This PDF file contains the front matter associated with SPIE Proceedings Volume 8091, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

We present a Bessel beam illumination FDOCT setup with FDML buffered swept source at 1300nm. An extended focus is achieved due to the Bessel beam that preserves its lateral extend over a large depth range. Decoupling the illumination from the Gaussian detection improves the sensitivity as compared to double passing the ring filter and enables dark field imaging. Dark field imaging is useful to avoid strong reflexes from the sample's surface that adversely affect the sensitivity due to the limited dynamic range of high-speed 8bit acquisition cards. Furthermore, Bessel beams exhibit a self-reconstruction property that allows imaging even behind obstacles such as hairs on skin. Densely sampled volumes of skin in-vivo with high lateral resolution are acquired at up to 440kHz A-Scan rate. In addition the possibility of contrasting capillaries with high sensitivity is shown, using inter-B-scan speckle variance analysis. High-speed imaging is of crucial importance for imaging small details since sample motion artifacts are reduced and high sampling can be maintained while increasing the B-Scan rate.

Nanoparticles with plasmon-resonance absorption in the near-IR (NIR) optical range are of great interest in optical coherence tomography (OCT) for contrast enhancement and diagnostic interventions in molecular imaging. In this study, we characterized the optical properties of multifunctional NIR dye-loaded PLGA nanoparticles (approved by the U.S. Food and Drug Administration) to assess the feasibility of using contrast agent for photo-thermal OCT (PT-OCT) imaging. Tissue phantoms containing NIR dye-doped PLGA nanoparticles were prepared in 2% agarose solution. To study the feasibility of detecting the particles using PT-OCT, imaging was performed with a custom built PT-OCT system, and specific contrast was obtained with the prepared tissue mimicking phantoms. The excellent photo-thermal properties in combination with the positive tissue phantom results qualify the feasibility of dye-loaded PLGA particles as promising candidate for PT-OCT imaging applications.

We present a novel full-field low-coherence interference (LCI) microscope, which exhibits ultra-high axial resolution due to a broadband super continuum light source and which is at the same time capable to generate different contrast modes by using Fourier-plane filtering with a spatial light modulator. By changing the phase and spatial frequencies of the backreflected wavefront of the specimen in the sample arm of the interferometer, we are able to change the contrast in the depth-resolved LCI images. By displaying different filters on the SLM, as e.g. spiral phase, the resulting images provide particular enhancement of edges and internal structures, and expose details within the specimen that are not visible in normal bright-field mode.

We demonstrate an ultra high speed fiber based polarization sensitive spectral domain optical coherence tomography system, using two ultra high speed CMOS line scan cameras. With this system an A-scan rate of up to 128 kHz was achieved. The system is based on polarization maintaining fibers and retrieves the backscattered intensity, retardation and optic axis orientation with only one A-scan per measurement location. This high speed data acquisition enables averaging of several acquired B-scans of intensity, retardation, optic axis orientation, and Stokes vectors, which strongly reduces speckle noise. We discuss different averaging techniques and compare the results in healthy human retinas.

A phase fluctuation calibration method is presented for polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) using continuous polarization modulation. The method consists of the generation of a continuous triggered tone-burst waveform rather than an asynchronous waveform by use of a function generator and the removal of the global phases of the measured Jones matrices by use of matrix normalization. This could remove the use of auxiliary optical components for the phase fluctuation compensation in the system, which reduces the system complexity. Phase fluctuation calibration is necessary to obtain the reference Jones matrix by averaging the measured Jones matrices at sample surfaces. Measurements on an equine tendon sample were made by the PS-SS-OCT system to validate the proposed method.

Polarization-sensitive optical coherence tomography (PSOCT) has established itself as an important non-invasive optical imaging tool to study the birefringent biological tissues. The complex 3D structure architecture of the collagen fibers in articular cartilage is investigated using a time domain PSOCT (TD-PSOCT) system and the depth-wise cumulative retardance profiles obtained are compared with a three layer cartilage model. The PSOCT result obtained from the variable incidence angle (VIA) experiment of bovine cartilage sample is found to be consistent with the proposed lamellar cartilage model based on scanning electron microscope studies. This shows potential use of PSOCT -VIA technique to obtain depth-wise information about the complex 3D architecture of collagen fibers in the cartilage. Further studies would have to be carried out to map out depth wise retardance information at different sites of the cartilage, which could establish the general validity of this approach.

