This PDF file contains the front matter associated with SPIE Proceedings Volume 7889, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

In-vivo full field (FF) optical coherence tomography (OCT) images of human retina with up to 6.8 million A-lines/s are presented by using a rapidly tunable laser source in combination with an ultra-high speed CMOS camera. It is shown that Fourier domain (FD) full field OCT could provide a way to overcome limitations in imaging speed which are posed by the maximal possible exposure (MPE) of the retina. With a 100~Hz sweep rate FF-OCT was fast enough to acquire OCT images without motion artifacts, but with rather low sensitivity of 77 dB limited by an undesired incoherent background. Nevertheless, FF-OCT may become an attractive alternative for ultrafast retinal imaging boosting image speed by a lack of moving parts and the use of considerably higher irradiation power, if it is possible to to increase the sensitivity by reducing incoherent straylight.

The dispersion mismatch between sample and reference arm in frequency-domain OCT can be used to iteratively suppress complex conjugate artifacts and thereby increase the imaging range. We propose a fast dispersion encoded full range (DEFR) algorithm that detects multiple signal components per iteration. The influence of different dispersion levels on the reconstruction quality is analyzed for in vivo retinal tomograms at 800 nm. Best results have been achieved with about 30 mm SF11, with neglectable resolution decrease due to finite resolution of the spectrometer. Our fast DEFR algorithm achieves an average suppression ratio of 55 dB and converges within 5 to 10 iterations. The processing time on non-dedicated hardware was 5 to 10 seconds for tomograms with 512 depth scans and 4096 sampling points per depth scan. Application of DEFR to the more challenging 1060 nm wavelength region is demonstrated by introducing an additional optical fibre in the sample arm.

Spectral domain dual-band optical coherence tomography for simultaneous imaging of rodent retina in the 0.8 μm and 1.3 μm wavelength region and non-invasive monitoring of the posterior eye microstructure in the field of retinal degeneration research is demonstrated. The system is illuminated by a supercontinuum laser source and allows three-dimensional imaging with high axial resolution better than 3.8 μm and 5.3 μm in tissue at 800 nm and 1250 nm, respectively, for precise retinal thickness measurements. A fan-shaped scanning pattern with the pivot point close to the eye's pupil and a contact lens are applied to obtain optical access to the eye's fundus. First in vivo experiments in a RCS (royal college of surgeons) rat model with gene-related degeneration of the photoreceptor cells show good visibility of the retinal microstructure with sufficient contrast for thickness measurement of individual retinal layers. An enhanced penetration depth at 1250 nm is clearly identifiable revealing sub-choroidal structures that are not visible at 800 nm. Furthermore, additional simultaneous imaging at 1250 nm improves image quality by frequency compounding speckle noise reduction. These results are encouraging for time course studies of the rodent retina concerning its development related to disease progression and treatment response.

Studying progression of congenital diseases in animal models can greatly benefit from live embryonic imaging Mouse have long served as a model of mammalian embryonic developmental processes, however, due to intra-uterine nature of mammalian development live imaging is challenging. In this report we present results on live mouse embryonic imaging in utero with Optical Coherence Tomography. Embryos from 12.5 through 17.5 days post-coitus (dpc) were studied through the uterine wall. In longitudinal studies, same embryos were imaged at developmental stages 13.5, 15.5 and 17.5 dpc. This study suggests that OCT can serve as a powerful tool for live mouse embryo imaging. Potentially this technique can contribute to our understanding developmental abnormalities associated with mutations, toxic drugs.

Optical coherence tomography (OCT), as a non-invasive technique for studying tissue morphology, is widely used in in vivo studies, requiring high resolution and fast three-dimensional imaging. Based on light scattering it reveals micrometer sized substructures of the samples due to changes in their optical properties and therefore allows quantification of the specimen's geometry. Utilizing fluorescence microscopy further information can be obtained from molecular compositions embedded in the investigated object. Fluorescent markers, specifically binding to the substance of interest, reveal the sample's chemical structure and give rise to functional studies. This research presents the application of a combined OCT and laser scanning confocal microscopy (LSCM) system to investigate structural details in lung tissue. OCT reveals the three-dimensional morphology of the alveoli whereas fluorescence detection, arising from the fluorophore Sulforhodamin B (SRB) which is binding to elastin, shows the elastic meshwork of the organs extracellular matrix. Different plains of fluorescence can be obtained by using a piezo driven objective and exploiting the confocal functionality of the setup. Both techniques combined in one optical system not only ease the experimental procedure but also contribute to a thorough description of tissue's morphology and chemical composition.

Considerable improvement in the reproducibility of retinal photocoagulation is expected if degree and extend of the heat-induced tissue damage can be visualized on-line during the treatment. Experimental laser treatments of the retina with enucleated pig eyes were investigated by high speed phase-sensitive OCT. OCT could visualize the increase of tissue scattering during the photocoagulation in a time-resolved way. Immediate and late tissue changes were visualized with more than 15 µm resolution. Changes of the reflectance in the OCT images had a similar sensitivity in detecting tissue changes than macroscopic imaging. By using Doppler OCT slight movements of the tissue in the irradiated spot were detected. At low irradiance the thermal expansion of the tissue is observed. At higher irradiance irreversible tissue changes dominate the tissue expansion. OCT may play an important role in understanding the mechanisms of photocoagulation. This may lead to new treatment strategies. First experiments with rabbits demonstrate the feasibility of in-vivo measurements.

Vitreoretinal surgical visualization by ophthalmic microscopy is limited in its ability to distinguish thin translucent tissues from other retinal substructures. Conventional methods for supplementing poor contrast, such as with increased illumination and application of exogenous contrast agents, have been limited by the risks of toxicity at the retina. Spectral domain optical coherence tomography (SDOCT) has demonstrated strong clinical success in retinal imaging, enabling high-resolution, motion-artifact-free cross-sectional imaging and rapid accumulation of volumetric macular datasets. Current generation SDOCT systems achieve <5 μm axial resolutions in tissue, and have been used to obtain high resolution datasets from patients with neovascular AMD, high risk drusen, and geographic atrophy. Recently, an intraoperative microscope-mounted OCT system (MMOCT) was presented as a method of augmenting a surgical microscope to concurrently acquire high-resolution, high-contrast SDOCT volumetric datasets. Here, we demonstrated the utility of intraoperative MMOCT for the visualization of vitreoretinal surgical procedures. Vitreoretinal surgery was simulated by performing procedures, through an ophthalmic surgical microscope, on cadaveric porcine eyes. The datasets acquired with the MMOCT show both instrument-tissue interaction as well as the ability of OCT to image certain surgical tools, which would directly translate to better surgical visualization and impact the treatment of ocular diseases.

