Optical Coherence Tomography (OCT) can provide 3D images with micrometer resolution. It is widely used in the field of ophthalmology. The other optical imaging techniques described above use the absorption of light as the contrast mechanism, whereas OCT uses the scattering of light for contrast. When scattered waves are superimposed to extract information about them, it is referred to as interferometry. When waves interfere, they form a pulse if they are coherent. Based on interference of two light beams, depth can be discriminated with high depth (axial) resolution, typically in the order of a few micrometers.
In OCT, a broad spectral range light source is being used for illumination and an interferometric setup is used, with a mirror in one part of the interferometer (the reference arm), the tissue in the sample arm. Reflected light from the tissue is again combined with the reference arm signal measured in a spectrometer, which yields one depth profile of the tissue. In order to obtain 3D images, the sample is being raster scanned in x and y direction, resulting in a 3D structural image of the tissue. The video featured shows an example of such a 3D volume of a human thumb.
Actinic Keratosis and Skin sun damage
In literature, OCT is shown to have specific features for sun protected skin versus sun damaged skin/actinic keratosis. Is is shown that patients with severe solar elastosis and/or actinic keratosis have much greater skin attenuation values relative to patients with minimal sun damage.
In mice with superficial wounds infected with Staphylcoccus aureus, OCT images were used to monitor healing. In this study, different phases of healing could be identified based on the OCT features and characteristics. Edema could be readily identified on OCT images of the mice with infected wounds.
OCT is the modality referred to as optical biopsy. Its tomographic characteristics proving image information with at X,Y, and Z axis can makes this modality and ideal one for further research and development for non-invasive optical biopsy. 2D images can be reconstructed with micron slices at XY and XZ, and YZ axis. As the next generations of this modaltity improve in various characteristics including the resolution and depth of imaging, this can place this technology at one of most compelling candidate for optical in-vivo biopsy (virtual biopsy). This modality is also a candidate as a hybrid modality combined with functional imaging modalities for added anatomical information.