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The range of genetic and genomic resources available makes the mouse a powerful model for the genetic dissection of complex traits. Because accurate, high-throughput phenotypic characterisation is crucial to the success of such endeavours, we recently developed an optical coherence tomography (OCT) system with extended depth range scanning capability for measuring ocular component dimensions in mice. In order to test whether the accuracy and reproducibility of our OCT system was sufficient for gene mapping studies, we carried out an experiment designed to estimate the heritability of mouse ocular component dimensions. High-resolution, two dimensional tomograms were obtained for both eyes of 11 pairs of 8 week-old outbred MF1 mice. Subsequently, images were obtained when their offspring were aged 8 weeks. Biometric data were extracted after image segmentation, reconstruction of the geometric shape of each surface, and calculation of intraocular distances. The repeatability of measurements was evaluated for 12 mice scanned on consecutive days. Heritability estimates were calculated using variance components analysis. Sets of tomograms took ∼2 s to acquire. Biometric data could be obtained for 98% of the 130 eyes scanned. The 95% limits of repeatability ranged from ±6 to ±16 μm for the axial ocular component dimensions. The heritability of the axial ocular components was 0.6–0.8, except for corneal thickness, which had a heritability not significantly different from zero. In conclusion, axial ocular component dimensions are highly heritable in mice, as they are in humans. OCT with extended depth range scanning can be used to rapidly phenotype individual mice with sufficient accuracy and precision to permit gene mapping studies.

PURPOSE To demonstrate high-speed, high axial resolution optical coherence tomography (OCT) at 1060 nm with penetration to the sclera. The clinical feasibility of dense, high-speed sampling for higher levels of detail at the macula and optic nerve head is explored with respect to motion artifacts. METHODS A three-dimensional (3D) OCT system making use of a high-speed camera operating at 47,000 depth scans/s was developed. The 1010- to 1080-nm wavelength band leads to 6.7 microm effective axial resolution and enables the acquisition of retinal and choroidal 130 Megavoxel volumes of human subjects within 7 seconds. Motion artifacts were reduced by numeric postprocessing techniques. RESULTS Drift motion artifacts could be suppressed within fields up to 38 degrees x 38 degrees (approximately 1 cm(2)) using acquisition speeds of up to 74 frames/s at 512 x 512 pixel/frame. This isotropic OCT sampling of the human retina in vivo allowed reconstruction of the retinal microvasculature solely on vessel reflectivity, without the use of contrast agents, and revealed three interconnected capillary meshworks. Simultaneously in the choroid, the structure of the choriocapillaris, Sattler's layer, and Haller's layer were differentiated, and the choroidal-scleral interface was clearly delineated in densely sampled narrow- and wide-angle scans (>38 degrees). At the optic nerve head, the 3D fine structure of the lamina cribrosa and the circle of Zinn-Haller were visualized. CONCLUSIONS OCT almost centered within the 1060-nm water transmission window significantly profits from lower scattering and allows investigation of the retina and choroid at an unprecedented combination of penetration and high speed at high resolution and may provide superior clinical feasibility to commercial 800-nm devices.

Detection of acoustic waves is the cornerstone of photoacoustic tomography (PAT). Detection has conventionally been performed mechanically using ultrasonic transducers, or optically by interferometric techniques. We propose an interferometric detection scheme using low coherence interferometry (LCI) and discuss the challenges, advantages and limitations of applying this technique to photoacoustics.