The measurement of ocular blood flow is important in studying the pathophysiology and treatment of several leading causes of blindness. A pilot study was performed to evaluate the total retinal blood flow in glaucoma patient using Fourier domain optical coherence tomography. For normal people, the measured total retinal flow was between 40.8 and 60.2 μl/minute. We found that eyes with glaucoma had decreased retinal blood flow and average flow veocity, while the venous cross sectional areas were essentially the same as normal. The decrease in blood flow was highly correlated with the severity of visual field loss.

We present high-speed Fourier-domain optical coherence tomography (Fd-OCT) with the phase variance based motion contrast method for visualizing retinal micro-circulation in vivo. This technique allows non-invasive visualization of a two-dimensional retinal perfusion map and concurrent volumetric morphology of retinal microvasculature with high sensitivity. The high-speed acquisition rate at 125kHz A-scans enables reduction of motion artifacts with increased scanning area if compared to previously reported results. Several scanning schemes with different sampling densities and scanning areas are evaluated to find optimal parameters for in vivo imaging. In order to evaluate this technique, we compare OCT micro-capillary imaging using the phase variance technique with fundus fluorescein angiography (FA). Additionally, volumetric visualization of blood flow for a normal subject is presented.

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 have outfitted a 1060nm Spectral Domain Optical Coherence Tomography system with a prototype, high speed infrared linear array camera and a custom spectrally reshaped superluminescent diode to achieve 5μm axial resolution at 91,911 A-scans/s image acquisition rate in-vivo in the human retina. 4dB loss of sensitivity was observed as a result of the reduced integration time (7μs) of the fast camera as compared to similar commercially available cameras with 14μs integration time and 47kHz readout rate. Fewer motion artefacts were observed in the retinal images acquired with the fast camera, while the higher axial resolution along with deeper penetration allowed for improved visualization of fine morphological details such as retinal and choroidal capillaries and the deep choroidal structure.

We have developed a multi-beam spectral-domain optical coherence tomography system with a single line sensor for human retina imaging. Three beams are used and the scan area is a 10-mm square on the fundus. These three beams focus on the fundus at locations 3.1 mm apart from each other to satisfy the ANSI safety standards. The line rate is 70k A-scans/s for each beam, equivalent to a total line rate of 210k A-scans/s for the three beams. The spectrometer has a single line sensor for the three beams, which leads to differences among the three beams such as pixel resolution, roll-off characteristic, and sensitivity. The 3D image is acquired by piecing the images together while calibrating the depth resolution and compensating the roll-off characteristics of each beam. We obtained an image of a healthy human retina.

Quantitative diagnosis of atherosclerosis can be facilitated by automatic segmentation of intravascular Optical Coherence Tomography (OCT) images. We report an automatic method of lumen and calcified plaque segmentation for commercial intravascular OCT systems. Lumen segmentation is based on a dynamic programming scheme. Calcified plaque is localized by edge detection and finely traced using an active contour model. The proposed methods yield promising results when applied to clinical images as validated by manual tracing. Lumen segmentation is useful for estimating the coronary artery stenosis and guiding stent implantation. Calcified plaque segmentation can be used to estimate the distribution of superficial calcification and inform strategies for coronary stenting.

Several studies have proven that intra-vascular OCT is an appropriate imaging modality able to evaluate stent strut apposition and coverage in coronary arteries. Currently image processing is performed manually resulting in a very time consuming and labor intensive procedure. We propose an algorithm for fully automatic individual stent strut apposition and coverage analysis in coronary arteries. The vessel lumen and stent strut are automatically detected and segmented through analysis of the intensity profiles of the A-scan lines. From these data, apposition and coverage can then be estimated automatically. The algorithm was validated using manual measurement (performed by two trained cardiologists) as a reference. 108 images were taken at random from in-vivo pullbacks from 9 different patient presenting 'real-life' situations (i.e. blood residual, small luminal objects and artifacts). High Pearson's correlation coefficients were found (R = 0.96 - 0.95) between the automated and manual measurements while Bland-Altman statistics showed no significant bias with good limits of agreement. As such, it was shown that the presented algorithm provides a robust and a fast tool to automatically estimate apposition and coverage of stent struts in in-vivo pullbacks. This will be important for the integration of this technology in clinical routine and large clinical trials.

Ionizing radiation is a standard treatment for various human solid tumors. However, several clinical studies showed that a significant proportion of patients undergoing radiotherapy for hepatocellular carcinoma (HCC) develop intrahepatic and extrahepatic metastasis. Understanding of radiation-induced cancer cell invasiveness and behavior is essential and of great important for developing suitable treatment strategies to contain cancer spread. Therefore, in this study we evaluated the effectiveness of using swept source optical coherence tomography (SS-OCT) to monitor the enhancement of HCC cell invasiveness by radiation. SS-OCT images were acquired and recorded to obtain three-dimensional data sets per four hours in 48 hours after irradiating HepG2 cells with 7.5 Gy. The cell migration behavior in three-dimensional tissue models was quantified from images of radiation-induced and sham-irradiated cells.

We present a single spectrometer functional spectral domain optical coherence tomography system, which allows for encoding additional information within the spatial frequencies. The method is based on a differentiation between orthogonal polarization channels through spatial modulation introduced by an electro-optic modulator. This method is used to perform Ultrahigh- speed retinal polarization sensitive optical coherence tomography (PSOCT). With this setup, we realized for the first time polarization sensitive OCT measurements of the human retina in-vivo, with camera line rates of up to 160.000 A-scans per second. Compared to PSOCT systems, operating at traditional line rates, this significantly improves patient comfort during the measurements and gives the possibility to resolve microscopic retinal details, while still gaining information of the polarization characteristics of the tissue. In this proceeding we present preliminary results acquired with this ultra-high speed PSOCT system.

We describe a fiber-based variable-incidence-angle (VIA) polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) system to determine the 3-D optical axis of birefringent biological tissues. Single-plane VIAPS- OCT is also explored which requires measurement of the absolute fast-axis orientation. A state-of-the-art PS-SS-OCT system with some improvements both in hardware and software was used to determine the apparent optical birefringence of equine tendon for a number of different illumination directions. Polar and azimuthal angles of cut equine tendon were produced by VIA method and compared with the nominal values. A quarter waveplate (QWP) and equine tendon were used as test targets to validate the fast-axis measurements using the system. Polar and azimuthal angles of cut equine tendon broadly agreed with the expected values within about 8% of the nominal values. A theoretical and experimental analysis of the effect of the sample arm fiber on determination of optical axis orientation using a proposed definition based on the orientation of the eigenpolarization ellipse experimentally confirms that this algorithm only works correctly for special settings of the sample arm fiber. A proposed algorithm based on the angle between Stokes vectors on the Poincaré sphere is confirmed to work for all settings of the sample arm fiber. A calibration procedure is proposed to remove the sign ambiguity of the measured orientation and was confirmed experimentally by using the QWP.

