Fiber-based hand-held RCM-OCT probe for noninvasive assessment of skin lesions and therapy guidance

Abstract

Noninvasive assessment of skin lesions, especially of basal cell carcinoma (BCC), has benefited more recently from the use of optical imaging techniques such as optical coherence tomography (OCT) and reflectance confocal microscopy (RCM). While RCM provides submicron scale resolution and thus enables identification of skin morphological changes of the skin, with the downside of limited penetration depth, OCT imaging of the same lesion brings the benefit of better resolving its depth of invasion. OCT and RCM can be used either individually or combined within the same instrument for the noninvasive diagnosis of nonmelanoma skin cancers (NMSCs). Their combined use has shown to provide certain benefits such as better characterization of the lesion's margins, both in depth and laterally, as well as improved sensitivity and specificity, as previously demonstrated by our team. In this paper we report a new "fiber-based" implementation of the second-generation RCM-OCT hand-held probe. The fiber-based implementation of both imaging modalities enabled the construction of a smaller footprint/lower weight hand-held probe. Its preliminary evaluation on the skin of healthy volunteers is reported here, demonstrating improved capabilities for resolving sub-cellular structures and image skin morphology with micron-scale resolution to a higher depth than in the previous implementation, while also enabling the construction of angiography maps showing vascular remodeling.

Keywords: noninvasive evaluation; optical coherence tomography; reflectance confocal microscopy; skin lesions.

Fig. 1.

Hand-held probe design and physical implementation. A- Simplified schematic; B- CAD design, C- Physical implementation

Fig. 2.

Schematic (A) and physical implementation (B) of the instrumentation unit CIR-Circulator; BS- Beam splitter; PC Polarization controller; APD- Avalanche photodetector; GPU- Graphical processing unit; DAQ- Data acquisition card; RR- retroreflector; SS- Swept source; SLD- Superluminescent diode.

Fig. 3.

RCM lateral resolution evaluation using the USAF1951–1X resolution chart. The imaging speed and the resolution of the probe is summarized in Table 1.

Fig. 4.

Example of instrument testing on team members.

Fig. 5.

Demonstration of the RCM/OCT imaging capabilities on a palm of a volunteer. A. 3D OCT volume, with cross-sectional and enface views; B, C- RCM images at various depths.

Fig. 6.

Demonstration of the RCM/OCT imaging capabilities on a volunteer’s forearm. A: 2D cross-sectional OCT image; B: OCT angiography image showing vascular details at the dermal-epidermal junction; C-J: RCM images collected at various depths showing different epidermal layers (stratum corneum, lucidum, granulosum, spinosum, basale) and collagen structures in the upper dermis.