A noninvasive, multimodal photoacoustic and optical coherence tomography (PAT/OCT) scanner for three-dimensional in vivo (3D) skin imaging is described. The system employs an integrated, all optical detection scheme for both modalities in backward mode utilizing a shared 2D optical scanner with a field-of-view of ~13 × 13 mm(2). The photoacoustic waves were detected using a Fabry Perot polymer film ultrasound sensor placed on the surface of the skin. The sensor is transparent in the spectral range 590-1200 nm. This permits the photoacoustic excitation beam (670-680 nm) and the OCT probe beam (1050 nm) to be transmitted through the sensor head and into the underlying tissue thus providing a backward mode imaging configuration. The respective OCT and PAT axial resolutions were 8 and 20 µm and the lateral resolutions were 18 and 50-100 µm. The system provides greater penetration depth than previous combined PA/OCT devices due to the longer wavelength of the OCT beam (1050 nm rather than 829-870 nm) and by operating in the tomographic rather than the optical resolution mode of photoacoustic imaging. Three-dimensional in vivo images of the vasculature and the surrounding tissue micro-morphology in murine and human skin were acquired. These studies demonstrated the complementary contrast and tissue information provided by each modality for high-resolution 3D imaging of vascular structures to depths of up to 5 mm. Potential applications include characterizing skin conditions such as tumors, vascular lesions, soft tissue damage such as burns and wounds, inflammatory conditions such as dermatitis and other superficial tissue abnormalities.

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.

Optical coherence tomography (OCT) is a non-invasive in vivo biomedical imaging modality capable of three-dimensional visualization of tissue morphology permitting imaging at high speed and sensitivity. Coherent Anti- Stokes Raman Scattering (CARS) is a nonlinear spectroscopic technique which provides molecular information due to a four wave mixing process. In order to extend the performance of OCT towards detecting the molecular fingerprint of biological samples a combined CARS/OCT setup has been developed that employs only a single ultrashort pulse Ti:Sapphire laser which enables high axial resolution OCT and simultaneously combined with a spectral shaper a CARS setup. During first measurements the same area of a sample was imaged twice, applying OCT and CARS consecutively. OCT was used to perform three-dimensional morphological screening. Due to CARS additional chemical information could be gained for two dimensions. The spectrum was modified computer controlled to match the requirements for the generation of a CARS signal whereas for OCT the unmodified spectrum was applied. Fluids such as dimethylsulfoxide (DMSO) and PBS were compared in a cuvette to demonstrate the functionality of the multimodal setup. As a biological sample a 100 m thickcr oss section through a human optic nerve surrounded by sclera was investigated.

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.

Visualization of cell migration during chemotaxis using spectral domain optical coherence tomography (OCT) requires non-standard processing techniques. Stripe artefacts and camera noise floor present in OCT data prevent detailed computer-assisted reconstruction and quantification of cell locomotion. Furthermore, imaging artefacts lead to unreliable results in automated texture based cell analysis. Here we characterize three pronounced artefacts that become visible when imaging sample structures with high dynamic range, e.g. cultured cells: (i) time-varying fixed-pattern noise; (ii) stripe artefacts generated by background estimation using tomogram averaging; (iii) image modulations due to spectral shaping. We evaluate techniques to minimize the above mentioned artefacts using an 800 nm optical coherence microscope. Effect of artefact reduction is shown exemplarily on two cell cultures, i.e. Dictyostelium on nitrocellulose substrate, and retinal ganglion cells (RGC-5) cultured on a glass coverslip. Retinal imaging also profits from the proposed processing techniques. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report a high-speed, dispersion-encoded, full-range (DEFR) swept-source optical coherence tomography system for in vivo ocular imaging and biometry of small animals. The fast DEFR algorithm removes the depth ambiguity, gives access to objects located at the zero delay position, and doubles the sampling depth to 2x5.0 mm (at -101 to -71 dB sensitivity) in a single scan using 2048 samples/depth scan 0.43 nm line width of a light source operating at 1056 nm with 70 nm tuning range. The acquisition speed (frames of 512 depth scans in 18.3 ms) permits precise on-line monitoring during positioning and provides cross-sectional views of the mouse eye. Preliminary studies demonstrate high-throughput, reproducible assessment of multiple biometric features (e.g., day-to-day reproducibility of axial length measurement +/-5.3 microm) that is insensitive to eye motion sufficient for long-term monitoring.