We present a method for the automated extraction of Doppler OCT flow information by using a support vector machine that combines different features for classification. We employ histogram equalization that makes it possible to distinguish vessels from bulk tissue by texture analysis. This method is particularly applicable to settings with significant phase noise as it is more robust to multiple scattering components than simple threshold-based methods.

We present a method to contrast the blood flow of retinal vessels from the surrounding static tissue. It is based on the extinction of the interference fringes by phase shifts of π. If moving particles within the sample introduce an additional phase shift, the signal from these particles will, in contrast to the signal from static tissue, not be attenuated. We demonstrate different variants of this method, where we introduce phase shifts during single A-scans, consecutive A-scans and consecutive B-scans. We show proof-of-principle measurements with a piezo mirror, as well as in-vivo measurements of the human retina for the different phase shifting schemes. We demonstrate its capability to contrast a wide range of perfused retinal vessels; from large vessels present in the optic nerve head region to the capillary network surrounding the fovea.

Recently, a new method called joint spectral and time domain optical coherence tomography (STdOCT) for flow velocity measurement in spectral domain OCT (SD OCT) was presented. This method analyzes the detected timeresolved interference fringe spectra by using a two-dimensional fast Fourier transformation (2D FFT) to determine directly the Doppler frequency shift instead of calculating the phase difference at each depth position of adjacent A-scans. There, it was found that STdOCT is more robust for measurements with low signal to noise ratio than the classic phase-resolved Doppler OCT (DOCT) making it attractive first for imaging fast flow velocities at which a strong Doppler angle dependent signal damping occurs due to interference fringe washout and second for investigating large blood vessels with a big diameter and a highly damped signal of blood with increasing depth due to strong scattering and absorption in the near-infrared wavelength range. In the present study, we would like to introduce an enhanced algorithm for STdOCT permitting a more precise flow velocity measurement in comparison to the conventional STdOCT. The new method determines the amplitude of the broadened Doppler frequency shift by calculating the center of gravity via the complex analytical signal as a result of the second FFT instead of detecting the maximum intensity signal. Furthermore, the comparison with phase-resolved DOCT was done experimentally by using a flow phantom consisting of a 1% Intralipid emulsion and a 320 μm glass capillary. As a result, the enhanced STdOCT and DOCT processed data are completely equivalent.

Contrasting of biotissue layers in OCT images after application of mechanical compression is discussed. The study is performed on ex vivo samples of human rectum, and in vivo on skin of human volunteers. We show that mechanical compression provides contrasting of biotissue layer boundaries due to different mechanical properties of layers. We show that alteration of pressure from 0 up to 0.45 N/mm² causes contrast increase from 1 to 10 dB in OCT imaging of human rectum ex vivo. Results of ex vivo studies are in good agreement with Monte Carlo simulations. Application of pressure of 0.45 N/mm² causes increase in contrast of epidermis-dermis junction in OCT-images of human skin in vivo for about 10 dB.

In this manuscript the application of a novel technique for axial resolution improvement in Fourier Domain Optical Coherence Tomography (FDOCT) is demonstrated. Axial resolution in FDOCT can be improved by ~7x without the need for a broader bandwidth light source using modulated deconvolution. In FDOCT the real part of FFT of each interferofram is modulated by a frequency which depends on the position of the interferogram. If an interferogram is shifted slightly, the frequency of the real part of the FFT changes. By adding two shifted interferograms, beating can be appeared in the OCT A-Scans. Subsequently deconvolution with suitable kernels can produce a significant resolution improvement in the FDOCT image.

We present a new method of numerical dispersion compensation in spectral domain optical coherence tomography based on the fractional Fourier transform. The dispersion induced by a 26 mm length water cell was compensated for a spectral bandwidth of 110 nm, allowing the theoretical axial resolution in air of 3.6 μm to be recovered from the dispersion degraded point spread function of 49 μm.

We present an integrated silicon Michelson interferometer for OCT fabricated with wafer scale deep UV lithography. Silicon waveguides of the interferometer are designed with GVD less than 50 ps/nm.km. The footprint of the device is 0.5 mm x 3 mm. The effect of sidewall roughness of silicon waveguides has been observed, possible solutions are discussed.