In this paper it is demonstrated, how research in optical coherence tomography (OCT) for biomedical diagnostics successfully triggered new developments in the field of mechanical material testing. With the help of a specifically designed, compact and robust spectral domain polarization sensitive OCT (SD-PS-OCT) setup, which is operating at 1.55 μm, dynamic investigations of technical materials - like bulk polymers and composite samples - can be performed under various conditions. Already by evaluating the speckle pattern of the standard SD-OCT images with advanced image processing methods, valuable information on the deformation and flow characteristics of samples subjected to tensile tests can be obtained. By additionally taking the birefringence properties into account, complementary knowledge on the evolvement of the internal stress situation is obtained in a spatially resolved way.

Sentinel lymph node (SLN) is the first lymph node to drain wastes originated from cancerous tissue. There is a need for an in vivo imaging method that can image the intact SLN in order to further our understanding of its normal as well as abnormal functions. We report the use of ultrahigh sensitive optical microangiography (UHS-OMAG) to image functional microvascular and lymphatic vessel networks that innervate the intact lymph node in mice in vivo. The promising results show a potential role of UHS-OMAG in the future understanding and diagnosis of the SLN involvement in cancer development.

Recent advances in Doppler and variance techniques have enabled high sensitivity imaging in regions of biological flow to measure blood velocities and vascular perfusion. In recent years, the sensitivity and imaging speed benefits of Fourier domain OCT have become apparent. Spectrometer-based and wavelength-swept implementations have both undergone rapid development. Comparative analysis of the potential benefits and limitations for the various configurations would be useful for matching technology capabilities to specific clinical problems. Here we take a first step in such a comparative analysis by presenting theoretical predictions and experimental results characterizing the lower and upper observable velocity limits in spectrometer-based versus swept-source Doppler OCT. Furthermore, we characterize the washout limit, the velocity at which signal degradation results in loss of flow information. We present comparative results from phantom flow data as well as retinal data obtained with a commercial spectrometer OCT system and a custom high-speed swept-source retinal OCT system.

Abnormal microcirculation within meninges is common in many neurological diseases. There is a need for an imaging method that is capable of visualizing functional meningeal microcirculations alone, preferably decoupled from the cortical blood flow. Optical microangiography (OMAG) is a recently developed label-free imaging method capable of producing 3D images of dynamic blood perfusion within micro-circulatory tissue beds at an imaging depth up to ~2 mm, with an unprecedented imaging sensitivity to the blood flow at ~4 μm/s. In this study, we demonstrate the utility of ultra-high sensitive OMAG in imaging the detailed blood flow distributions, at a capillary level resolution, within meninges and cortex in mice with the cranium left intact. The results indicate that OMAG can be a valuable tool for the study of meningeal circulations.

In this paper we demonstrate applicability of Optical Coherence Tomography (OCT) for three-dimensional analysis of blood flow in brain of small animals. We proposed scanning protocols that enable receiving both qualitative and quantitative information about flow. Presented data are obtained with a laboratory high resolution and high speed Spectral OCT system. Data analysis is performed using joint Spectral and Time domain OCT.

In spectral domain Doppler OCT, any transverse motion component of the obliquely moving sample relative to the incident sample beam causes a damping of the correlation between subsequent backscattering signals or even the loss of it making a phase-resolved Doppler flow analysis difficult because of the strong mean error of the Doppler phase shift. To circumvent this effect, a new method for resonant Doppler flow imaging and quantification in spectral domain OCT is proposed where the scanner movement velocity is approximately matched to the transverse velocity component of the oblique sample motion similar to a tracking shot where the camera is moved with respect to the sample. As a result, the backscattering signals corresponding to the moving sample will be highly correlated whereas those of static sample structures and slowly moving scatterers will be less correlated and damped depending on the scanner velocity. Advantageously, for the exact flow velocity quantification the new Doppler relationship of phase shift and sample velocity has not to be applied and the linear relation of the classic Doppler model can still be used. In the present work, first results of the lateral resonant Doppler imaging are shown for an 1 percent Intralipid flow phantom study.

In this paper, we demonstrate for the first time utilizing a super continuum light source to achieve ultra high sensitive Optical Micro-Angiography (UHS-OMAG) system. The broad band light with central wavelength around 800nm, emitted from the super continuum light source, could provide a ~2μm coherence gate for the system. Based on a fast CMOS camera, we could successfully develop a high speed (~70 kHz line rate) Fourier Domain Optical coherence tomography system. Applying the ultra high sensitive OMAG algorithm onto the system, we could visualize blood vessel networks buried within the tissue bed in a high resolution and high sensitivity mode. The modality is performed on imaging the human finger nail fold and the mouse pinna to obtain both high resolution structure image and detailed blood perfusion map. The excellent performance shows a great potential of our system in future biological imaging application.

A novel non-invasive in vivo multimodal optical coherence tomography (OCT)/photoacoustic tomography (PAT) imaging system capable of obtaining structural and functional information simultaneously has been demonstrated in skin. A 1060 nm OCT system acquiring 47k depth-scans/s with ~ 7 μm axial and ~ 20 μm transverse resolutions has been incorporated into a backward-mode PA system based on a planar, optically-transparent Fabry-Perot interferometer (FPI) sensor. In this study, the excitation wavelength was set to 670 nm and a focused laser beam at 1550 nm was used as the sensor interrogation beam. OCT and PAT images were obtained sequentially and the coregistered images were combined to form the final 3D image. OCT/PAT images obtained in vivo from the skin of a hairless mouse and human palmar skin demonstrated the ability of this multimodal imaging system to provide complementary structural and functional information from deeper depths with increased contrast.

We report on the development of a multimodal optical coherence tomography (OCT) - ultrasound (US) system and miniaturized OCT-US probe for intravascular imaging. Both OCT optical components and a US transducer were integrated into a single probe, enabling both OCT and US imaging at the same time. A miniaturized OCT-US probe using a single element transducer was designed with a maximum outer diameter of 0.8 mm, which is suitable for in vivo intravascular imaging. The integrated OCT-US imaging system adopted a two-channel data acquisition card to digitize both OCT and US signals. Simultaneous OCT and US data processing and image display were also achieved using our home-developed software. In vitro OCT and US imaging of human aortic tissue was performed using this multimodal imaging system, which demonstrated the feasibility of the OCT-US system in intravascular imaging and its potential in detection of atherosclerotic plaques.

