In vivo tissue measurements with optical low coherence tomography

Optical low coherence tomography (OCT) is a promising new method for non invasive, in vivo measurements of biological high scattering tissue. Crossectional images with microscale resolution in a range of about 15 mu m can be produced. A scanning point detection system is realized which combines an interferometric method with an endoscope. A superluminescence diode with a center wavelength of 830nm and a coherence length of 15 mu m is coupled into the interferometrical setup. The backscattered light from a tissue sample and the reflected light from the scanning reference mirror is recombined at the detector. Interference occurs only if the pathlength difference is within the coherence length of the light source. Heterodyne detection is used to obtain high speed and high dynamic range measurements of the interferometric signals. We present in vivo OCT skin measurements, where we analyze the borders between the upper skin layers. We describe the influence to the light attenuation inside the skin after treating the skin with oil. We compare in vivo OCT skin measurements with in vitro skin measurements. Additionally first in vivo skin measurements of malignant melanoma show that OCT is a promising diagnostic method in dermatology.