In this contribution we describe a specialised data processing system for Spectral Optical Coherence Tomography (SOCT) biomedical imaging which utilises massively parallel data processing on a low-cost, Graphics Processing Unit (GPU). One of the most significant limitations of SOCT is the data processing time on the main processor of the computer (CPU), which is generally longer than the data acquisition. Therefore, real-time imaging with acceptable quality is limited to a small number of tomogram lines (A-scans). Recent progress in graphics cards technology gives a promising solution of this problem. The newest graphics processing units allow not only for a very high speed three dimensional (3D) rendering, but also for a general purpose parallel numerical calculations with efficiency higher than provided by the CPU. The presented system utilizes CUDA^TM graphic card and allows for a very effective real time SOCT imaging. The total imaging speed for 2D data consisting of 1200 A-scans is higher than refresh rate of a 120 Hz monitor. 3D rendering of the volume data build of 10 000 A-scans is performed with frame rate of about 9 frames per second. These frame rates include data transfer from a frame grabber to GPU, data processing and 3D rendering to the screen. The software description includes data flow, parallel processing and organization of threads. For illustration we show real time high resolution SOCT imaging of human skin and eye.

We report experimental evidence of a novel method to quench the resonances of a Fabry-Perot tunable filter typically used as a wavelength selective element in swept source OCT systems. The method is based on applying a non-sinusoidal, synthesized waveform to the tunable filter, waveform that can be found experimentally in a few iteration steps. A significant improvement in the OCT image quality has been obtained without any software recalibration method.

Optical coherence tomography (OCT) is an imaging modality that enables micrometer-scale contactless subsurface imaging of biological tissue. Endoscopy, as another imaging method, has the potential of imaging tubular organs and cavities and therefore has opened up several application areas not accessible before. The combination of OCT and endoscopy uses the advantages of both methods and consequently allows additional imaging of structures beneath surfaces inside cavities. Currently, visual investigations on the surface of the human tympanic membrane are possible but only with expert eyes. up to now, visual imaging of the outer ear up to the tympanic membrane can be carried out by an otoscope, an operating microscope or an endoscope. In contrast to these devices, endoscopy has the advantage of imaging the whole tympanic membrane with one view. The intention of this research is the development of an endoscopic optical coherence tomography (EOCT) device for imaging the tympanic membrane depth-resolved and structures behind it. Detection of fluids in the middle ear, which function as an indicator for otitis media, could help to avoid the application of antibiotics. It is possible to detect a congeries of fluids with the otoscope but the ambition is to the early detection by OCT. The developed scanner head allows imaging in working distances in the range from zero up to 5 mm with a field of view of 2 mm. In the next step, the scanner head should be improved to increase the working distance and the field of view.

Intra-vascular Optical Coherence Tomography (IV-OCT) is an appropriate imaging modality for the evaluation of stent struts apposition and coverage in the coronary arteries. Most often, image analysis is performed by a time-consuming manual contour tracing process. Recently, we proposed an algorithm for fully automated lumen morphology and individual stent struts apposition/coverage quantification. In this manuscript further developments allowing for automatic segmentation of the stent contour are presented. As such, quantification of in-stent area, malapposition cross-sectional area (i.e. the area representing the space from the stent surface to the vessel wall) and coverage cross-sectional area (i.e. the area of the tissue covering the stent surface) are automatically obtained. Volumetric measurements of malapposition and coverage are then achieved through the analysis of equally-spaced consecutive IV-OCT cross-sectional images. In addition, uncovered and malapposed struts are automatically clustered through consecutive slices according to their three-dimensional spatial position. Finally, properties of each cluster (e.g. malapposition/coverage volumes and struts spatial location and distribution) are quantified allowing for a volumetric analysis of the implanted device. Validation of the algorithm was obtained taking as a reference manual measurements performed by an expert cardiologist. 102 in-vivo images, taken at random from 8 different patients, were both automatically and manually analyzed quantifying lumen and stent area. High Pearson's correlation coefficients (R_area = 0.99) and Bland-Altman statistics, showing no significant bias and good limits of agreement, proved that the presented algorithm provides a robust and fast tool to automatically estimate apposition and coverage of stent through an entire in-vivo IV-OCT pullback. Such a tool will be important for the integration of this technology in clinical routine and large clinical trials.

