Video-mosaicing of reflectance confocal images for examination of extended areas of skin in vivo

Abstract

Background: With reflectance confocal microscopy (RCM) imaging, skin cancers can be diagnosed in vivo and margins detected to guide treatment. Since the field of view of an RCM image is much smaller than the typical size of lesions, mosaicing approaches have been developed to display larger areas of skin. However, the current paradigm for RCM mosaicing in vivo is limited both in speed and to pre-selected rectangular-shaped small areas. Another approach, called “video-mosaicing,” enables higher speeds and real-time operator-selected areas of any size and shape, and will be more useful for RCM examination of skin in vivo.

Objectives: To demonstrate the feasibility and clinical potential of video-mosaicing of RCM images to rapidly display large areas of skin in vivo.

Methods: Thirteen videos of benign lesions, melanocytic cancers and residual basal cell carcinoma margins were collected on volunteer subjects with a handheld RCM scanner. The images from each video were processed and stitched into mosaics to display the entire area that was imaged.

Results: Acquisition of RCM videos covering 5.0–16.0 mm² was performed in 20–60 seconds. The video-mosaics were visually determined to be of high quality for resolution, contrast and seamless contiguity, and the appearance of cellular-level and morphologic detail.

Conclusion: Video-mosaicing confocal microscopy, with real-time operator-choice of the shape and size of the area to be imaged, will enable rapid examination of large areas of skin in vivo. This approach may further advance noninvasive detection of skin cancer and, eventually, facilitate wider adoption of RCM imaging in the clinic.

Figure 1

Video mosaic of a benign melanocytic nevus over a 9.4 mm² area, acquired in 50 seconds (~400 frames). Imaging was in the lower epidermis and at the dermo-epidermal junction. Features seen include normal skin (outside green boundary), nevus region (inside green boundary), hair follicle (yellow asterisks), and rings of dermal papillae (examples seen in the red ellipses).

Figure 2

Video mosaic of residual BCC margins, obtained intra-operatively in the surgical wound on a Mohs patient, over an area of 15.8 mm², acquired in 40 seconds (~400 frames). Structures seen include dark nuclei within the honeycomb pattern of keratinocytes in the surrounding intact epidermis (outside blue boundary, appears saturated here), exposed epidermis in the wound (between blue and yellow boundaries), in which the nuclei (examples in orange oval) appear bright due to the application of aluminum chloride for contrast enhancement, and the underlying papillary and reticular dermis (inside the yellow boundary). Other structures, such as collagen bundles in dermis (for example, inside orange square), rings of dermal papillae (for example, red ellipses) and hair shaft (green ellipse) can be seen in the mosaic.

Figure 3

Video mosaic of a lentigo maligna over a 6.5 mm² area, acquired in 1 minute (500 frames). Atypical perifollicular infiltration (yellow ellipse), cluster of atypical cells above the dermal-epidermal junction (orange ellipse), hair follicle (yellow asterisks), and epidermal disarray (red ellipse) can be observed.