A novel combined photoacoustic tomography (PAT), optical resolution photoacoustic microscopy (ORPAM) and optical coherence tomography (OCT) instrument has been developed for imaging biological tissues. The system is based on the use of a Fabry-Perot (FP) polymer film ultrasound sensor. This is designed to be transparent to wavelengths between 590nm and 1200nm so that photoacoustic excitation laser pulses in this spectral range can be transmitted through the sensor into the underlying tissue to allow backward mode operation. The dual PAT-ORPAM capability of the system was demonstrated by imaging a tissue phantom composed of 7μm diameter carbon fibres immersed in an optically scattering liquid. The lateral and vertical spatial resolutions in ORPAM mode are approximately 7μm and 10μm respectively for sub-mm depths. In PAT mode, the lateral spatial resolution is less than 50μm for depths up to 5mm and the vertical resolution is approximately 10μm. The transparent nature of the FP polymer film ultrasound sensor offers a convenient platform for combining other optical imaging modalities with PAT and ORPAM. To illustrate this, a frequency-domain OCT system operating at 1060nm was integrated into the system and combined PAT/OCT images of the skin of a mouse were obtained in vivo.

Weakly scattering tree shrew retina has been imaged in vitro with full field swept source optical coherence tomography, visualising multiple intraretinal layers. The system utilises a 50nm bandwidth Superlum SLD, to acheive ~8μm of axial resolution and 4μm of transversal resolution. Volumetric images of retinal tissue with dimensions of 1248x936x678μm (horizontal by vertical by axial) were recorded in two second (equivalent of 153,600 A-scans per second) with a measured signal to noise ratio of 75dB. From the 5mW of SLD optical power available, 720μW illuminates the sample, giving a power per pixel of 4.6nW, ten times less power per pixel then standard FDOCT systems. After upgrading the camera and redesigning the optical beam path, 82dB of SNR was realised.

Conventionally, cell chemotaxis is studied on two-dimensional (2D) transparent surfaces due to limitations in optical and image data-collection techniques. However, substrates which more closely mimic the natural environment of cells are often opaque or three-dimensional (3D). The non-invasive label-free imaging technique of frequency domain optical coherence tomography (OCT) has high axial and transverse resolution of >4μm, comparatively high penetration depth and the ability to acquire volumes in a few seconds, therefore offering the potential to visualize moving cells in 3D (2D+time) and 4D (3D+time). Cell migration is demonstrated in 3D on opaque surfaces, and in 4D within an agarose gel. The speed and directionality of wild type (Ax2) cell movement is seen to be comparable on agar and nitrocellulose filter substrates. Differences can be clearly seen in the character of cell movement between Ax2, myosin knockout (mhcA-) and PLC null ~10μm Dictyostelium discoideum cells in 4D using ultrahigh resolution OCT. OCT is therefore shown to be a useful technique for the study of cell migration.

In this study, depth resolved measurements of absorption profiles in the wavelength range of 800 nm with a bandwidth of 140 nm are demonstrated using high speed spectroscopic frequency domain OCT (SOCT). With proper calibration, SOCT is able to extract absolute, depth resolved absorption profiles over the whole wavelength range at once without the need of tuning and performing measurements at single wavelengths sequentially. In addition, high acquisition speed in excess of 20 kHz allows to measure absorption dynamics with 50 µs time resolution, which might be useful for the investigation of pharmacokinetics or pharmacodynamics. SOCT of ∼600 µm thick single- and multilayered, weakly scattering phantoms with varying absorption in the range of 10–60 cm-1, equivalent to blood absorption in capillaries, is presented. SOCT measurements are compared with those using a spectrometer in transmission mode. For Indocyanine Green (ICG), a dynamic absorption measurement is demonstrated.

