Optical coherence tomography and its role for delineating the thickness of keratinocyte dysplasia and neoplasia.

Optical coherence tomography (OCT) can produce cross-sectional and en face, non-invasive, real-time images of skin. OCT produces high-resolution images at a micrometre resolution and has a maximum 2-mm penetration depth, which places OCT in the imaging gap between ultrasound and confocal microscopy. Much OCT research has been performed on keratinocyte dysplasia and neoplasia, primarily including basal cell carcinoma (BCC) and actinic keratosis. In regards to BCC and actinic keratosis, architectural disarray of the epidermis is an overall characteristic finding in OCT images. OCT can reliably differentiate between normal and lesional skin, which is of great importance when identifying tumour borders. Therefore, it has been suggested that OCT may aid in the evaluation of sub-surface tumour margins prior to surgical and non-invasive treatments of keratinocyte neoplastic lesions. Studies on in vivo presurgical margin assessments found that OCT correctly identified the laterally defined tumour margin in 84% of cases and that the borders determined by the surgeon never came below the OCT margin, indicating the utility of OCT. These reports imply a scope for reducing the final size of an excision defect using OCT. The main limitation to assessing tumour thickness using OCT is its maximum scan depth of 2 mm, indicating that the primary potential of OCT may lie in the evaluation of superficial tumours.