We developed a piezoelectric transducer (PZT) based miniature catheter with an outer diameter of 3 mm for ultrahigh speed endoscopic optical coherence tomography (OCT) using Fourier domain modelocked (FDML) laser at a 480 kHz axial scan rate. The miniaturized PZT bender actuates a fiber to provide high scanning speed. The side-viewing probe can be pulled back for a long distance to acquire three-dimensional (3D) dataset covering a large area on the specimen. Operating with a high speed data acquisition (DAQ) system, OCT imaging with 6.5 mm imaging range, 10 μm axial resolution, 20 μm lateral resolution, and frame rate of 480 frames per second (fps) is demonstrated.

We present an extended focus FDOCT setup with FDML swept source centered at 1310nm. The illumination, preserving its lateral extend over a large depth range thanks to the use of a Bessel beam, is decoupled from the Gaussian detection in order to increase the global sensitivity. The efficient spatial separation enables dark-field imaging. In-vivo measurements in the skin were performed to demonstrate the gain in lateral resolution while preserving the imaging depth. More, the calculation of the speckle variance between B-Scans allows a clear visualization of the microvasculature.

We present a new light source for the swept-source OCT, that is, an external-cavity LD incorporating an electro-optic deflector. We use a KTN deflector that is unique in being very fast and simultaneously providing an appreciable deflection caused by injected carriers. Particularly, high-speed and nearly linear to the applied voltage operation is attained when KTN crystal is pre-charged. Our 1.3-μm Littman-Metcalf external-cavity laser exhibits static linewidth < 0.1 nm, and a 110-nm scanning range up to 150-kHz under a ±200 V sinusoidal driving voltage to the deflector. Being free of mechanical resonance, the laser would hopefully realize a faster (in a separate study, deflector itself worked up to 400 kHz) and wavenumber-linear scan that is ideal for the swept-source OCT by designing the waveform of driving voltage. And as for the resolving power of deflector, while our KTN deflector has only 35 spatial resolvable points, the number of wavelength points for the swept source clearly exceeds to this limit, which we attribute to line narrowing effect accompanied by the laser operation. Preliminary OCT images taken using the swept source are also presented.

This paper presents a unique and novel picosecond laser source that offers complete tailoring of the wavelength sweep and that benefits swept-source optical coherence tomography (SS-OCT) applications. Along with the advantages of a fiber-based architecture, the source is a fully programmable, electronically controlled actively mode-locked laser capable of rapidly tuning the wavelength and pulse characteristics. Furthermore, several sweep modes and configurations are available which can be defined by range, with linear sweeps in wavelength or k-space, or by arbitrary wavelengths. The source design is discussed and its use in SS-OCT with a prototype using a semiconductor optical amplifier as a gain medium is illustrated.

Interferometric synthetic aperture microscopy (ISAM) reconstructs the scattering potential of a sample with spatially invariant resolution, based on the incident beam profile, the beam scan pattern, the physical model of light sample interaction, and subsequent light collection by the system. In practice, aberrations may influence the beam profile, particularly at higher NA, when ISAM is expected to provide maximum benefit over optical coherence microscopy. Thus it is of interest to determine the effects of aberrations on ISAM reconstructions. In this paper we present the forward model incorporating the effects of aberrations, which forms the basis for aberration correction in ISAM. Simulations and experimental results show that when operating far from focus, modest amounts of spherical aberration can introduce artifacts to the point-spread function, even at relatively low NA ~ 0.1-0.2. Further work will investigate computational methods to correct the effects of aberrations, i.e. to perform virtual adaptive optics.

A novel microscopy technique, spatial-domain low-coherence quantitative phase microscopy (SL-QPM), is proposed to obtain quantitative phase imaging of sub-cellular structures with sub-nanometer sensitivity. This technique utilizes a low spatial-coherence from a thermal light source and produces a speckle-free, nanoscale-sensitive quantitative phase map of scattering objects. With this technique, for the first time to our knowledge, we quantified the refractive index of the cell nuclei on the original unmodified histology specimens. The results show that the average refractive index of the cell nucleus is significantly increased in cells from cancer patients compared to that of the histologically normal cells from healthy patients. More importantly, we demonstrate the superior sensitivity of refractive index of cell nucleus in detecting cancer from histologically normal cells from cancer patients. Because this technique is simple, sensitive, does not require special tissue processing, and can be applied to archived specimens, it can be disseminated to all clinical settings.

Polarization-sensitive OCT is used to examine tissue microstructure by providing imaging of birefringent properties. Single-camera spectral-domain polarization-sensitive OCT has been of recent interest, whereby a custom spectrometer is employed to simultaneously measure orthogonal polarization states scattered from the sample. This avoids synchronization and triggering issues associated with multiple-camera setups. It also has the advantage that the optic axis can be extracted without polarization modulating the incident light. However, the disadvantage is that the line camera pixel-to-wavenumber nonlinearity requires either careful spectrometer alignment, or digital compensation. In fact, this problem is further exacerbated in high resolution PSOCT systems as they require compensation over larger bandwidths. Here we report the construction of an ultrabroad-bandwidth PSOCT system using a single camera spectrometer similar to Baumann et al. In order to enjoy the benefits of this instrument, we outline a method for digital dispersion compensation that removes the necessity for special camera alignment. We find that there are three non-negligible types of dispersion to consider: 1) the aforementioned camera pixel-to-wavenumber nonlinearity, 2) the refractive index dispersion in the sample itself, and 3) the dispersion imbalance between the arms of the OCT interferometer. The latter two were previously recognized for time-domain high-resolution OCT, where a digital dispersion compensation method was successfully employed to treat them both. For our SDOCT application, we find that dispersion types 1 and 2 have the same functional effect and can be combined into one compensation step, and as such, much of the previous compensation method can be used. However, we find that it is necessary to add two steps to the analysis technique whereby the relative scaling and positioning of the two polarization images is adjusted to align the scatterers. We also find that better results are achieved by fitting to larger polynomial orders. We show how our technique provides high-resolution PSOCT with precise alignment between the orthogonal polarization images.

Recently introduced smart scanning protocols called segmented protocols offer possibility to create Spectral Optical Coherence Tomography images with strongly reduced speckle contrast. The algorithm is fast, robust and gives cross-sectional images with preserved high lateral resolution. To obtain efficient speckle reduction only slight modification to the optical setup is required. Cross-sectional images of anterior and posterior parts of the human eye with reduced speckle noise are presented.

