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Η τεχνολογία της οπτικής τομογραφίας συνοχής (OCT) και η χρησιμότητά της στην οφθαλμολογία (Master thesis)

Πορτοκάλη, Γεωργία Ζηνοβία

Optical Coherence Tomography (OCT) is a new imaging technique that is used in numerous medical fields. The greatest interest of OCT appears in Ophthalmology, presenting various different applications. OCT uses low coherent light in order to measure the intensity of light that reflects or scatters from tissue, producing this way tomographic images of similar resolution and morphology to histological sections. The two major OCT methods are time domain OCT and frequency domain OCT. The second is further divided into Spectral Domain OCT and Swept source OCT. Lately, frequency domain OCT has prevailed, due to the fast scanning speed and the quality of image resolution it offers. Broadband light sources assisted in capturing images of higher resolution. Also, using larger wavelengths achieved deeper penetration depth. Most of the OCT systems operate at wavelengths of 800 nm and 1300 nm. Two or three dimensional images are defined by the scanning direction (en face view) and the system’s software (volume rendering). Based upon the two main OCT methods, new system setups have been developed, that not only allow the visualization of various eye structures, but also give functional information. The most important ones are Polarization Sensitive OCT (PS-OCT), using different polarization states of specific tissues for extracting functional information about the thickness of the retinal nerve fiber layer, and Doppler OCT (D-OCT) which utilizes the Doppler effect (Doppler shift) so, as to quantitatively measure the flow of the blood cells within the retinal blood.