD-OCT), the results obtained at single wavelength are often used to reconstruct the image despite of FD-OCT’s broadband nature. Here, we propose a novel image simulator for full-wavelength MC simulation of FD-OCT based on Mie theory, which combines the inverse discrete Fourier transform (IDFT) with a probability distribution-based signal pre-processing to eliminate the excessive noises in image reconstruction via IDFT caused by missing certain wavelength’s signals in some scattering events. Compared with the conventional method, the proposed simulator is more accurate and could better preserve the wavelength-dependent features.
Fluorescence lifetime imaging (FLIM) can reveal information about the spatial distribution of a fluorescent molecule together with information about its microenvironment, which makes FLIM find wide applications in biomedical research. In this paper, we implemented time-correlated single-photon counting-based fluorescence lifetime imaging microscopy (TCSPC-based FLIM) in skin cancer diagnosis, including malignant melanoma (MM), squamous cell carcinoma (SCC) and basal cell carcinoma (BCC). The fluorescence lifetime images and two-dimensional vector analysis of normal and several cancerous skin tissue sections stained with hematoxylin-eosin (H&E) were mapped and the results showed that cancerous skin tissue has a relatively shorter fluorescence lifetime compared with normal skin tissue. Moreover, the fluorescence lifetime of skin cancer tissue sections with different clinical stages was measured, and the quantitative relationship between fluorescence lifetime and pathological stage of skin cancer was explored.
KEYWORDS: Cameras, Optical coherence tomography, CCD cameras, Compressed sensing, Data acquisition, Charge-coupled devices, Imaging systems, Signal to noise ratio, Reconstruction algorithms, Real time imaging
We present a sparse-sampled camera for compressed sensing spectral domain optical coherence tomography (CS SD-OCT), which is mainly composed of a novel mask with specially designed coating and a commercially available CCD camera. Compared with conventional SD-OCT system, the CS SD-OCT system equipped with the sparse-sampled camera has better fall-off and SNR performance.
We present an ultrahigh-speed optical coherence tomography (OCT) based on an all-optical swept-source with an A-scan rate of 40 MHz. The inertia-free swept-source, which has its output power of 41.2 mW and tuning range of 40 nm and high scan linearity in wavenumber with Pearson’s correlation coefficients r of 0.9996, consists of a supercontinuum laser, an optical band-pass filter, a linearly chirped fiber Bragg grating, an erbium-doped fiber amplifier, and two buffer stages. With sensitivity of 87 dB, high-speed OCT imaging of biological tissue in vivo is also demonstrated.
We present an endoscopic probe for optical coherence tomography (OCT) equipped with a miniaturized hollow ultrasonic motor that rotates the objective lens and provides an internal channel for the fiber to pass through, enabling 360 deg unobstructed circumferential scanning. This probe has an outer diameter of 1.5 mm, which is ultra-small for motorized probes with an unobstructed view in distal scanning endoscopic OCT. Instead of a mirror or prism, a customized aspheric right-angle lens is utilized, leading to an enlargement of the numerical aperture and thus high transverse resolution. Spectral-domain OCT imaging of bio-tissue and a phantom are demonstrated with resolution of 7.5 μm(axial)×6.6 μm(lateral) and sensitivity of 96 dB.
The spindle plays a crucial role in normal chromosome alignment and segregation during meiosis and mitosis. Studying spindles in living cells noninvasively is of great value in assisted reproduction technology (ART). Here, we present a novel spindle imaging methodology, full-field optical coherence tomography (FF-OCT). Without any dye labeling and fixation, we demonstrate the first successful application of FF-OCT to noninvasive three-dimensional (3-D) live imaging of the meiotic spindles within the mouse living oocytes at metaphase II as well as the mitotic spindles in the living zygotes at metaphase and telophase. By post-processing of the 3-D dataset obtained with FF-OCT, the important morphological and spatial parameters of the spindles, such as short and long axes, spatial localization, and the angle of meiotic spindle deviation from the first polar body in the oocyte were precisely measured with the spatial resolution of 0.7 μm. Our results reveal the potential of FF-OCT as an imaging tool capable of noninvasive 3-D live morphological analysis for spindles, which might be useful to ART related procedures and many other spindle related studies.