In this manuscript, a novel low coherence interferometer configuration is presented, equipped in each arm with an adjustable optical path length ring. By compensating the losses in the two rings using semiconductor optical amplifiers, interference of low coherence light after traversing the two rings 18 times is obtained. This configuration can successfully be employed to produce simultaneous en-face OCT images from different depths.

Optical coherence tomography (OCT) has become a promising diagnostic method in many medical fields. Non-invasive real-time optical biopsy of internal organs is one of the most attractive applications of OCT enabling in-situ diagnostic of cancer in its early stage, i.e. optical biopsy. For the application, faster OCT methods are required to reduce the inspection time and motion artifacts in images. A criterion to satisfy the purpose is an endoscopic-OCT method capable to display volumetric tomography continuously in real-time at a rate of video movie like conventional endoscopes. In our previous work, we demonstrated ultra-high speed OCT at an A-scan rate of 60 MHz. However, movies were rendered after the data acquisition. In this work, we have developed an ultra-fast data processing system, installed it in the ultra-high speed OCT system, and enabled real time display of various 3D tomography images without limitation of diagnostic time, i.e. 4D OCT imaging, at an A-scan rate, B-scan rate and volume rate of 10 MHz, 4 kHz and 12 volumes/sec, respectively. Various image presentations in real-time are demonstrated such as continuous rendered 3D imaging and continuous 2D-slice scanning 3D imaging.

We report a technique, which uses an area-scan camera to record the interference spectrum. Traditional point-scanning is remained in this streak-mode FDOCT so that the small aperture of the single-mode fiber functions as a confocal gate and screens multiply scattered photons very well. While the sample beam is scanning the specimen laterally, the interference spectrum is physically scanned on the area scan camera using a streak scanner. Therefore, pixels of the camera are illuminated by the spectrum of OCT signal row by row, corresponding to each A-scan at different lateral position. A unidirectional B-scan of 700 lines is obtained in 1 ms; thus, an A-scan time of 1.4 μs is achieved. A Day 4 chick embryo sampled is imaged using this method. This technique is highly potential for multi-Megahertz OCT imaging.

We present a spectral domain refractive low coherence interferometry technique (SD-rLCI) using a novel extreme broadband Super Continuum laser source equipped with a dual spectrometer system which is able to measure the dispersion in the visual and near infrared range simultaneously. The setup was verified obtaining the second order dispersion of distilled water. We will use this system for measuring the dispersion sensitivities of important tissue substances in order to determine analyte concentrations within mixtures.

An efficient technique of simultaneous obtaining of quadrature spectral components of interference signal in spectrometer-based OCT is proposed. The components are obtained in air-spaced non-polarization interferometer by partition of reference beam onto two parts and using an achromatic phase shifter. Several setups of phase sifter are described and compared.

Magnetomotive microscopy techniques are introduced to investigate cell dynamics and biomechanics. These techniques are based on magnetomotive transducers present in cells and optical coherence imaging techniques. In this study, magnetomotive transducers include magnetic nanoparticles (MNPs) and fluorescently labeled magnetic microspheres, while the optical coherence imaging techniques include integrated optical coherence (OCM)and multiphoton (MPM) microscopy,and diffraction phase microscopy (DPM). Samples used in this study are murine macrophage cells in culture that were incubated with magnetomotive transducers. MPMis used to visualize multifunctional microspheres based on their fluorescence, while magnetomotive OCM detects sinusoidal displacements of the sample induced by a magnetic field. DPM is used to image single cells at a lower frequency magnetic excitation, and with its Fourier transform light scattering (FTLS) analysis, oscillation amplitude is obtained, indicating the relative biomechanical properties of macrophage cells. These magnetomotive microscopy method shave potential to be used to image and measure cell dynamics and biomechanical properties. The ability to measure and understand biomechanical properties of cells and their microenvironments, especially for tumor cells, is of great importance and may provide insight for diagnostic and subsequently therapeutic interventions.

In imaging of turbid biological samples using optical techniques, optical clearing methods can compensate for the lack of light penetration due to strong attenuation. The addition of optical clearing agents into scattering media increases the optical homogeneity of the sample and reduces its turbidity, allowing for the increased light penetration. In this study we investigated the extent of optical clearing in porcine skin by utilizing various concentrations of glucose solution. A goldplated mirror was fixed beneath the tissue and percentage clearing was determined by measuring the change in intensity of optical coherence tomography light returning from the mirror over time. A ratio of percentage clearing per tissue thickness for 10%, 30%, and 50% glucose was determined to be to be (4.7 ± 1.6%) mm^-1 (n = 6), (10.6 ± 2.0%) mm^-1 (n = 7), and (21.8 ± 2.2%) mm^-1 (n = 5), respectively. Although the extent of optical clearing in porcine skin was more significant for 50% glucose, the osmotic stress on the sample can cause considerable morphology change, thus a suitable concentration must be chosen for particular circumstances.

Diffusion-sensitive optical coherence tomography (DS-OCT) is presented as a functional extension to OCT. Fluctuations of signal intensity and phase, which are caused by Brownian motion, are analysed by an autocorrelation function similar to dynamic light scattering measurements. Based on an ultra-fast Fourier-domain OCT, DS-OCT can determine quantitatively diffusion properties with high depth resolution, e.g. the hydrodynamic diameter of colloidal suspensions . Performance of DS-OCT is demonstrated with polystyrene particle suspensions and compared to conventional DLS measurements. Applications for DS-OCT may be found in the measurement of particle size distributions of inhomogeneous samples or measurements of diffusion properties at boundary surfaces. Additionally, the method has the capability to become a useful benefit in clinical diagnostics, especially in ophthalmology, where the molecular compositions and pathological changes of anterior eye components could be detected.

Fourier domain optical coherence tomography requires either a linear-in-wavenumber spectrometer or a computationally heavy software algorithm to recalibrate the acquired optical signal from wavelength to wavenumber. The first method is very sensitive to the position of the prism incorporated in the spectrometer, while the second method drastically slows down the system speed when it is implemented on a serially oriented central processing unit. In this manuscript, a Fourier domain ultra-fast optical coherence tomography system operating in the 1 μm range with real-time data resampling is presented for the first time. It utilizes a newly released 1024 pixels line scan InGaAs camera able to acquire data as fast as 91,900 lines per second. To demonstrate the performance of the system, images from a thumb of a volunteer obtained with real-time processing and displaying are shown.

