The Dermal Echo-Void (DEV) Index: A Reproducible Computer-Assisted High-Frequency Ultrasound Measure of Superficial-Dermis Structure Beyond Skin Density

Background: High-frequency ultrasound (HFUS) quantifies dermal skin density well, yet the low-echogenic (hypoechoic) regions in the image have not been treated as having informative value. Analyzing HFUS B-scans, we found that skins with near-identical aggregate density can differ markedly in their hypoechoic area fraction. To capture this, we introduce the dermal echo-void (DEV) area fraction index, a computer-assisted parameter measuring hypoechoic voids within a fixed 0.45 mm superficial-dermis band (T45), and assess its reproducibility and non-redundancy with skin density. Methods: In a single-arm proof-of-concept study of 23 Korean women, DEV and density were computed from the same 22 MHz B-scans. Results: DEV was reproducible across analysis-band depths (ICC = 0.93, 95% CI 0.86–0.97). Although DEV correlated inversely with density (r = −0.675), the two measures were non-redundant: among 39 density-matched pairs (Δ ≤ 1 percentage point), DEV differed by a mean of 5.6 percentage points. After one application, density rose +16.44% and DEV fell −35.75% (both p < 0.001). A secondary density–pigmentation association was non-significant (Spearman ρ = −0.224, p = 0.485). Conclusions: DEV is a reproducible, spatially resolved complement to HFUS skin density that captures dermal structure beyond an aggregate value. How the hypoechoic fraction relates to melanocyte-associated dermal processes warrants histologically validated study.