This paper proposes a novel rotary endoscopic probe for spectral-domain optical coherence tomography (SD-OCT). The probe with a large N.A. objective lens is driven by an ultra-small hollow rectangular ultrasonic motor for circular scanning. Compared to the conventional driven techniques, the hollow ultrasonic motor enables the fiber to pass through its inside. Therefore the fiber, the objective lens and the motor are all at the same side. This enables 360 degree unobstructed imaging without any shadow resulted from power wire as in the conventional motor-driven endoscopic OCT. Moreover, it shortens the length of the rigid tip and enhances the flexibility of the probe. Meanwhile, the ultrasonic motor is robust, simple, quiet and of high torque, very suitable for OCT endoscopic probe. The side length of the motor is 0.7 mm with 5mm in length. The outer diameter of the probe is 1.5mm. A significant improvement in the lateral resolution is demonstrated due to the novel design of the objective lens. A right-angle lens is utilized instead of the traditional right-angle prism as the last optics close to the sample, leading to a reduction of the working distance and an enlargement of the N.A. of the objective lens. It is demonstrated that the endoscopic SD-OCT system achieves an axial resolution of ~7μm, a lateral resolution of ~6μm and a SNR of ~96dB.
The morphogenetic relationship between early patterning and polarity formation is of fundamental interest and remains a controversial issue in preimplantation embryonic development. We use a label-free three-dimensional (3-D) imaging technique of full-field optical coherence tomography (FF-OCT) successfully for the first time to study the dynamics of developmental processes in mouse preimplantation lives. Label-free 3-D subcellular time-lapse images are demonstrated to investigate 3-D spatial relationship between the second polar body (2PB) and the first cleavage plane. By using FF-OCT together with quantitative study, we show that only 25% of the predicted first cleavage planes, defined by the apposing plane of two pronuclei, pass through the 2PB. Also only 27% of the real cleavage planes pass through the 2PB. These results suggest that the 2PB is not a convincing spatial cue for the event of the first cleavage. Our studies demonstrate the feasibility of FF-OCT in providing new insights and potential breakthroughs to the controversial issues of early patterning and polarity in mammalian developmental biology.
Early patterning and polarity is of fundamental interest in preimplantation embryonic development. Label-free subcellular 3D live imaging is very helpful to its related studies. We have developed a novel system of full-field optical coherence tomography (FF-OCT) for noninvasive 3D subcellular live imaging of preimplantation mouse embryos with no need of dye labeling. 3D digitized embryos can be obtained by image processing. Label-free 3D live imaging is demonstrated for the mouse embryos at various typical preimplantation stages with a spatial resolution of 0.7 µm and imaging rate of 24 fps. Factors that relate to early patterning and polarity, such as pronuclei in zygote, shapes of zona pellucida, location of second polar body, cleavage planes, and the blastocyst axis, can be quantitatively measured. The angle between the two second cleavage planes is accurately measured to be 87 deg. It is shown that FF-OCT provides a potential breakthrough for early patterning, polarity formation, and many other preimplantation-related studies in mammalian developmental biology.
We develop a fiber optical coherence tomography (OCT) system in the clinical utility of imaging port wine stains (PWS). We use our OCT system on 41 patients with PWS to document the difference between PWS skin and contralateral normal skin. The system, which operates at 4 frames/s with axial and transverse resolutions of 10 and 9 µm, respectively, in the skin tissue, can clearly distinguish the dilated dermal blood vessels from normal tissue. We present OCT images of patients with PWS and normal human skin. We obtain the structural parameters, including epidermal thickness and diameter and depth of dilated blood vessels. We demonstrate that OCT may be a useful tool for the noninvasive imaging of PWS. It may help determine the photosensitizer dose and laser parameters in photodynamic therapy for treating port wine stains.
Optical coherence tomography is a new emerging technique for cross-sectional imaging with high spatial
resolution of micrometer scale. It enables in vivo and non-invasive imaging with no need to contact the
sample and is widely used in biological and clinic application. In this paper optical coherence tomography is
demonstrated for both biological and clinic applications.
For biological application, a white-light interference microscope is developed for ultrahigh-resolution
full-field optical coherence tomography (full-field OCT) to implement 3D imaging of biological tissue.
Spatial resolution of 0.9μm×1.1μm (transverse×axial) is achieved A system sensitivity of 85 dB is obtained at
an acquisition time of 5s per image. The development of a mouse embryo is studied layer by layer with our
ultrahigh-resolution full-filed OCT.
For clinic application, a handheld optical coherence tomography system is designed for real-time and in situ
imaging of the port wine stains (PWS) patient and supplying surgery guidance for photodynamic therapy
(PDT) treatment. The light source with center wavelength of 1310nm, -3 dB wavelength range of 90 nm and
optical power of 9mw is utilized. Lateral resolution of 8 μm and axial resolution of 7μm at a rate of 2 frames
per second and with 102dB sensitivity are achieved in biological tissue. It is shown that OCT images
distinguish very well the normal and PWS tissues in clinic and are good to serve as a valuable diagnosis tool
for PDT treatment.
