RF-Induced Heating of Various Tattoos at Magnetic Resonance Imaging Systems

This paper presents radiofrequency (RF)-induced heating of single and multiple tattoos during magnetic resonance imaging (MRI) at 1.5 T and 3 T. Various tattoos of different shapes, positions, pigment, length, diameter, and gap between the tattoos was investigated. Finite-difference time-domain based electromagnetic and thermal simulations were performed to study the specific absorption rate (SAR) and temperature rise, respectively. The results indicated that tattoos influenced the induced electric field distribution and maximum magnitude of the SAR on the surface of the skin. A notable enhancement in the SAR were observed around the sharp edges, long strips, and circular loops of tattoos. Interestingly, the maximum local SAR and increase in tissue temperature strongly depend on the shape of the tattoo. Furthermore, the relative position and size of the tattoos affected RF-induced heating. The RF-induced heating of multiple tattoos were investigated considering the worst case scenarios. Our results confirm that RF-induced heating of multiple tattoos is quite different from that of single tattoo and does not follow a simple superposition of the results from a single tattoos. Moreover, the procedures presented in the simulation environment are used to facilitate RF-induced heating for patients with tattoos undergoing clinical MRI.