Optical coherence tomography (OCT) is used for imaging subpleural alveoli in animal models to gain information about dynamic and morphological changes of lung tissue during mechanical ventilation. The quality of OCT images can be increased if the refraction index inside the alveoli is matched to the one of tissue via liquid-filling. Thereby, scattering loss can be decreased and higher penetration depth and tissue contrast can be achieved. Until now, images of liquid-filled lungs were acquired in isolated and fixated lungs only, so that an in vivo measurement situation is not present. To use the advantages of liquid-filling for in vivo imaging of small rodent lungs, it was necessary to develop a liquid ventilator. Perfluorodecalin, a perfluorocarbon, was selected as breathing fluid because of its refraction index being similar to the one of water and the high transport capacity for carbon dioxide and oxygen. The setup is characterized by two independent syringe pumps to insert and withdraw the fluid into and from the lung and a custom-made control program for volume- or pressure-controlled ventilation modes. The presented results demonstrate the liquid-filling verified by optical coherence tomography and intravital microscopy (IVM) and the advantages of liquid-filling to OCT imaging of subpleural alveoli.

Optical coherence tomography (OCT) is a noninvasive imaging modality generating cross sectional and volumetric images of translucent samples. In Fourier domain OCT (FD OCT), the depth profile is calculated by a fast Fourier transformation of the interference spectrum, providing speed and SNR advantage and thus making FD OCT well suitable in biomedical applications. The interference spectrum can be acquired spectrally resolved in spectral domain OCT or time-resolved in optical frequency domain imaging (OFDI). Since OCT images still suffer from motion artifacts, especially under in vivo conditions, increased depth scan rates are required. Therefor, the principle of Fourier domain mode locking has been presented by R. Huber et al. circumventing the speed limitations of conventional FD OCT systems. In FDML lasers, a long single mode fiber is inserted in the ring resonator of the laser resulting in an optical round trip time of a few microseconds. Sweeping the wavelength synchronously by a tunable Fabry-Perot filter can provide wavelength sweeps with repetition rates up to a few MHz used for OFDI. Imaging of subpleural lung tissue for investigation of lung dynamics and its elastic properties is a further biomedical application demanding high-speed OCT imaging techniques. For the first time, the visualization of subpleural alveolar structures of a rabbit lung is presented by the use of an FDML-based OCT system enabling repetition rates of 49.5 kHz and 122.6 kHz, respectively.

The cornea is the single human tissue being transparent. This unique property may be explained by the particular structure of the cornea, but the precise role of each of its constituents remains unsolved. On other matter, prior to corneal transplant, graft must be evaluated during a sorting procedure where a technician assesses of its transparency quality. Nevertheless, this criterion remains subjective and qualitative. This study proposes to combine 3D imagery using Full-Field Optical Coherence Tomography jointly with angular resolved scattering measurement to achieve a quantitative transparency characterization of the cornea. The OCT provides micrometric resolution structural information about the cornea, and we observe the evolution occurring when oedema develops within the tissue. Scattering properties are evaluated and compared parallely, as the transparency of the graft. A close link between the scattering intensity level of the cornea and its thickness is highlighted through this study. Furthermore, the three-dimensional imagery offers a view over the structural modifications leading to a change in transparency, and the combination with scattering properties measurement provides clues over the characteristic scale of scatterers to consider for a better understanding of corneal transparency evolution. Achieving an objective and quantified parameter for the transparency would be helpful for a more efficient corneal graft sorting, and may be able to detect the presence of localized wounds as the ones related to a previous refractive surgery. However, the study of graft nearly eligible for corneal transplant would be needed to confirm the results this study presents.

We demonstrate Holoscopy -- a combination of full-field swept-source optical coherence tomography and digital holography. By using a simple Michelson interferometer setup, a rapidly tunable laser and combining scalar diffraction theory with standard Fourier-domain OCT signal processing we obtain depth invariant imaging quality.

Recently, in-vivo full eld (FF) optical coherence tomography (OCT) with an ultra-high speed camera has been presented for fast in vivo retinal imaging. By parallel A-scans acquisition, imaging with 1,5 million A-scans/s was shown with an extended illumination of the retina. In this paper, the image quality of FF-OCT images will be compared to conventional scanning OCT systems. The eect of the absence of a confocal aperture leading to crosstalk between adjacent image points will be shown and an experimental analysis of the systems lateral point spread function (PSF) in dependence of depth will be given and discussed.

