Abstract
Reflectance confocal microscopy (RCM) has seen increasing clinical application for noninvasive diagnosis of skin
cancer. Identifying the location of the dermal-epidermal junction (DEJ) in the image stacks is key for effective clinical
imaging. For example, one clinical imaging procedure acquires a dense stack of 0.5x0.5mm FOV images and then,
after manual determination of DEJ depth, collects a 5x5mm mosaic at that depth for diagnosis. However, especially in
lightly pigmented skin, RCM images have low contrast at the DEJ which makes repeatable, objective visual
identification challenging. We have previously published proof of concept for an automated algorithm for DEJ
detection in both highly- and lightly-pigmented skin types based on sequential feature segmentation and classification.
In lightly-pigmented skin the change of skin texture with depth was detected by the algorithm and used to locate the
DEJ. Here we report on further validation of our algorithm on a more extensive collection of 24 image stacks (15 fair
skin, 9 dark skin). We compare algorithm performance against classification by three clinical experts. We also
evaluate inter-expert consistency among the experts. The average correlation across experts was 0.81 for lightly
pigmented skin, indicating the difficulty of the problem. The algorithm achieved epidermis/dermis misclassification
rates smaller than 10% (based on 25x25 mm tiles) and average distance from the expert labeled boundaries of ~6.4 μm
for fair skin and ~5.3 μm for dark skin, well within average cell size and less than 2x the instrument resolution in the
optical axis.