By integrating two-photon excited fluorescence (TPEF) technique into confocal optical system, TPEF images of zygote
spindles of ICR (Internal Control Region) rats have been obtained in high resolution for the first time. Experimental
results demonstrate the validity of TPEF as an efficient probe in investigating cell spindles at early embryonic
developmental stage.
We present a parallel Fourier domain optical coherence tomography (FD-OCT) system using Xenon flash lamp. Parallel
configuration is implemented by one dimensional illumination and two dimensional detection with a CCD camera. The
imaging axial resolution is 2.6μm in air with maximum depth range of ~650μm. The dynamic range is ~70DB with
exposure time less than 1ms for a 1000*512 pixel image.
A power-conserving wave-front division Fourier domain optical coherence tomography (WD FDOCT) has been
successfully demonstrated. Unlike conventional Michelson-based FDOCT system, splitting ratio of WD FDOCT can be
arbitrarily adjusted to enhance signal-to-noise ratio (SNR). Both theoretical and experimental SNR of this system are
evaluated. WD FDOCT imaging of the anterior eye of a rat is also demonstrated.
In this paper, we developed a full-field OCT system using thermal light as the low-coherence light source. A well-known
Linnik interferometer configuration was used. Broad spectral width of the thermal light 450-650nm was used to achieve
high axial resolution of 1.1&mgr;m in biological sample for OCT imaging. Two water immersion objectives of 0.5N.A were
used to balance the dispersion and a transverse resolution of 0.7μm was obtained. With a fast machine-coding algorithm,
system sensitivity of more than 80dB and imaging rate as high as 18frame/s with 500x500 pixels per frame could be
achieved. Mouse embryos were imaged in vivo with full-field OCT at different depth for the developmental study. Useful
information for pre-implementation genetic diagnosis (PGD) was obtained by image analysis and segmentation. As far as
known, for the fist time, 3D images of mammalian embryos were obtained with full-field OCT without the need of dye
labeling.
We developed a full-field OCT system using thermal light as the low-coherence light source. The whole system is
combined with a commercial fluorescent microscope. A compact Linnik interferometnc adapter is designed as
reference arm. Due to the broad spectral width of the thermal light, a sub micrometer axial resolution can be achieved
for OCT imaging. As the acquisition rate of CCD is fast enough, real time OCT imaging can be achieved. The whole
system is compact and robust, very suitable for biomedical applications.
Optical Coherence Tomography is a new technique mainly used in biomedical imaging. Here we present a Particle-Fixed Monte Carlo (PFMC) simulation for OCT signal. In PFMC model the scattering particles of the sample are assumed to be temporarily fixed randomly in simulation process of the backscattering light. The new model, beyond the convention Monte Carlo simulation, explains very well the exponential decay signal at the interface of different media layers in OCT experimental measurement.
This paper presents a novel ophthamological optical coherence tomography detecting instrument that we design and introduces measuring arm emphatically. For the glaucoma is very common in the orient, this system can achieve both the eyeground detection and the canthus detection. And it combines the cranny lamp's conventional detection with optical coherence tomography. In order to gain the best resolution and the largest scanning range in the OCT detection, we find the optical system should obey these principles in the measuring arm design: (i) the parallel light from the collimator goes through the lens and focuses on the slot of the cranny lamp. The movement of the scanning point produced by the scanner is carrying on along the slot. (Ii) In the whole light route, the scanner images on the laser object lens of the OCT. The center light of the infrared goes through the center of the object lens all the time. Considering all the system, this design has a longitudinal resolution of 15micrometers , and a transverse resolution of 20micrometers at imaging velocity of 4 frames per second.
This paper presents a novel ophthamological optical coherence tomography detecting instrument, which we design, and introduces measuring arm emphatically. For glaucoma which is very common in the Orient, this system can achieve both the eyeground detection and the canthus detection. And it combines the cranny lamp's conventional detection with optical coherence tomography. Considering all the system, this design has a longitudinal resolution of 15 um, and a transverse resolution of 20 um at imaging velocity of 4 frames per second.
Optical tomography is a kind of noninvasive technology in CT field using multiple photon diffusion. With the method of Monte Carlo simulation we carried out some numerical computation of the diffusion transmission disciplinarian in two kinds of simple biological texture. A ring distribution of diffuse light intensity is found and is sensitive to the incident light relative position to the absorption sphere at some certain conditions. The resolution and incident depth are also discussed through analysis of the image in numeric simulation.
A new model (3D) of OCT based on wave optics and Huygens- Fresnel Principle is derived in this paper. In this model, both axial and transverse information is included so that it can be used to discuss the image properties in both directions. The model is further simplified by narrow-band approximation and plane wave approximation. As applications of the simplified model, we developed Monte Carlo simulation programs to calculate the transverse resolution and to simulate the axial signal of our OCT system. The results well coincides the experiments.