In the present paper we investigate the possibility of narrowing the depth range of a physical Shack - Hartmann wavefront sensor (SH-WFS) by using coherence gating. We have already demonstrated a low coherence interferometry (LCI) set-up, capable of generating similar spots patterns as a conventional SH-WFS and also capable of eliminating stray reflections. Here, we evaluate the accuracy of wavefront measurements using a coherence-gated (CG)/SH-WFS. This is based on a Mach-Zehnder interferometer combined with a SH-WFS, that implements time-domain (TD)-LCI acquisition. The wavefront measurement errors introduced by the non-uniform distribution of the reference power over the photo-detector array were investigated. The effect on the centroid nodes accuracy due to different numbers of phaseshifting interferometry (PSI) steps applied was also evaluated. This novel technique has the potential of providing depth resolved aberration information, which can guide better correction in adaptive optics assisted OCT and confocal imaging instruments.

A method for axial resolution improvement by adequate spectral data fusion of two parallel acquired disjunct wavelength bands in the 0.8 μm and 1.3 μm region in the field of simultaneous dual-band optical coherence tomography (OCT) is presented. The applied spectral domain dual-band OCT system is illuminated by a supercontinuum laser light source and allows simultaneous imaging at 800 nm and 1250 nm with free-space axial resolutions better than 4.5 μm and 7 μm, respectively, over the entire depth scan range. Each wavelength band is analyzed with an individual spectrometer at an A-scan rate of 12 kHz. To further improve axial resolution, the 1250 nm spectra are fused with the 800 nm spectra considering the spectrometer-inherent non-linear fringe frequency course of the interference light. The phase and amplitude of the 1250 nm spectra are matched to the 800 nm spectra by means of short time Fourier transform analysis in order to obtain ideally continuous joint spectra. The joint spectra then undergo conventional spectral shaping, wave number resampling, windowing and fast Fourier transformation. First results for single A-scans of a glass slide as well as entire cross-sectional images of biological tissue yield an axial resolution improvement of 52 % compared to conventional single band imaging at 800 nm. The obtained A-scans show a good sharpness with a side lobe suppression of 30 dB. Additional investigations have to be employed for the full understanding of the underlying physical background and the optimization of the applied data processing for further image quality enhancement.

Retinal dystrophies (RD) are blinding diseases affecting visual acuity mostly at young age. Intrinsic optical signals (IOS) on optical coherence tomography (OCT) may give topographical information on injure of retinal function in these patients. We demonstrate light response of the healthy and diseased human retina by IOS on a commercially available spectral-domain OCT. Significant IOS could be measured in the healthy retina and in unchanged retinal sectors of the RD patients. Main responses were located in the outer retina (photoreceptors) and the nerve fiber layer. In affected areas of RD eyes IOS were significantly reduced or even absent. Functional OCT imaging was able to give information about retinal function in RD patients on a micrometer scale. These results could be of value for refined disease analysis and control of upcoming gene therapy studies.

In critical care medicine, artificial ventilation is a life saving tool providing sufficient blood oxygenation to patients suffering from respiratory failure. Essential for their survival is the use of protective ventilation strategies to prevent further lung damage due to ventilator induced lung injury (VILI). Since there is only little known about implications of lung tissue overdistension on the alveolar level, especially in the case of diseased lungs, this research deals with the investigation of lung tissue deformation on a microscale. A combined setup utilizing optical coherence tomography (OCT) and confocal fluorescence microscopy, is used to study the elastic behavior of the alveolar tissue. Three-dimensional geometrical information with voxel sizes of 6 μm × 6 μm × 11 μm (in air) is provided by OCT, structural information about localization of elastin fibers is elucidated via confocal fluorescence microscopy with a lateral resolution of around 1 μm. Imaging depths of 90 μm for OCT and 20 μm for confocal fluorescence microscopy were obtained. Dynamic studies of subpleural tissue were carried out on the basis of an in vivo mouse model post mortem, mimicking the physiological environment of an intact thorax and facilitating a window for the application of optical methods. Morphological changes were recorded by applying constant positive airway pressures of different values. With this, alveolar volume changes could clearly be recognized and quantified to form a compliance value of 3.5 • 10^-6(see manuscript). The distribution of elastin fibers was detected and will be subject to further elasticity analysis.

