Special issue: MR safety (2007)

THIS ISSUE OF JMRI has a focus on MR safety. It differs from previous JMRI special issues in that it does not primarily contain invited reviews recruited by guest editors, but instead mainly contains new, original works submitted in response to a call for the submission of scientific investigations in this area. The original call was as follows: Regulatory authorities are concerned about occupational exposure to the MRI environment, and various exposure limits and guidelines have been proposed (for example, by the IEC (International Electrotechnical Commission), IEEE, (Institute of Electrical and Electronics Engineers), ICNIRP, [International Commission on Non-Ionizing Radiation Protection] and recently by the European Union in the form of the Physical Agents [EMF] Directive). Yet there are only a limited number of scientific studies that specifically address exposure to the MRI environment, and thus MRI exposure limits are sometimes extrapolated from sparse data or data acquired at power transmission frequencies or mobile phone frequencies. The ISMRM Safety Committee is encouraging MRI researchers, in collaboration with specialists in other relevant fields such as physiology or psychology, to submit manuscripts to the Journal of Magnetic Resonance Imaging describing original research or reviewing the literature specifically to address the issue of exposure to the MRI environment. Since the original call was made, a relationship between the use of gadolinium-based contrast agents and nephrogenic systemic fibrosis (NSF) has been reported. NSF can be a serious problem and it is important to the MR community. Hence we have widened the scope of this special issue to include works on NSF and contrast agent safety. At the ISMRM meeting in Berlin, this topic was the subject of the special workshop on risk of gadolinium contrast agents as related to NSF (1). In recent years, a number of organizations have proposed regulations and guidelines that were aimed at controlling the exposure of staff to electromagnetic fields (EMFs), but which would have had a severe impact on the practice of MRI, most notably the European Physical Agents (EMF) Directive referred to above. Sometimes these guidelines were based upon, or designed to be consistent with, older limits that had been established before the technology allowed certain types of exposure. In other cases the guidelines were extrapolated from sometimes sparse data, into frequency or amplitude ranges in which no data existed. Furthermore these guidelines were often very cautious, arguably even precautionary in nature, aiming to eliminate the possibility of any adverse effects rather than aiming to avoid any actual established effects. This may be appropriate for controlling general public or environmental exposure, but is not consistent with the level of risk routinely accepted by workers, including staff working with ionizing radiation in radiology. Our community must accept that one of the reasons that this situation arose is because of the lack of available data in some areas. MRI is not the only source of large exposures to EMFs; other affected groups include aluminum smelters, power line workers, and even sailors working with powerful radar systems. However, as a large group of scientists with expertise in EMF and biomedicine, MR workers are uniquely placed to publish safety studies. So why have we not performed as many safety studies as the regulators would have wished? The problem is that performing safety studies in this area is rather similar to searching for a needle in a haystack. Ideally, science should proceed by testing hypotheses, but it is hard to establish hypotheses when there is little anecdotal evidence of any health risks related to MRI-relevant EMF exposures, and when there are few proven biological mechanisms for the interaction of such fields with tissues. This means that many safety studies are likely to yield negative results, and thus safety research may not appeal to research funders, the rest of the scientific community, or even some journals. Therefore the MRI community has not generally considered safety studies to be its top priority, except when opening up new frontiers (e.g., the work at 8T). Nonetheless, there are areas of some concern, as highlighted in a recent World Health Organization research agenda (2), and it remains critically important to monitor the effects of MRI on subjects and staff. Therefore the ISMRM safety committee decided that it was essential to encourage more research in this area, and turned to the editor of JMRI for assistance. JMRI has a long history of publishing on MR safety, notably publishing a special issue on safety in 2000 under the guest editorship of Ordidge, Shellock, and Kanal (3), and the editor in chief has assisted the safety committee by designing a format particularly aimed at encouraging new research. The submitted works cover most areas of interest, from studies of protein–gene expression in static fields to the definite dangers associated with medical implants, as well as dosimetry. It should be noted that a major concern of the regulatory authorities is the lack of long-term epidemiological studies of MR workers or subjects, and no such study has been submitted to this issue. This is not surprising since such a study would take a long time to perform and would need to be undertaken by epidemiologists. However, it is important that we keep good staff exposure records to facilitate such a study in the future. During the development of this special issue, a specific risk associated with gadolinium-based contrast agents became apparent—NSF. NSF was first observed in 1997 and formally described in 2000. It is a disease characterized by fibrosis of the skin, and occasionally other organs, including the diaphragm, heart, lung, vasculature, and muscles. It has been observed only in patients with renal failure. Unlike other adverse effects observed with MRI contrast agents, which generally occur immediately and in the MRI suite, NSF develops days to weeks after the patient had the MRI scan. It is a serious disorder, and its recent recognition has changed how we practice, how we screen patients for gadolinium-based contrast-agent injection, how we determine which agents we use, and whether or not we inject some patients at all. Data on the frequency of NSF and risk factors associated with developing NSF continue to be actively accumulated, and NSF is an important and timely topic of discussion; hence its inclusion in this safety issue. We hope that the evidence provided here will be of value to regulators in defining and reviewing safety guidelines and regulations, as well as to MRI practitioners. We call upon the MR community to continue to produce safety studies targeted in areas of concern to the regulatory bodies (2). It is important to stress that every work in this issue underwent standard peer review, and we would like to thank the contributors and reviewers involved for working to ensure rapid publication of this issue.