We compare true 8 and 14 bit-depth imaging of SS-OCT and polarization-sensitive SS-OCT (PS-SS-OCT) at 1.3μm wavelength by using two hardware-synchronized high-speed data acquisition (DAQ) boards. The two DAQ boards read exactly the same imaging data for comparison. The measured system sensitivity at 8-bit depth is comparable to that for 14-bit acquisition when using the more sensitive of the available full analog input voltage ranges of the ADC. Ex-vivo structural and birefringence images of an equine tendon sample indicate no significant differences between images acquired by the two DAQ boards suggesting that 8-bit DAQ boards can be employed to increase imaging speeds and reduce storage in clinical SS-OCT/PS-SS-OCT systems. We also compare the resulting image quality when the image data sampled with the 14-bit DAQ from human finger skin is artificially bit-reduced during post-processing. However, in agreement with the results reported previously, we also observe that in our system that real-world 8-bit image shows more artifacts than the image acquired by numerically truncating to 8-bits from the raw 14-bit image data, especially in low intensity image area. This is due to the higher noise floor and reduced dynamic range of the 8-bit DAQ. One possible disadvantage is a reduced imaging dynamic range which can manifest itself as an increase in image artefacts due to strong Fresnel reflection.

We demonstrate a real-time display of processed OCT images using multi-thread parallel computing with a quad-core CPU of a personal computer. The data of each A-line are treated as one vector to maximize the data translation rate between the cores of the CPU and RAM stored image data. A display rate of 29.9 frames/sec for processed OCT data (4096 FFT-size x 500 A-scans) is achieved in our system using a wavelength swept source with 52-kHz swept frequency. The data processing times of the OCT image and a Doppler OCT image with a 4-time average are 23.8 msec and 91.4 msec.

Two factors are of importance to optical coherence tomography (OCT), resolution and sensitivity. Adaptive optics improves the resolution of a system by correcting for aberrations causing distortions in the wave-front. Balanced detection has been used in time domain OCT systems by removing excess photon noise, however it has not been used in Fourier domain systems, as the cameras used in the spectrometers saturated before excess photon noise becomes a problem. Advances in camera technology mean that this is no longer the case and balanced detection can now be used to improve the signal to noise ratio in a Fourier domain (FD) OCT system. An FD-OCT system, enhanced with adaptive optics, is presented and is used to show the improvement that balanced detection can provide. The signal to noise ratios of single camera detection and balanced detection are assessed and in-vivo retinal images are acquired to demonstrate better image quality when using balance detection.

In this manuscript, we present the design and realization of a Fourier-Domain Spectroscopic-OCT system with a simple spectrometer, based on off-the-shelf parts and a low-cost, state-of-the-art broadband S-LED light source with three spectrally shifted S-LED modules. Depth resolved spectral absorption measurements in the wavelength range from 750 nm to 850 nm are demonstrated using an expansion of OCT called spectroscopic OCT (SOCT). The realized setup was tested and evaluated towards its ability to measure physical parameters such as blood oxygen saturation quantitatively in vivo. Different sample configurations including multilayer setups and scattering layers were used. Additionally, we present the theoretical model and experimental verification of interferences between autocorrelation terms and the signal carrying crosscorrelation terms, strongly affecting the absorption measurements. A simple background subtraction, minimizing the artifacts caused by the interferences of autocorrelation and crosscorrelation terms is presented and verified.

Optical Coherence Tomography (OCT) imaging is a high-resolution, sub-surface non-invasive imaging technique, using the principle of low coherence interferometry, that has become increasingly popular for various applications for structural and quantitative imaging [1]. Applications for OCT technology have been demonstrated in ophthalmology, dentistry, cardiology/intravascular imaging, endoscopy and intra-operative surgery, and many new applications are being researched. Due to higher sensitivity and faster rate of image acquisition, frequency domain OCT systems are now replacing the first generation time domain systems. These include spectral domain systems, which use a broadband low coherent source with spectrometer and a line scan camera based receive system, and swept source systems, that use wavelength sweeping source with a photo-detector based receive system. Both of these systems require very similar signal processing to recover the desired image from the captured digitized interference or fringe data.

We present a common path Fourier domain optical coherence tomography (FDOCT) setup where the reference signal arises from multiple reflections within the sample arm. Two configurations are demonstrated. The first is based on a reflective microscope objective while the second is based on a normal (refractive) microscope objective. The second configuration is effectively a Mireau interferometer. We present sensitivity analysis of these setups and images of in vivo skin. Advantages of both common path arrangements include: 1) the reference surface is not close to the sample surface while keeping the optical path lengths matched (so the additional interferometer is not needed) and 2) the user can independently control reference and sample arm power. Additionally, the configuration using the refractive objective ensures that the coherence gate and focus gate always match. A disadvantage is that the reference arm power in certain circumstances is not optimal (i.e. is not close to saturating the CCD). However, this issue can be removed by a light source of sufficient output power. We believe the idea is scalable and therefore of interest to endoscopy applications.

Optical coherence tomography (OCT) is a non invasive optical imaging technology for micron-scale cross-sectional imaging of biological tissue and materials. Although OCT has many advantages in medical equipments, low penetration depth is a serious limitation for other applications. To realize the ultrahigh resolution and the high penetration depth at the same time, it is effective to choose the proper wavelength to maximize the light penetration and enhance the image contrast at deeper depths. Recently, we have demonstrated ultrahigh resolution and high penetration depth OCT by use of all-fiber based Gaussian shaped supercontinuum source at 1.7 μm center wavelength. Gaussian-like supercontinuum with 360 nm bandwidth at center wavelength of 1.7 μm was generated by ultrashort pulse Er doped fiber laser based system. In this paper, using 0.8 μm and 1.3 μm SC sources in addition to the 1.7 μm SC source, we have investigated the wavelength dependence of ultrahigh resolution OCT in terms of penetration depth. Longitudinal resolutions at each wavelength region are almost 4.6 μm in air. The obtained sensitivity was 95 dB for all wavelength regions. We confirmed the difference of imaging contrast and penetration depth with hamster's cheek pouch and so on. As the wavelength was increased, the magnitude of penetration depth was increased for these samples.

Full-field optical coherence tomography (FF-OCT) is an emerging non-invasive, label-free, interferometric technique for 3D imaging of biomedical objects with micron-scale resolutions. The conventional phase-shifting technique in FF-OCT involves in mechanically moving a mirror to change the optical path difference for obtaining en face OCT images, but with the use of a broadband source in FF-OCT, the phase shifts of different spectral components are not the same, resulting in the ambiguities in 3-D image reconstruction. In this study, we propose to utilize the ferroelectric liquid crystal (FLC) device-controlled geometric phase shifting technique to realize achromatic phase shifting for rapid 3-D imaging. We demonstrate this FLC-controlled FF-OCT technique by imaging biological samples (e.g., onion tissue).