Artificial skin equivalents ASEs based on primary fibroblasts and keratinocytes show a high batch variance in their structural and morphological characteristics. Due to biological fluctuations and variable donor age, the growth processes of 3D tissue structure show a non constant quality. Since theses ASEs are used as testing system for chemicals, pharmaceuticals or cosmetics it is of major interest to know detailed and significant characteristics about each individual ASE. Until now, the microscopic analysis process is based on the destructive preparation of histologies allowing only the characterization on a random basis. In this study we present analytical methods to characterise each individual ASE by Optical Coherence Tomography OCT in combination with image processing tools. Therefore, we developed a fully automated OCT device, that performs automatic measurements of microtiter plates MTPs holing the ASEs in a sterile environment. We developed image processing algorithms to characterize the surface structure which may function as an indicator for defects in the epidermal stratum corneum. Further, we analysed the tomographic morphological structure of the ASEs. The results show, that variances in the growth state as well different collagen formation is detectable. In combination with dynamic threshold levels, we found, that OCT is a well suited technology for automatically characterizing artificial skin equivalents and may partly substitute the preparation of histologies.

We report about manufacturing of fully functional capillary network embedded into the multilayer tissue phantom. Polyvinyl chloride-plastisol was used as a host transparent medium. Scattering was introduced by adding the TiO₂submicron particles. OCT technique was used to characterize the manufactured phantoms and to monitor the vessels filling with different liquids.

We describe a simple swept-laser design that characterizes the emission bandwidth, linewidth, spectral shape and output noise. A short cavity Littmann configuration is used in which the semiconductor optical amplifier (SOA) lasing wavelength is tuned by a galvanometer with an 830 grooves per mm diffraction grating. A 3dB coupler extracts light from the cavity formed by the grating and end-mirror and the optical output uses to illuminate a balanced swept source optical coherence tomography (SS-OCT) interferometer incorporating a circulator, 3dB coupler, dispersion compensator and balanced detector. The SOA (SOA-1200-70-PM-20sB, Innolume GmbH) uses a novel III-V semiconductor quantum-dot gain medium. ASE is emitted between 1150nm and 1300nm at a drive current of 700mA. When used in the Littmann cavity laser a coherence length of about 10mm is produced, which is tunable over 60nm. The peak output power is 12mW. The swept-laser has been incorporated into a fiber-based SS-OCT system and used to image biological tissues. Axial resolution in air is 12 microns. Images of human palmar skin in-vivo are demonstrated, showing good resolution and contrast, with the stratum corneum, epidermis, rete ridges and epidermal-dermal junction visualized.

There are several methods known which are used to assess the quality of direct dental restorations, but most of them are invasive. These lead to the destruction of the probes and often no conclusion could be drawn in respect to the existence of any microleakage in the investigated areas of interest. Optical tomographic techniques are of particular importance in the medical imaging field, because these techniques can provide non-invasive diagnostic images. Using an en-face version of OCT, we have recently demonstrated real time thorough evaluation of quality of dental fillings. The purpose of this in vitro study was to validate the en face OCT imagistic evaluation of direct dental restoration by using scanning electron microscopy (SEM) and microcomputer tomography (μCT). Teeth after several treatment methods are imaged in order to detect material defects and to asses the marginal adaptation at the dental hard tissue walls. SEM investigations evidenced the nonlinear aspect of the interface between the filling material and the buccal and lingual walls in some samples. The results obtained by μCT revealed also some material defects inside the fillings and at the interfaces with the rootcanal walls. The advantages of the OCT method consist in non-invasiveness and high resolution. En face OCT investigations permit to visualize a more complex stratificated structure at the interface filling material/dental hard tissue and in the apical region.

We use Spectroscopic Optical Coherence Tomography (S-OCT) to identify substances by their spectral features in multi layer non-scattering samples. Depth resolved spectra are calculated by a windowed Fourier Transform in the spatial regime at discrete layer borders. By dividing subsequent spectra in an iterative manner transfer functions of the samples layers are calculated. Estimating these spectral transfer functions with high accuracy is still challenging, since the system´s transfer function introduces an error, which can be orders of magnitude higher than the spectroscopic information of the sample. We retrieve the buried spectroscopic information of the sample with high accuracy by correcting the spectral transfer functions with an identically structured reference sample. This spectral calibration method has many critical parameters and is in many cases not even possible. To perform substance identification without spectral calibration we implemented a pattern recognition algorithm, which allocates the transfer functions to known substances. Our results show that substance identification by spectral features with high performance without spectral calibration is feasible. Aside from that we modeled a simplified set up of our OCT system to minimize the error which is introduced by the optical system. The error can be reduced by orders of magnitude, when our improved optical set-up is used. This is an important step towards an improved system for S-OCT.

