Safety and health effects in high and ultra-high field MR
Sammanfattning: Background: More than 70 million magnetic resonance (MR) examinations are produced every year. Patients and personnel are exposed to electromagnetic fields at levels that exceed those normally found in our surroundings or in industry. Three types of electromagnetic field exposure must be considered in regard to MR safety: the strong force of the static magnetic field, the time-varying gradient magnetic field present during scanning, and the radio frequency field from the transmit coil. Most clinical MR scanners operate at 1.5Tesla (T) or 3T, but the number of ultra-high field scanners (UHF; above 4T) has increased over the last 15 years. This development has led to imaging of higher quality and provides the possibility of new insights into the pathophysiology of disease. MR safety work is a continuous effort of improvement to ensure the safety and health of our patients, healthy volunteers and personnel. Aim: The overall aim of this thesis was to analyse health effects of MR, including short-term effects of UHF MR, and MR safety issues from the perspective of patients, healthy volunteers, and personnel. Method: In paper I and II the individuals undergoing an MR examination at the National 7T MR facility at Skåne University Hospital were asked to fill in a questionnaire regarding their experience of short-term effects and health effects after the examination. In paper III MR and/or computed tomography (CT; control group) users in Sweden were invited to answer a web-based safety questionnaire sent to their units. Reported MR safety incidents were analysed and a risk assessment was performed. Documented screening procedures of subjects scheduled for a 7T MR examination during a period of four years (2016-2019) were analysed in paper IV.Results: Papers I and II showed that short-term effects representing physiological responses such as dizziness, inconsistent movement, nausea, headache, and metallic taste do occur in UHF, as well as individual psychological issues such as anxiety. Compared to the literature on older UHF systems, frequencies of short-term effects are higher in our studies. However, willingness to undergo future examinations was still high and suggestions for care improvement are given. In paper III results showed that safety incidents in clinical MR environments do occur and the risk levels of these incidents are high. MR personnel tended to have a false sense of security, as a high proportion of personnel members were sure that they would have been aware of any incident at their own department, while in reality, incidents had occurred without their knowledge. Paper IV showed benefits of a multi-step MR safety procedure with regard to detection of MR safety risks, at the same time as inadequacies in compliance with documentation routines were detected. Conclusion: Health effects do occur in ultra-high field MR, but few subjects experience these effects as being so uncomfortable that they would lead to an aversion towards future examinations. Further, compliance and experience might be improved by focusing on pre-examination anxiety, communication, and supplying information before and during the examination. Safety incidents in clinical MR environments occur, have high potential risk levels and stay in contrast to a partly false sense of security among personnel. Although afflicted with inadequacies in compliance, a multi-step screening process offered benefits trough repetition and through the use of a documented structured screening interview and as result potential MR safety incidents are avoided.
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