Optical coherence tomography (OCT) is an emerging technology for non-invasive cross-sectional imaging of biological tissue and material with um resolution. In the field of pulmonary medicine, non-invasive high resolution cross-sectional imaging is desired for investigation of diseases in lung. So far, a few works have been reported about OCT imaging of lung. Since the lung consists of alveoli separated by thin wall, ultrahigh resolution (UHR) OCT is supposed to be effective for the imaging of fine structure in lung tissue. In this work, ex vivo cross-sectional imaging of isolated rat and hamster lungs was demonstrated using UHR-OCT. A 120 nm-wide, high-power, Gaussian-like supercontinuum (SC) was generated at wavelength of 0.8 um region. The generated SC was used in a time-domain OCT system, and UHR-OCT imaging was demonstrated. An ultrahigh resolution of 2.9 um in air and 2.1 um in tissue was obtained. The achieved sensitivity was 105 dB. Using this system, ex vivo UHR-OCT imaging of isolated rat and hamster lungs was demonstrated for the first time. The structures of the trachea, visceral pleura, and alveoli were observed clearly. When saline was instilled into the lung, the penetration depth was improved, and clear images of the fine structure of the lung, including alveoli, were observed owing to the index matching effect. We have also demonstrated the UHR-OCT imaging of lung tissue using 1.3 um and 1.7 um SC sources. As the results, owing to the precise structures of lung tissues and index matching by saline, the finest images were observed with 0.8 um UHR-OCT system.

A narrow line-width dual band Fourier domain mode-locked (FDML) swept source at center wavelength of 1310 nm for long imaging range high speed and high resolution Fourier domain optical coherence tomography was demonstrated. A fiber Fabry-Perot tunable filter working at multi-spectral band mode is used for wavelength selection in the FDML swept source. The interference signals in two spectral bands are separated into two channels for detection by use of WDM couplers with pass-bands matching the spectral bands of the Fabry-Perot tunable filter. The line-width of the output light from the swept source can be as narrow as 0.04 nm thanks to the small tuning range within each spectral band, while high axial resolution of the FDOCT system can still be obtained since the total scanning range combining multi bands is more than 100 nm.

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.

We present a measurement method which is capable of measuring the instantaneous coherence length as a function of the wavelength while the source is working at its full sweep rate. The measurement principle is based on the dynamic decrease of fringe contrast as a function of the optical path difference. The measurement setup consists of a free-space Mach-Zehnder interferometer with a variable optical path difference. We present results for instantaneous coherence lengths in a range from 0 mm to 50 mm with a mean standard deviation of 0.42 mm at sweep rates of up to 120 kHz.

We report the development of a swept wavelength laser at 1 micron based on a linear cavity fibre configuration with an intra-cavity half symmetrical confocal Fabry-Perot tunable filter and a semiconductor optical amplifier as a gain medium. The performances of the source in terms of parameters like: sweep repetition rate (1-20 kHz), center wavelength (1065 nm), wavelength scanning range (max. 50nm), instantaneous line-width (<0.1nm) and a boosted output power of around 40 mW are demonstrated. The new source tested on an OCT system is exhibiting sufficient linearity in wave-number (k-space) at 1 kHz repetition rate; therefore no k-trigger, or wavelength rescaling process was needed.

In this paper, an ultra high speed (92 kHz A-line rate) one micron spectral domain ultra high sensitive optical microangiography system was demonstrated and successfully applied on posterior part of human eye for in vivo visualizing blood perfusions of both retina and choroid. A 1 μm ASE module was utilized as the light source, which could provide much more penetration depth than conventional 800 nm system. Running at 200 frames per second, it would cost ~5 seconds for the system to finish acquiring one 3D data set, which covers ~3×3 mm2 on the retina. Applying the OMAG algorithm onto the slow axis (C-scan direction), our system can extract detailed capillary level ocular perfusion maps for different layers of both retina and choroid. The excellent agreement with the standard text book shows great potential in clinical application.

Studying the inner ear microstructures and microvascular dynamics is extremely important to understand the cochlear function and to further advance the diagnosis, prevention and treatment of many otologic disorders. There is considerable interest in developing new methods for in vivo imaging of the complex anatomy of the mammalian cochlea and the micro vascular perfusion within it for both clinical as well as fundamental studies. In this study, we explored the feasibility of high-speed spectral domain optical coherence tomography (SD-OCT) and ultra-high sensitive optical microangiography (UHS-OMAG) for volumetric in vivo imaging of intracochlear microstructures and microvascular perfusion in mice, respectively.

In vivo measurement of blood flow in the retina has been made possible with the advent of Fourier domain optical coherence tomography (OCT). Doppler OCT has seen many advances in recent years in algorithms used for quantifying blood flow. We compare the relative retinal blood flow estimates as measured by the standard phase-resolved (PR) algorithm and the more recent moving-scatterer-sensitive (MSS) algorithm as a function of vessel size. We find that the PR-to-MSS flow ratio significantly decreases with decreasing vessel diameter. We also develop a simulation to approximate the scattering from blood cells in tissue and compare the relative blood flow estimates. The flow ratio measured with simulation closely matches that found in vivo. Our simulation predicts that whereas PR underestimates the flow, MSS overestimates it. Our simulation may help to correct for algorithm bias in in vivo retinal flow estimates.

OCT is highly potential for development of a new field of dynamic skin physiology, as recently reported by the authors. In this paper, we demonstrate dynamic analysis of a small artery of a human finger by the SS-OCT. Among the vascular system, only the small artery has two physiological functions both for the elastic artery (like main and middle arteries) and for muscle-controlled one (like arterioles). It, therefore, is important for dynamic analysis of blood flow and circulation. In the time-sequential OCT images obtained with 25 frames/s, it is found that the small artery makes a sharp response to sound stress for contraction and expansion while it continues pulsation in synchronization with the heartbeats. This result indicates that the small artery exhibits clearly the two physiological functions for blood flow and circulation. In response to sound stress, blood flow is controlled effectively by thickness change of the tunica media which consists of five to six layers of smooth muscles. It is thus found that the thickness of the tunica media changes remarkably in response to external stress, reflecting activity of the sympathetic nerve. The dynamic OCT of the small artery presented here will allow us not only to understand the mechanism of blood flow control and also to detect abnormal physiological functions in the whole vascular system.

