High-frequency ultrasound skin thickness: Comparison of manual reading and automatic border detection includes assessment of interobserver variation of measurement.

BACKGROUND

Twenty megahertz ultrasound is the preferred method for in vivo measurement of skin thickness. This study on methodology aimed to compare operator-managed or "manual" measurement of skin thickness (MM) with measurement by automatic border detection (ABD).

METHODS

The skin thickness of the flexor mid-forearm was measured in 48 subjects (subgroups 32 and 16) with the DermaScan C (Cortex Technology). MM and ABD were performed on the same scans by two experienced operators. MM is measured on the peak of interface A-mode echoes representing the epidermal surface and the dermis-subcutis interface, while ABD measures on the slope of the echoes, for example, the acoustic contour.

RESULT

Automatic border detection measured the skin about 20% thicker (mean: 0.94/0.89 mm, SD: 0.09/0.11) in comparison with MM (mean: 1.25/1.22 mm, SD: 0.09/0.12), P < .001. The two methods correlated, r = .9443 and .8663. Two individual researchers reached very close results using MM, that is, mean 0.91 and 0.93 mm, and the interobserver variation was nonsignificant.

CONCLUSION

MM and ABD for ultrasound skin thickness measurement rely on different principles and consequently measure skin thickness differently, with ABD overestimating the thickness with about 20%. MM measures anatomically more correct and is preferred in research. MM has been validated against area-based thickness measurement without contour artifact and produced identical results. ABD is less operator-dependent and applicable to field studies, and useful in the beauty industry to characterize aged skin. The two methods of recording each have a scene of use.