Conventionally, cell chemotaxis is studied on two-dimensional (2D) transparent surfaces, due to limitations in optical and image data-collection techniques. However, surfaces that more closely mimic the natural environment of cells are often opaque. Optical coherence tomography (OCT) is a noninvasive label-free imaging technique, which offers the potential to visualize moving cells on opaque surfaces and in three dimensions (3D). Here, we demonstrate that OCT is an effective means of time-lapse videomicroscopy of Dictyostelium cells undergoing 3D (2D+time) cell migration on nitrocellulose substrates and 4D (3D+time) chemotaxis within low-density agarose gels. The generated image sequences are compatible with current computer-based image-analysis software for quantification of cell motility. This demonstrates the utility of OCT for cell tracking and analysis of cell chemotaxis in complex environments. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We propose an algorithm that effectively cancels complex conjugate mirror terms from single OCT A-scans by utilizing the dispersion mismatch between reference and sample arm to generate full range tomograms. This allows distinguishing between complex conjugate mirror terms and real structures and is therefore called dispersion encoded full range (DEFR). Whereas the computational complexity is higher, acquisition speed is not compromised since no additional A-scans need to be measured which makes this technique also robust against phase fluctuations. The iterative algorithm uses numeric dispersion compensation and exhibits no reduction in resolution compared to standard processing. Residual leakage of mirror terms is reduced by incorporating further knowledge such as the power spectrum of the light source. The suppression ratio of mirror signals is more than 50 dB and thus comparable to other complex FD-OCT techniques which use more than one A-scan.

In this study, depth resolved measurements of absorption pro“les in the wavelength range of 800 nm with abandwidth of 140 nm are demonstrated using high speed spectroscopic frequency domain OCT (SOCT). Withproper calibration, SOCT is able to extract absolute, depth resolved absorption pro“les over the whole wavelengthrange at once without the need of tuning and performing measurements at single wavelengths sequentially. Inaddition, high acquisition speed in excess of 20 kHz allows to measure absorption dynamics with 50 µ s timeresolution, which might be useful for the investigation of pharmacokinetics or pharmacodynamics.SOCT of 600 µ m thick single- and multilayered, weakly scattering phantoms with varying absorption inthe range of 10 60 cm 1 , equivalent to blood absorption in capillaries, is presented. SOCT measurements arecompared with those using a spectrometer in transmission mode. For Indocyanine Green (ICG), a dynamicabsorption measurement is demonstrated.Keywords: optical coherence tomography, spectroscopy, depth-resolved, functional imaging

Using high speed ultrahigh resolution optical coherence tomography (OCT) at 800nm, non-invasive 3D cellular imaging has been accomplished. Cellular resolution imaging on and within these types of substrates is not possible with conventional microscopy techniques such as interference contrast microscopy, and requires the use of fluorescent staining. It is possible to achieve data acquisition rates of 20,000 samples per second with OCT which, in combination with its high axial and transverse resolution (>2-3μm), allows it to be used as a non-invasive technique to analyze cell migration in 3D with time. Comparatively high penetration depth also makes OCT a uniquely suited imaging technique for visualization of cells within a 3D construct. In this paper it is demonstrated that it is possible to resolve ~10μm Dictyostelium discoideum cells, a well established and useful model for investigation of cell motility and chemotaxis, in 3D and follow them in time lapse using an 800nm ultrahigh resolution high speed frequency domain based OCT microscope. Ultimately, these visualization techniques could enable monitoring of cell behavior in regenerative medicine, for example tracking of individual cells within a cell scaffold.

We present in vivo frequency domain optical coherence tomography of the human retina and choroid in the 1060 nm water transmission window with 72 nm optical bandwidth (

Purpose To demonstrate acquisition and analysis methods for depth-resolved observation of slow retinal physiology induced changes in infrared backscatter in vivo. Methods A dark-adapted human was briefly subjected to a localized photobleach. For 20 min before and 30 min after the stimulus, volumetric optical coherence tomograms were collected partially overlapping the bleached region. Tomograms were segmented into retinal layers by a newly described algorithm exploiting information in adjacent B-scans. En face fundus images extracted from major intraretinal layers were laterally registered manually. Time series summarizing the observed backscatter in selected layers for the bleached and unbleached areas are shown with a variety of corrections and normalizations applied: tomograms were corrected for inherent sensitivity roll-off, and the ratio between other layers and an assumed unchanging layer (retinal pigment epithelium), as well as the ratio of the stimulated area to the unstimulated area, were calculated. Results Adjacent B-scan information allows a simpler segmentation algorithm to be used. Sensitivity roll-off correction reduces signal variability due to eye motion. After normalizations, the signal correlated with the stimulus appears strongest at the photoreceptor inner-outer segment junction. Conclusions Demonstrated methods manage data complexity and reduce uncorrelated signal variability. This single trial warrants further investigation of intrinsic optical signals to observe slow physiologic responses.