Studying the sound stimulated vibrations of various membranes that form the complex structure of the organ of Corti in the cochlea of the inner ear is essential for understanding how the travelling sound wave of the basilar membrane couples its energy to the organ structures. In this paper we report the feasibility of using phase-sensitive Fourier domain optical coherence tomography (FD-OCT) to image the vibration of various micro-structures of the cochlea at the same time. An excised cochlea of a guinea pig was stimulated using sounds at various frequencies and vibration image was obtained. When measuring the apex area, vibration signal from different turns, which have different best response frequencies are obtained in the same image. The method has the potential to measure the response from a much wider region of the cochlea than any other currently used method. The noise floor for vibration image for the system at 200 Hz was ~0.3nm.

Current medical imaging modalities, such as MRI and CT, do not provide high enough resolution to detect many changes within the cochlea that cause hearing loss. We sought to develop the technique of optical coherence tomography (OCT) to image the cochlea noninvasively and within its native environment. We used spectral domain OCT with 950 nm as the center wavelength and a bandwidth of ~100 nm to image freshly excised normal mouse cochlea at different developmental ages. The OCT system has an axial resolution of ~4 μm (in air) and a lateral resolution of ~10 μm. When we imaged normal adult mouse cochleae through the round window membrane, Reissner's membrane, the basilar membrane, the tectorial membrane, the spiral ligament, the spiral limbus, and the modiolus could be clearly identified. When we imaged intact adult cochleae, we were able to image through ~130 μm of bone and tissue to see up to a depth of ~600 μm, and all of the previously identified structures were still visible. Imaging of early postnatal mice during the timeline of cochlear development permitted visualization of the expected structural differences from adult cochleae. Therefore, we conclude that spectral domain OCT is an effective technique for noninvasive imaging of the murine cochlea.

In this paper we present imaging and morphometric analysis of a myopic Optic Nerve Head (ONH) using an 830nm wavelength Fourier domain optical coherence tomography system. The thinner prelaminar neural tissue and shallower optic cup in the myopic subject allows visualization of the tissue structures such as anterior laminar surface and lamina cribrosa that are often challenging to image due to their depth. From these structures we measured volumetric anatomical parameters and topographical tissue thickness correlated with glaucomatous structural damage in the ONH.

Fast method for identifying the internal limiting membrane (ILM) and retinal pigment epithelium (RPE) from optical coherence tomography images is demonstrated. To avoid unnecessary increment of calculation time, a strong downsampling of the original data set is performed to reduce a number of processed pixels. In ILM segmentation, the obtained data cube is filtered with two different kinds of parameters and two estimates for the position of ILM is determined. A simple smoothness value is determined for both estimates and better estimate is used for future processing. A smaller portion of pixels around estimated ILM are extracted from the down sampled data and filtered again and new estimation for ILM position is determined. That procedure is repeated with smaller portion of pixels around ILM and with different filtering parameters. The principle of RPE segmentation is very much similar with ILM identification. Only the used filtering and processing parameters are changed. Algorithm was tested with eight data sets with good reliability. Over 97% of each scans had smaller segmentation error than 5 pixels. Total required data processing time (ILM and RPE segmentation) for data volume with (600x1500x128) pixels was less than 9 seconds.

In a recent publication, Tomlins and Wang pointed out an SNR improvement that could be gained in optical coherence tomography (OCT), by altering the averaging scheme used. Specifically they noticed that, given a large number of noisy OCT A-scans, it is preferable if possible to perform the ensemble-averaging over the A-scans and then extract the OCT envelope rather than extract the envelope from each noisy A-scan and then average. In this paper we demonstrate that a similar argument can be applied to the calculation of the degree of polarization (DOP) using polarization-sensitive OCT. However, the difference now is that direct A-scan averaging can reduce the systematic error in DOP calculation that occurs in the presence of noise due to noise-bias terms.

The present work developed a Polarization Sensitive Optical Coherence Tomography system capable of perform birrefringence images and also determine completely the Mueller Matrix of a sample, in depth. In this way many measurements were needed to be done, with different combinations of polarization states of the incident beam on the sample and the reference arm of the interferometer. After calibrating the system, a roll of adhesive tape was used as sample for two main reasons: presents birrefringent and has a periodic structure. Firstly the system was set to gather data about the horizontal polarization state and then vertical polarization state of light to construct a birrefringence image. The birrefringence (δn) of ordinary adhesive tape was evaluated as 4.03(26)x10^-4. Latter a system capable of measure any polarization state was implemented and 16 scattering profiles for different polarizations were collected. Software also was developed to solve a linear equations system. As a result a 4x4 matrix of images were calculated. Some of the features, as birefringence were easily indentified in some elements of this matrix, others, more subtle, can be founded in the literature. We also decomposed the matrix as linear combinations of other known optical elements.

This manuscript presents a novel technique for axial resolution improvement in Fourier Domain Optical Coherence Tomography (FDOCT). The technique is based on the modulated deconvolution of OCT signals which results in a resolution improvement by a factor of ~ 7 without the need for a broader bandwidth light source. This method relies on a combination of two basic properties: beating, which appears when adding two signals of slightly different frequencies, and the resolution improvement, achieved by deconvolution of an OCT image with the encoded source autocorrelation function. In FDOCT the real part of the FFT of the interferogram is modulated by a frequency which depends on the shift in position of the interferogram. A slightly shifted interferogram will, therefore, result in an A-Scan which will have a different modulation frequency. Beating will appear when two such A-Scans, with an appropriately selected amount of shift, are added. Deconvolution of the resulting signal, using suitable kernels, results in a narrower resolution width.

Imaging time can be reduced using despeckled tomograms, which have similar image metrics to those obtained by averaging several low speed tomograms or many high speed tomograms. Quantitative analysis was used to compare the performance of two speckle denoising approaches, algorithmic despeckling and frame averaging, as applied to retinal OCT images. Human retinal tomograms were acquired from healthy subjects with a research grade 1060nm spectral domain UHROCT system with 5μm axial resolution in the retina. Single cross-sectional retinal tomograms were processed with a novel speckle denoising algorithm and compared with frame averaged retinal images acquired at the same location. Image quality metrics such as the image SNR and contrast-to-noise ratio (CNR) were evaluated for both cases.

In this paper we show the ability of well known in Synthetic Aperture Radar applications Phase Gradient Autofocus to recover defocused Optical Coherence Tomography images and achieve lateral resolution about 5 um at wide depth range. High-resolution details could be recovered from far-from-focal plane (defocused) regions. Both numerical simulations and experiment have been performed to demonstrate the ability of the method.