In order to ensure the participants safety from potential burns, they were carefully vetted-exclusion criteria concerned the size and number of tattoos. However, this unpleasant feeling disappeared within 24 hours without the affected person having required medical treatment." "There was one specific case where the study doctor found that side effects-a tingling sensation on the skin-were related to scanning. "We found that the majority of the participants did not notice any side effects with tattoos," says Weiskopf.
The majority of the tattoos were black ink, but many colors were also registered. Patient countries of origin were in Europe, America, Asia, Africa and Australia. The team systematically collected information about participants' tattoos-how big they were, where they were located, and what colors were used. Together with his colleagues at University College in London, he examined 330 study participants before and after MRI scans and tested a total of 932 tattoos. In the worst case, this can lead to burns," says Nikolaus Weiskopf. In this case, the tattoo may absorb much of the energy of the high-frequency field, which would normally be spread out more widely. That happens to correspond to the resonance lengths of conductive structures similarly sized as tattoos. "High-frequency fields usually have a frequency of a few hundred megahertz. This is an issue because in MR imaging uses high-frequency magnetic fields to generate the images by effectively labeling protons. However, another potential interaction may represent a far greater risk, according to the researchers. The strong magnetic fields involved in the procedure can interact with these small particles, which in turn can lead to a pulling sensation on the tattooed skin. It is possible that the pigments in tattoos can interact with the static magnetic field of the scanner if the ink contains ferrous particles. Reports of adverse reactions are usually based on individual cases and describe two reactions. Until now, there has not been a systematic prospective study on how safe it is to scan tattooed patients in an MRI scanner. Millions of people with tattoos are scanned every year in hospitals and research facilities without any side effects. "Based on our investigations, we can now state, on the basis of meaningful numbers, that if a tattooed individual is scanned under the conditions tested in the study, the risk of side effects is very small," the physicist explains. His former colleague in London, Martina Callaghan, completed the study after Weiskopf left London to become director at the MPI CBS in Leipzig. At the time, there simply was not enough data to determine the likelihood of tattoo-related side effects arising from MRI examinations." According to Weiskopf, director at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig (MPI CBS), "the most important questions for us were: Can we conduct our studies with tattooed subjects without hesitation? What restrictions may exist? At the Wellcome Centre for Human Neuroimaging, part of Queen Square Institute of Neurology at University College in London, where I started the study in 2011, there were increasing numbers of volunteers with tattoos.
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