Optical coherence tomography
Optical coherence tomography (OCT) is a non-invasive optical medical diagnostic imaging modality which enables in vivo cross-sectional tomographic visualization of the internal microstructure in biological systems. OCT is analogous to ultrasound B mode imaging except that it uses light rather than sound, therefore achieving unprecedented image resolutions (1-10 µm), approximately 100 times higher than conventional ultrasound by using broad bandwidth light sources in combination with interferometric detection techniques.
Since its invention (pioneered in Vienna by Prof. A.F. Fercher) in the late 1980s and early 1990s, the original concept of OCT was to enable non-invasive optical biopsy, i.e. the real time, in situ imaging of tissue microstructure with a resolution approaching that of histology, but without the need for tissue excision and post-processing. In order to accomplish – or to approach – this challenging goal, recent research in OCT has achieved quantum advances in resolution (sub-µm), data acquisition speed (more than 1.000.000 measurements/s), optimization of tissue penetration (up to 2 mm). Hence OCT can now be considered as an optical analogue to CT or MRI, but with microscopic resolution for superficial tissue. Development of state of the art delivery systems, facilitated the application of OCT in a variety of medical fields, enable the imaging of internal body organs.
Furthermore, extensions of OCT have been developed that enable non-invasive depth resolved functional or contrast enhanced imaging, providing spectroscopic, metabolic, polarization-sensitive, blood flow or physiologic tissue information. These new OCT technologies promise to not only improve image contrast, but should also to enable the differentiation of pathologies via localized metabolic properties or functional (physiologic) state.
It is unlikely, though, that OCT will replace excisional biopsy and histology or other existing diagnostic modalities. However, from the viewpoint of screening and diagnosis of diseases, OCT might enable significantly new insight in the pathogenesis, early diagnosis and therapy control of several diseases.