Biomedical Imaging Group, School of Optometry & Vision Sciences,Cardiff University, Wales, UKAbstract. Ultra-high speed optical coherence tomography employing an ultra-broadband lightsource has been combined with adaptive optics utilizing a single high stroke deformable mirrorandchromaticaberrationcompensation. Thereductionofmotionartefacts,geometricandchro-matic aberrations (pancorrection) permits to achieve an isotropic resolution of 2 3 µminthehuman eye. The performance of this non-invasive imaging modality enables to resolve cellularstructuresincludingconephotoreceptors, nerve“brebundlesandcollagenousplatesofthelam-ina cribrosa, and retinal pigment epithelial (RPE) cells in the human retina in vivo with superiordetail. Alterations of cellular morphology due to cone degeneration in a colour-blind subjectare investigated in ultra-high resolution with selective depth sectioning for the “rst time.Keywords: adaptive optics, achromatizer, pancorrection, photoreceptors, retinal pigment ep-ithelial (RPE) cells, lamina cribrosa, colour-blind, retinal pathology

The amount of light backscattered from neural tissues changes as a function of activation and is the basis of intrinsic optical signal (IOS). Typically IOS is observed by looking at darkfield scatter with a CCD camera. The retina is a calculating portion of the central nervous grey matter with an optical quality window, and is likewise easily stimulated optically. Therefore the retina makes a natural model for observing neural interactions with optical tools. Optical coherence tomography (OCT) is an imaging modality that provides depth resolved maps of the amount of light backscattered from tissue that has wide clinical use for observing structural defects associated with ophthalmic disease. It is therefore also natural to use OCT as means to observe intrinsic optical signal in the retina. Indeed, OCT has recently been used to observe an increase in backscatter at the level of the outer photoreceptor segment after bleaching light stimulation in an excised rabbit retina. We are currently attempting to translate this result towards a diagnostic technique for photoreceptor dysfunction in human patients. Currently patient motion and physiological noise present barriers that must be overcome with increases in technological and experimental sophistication. This proceeding reviews current understanding of retinal intrinsic optical signal and discusses its measurement challenge.

Cellular in vivo visualization of the three dimensional architecture of individual human foveal cone photoreceptors is demonstrated by combining ultrahigh resolution optical coherence tomography and a novel adaptive optics modality. Isotropic resolution in the order of 2-3 microm, estimated from comparison with histology, is accomplished by employing an ultrabroad bandwidth Titanium:sapphire laser with 140 nm bandwidth and previous correction of chromatic and monochromatic ocular aberrations. The latter, referred to as pancorrection, is enabled by the simultaneous use of a specially designed lens and an electromagnetically driven deformable mirror with unprecedented stroke for correcting chromatic and monochromatic aberrations, respectively. The increase in imaging resolution allows for resolving structural details of distal elements of individual foveal cones: inner segment zones--myoids and ellipsoids--are differentiated from outer segments protruding into pigment epithelial processes in the retina. The presented technique has the potential to unveil photoreceptor development and pathogenesis as well as improved therapy monitoring of numerous retinal diseases.

Spectrometer based optical coherence tomography at 1050nm with >70nm of spectral bandwidth, acquiring 48k depth scans per second for deeper penetration and isotropic visualisation of the full three dimensional choroidal vasculature is demonstrated in vivo.

The integration of adaptive optics and an achromatizing lens into an ultra-high resolution OCT system enables three-dimensional imaging of photoreceptor morphology. Optophysiology might lead to the extraction of depth-resolved information about retinal function.