The detection and diagnosis of diseases have improved in recent years. Developments in diagnostic techniques have helped to improve treatment in the early stages and to avoid many risks to patients. One such technique is optical coherence tomography (OCT), which is used in many medical applications to perform internal microstructural imaging of the human body at high resolution (typically 10 μm), at high speed and in real time. OCT is non-invasive and can be used as a contact or non-contact technique to obtain an image. In medicine, there are many applications that involve OCT, such as in ophthalmology, gastroenterology, cardiology and oncology. This work demonstrates the use of an OCT system incorporating a swept laser source with a high sweep rate of 16 kHz over a wide range of wavelengths (1260 nm to 1390 nm) to measure the thickness of the peritoneal membrane in mice of different sizes and weights. The real axial line speed is limited by the source that is used in the OCT system. The optical source has a bandwidth of ▵λ =110 nm, centred at λ0 =1325 nm. The aim of this study is to investigate the thickening of the peritoneal membrane which can occur during prolonged peritoneal dialysis in mice. As part of this preliminary study, healthy mice of different weights were euthanized and the thickness of the peritoneal membrane was measured using OCT. The aim was to gather data on the expected range of thicknesses present in healthy animals for future studies. For this work, two locations on the peritoneal membrane of each of 20 mice were imaged.

In this paper we describe an algorithm which is able to compensate an unknown defocus. This algorithm has been applied to recovering defocused en-face Optical Coherence Tomography images. Lateral resolution about 5 um has been achieved at distance from focal plane about 10 Rayleigh lengths.. Both numerical simulations and experiment have been performed to demonstrate the ability of the method.

Early diagnosis of occlusal overload is an important issue in dental medicine. The high occlusal forces can cause irreversible damage to the dental hard tissues. Our study proposes the early microstructural characterization of occlusal overloaded bicuspids, with abnormal crown morphology, by en face optical coherence tomography (eFOCT). The dental samples were investigated using an eFOCT system operating at 1300 nm in B-scan and C-scan mode. The eFOCT images obtained from these teeth visualized cracks, which didn't reach the tooth surface. The μCT and histological images confirmed the microstructural defects identified on eFOCT images. In conclusion, eFOCT is a promising imaging method for the early diagnosis of occlusal overload on bicuspids with normal crown morphology and for the prophylaxis of dental wear.

Most of the colorectal cancer has grown from the adenomatous polyp. Adenomatous lesions have a well-documented relationship to colorectal cancer in previous studies. Thus, to detect the morphological changes between polyp and tumor can allow early diagnosis of colorectal cancer and simultaneous removal of lesions. OCT (Optical coherence tomography) has been several advantages including high resolution and non-invasive cross-sectional image in vivo. In this study, we investigated the relationship between the B-scan OCT image features and histology of malignant human colorectal tissues, also en-face OCT image and the endoscopic image pattern. The in-vitro experiments were performed by a swept-source optical coherence tomography (SS-OCT) system; the swept source has a center wavelength at 1310 nm and 160nm in wavelength scanning range which produced 6 um axial resolution. In the study, the en-face images were reconstructed by integrating the axial values in 3D OCT images. The reconstructed en-face images show the same roundish or gyrus-like pattern with endoscopy images. The pattern of en-face images relate to the stages of colon cancer. Endoscopic OCT technique would provide three-dimensional imaging and rapidly reconstruct en-face images which can increase the speed of colon cancer diagnosis. Our results indicate a great potential for early detection of colorectal adenomas by using the OCT imaging.

Optical Coherence Tomography (OCT) is a promising non-invasive imaging technology capable of carrying out 3D high-resolution cross-sectional images of the internal microstructure of examined material. However, almost all of these systems are expensive, requiring the use of complex optical setups, expensive light sources and complicated scanning of the sample under test. In addition most of these systems have not taken advantage of the competitively priced optical components available at wavelength within the main optical communications band located in the 1550 nm region. A comparatively simple and inexpensive full-field OCT system (FF-OCT), based on a superluminescent diode (SLD) light source and anti-stokes imaging device was constructed, to perform 3D cross-sectional imaging. This kind of inexpensive setup with moderate resolution could be easily applicable in low-level biomedical and industrial diagnostics. This paper involves calibration of the system and determines its suitability for imaging structures of biological tissues such as teeth, which has low absorption at 1550 nm.

