Optical Coherence Tomography as a non-invasive imaging technology for tissue examination

OCT is an imaging technology that allows the non-invasive and structure-preserving acquisition of cross-sectional images of semi-transparent materials and the characterization of tissue morphologies. The method is based on short-coherent interferometry with infrared light and achieves penetration depths in the tissue of several millimeters with a resolution of a few micrometers. This opens up various opportunities for clinical applications, for example in minimally invasive surgery, non-invasive fields of application or point-of-care diagnostics.

Optical Coherence Tomography as a non-invasive imaging technology for tissue examination

The tomographic representation of internal structures is an important measurement technology as it is fundamental for the analysis of semi-transparent materials. In many applications it is necessary to examine the near-surface structures down to a depth of 3 millimetres – for example in the examination of skin tissue in medicine or foil structures in the manufacturing industry. However, some of the best-known non-invasive tomographic imaging techniques, such as sonography or magnetic resonance imaging (MRI), cannot provide the high resolution required to display very thin and fine layers or tissue details in the micrometer range. OCT is a technology that has the potential to improve imaging in all medical disciplines, including minimally invasive surgery with a focus on laparoscopy, otorhinolaryngology, neurosurgery and cardiology. Non-invasive application fields include dermatology and dental medicine. Another possible field of application for OCT is point-of-care diagnostics, available as cost-effective applications for growth markets.

The Research Alliance for Biophotonics expects significant market growth for these biomedical applications and will drive its advancements in OCT technology. The transfer of the temporary project structures to a permanent regular operation should result in a research institution that will be able to operate itself at the end of the funding period.

Technology

The measuring principle of OCT is based on the interference of light. A typical OCT system consists of a short coherent light source, an interferometer with a reference path and a measurement path with x-y scan mirrors and a spectrometer. The depth information of a sample is obtained by recording and evaluating the interference from backscattered light of different sample depths as well as light from the reference path. A single scan, the so-called A-scan, shows the reflection profile of the measuring object in vertical direction. Using x-y scan mirrors, the measurement beam can be shifted to capture images in 2D (B scan) and 3D (C scan).

Principle of tomographic image composition from different depth profiles (A-Scans).

Typical setup of a spectral domain (SD) OCT system consisting of a superluminsescent diode, a reference path, a sample path and a spectrometer.

Principle of A-Scan acquisition from backscattered light from within the sample.