20-MHz high-intensity focused ultrasound for tattoo removal without pigment-specific optical targeting and with evidence for an ablation-associated transepidermal extrusion pathway.

INTRODUCTION

Radiotherapy tattoos can impose a cosmetic burden, while laser removal requires selection of optical wavelengths according to the absorption characteristics of individual tattoo pigments. We evaluated a handheld 20 MHz high-intensity focused ultrasound (HIFU) device as a potential non-optical approach to reducing red, black, and blue tattoo pigments.

METHODS

Thermal injury zone (TIZ) geometry was characterized ex vivo in avian muscle and full-thickness porcine skin tissue. Rat dot tattoos (red/black/blue) received a single-session exposure (10 shots; 6 W, 1,000 ms) and were followed for 21 days with histology and morphometry. In Yucatan minipigs, multispectral 3D imaging quantified acute (minutes) and chronic (Day 4-98) responses in normal and tattooed skin, and was extended to multicolor tattoos with >100-day follow-up. A pilot substudy applied a hydrocolloid dressing.

RESULTS

Ex vivo TIZs scaled with energy, with restricted axial expansion in porcine tissue. In rats, frosting progressed to crust formation (Days 7-14) and pigment lightening by Day 21; pigment debris was observed near the dermo-epidermal junction and within crusts, consistent with transepidermal elimination. TIZ depth decreased from 730 ± 196 μm at 1 h to 362 ± 125 μm at Day 21, while peripheral ring-like traces were noted in some sites. In minipigs, tattoo contrast decreased (ΔE * a b 9.87 → 3.30 by Day 98), and similar contrast reductions were observed across red, black, and blue tattoos by Day 101-105. Hydrocolloid coverage was associated with earlier eschar detachment and faster normalization by Day 14.

DISCUSSION: These feasibility data suggest that 20 MHz HIFU may support an ablation-associated transepidermal extrusion pathway for reducing red, black, and blue tattoo pigments without requiring pigment-specific optical wavelength matching. The findings provide preliminary histology-linked and imaging-supported evidence for this non-optical tattoo-treatment approach, while underscoring the need for larger controlled studies and dose optimization to improve cosmetic outcomes and minimize residual traces.