S. Hayat, Y. Cho, S. Oh and H. Yoo, “RF-Induced Heating of Various Tattoos at Magnetic Resonance Imaging Systems,” in IEEE Access, vol. 9, pp. 100951-100961, 2021, doi: 10.1109/ACCESS.2021.3097145.
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.
This study presents data regarding RF-induced heating around different types and positions of tattoos at different field strengths of MRI and investigated a substantial factors that may impact RF-induced heating. These factors include tattoo pigment, tattoo shape, tattoo thickness, multiple tattoos, gap between the tattoos, position of tattoos on a human phantom, and conductivity of iron oxide. The study reveals that tattoo shapes, and positions are the major factors that affect RF-induced heating during MRI. Furthermore, the size of the tattoos and the gap between multiple tattoos could lead to higher RF-induced heating at different field strengths of MRI. Moreover, tattoo thickness is associated with small variations in RF-induced heating.
The radio frequency of MRI interacts with the ferromagnetic material found in tattoos, especially iron oxide. In addition, the RF-induced heating is different for different types of tattoos due to the different scattered E-fields. Thus, it is essential to study RF-induced heating in tattooed patients or follow the current recommendations of the FDA guidelines to avoid tattoo patient from MRI examination. Future studies on RF-induced heating of tattoos during MRI should consider patient orientation, landmark position, location of tattoos on the human body, tattoo pigments, and imaging studies.