Evaluation of a cheap ultrasonic stage for light source coherence function measurement, optical coherence tomography and dynamic focusing

We evaluate the performance of a cheap ultrasonic stage in setups related to optical coherence tomography. The stage was used in several configurations: (1) optical delay line in an optical coherence tomography (OCT) setup; (2) as a delay line measuring coherence function of a low coherence source (e. g. superluminescent diode) and (3) in a dynamic focusing arrangement. The results are as follows: the stage is suitable for coherence function measurement (coherence length up to 70 mu m) of the light source and dynamic focusing. We found it unsuitable for OCT due to an unstable velocity profile. Despite this, the velocity profile has a repeatable shape (4% over 1000 A-scans) and slight modifications to the stage promise wider applications

In vivo measurement of skin surface strain and sub-surface layer deformation induced by natural tissue stretching.

Stratum corneum and epidermal layers change in terms of thickness and roughness with gender, age and anatomical site. Knowledge of the mechanical and tribological properties of skin associated with these structural changes are needed to aid in the design of exoskeletons, prostheses, orthotics, body mounted sensors used for kinematics measurements and in optimum use of wearable on-body devices. In this case study, optical coherence tomography (OCT) and digital image correlation (DIC) were combined to determine skin surface strain and sub-surface deformation behaviour of the volar forearm due to natural tissue stretching. The thickness of the epidermis together with geometry changes of the dermal-epidermal junction boundary were calculated during change in the arm angle, from flexion (90°) to full extension (180°). This posture change caused an increase in skin surface Lagrange strain, typically by 25% which induced considerable morphological changes in the upper skin layers evidenced by reduction of epidermal layer thickness (20%), flattening of the dermal-epidermal junction undulation (45-50% reduction of flatness being expressed as Ra and Rz roughness profile height change) and reduction of skin surface roughness Ra and Rz (40-50%). The newly developed method, DIC combined with OCT imaging, is a powerful, fast and non-invasive methodology to study structural skin changes in real time and the tissue response provoked by mechanical loading or stretching

Common path michelson interferometer based on multiple reflections within the sample arm:Sensor applications and imaging artefacts

We present a simple common path dual beam interferometric sensor platform using a low-coherence source. In our implementation we exploit (in a controlled manner) the multiple reflections within the sample arm to provide the reference arm. This simple setup removes the need for a separate reference arm and allows an alternative architecture for using low-coherence sources in interferometric sensors. We demonstrate the sensor characteristics by using it as a vibrometer and displacement sensor (without directional sensitivity). Vibration frequencies from 50 to 300 Hz were measured with 1% precision while displacements from 6 to 24 mu m were measured with 125 nm precision and 625 nm resolution. We discuss improvements, limitations and potential applications. Lastly, we point to the artefactual appearance of this sensor in optical coherence tomography setups.</p

Application of intravital microscopy in studies of tumor microcirculation

To grow and progress, solid tumors develop a vascular network through co-option and angiogenesis that is characterized by multiple structural and functional abnormalities, which negatively influence therapeutic outcome through direct and indirect mechanisms. As such, the morphology and function of tumor blood vessels, plus their response to different treatments, are a vital and active area of biological research. Intravital microscopy (IVM) has played a key role in studies of tumor angiogenesis, and ongoing developments in molecular probes, imaging techniques, and postimage analysis methods have ensured its continued and widespread use. In this review we discuss some of the primary advantages and disadvantages of IVM approaches and describe recent technological advances in optical microscopy (e.g., confocal microscopy, multiphoton microscopy, hyperspectral imaging, and optical coherence tomography) with examples of their application to studies of tumor angiogenesis

Evaluation of a swept-laser optical coherence tomography light source based on a novel quantum-dot based semiconductor optical amplifier

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.</p

HDF morphology on PCL fibres.

<p>Nucleus (DAPI in blue) and cytoskeleton (phalloidin-TRITC in red) of HDFs seeded on random and aligned scaffolds. HDF morphology was visualised at day 7 (top) and 21 (bottom) imaged at different depths (5–40 µm). Cells on random fibres were generally attached in multiple directions while cells on aligned fibres were spindle shaped and aligned in the fibre direction. White arrows indicate direction of scaffold fibre alignment. Scale bars are 50 µm.</p

3D images of collagen SHG from HDF-seeded constructs at day 21.

<p>Images of HDF deposited-collagen on random and aligned scaffolds were compiled from 35 µm z-stacks (2.5 µm slices). A rotated 3D view from the top and bottom of the constructs are shown along with 2D images in the z-plane taken from both the horizontal and longitudinal edges.</p