Purpose: Optical coherence tomography is a well established imaging modality for the retina at 800 nm, but is limited in its capability to visualize through scattering tissue, like through cataract or into the choroid. Methods: Utilizing the lower scattering at longer wavelengths (1050 nm) high speed (>17 kHz), high axial resolution (~7 μm) optical coherence tomography (OCT) demonstrates its abil-ity to exploit the three dimensional anatomic microstructure of the choroid. Volumetric images, obtained with spectrometer based frequency domain OCT system are presented and compared with their counterparts acquired at the commonly used 800 nm range. Results: Tomograms of normals and patients with pathologic morphological changes of the retinal structure as well as with cataract depict improved signal strength and image contrast at the longer wavelength. The deeper penetration allows reconstruction of the choroidal vascular structure despite strong scattering of superficial tissues at the retinal pigment epithelium, the choriocapillaris also including pathologic retinal thickening. Visualisation of modifications in the choroidal vascular structure associated with wet age related macu-lar degeneration or diabetic retinopathy indicate the diagnostic potential of this technique. Furthermore, being well outside the spectral sensitivity of the eye the wavelength band at 1050 nm also allows for depth resolved profiling of reflectivity changes to directly moni-tor light stimulus related retinal activity, without interference due to the sampling OCT beam. Conclusions: Imaging at 1050 nm enables not only to track morphological but also functional changes of the retina.

Objective imaging of the optic nerve structure has become central to the management of patients with glaucoma. There is an urgent need in diagnosis and staging for reliable objective precursors and markers. Three-dimensional ultrahigh-resolution frequency domain optical coherence tomography (3D UHR OCT) holds particular promise in this respect since it enables volumetric assessment of intraretinal layers including tomographic data for the retinal nerve fiber layer (RNFL) and optic nerve head. The integrated analysis of this information and the resolution advantage has enabled the development of more informative indices of axonal damage in glaucoma compared with measurements of RNFL thickness and cup-to-disc ratio provided by commercial OCT devices. The potential for UHR OCT in enabling the combined analysis of tomographic and volumetric data on retinal structure is explored. A novel parameter was developed; the three-dimensional minimal distance as the optical correlate of true retinal nerve fiber layer thickness around the optic nerve head region. For the purposes of this pilot study, we present data from a normal subject and from two patients with characteristic optic nerve and retinal nerve fiber layer changes secondary to glaucoma.

Current signal post processing in spectrally encoded frequency domain (FD) optical coherence microscopy (OCM) and optical coherence tomography (OCT) uses Fourier transforms in combination with non-uniform resampling strategies to map the k-space data acquired by the spectrometer to spatial domain signals which are necessary for tomogram generation. We propose to use a filter bank (FB) framework for the remapping process. With our new approach, the spectrometer is modeled as a critically sampled analysis FB, whose outputs are quantized subband signals that constitute the k-space spectroscopic data. The optimal procedure to map this data to the spatial domain is via a suitably designed synthesis FB which has low complexity. FB theory additionally states that 1) it is possible to find a synthesis FB such that the overall system has the perfect reconstruction (PR) property; 2) any processing on critically sampled subband signals (as done in current schemes) results in aliasing artifacts. These perspectives are evaluated both theoretically and experimentally. We determine the analysis FB corresponding to our FD-OCM system by using a tunable laser and show that for our grating-based spectrometer - employing a CCD-line camera - the non-uniform resampling together with FFT indeed causes aliasing terms and depth dependent signal attenuation. Furthermore, we compute a finite impulse response based synthesis FB and assess the desired PR property by means of layered samples. The resulting images exhibit higher resolution and improved SNR compared to the common FFT-based approach. The potential of the proposed FB approach opens a new perspective also for other spectroscopic applications.

A new Aerosol Raman Lidar equipped with a frequency doubled and tripled Nd:YAG laser, and a 1140 mm diameter receiving telescope has been developed for measurements of aerosol backscatter and extinction coefficients and depolarization in the altitude range 5 to 50 km. Light collected by the telescope is split according to polarizational status and fed via glass fibres to the ten channel filter polychromator and afterwards to photon counting devices. The lidar optics are mounted on a removable carrier inside a rugged and air-conditioned 20 ft standard container. The system can be operated under extreme climatic conditions. It will be tested on a cruise of the German research vessel Polarstern from Europe to South America in late 1996.

