Optical Coherence Tomography for Dermatological Applications
Abstract: Optical coherence tomography (OCT) is a non-invasive optical imaging technique providing approximately 10 micrometer resolution of tissue in vivo. Within ophthalmology, OCT has already proven its value and is routinely used for diagnosing retinal diseases. In many other areas the potential of OCT is explored worldwide, while the technique itself is further developed with improved imaging speed, resolution and extensions such as functional imaging. This thesis focuses on improvements and tailoring of OCT for applications within dermatology, especially skin cancer diagnostics. A two-fold approach combining clinical measurements and development of better suited OCT equipment has been attempted. The diagnostic value at the current stage of OCT has been evaluated in a cooperation with medical doctors. The study included 100 patients and showed a need for further improvements of the technique to make accurate diagnosis possible. Studies with a smaller number of patients investigated the possibility of using OCT for thickness measurements of lesions and human nails. The results were in correlation with ultrasound measurements, but with a higher precision. In addition to these diagnostic studies, an attempt to monitor treatment progress of photodynamic therapy was initiated. The use of Doppler OCT for measuring blood flow changes has the potential to tailor the treatment individually eventually with an improved outcome. A Doppler OCT system was tested using phantoms and normal skin followed by patient investigations. Addressing the technical difficulties of performing these measurements and suggesting possible solutions was the major outcome. Regarding the technical development, the primary concern was to improve the resolution of the imaging technique, in particular the depth resolution. A high depth resolution OCT system was constructed for imaging with a resolution of about 2 micrometer and this system was tested with a number of light sources. The possible advantages for diagnostic purposes were not evaluated because none of the light sources were suited for imaging. The focus has therefore been testing of the system showing promising results. With a suited light source the diagnostic value of an increased resolution might be evaluated using this system.
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