A simplified method to measure choroidal thickness using adaptive compensation in enhanced depth imaging optical coherence tomography

10.1371/journal.pone.0096661PLoS ONE95-POLN

Multimodal simultaneous photoacoustic tomography, optical resolution microscopy, and OCT system

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 7 mu m diameter carbon fibres immersed in an optically scattering liquid. The lateral and vertical spatial resolutions in ORPAM mode are approximately 7 mu m and 10 mu m respectively for sub-mm depths. In PAT mode, the lateral spatial resolution is less than 50 mu m for depths up to 5mm and the vertical resolution is approximately 10 mu m. 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

Miniature spectrometer and beam splitter for an optical coherence tomography on a silicon chip

Optical coherence tomography (OCT) has enabled clinical applications that revolutionized in vivo medical diagnostics. Nevertheless, its current limitations owing to cost, size, complexity, and the need for accurate alignment must be overcome by radically novel approaches. Exploiting integrated optics, we assemble the central components of a spectral-domain OCT system on a silicon chip. The spectrometer comprises an arrayed-waveguide grating with 136-nm free spectral range and 0.21-nm wavelength resolution. The beam splitter is realized by a non-uniform adiabatic coupler with its 3-dB splitting ratio being nearly constant over 150 nm. With this device whose overall volume is 0.36 cm3 we demonstrate high-quality in vivo imaging in human skin with 1.4-mm penetration depth, 7.5-μm axial resolution, and a signal-to-noise ratio of 74 dB. Considering the reasonable performance of this early OCT on-a-chip system and the anticipated improvements in this technology, a completely different range of devices and new fields of applications may become feasible

Miniature spectrometer and beam splitter for an integrated optical coherence tomography system

In this paper we present an important step toward a cheap, compact, and quasi-maintenance-free spectral-domain OCT system by integrating its central components, the beam splitter and spectrometer, on a silicon chip

Toward spectral-domain optical coherence tomography on a silicon chip

In-vivo imaging was demonstrated with a depth range of 1.4 mm and axial resolution of 7.5 µm by using a miniaturized spectral-domain optical coherence tomography system comprising an integrated spectrometer and a beam splitter

Advanced integrated spectrometer designs for miniaturized optical coherence tomography systems

Optical coherence tomography (OCT) has enabled clinical applications that revolutionized in vivo medical diagnostics. Nevertheless, its current limitations owing to cost, size, complexity, and the need for accurate alignment must be overcome by radically novel approaches. Exploiting integrated optics, the central components of a spectral-domain OCT (SD-OCT) system can be integrated on a chip. Arrayed-waveguide grating (AWG) spectrometers with their high spectral resolution and compactness are excellent candidates for on-chip SD-OCT systems. However, specific design-related issues of AWG spectrometers limit the performance of on-chip SD-OCT systems. Here we present advanced AWG designs which could overcome the limitations arising from free spectral range, polarization dependency, and curved focal plane of the AWG spectrometers. Using these advanced AWG designs in an SD-OCT system can provide not only better overall performance but also some unique aspects that a commercial system does not have. Additionally, a partially integrated OCT system comprising an AWG spectrometer and an integrated beam splitter, as well as the in vivo imaging using this system are demonstrated

Endoscope-tip interferometer for ultrahigh resolution frequency domain optical coherence tomography in mouse colon

Frequency domain optical coherence tomography (FD-OCT) allows interferometer topologies with simplified system construction and handling. Problems of dispersion and polarization matching between the sample and reference arms, as well as beamsplitter spectral non-uniformity, are mitigated when the interferometer is wholly contained in the endoscope tip. A common path set-up, using a reference reflection originating from the inside surface of the glass envelope at the distal end of the endoscope, and an alternative approach with more efficient collection of the reference light using a novel beamsplitter design have been developed. High speed (20,000 A-lines/s) ultrahigh axial resolution (2.4 μm) tomograms of mouse colon have been acquired using a 2 mm outer diameter endoscope in vivo. The FD-OCT system uses a compact mode-locked Ti:Al2O3 laser emitting a broad spectrum (160 nm full- width-half-maximum) centered at 800 nm in combination with a CCD based, spectrally sensitive detector

Adaptive optics using a liquid crystal spatial light modulator for ultrahigh-resolution optical coherence tomography

Three-dimensional ultrahigh resolution optical coherence tomography (UHR OCT) and adaptive optics (AO) are combined using a liquid crystal programmable phase modulator (PPM) as a correcting device for the first time. AO is required for correcting ocular aberrations in moderate and large pupils in order to achieve high resolution retinal images. The capabilities of the PPM are studied using polychromatic light. Volumetric UHR OCT images of the living retina with AO, obtained with up 25000 A scans/s and high resolution (~5x5x3 µm; transverse (x) x transverse (y) x axial) are recorded, enabling visualization of interesting intraretinal morphological structures. Cellular retinal features, which might correspond to groups of terminal bars of photoreceptors at the level of the external limiting membrane, are resolved. Benefits and limitations of the presented technique are finally discussed