Dispersion encoded full-range (DEFR) frequency-domain optical coherence tomography (FD-OCT) and its enhanced version, fast DEFR, utilize dispersion mismatch between sample and reference arm to eliminate the ambiguity in OCT signals caused by non-complex valued spectral measurement, thereby numerically doubling the usable information content. By iteratively suppressing asymmetrically dispersed complex conjugate artifacts of OCT-signal pulses the complex valued signal can be recovered without additional measurements, thus doubling the spatial signal range to cover the full positive and negative sampling range. Previously the computational complexity and low processing speed limited application of DEFR to smaller amounts of data and did not allow for interactive operation at high resolution. We report a graphics processing unit (GPU)-based implementation of fast DEFR, which significantly improves reconstruction speed by a factor of more than 90 in respect to CPU-based processing and thereby overcomes these limitations. Implemented on a commercial low-cost GPU, a display line rate of ∼21;000 depthscans∕s for 2048 samples∕depth scan using 10 iterations of the fast DEFR algorithm has been achieved, sufficient for real-time visualization in situ. © 2012 Society of Photo-Optical Instrumentation Engi

A novel statistical model based on texture and shape for fully automatic intraretinal layer segmentation of normal retinal tomograms obtained by a commercial 800nm optical coherence tomography (OCT) system is developed. While existing algorithms often fail dramatically due to strong speckle noise, non-optimal imaging conditions, shadows and other artefacts, the novel algorithm’s accuracy only slowly deteriorates when progressively increasing segmentation task difficulty. Evaluation against a large set of manual segmentations shows unprecedented robustness, even in the presence of additional strong speckle noise, with dynamic range tested down to 12dB, enabling segmentation of almost all intraretinal layers in cases previously inaccessible to the existing algorithms. For the first time, an error measure is computed from a large, representative manually segmented data set (466 B-scans from 17 eyes, segmented twice by different operators) and compared to the automatic segmentation with a difference of only 2.6% against the inter-observer variability.

The dispersion mismatch between sample and reference arm in frequency-domain optical coherence tomography (OCT) can be used to iteratively suppress complex conjugate artifacts and thereby increase the imaging range. In this paper, 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 experimentally using a multilayered scattering phantom and in vivo retinal tomograms at 800 nm. Best results have been achieved with 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 typically 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 also demonstrated by introducing an additional optical fibre in the sample arm.

The capability of optical coherence tomography (OCT) to perform "optical biopsy" of tissues within a depth range of 1 to 2 mm with micron-scale resolution in real time makes it a promising biomedical imaging modality for dermatologic applications. Three high-speed, spectrometer-based frequency-domain OCT systems operating at 800 nm (20,000 A-scans/s), 1060 nm, and 1300 nm (both 47,000 A-scans/s) at comparable signal-to-noise ratio (SNR), SNR roll-off with scanning depth, and transverse resolution (

In this study, depth resolved measurements of absorption profiles in the wavelength range of 800 nm with a bandwidth of 140 nm are demonstrated using high speed spectroscopic frequency domain OCT(SOCT) and a full range reconstruction algorithm (dispersion encoded full range, DEFR). The feasibility of the algorithm for SOCT is tested in simulation and experiment. With proper calibration, SOCT with DEFR is able to extract absolute, depth resolved absorption profiles over the whole wavelength range at once without the need of tuning and performing measurements at single wavelengths sequentially. The superior acquisition speed and better phase stability in frequency domain as compared to time domain results in a better reproducibility and practicability for spectroscopic measurements. In addition, high acquisition speed in excess of 20 kHz allows to measure absorption dynamics with 50 micros time resolution, which might be useful for the investigation of pharmacokinetics or pharmacodynamics. SOCT of approximately 600 microm thick single- and multilayered, weakly scattering phantoms with varying absorption in the range of 5-80 cm(-1), equivalent to blood absorption in capillaries, is presented. SOCT measurements are compared with those using a spectrometer in transmission mode. For Indocyanine Green (ICG), a dynamic absorption measurements are demonstrated.