Optical Coherence Tomography (OCT) is a kind of new tomography technology, which has much important application in biological, medical and material science. In this paper, we make continuations of this technology to found en face imaging of arbitrary object. This enables us to get digital information about the geometrical configuration of a sample with resolution of micrometers in a non-touching mode.
The early detection and treatment of pathological change tissue has long been a medical priority. Optical coherence tomography (OCT) is a new kind of noninvasive cross- sectional imaging technique. In this paper, experimentally we set up the first OCT system in China that can be obtaining 2D image of biological samples. OCT performs optical ranging in tissue by use of a fiber-optic Michelson interferometer with a low illuminating source, a tunable mode-locked Ti:Sapphire femtosecond pulse laser source, with center wavelength of 830 nm. A matching length of single- mode optical fiber wrapped around a piezoelectric modulator is placed in the reference arm for phase modulation. The properties and experimental results of our OCT system are analyzed. We got cross-sectional images of animal tissue samples. The OCT image of a mouse nephridium cortex tissue is agreed with the histological images. On the other hand, mouse brain (animal model of cerebral embolism) pathological changes tissue and normal tissue can be discriminated. The blood rheology characteristic of brain blood vessel block is discussed. It shows that this technique holds promise as a potential tool for the tissue diagnosis.
Optical coherence tomography (OCT) takes the advantage of the low coherence property of a light source to get the image of biological tissue structures. It provides important information on the contour and thickness of tissue structures, which can be of great help for clinical diagnostic procedures. Usually, the resolution of OCT image ranges from 2 to 20 microns. At the beginning of tissue pathologic changes, the foci could be located with OCT and cured in time. In this paper, some images of rabbit' femoral artery wall taken by our OCT system are presented. From these pictures, the three-layered structure coincides with the atlas well. In addition, the image of femoral artery wall with fat deposit is shown and the tunica media is thicker than that of normal vessel wall. The ability of OCT to image tissue microstructure near the cellular level make it potential for minimally invasive probing of tissue diseases. The high resolution of OCT, which is greater than any other conventional clinic imaging modality, and based on fiber, makes it particularly attractive for the assessment of early cardiovascular plaque.
Monte Carlo method is employed to simulate optical path-length- resolved reflectance from samples in optical coherence tomography. Four different models are often used in such simulations to treat the scattering and absorption process. This paper presents a detailed probability analysis on the equivalence of the four different models under certain conditions. We found that the photon's statistical contributions after the same times of scattering are equal in these four models.
Optical coherence tomography (OCT) is a new noninvasive tomographic imaging techniques with resolution of micron scale. It has high potential for the application in many fields such as medicine, biology, material and so no. In this paper, our OCT system is shown to be successful in the study of both botanic and creatural tissue imaging. Furthermore we also use the Monte-Carlo simulation method to analyze 2D OCT image. The differences between single scattered light and multiply scattered light and also its influence on the quality of OCT image are discussed. To show an example, a conduit immersing in a high scattering medium as the model of blood vessel is simulated and the theoretical result is directly shown in the form of image. The conduit immersing in the high scattering medium can be clearly seen in the imags. Comparing with the experimental image they are basically accordant. Some results helpful for experimental research area draw through the simulation. To further enhance the resolution of OCT imaging, computer processing and image deconvolution are introduced. The depth resolution is improved by more than one order for the sample image and thus enables intracellular imaging.
Utilizing the ultra-fast laser or superluminescence diode (SLD) as the light source, optical coherence tomography (OCT) is a new tomographic imaging technique. It has great applying foreground in many fields such as medicine, biology, material and so on. We founded an OCT system and applied it in biological imaging successfully. Furthermore, we found a potential great application for this technique in measuring the inner structure of bedded samples such as paint films. The experiment in OCT has made prompt development, while only a little work has been done on the theoretical analysis. Some experimental results, thus, can't be explained clearly. In this paper, we use the Monte-Carlo simulation method to analyze OCT image. The differences between single scattered (or least scattered) light and multiply scattered light and its influence to the quality of OCT image are discussed in detail. To show an example, our simulating calculation object is a conduit immersing in a high scattering medium that can be regarded as the approximation of blood vessel. After programming and calculating we get the theoretical result as the form of pseudo color image. The images of conduit immersing in the high scattering medium are clearly seen. Comparing with the experimental imaging of vein they are accordant basically. All above prove the Monte-Carlo simulation method correct and effective in theoretical research of OCT. Many significant results, which are very helpful for experimental research, are draw through this method.
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