Use of optical coherence tomography to monitor biological tissue freezing during cryosurgery.

The use of optical coherence tomography (OCT) for imaging skin during cryosurgery is evaluated. OCT provides high spatial resolution (5-10 microm) images of optical backscattering due to local variations in refractive index, such as the boundary between liquid and frozen water in tissue. Time resolved OCT images were acquired during freezing of water, Intralipid trade mark, and in vivo hamster skin. Subsurface morphological changes were evident only during freezing of Intralipid and skin. A simple thermal model was applied which predicted freezing times on the same order of magnitude as those observed in OCT images. OCT can be used as a feedback tool during cryosurgical procedures to monitor progression of the freezing front.