This paper presents a successful combination of ultra-high speed (120,000 depth scans/s), ultra-high resolution optical coherence tomography with adaptive optics and an achromatizing lens for compensation of monochromatic and longitudinal chromatic ocular aberrations, respectively, allowing for non-invasive volumetric imaging in normal and pathologic human retinas at cellular resolution. The capability of this imaging system is demonstrated here through preliminary studies by probing cellular intraretinal structures that have not been accessible so far with in vivo, non-invasive, label-free imaging techniques, including pigment epithelial cells, micro-vasculature of the choriocapillaris, single nerve fibre bundles and collagenous plates of the lamina cribrosa in the optic nerve head. In addition, the volumetric extent of cone loss in two colour-blinds could be quantified for the first time. This novel technique provides opportunities to enhance the understanding of retinal pathogenesis and early diagnosis of retinal diseases.

Recent substantial developments in light source and detector technology have initiated a paradigm shift in retinal optical coherence tomography (OCT) performance. Broad bandwidth light sources in the 800 nm and 1060 nm wavelength region enable axial OCT resolutions of 2-3 mum and 5-7 mum, respectively. Novel high speed silicon based CMOS cameras at 800 nm and InGaAs based CCD cameras in combination with frequency domain OCT technology enable data acquisition speeds of up to 47,000 A-scans/s at 1060 nm and up to 312,500 A-scans/s at 800 nm. Combining ultrahigh axial resolution, ultrahigh speed OCT at 800 nm with pancorrected adaptive optics allows volumetric in vivo cellular resolution retinal imaging. Commercially available three-dimensional (3D) retinal OCT at 800 nm (20,000 A-scans/s, 6 mum axial resolution) is compared to ultrahigh speed 3D retinal imaging at 800 nm (160,000 A-scans/s, 2-3 mum axial resolution), high speed 3D choroidal imaging at 1060 nm (47,000 Ascan/ second, 6-7 mum axial resolution) and cellular resolution retinal imaging at 800 nm using adaptive optics OCT at 160,000 A-scans/second with isotropic resolution of ~2 mum. Analysis of the performance of these four imaging modalities applied in normal and pathologic eyes focusing on motion artifact free volumetric retinal imaging and revealing novel, complementary morphological information due to enhanced resolution, speed and penetration is presented.

We propose an iterative algorithm that exploits the dispersion mismatch between reference and sample arm in frequency-domain optical coherence tomography (FD-OCT) to effectively cancel complex conjugate mirror terms in individual A-scans and thereby generate full range tomograms. The resulting scheme, termed dispersion encoded full range (DEFR) OCT, allows distinguishing real structures from complex conjugate mirror artifacts. Even though DEFR-OCT has higher post-processing complexity than conventional FD-OCT, acquisition speed is not compromised since no additional A-scans need to be measured, thereby rendering this technique robust against phase fluctuations. The algorithm uses numerical dispersion compensation and exhibits similar resolution as standard processing. The residual leakage of mirror terms is further reduced by incorporating additional knowledge such as the power spectrum of the light source. The suppression ratio of mirror signals is more than 50 dB and thus comparable to complex FD-OCT techniques which use multiple A-scans.

Depth dependent broadening of the axial point spread function due to dispersion in the imaged media, and algorithms for postprocess correction, have been previously described for both time domain and frequency domain optical coherence tomography. We show that homogeneous media dispersion artifacts disappear when frequency domain samples are acquired with uniform spacing in circular wavenumber, as opposed to uniform sampling in optical frequency. We further explicate the source of this point spread broadening and simulate its magnitude in aqueous media. We experimentally demonstrate media dispersion compensation in high dispersion glass by choosing sample frequencies at equal intervals of media index of refraction divided by vacuum wavelength, and we recover unbroadened reflections without an additional postprocessing step.

Two high speed systems for spectrometer based frequency domain optical coherence tomography are presented. A device operating at 800 nm, based on the Basler Sprint CMOS camera with linerates of up to 312,000 lps and a device based on the Goodrich SUI LHD 1024 px camera at 1060 nm with 47,000 lps are applied in a clinical environment to normal subjects. The feasibility of clinical high and ultra high-resolution optical coherence tomography (OCT) devices for retinal imaging at different wavelengths, capable of isotropic sampling with 70 to 600 frames per second at 512 depth scans/frame for widefield imaging and high density sampling at 1 Gvoxel are demostrated.