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.
We investigate optical coherence tomography (OCT) as a method for imaging bone. The OCT images are compared directly to those of the standard methods of bone histology and microcomputed tomography (µCT) on a single, fixed human femoral trabecular bone sample. An advantage of OCT over bone histology is its noninvasive nature. OCT also images the lamellar structure of trabeculae at slightly higher contrast than normal bone histology. While µCT visualizes the trabecular framework of the whole sample, OCT can image additionally cells with a penetration depth limited approximately to 1 mm. The most significant advantage of OCT, however, is the absence of toxic effects (no ionizing radiation), i.e., continuous images may be made and individual cell tracking may be performed. The penetration depth of OCT, however, limits its use to small animal models and small bone organ cultures.
We present a method to obtain additional depth resolved spectroscopic information from standard
frequency domain optical coherence tomography (FDOCT) images. This method utilizes Fourier transforms of signal peaks within the complex FDOCT depth profiles to extract depth resolved spectroscopic information. For verification of the depth resolved spectroscopic image analysis method, theoretical simulations as well as experimental studies are demonstrated. Both show accurate depth resolved spectroscopic reconstruction enabling a depth allocation of material specific transmission spectra due to absorption. This analysis tool improves significantly the image contrast and allows image mapping of material specific spectral characteristics.
Optical coherence tomography (OCT) and micro-computed tomography (μCT) were applied to a bone sample, a
3x4x4mm cube of fixed substantia spongiosa from an arthritic human hip. Three-dimensional image sets (1.0mm x
0.9mm x 1.6mm) were acquired with both imaging systems for the same volume of interest. For better navigation, the
sample surface was additionally imaged with microscopy. The resulting OCT images were compared stepwise to the
according μCT images, showing a high correlation regarding the visualization of individual trabeculae. System based
imaging differences were also found: due to scattering, OCT is limited to an imaging depth of about 1mm, while μCT is
capable of imaging the complete trabecular bone architecture. However, OCT images cells and the inner bone structures
in contrast to μCT at similar nominal resolutions (5μm respectively 6.5μm).
We present a new method to obtain additional spectroscopic information by analyzing conventional Fourier domain
optical coherence tomography (FDOCT) data. Conventional FDOCT data are based on the analysis of backscattered
light, while spectral FDOCT (SFDOCT) also evaluates the absorption characteristics of the different sample layers. This
is a result of analyzing the peak shapes of the single, one dimensional depth profiles regarding their modification due to
absorption characteristics of the sample layers. A concept for depth allocation of different absorption characteristics is
We present an electronically tuneable external cavity diode laser that incorporates a digital micromirror device for
spectral tuning. The design allows for high tuning speed of 0.85nm/ms over a typical tuning range of 47.4nm. The laser-system
is characterized concerning spectral and time-related aspects. Application of the laser in a swept-source optical
coherence tomography system is demonstrated.