On the attenuation of ultrasound by pure black tattoo ink

Black tattoo ink comprises hydrophobic carbonblack nanoparticles. We hypothesized that black tattoo inkdemonstrates transient dynamic activity in an ultrasound field. Brightness-mode sonography was performed on cylindrical receptacles of different bore diameters, filled with black tattooink, water, saline, or air, using pulsed ultrasound with center frequencies of 13 MHz and 5 MHz. The scattering from black ink itself lasted less than tenminutes. At 13-MHz sonication, a transient drop in sound speed was observed, as well as a transient lessening of scattering from distal phantom tissue. The linear acoustic attenuation coefficient of pure black ink was measured to be 0.15±0.01 dB cm⁻¹ MHz⁻¹, equal to whole blood. Low-intensity ultrasonic tattoo removal would be of interestas an alternative to techniques that damage surrounding tissue.