Conventional perimeters are used routinely in various eye disease states to evaluate the central visual field and to quantitatively map sensitivity. However, standard automated perimetry proves difficult for retina and specifically macular disease due to the need for central and steady fixation. Advances in instrumentation have led to microperimetry, which incorporates eye tracking for placement of macular sensitivity values onto an image of the macular fundus thus enabling a precise functional and anatomical mapping of the central visual field. Functional sensitivity of the retina can be compared with the observed structural parameters that are acquired with high-resolution spectral domain optical coherence tomography and by integration of scanning laser ophthalmoscope-driven imaging. Findings of the present study generate a basis for age-matched comparison of sensitivity values in patients with macular pathology. Microperimetry registered with detailed structural data performed before and after intervention treatments provides valuable information about macular function, disease progression and treatment success. This approach also allows for the detection of disease or treatment related changes in retinal sensitivity when visual acuity is not affected and can drive the decision making process in choosing different treatment regimens and guiding visual rehabilitation. This has immediate relevance for applications in central retinal vein occlusion, central serous choroidopathy, age-related macular degeneration, familial macular dystrophy and several other forms of retina related visual disability.

This paper reports initial experimentation of a dual beam flow velocity estimation setup based on optical coherence tomography (OCT) for biomedical applications. The proposed work incorporates a low cost switching mechanism (rotating galvanometer mirror) for optical signal discrimination between adjacent fiber channels enabling quasisimultaneous multiple specimen scanning. A cascaded interferometric design is used with two sample output arms orientated in parallel to eachother. A cross-correlation computation between these two parallel sample beams yields a relative time delay, enabling assessment and quantification of flow velocities.

Optical Coherence Tomography (OCT) is a technique that allows imaging tissue in three spatial dimensions. Such a technique makes it possible to examine the subsurface of the tissue. The depth of penetration into the tissue can be tailored by tuning the wavelength of the light source. While in some cases it is desirable to obtain deep penetration of the sample, when scanning for cancerous changes, it may only be necessary to penetrate the first few hundred micrometres. The use of a shorter wavelength, while decreasing the penetration depth, will improve the resolution of the instrument. While images from OCT systems contain speckle and other artefacts, there are methods of evaluating the information by using image processing techniques. Of particular interest is the scattering coefficient that can be derived from the OCT data. Using discriminant techniques on the scattering data (such as principal components analysis), gives a sensitive way of differentiating between changes in structure in the tissue. An extensive data collection was performed on cervical tissue using samples that ranged from normal to invasive cancer. The histopathology of each sample was gathered and was classified from normal to cancer. The scattering profiles of the data were averaged and gradient analysis was performed, showing that for small distances into the sample there is a significant difference between scattering profiles between cancerous and normal tissue. PCA was also performed on the data showing grouping into various stages of cancer.

The study is aimed at developing new methods for diagnosing causes of impairment of female reproductive function. An increase of infertility and chronic pelvic pains syndrome, a growing level of latent diseases of this group, as well as a stably high percentage (up to 25% for infertility and up to 60% for the chronic pelvic pains syndrome) of undetermined origin make this research extremely important. As a complementary technique to laparoscopy we propose to use optical coherence tomography. We have acquired OCT images of different parts of fallopian tubes and pelvic peritoneum and analyzed OCT criteria of unaltered tissues. The OCT images of the isthmic part of fallopian tubes and peritoneum have been morphologically verified for pelvic inflammatory diseases (PID) and endometriosis. Changes in the optical properties of the studied organs typical of PID and endometriosis have been investigated. Based on comparative analysis of the OCT data and the results of histological studies OCT criteria of the considered diseases have been developed. Statistical analysis of diagnostic efficacy of OCT in the case of PID has been carried out. High (75-85%) diagnostic accuracy of OCT in PID is shown.

We demonstrate the use of a programmable optical spectral filter to compensate all orders of chromatic dispersion in an all-fibre Fourier-domain optical coherence tomography system at 1550 nm. The pointspread- function, originally 58 μm wide, asymmetric, with strong sidelobes, is successfully made symmetric and recompressed to 37 μm, close to the theoretical limit of 36 μm.

Three dimensional optical coherence tomography (OCT) is introduced as a valuable tool to analyze the pathogenesis of corneal diseases. Here, OCT in combination with a novel in vitro model for the dry eye syndrome enables an improved understanding of the underlying damaging process of the ocular surface. En-face OCT projections indicate a deep structural damage of the epithelium and anterior stroma by osmotic forces.