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- Frankel, Jennifer, 1981-
(författare)
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Characterization of the MRI patient exposure environment and exposure assessment methods for magnetic fields in MRI scanners
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Magnetic resonance imaging (MRI) has become one of the most common imaging modalities available in modern medicine, and it is an indispensable diagnostic tool thanks to the unparalleled soft-tissue contrast and high image resolution. It is also a unique exposure environment consisting of a complex mix of magnetic fields. During an MRI scan, the patient is simultaneously exposed to a strong static magnetic field, a fast-switching gradient magnetic field, and a pulsed radiofrequency (RF) magnetic field. Transient acute effects, such as nerve excitation and tissue heating, are well known and limited by universal safety guidelines. Long-term health effects related to MRI exposure have, however, not been scientifically established, and no interaction mechanisms have been verified, despite a growing body of research on electromagnetic field exposure. Further epidemiological and experimental research on MRI exposure has been recommended but the lack of a common definition of dose or exposure metric makes evaluation of past research and the design of future experiments difficult.The objectives of this thesis were to characterize the MRI patient exposure environment in terms of the magnetic fields involved, suggest relevant exposure metrics, and introduce exposure assessment methods suitable for epidemiological and experimental research on MRI and long-term health effects.In Paper I, we discussed the MRI exposure environment and its complexity and gave an overview of the current scientific situation. In Paper II, we investigated the exposure variability between different MRI sequences and suggested patient-independent exposure metrics that describe different characteristics of the magnetic field exposure, including mean, peak, and threshold values. In Paper III, we presented three exposure assessment methods, specifically suited to the complex MRI exposure environment: a measurement-based method, a calculation-based method, and a proxy method.Papers I and II showed that MRI exams are not homogenous in terms of exposure, and exposure variability exists between the individual sequences that comprise an exam. Differences in mean exposure between sequences were several-fold, peak exposure differences up to 30-fold, and differences in threshold exposure were in some cases more than 100-fold. Furthermore, within-sequence exposure variability, related to the parameter adjustments that can be made at the scanner console before the start of a scan, gave rise to 5-to-8-fold exposure increases. Paper III showed that magnetic field models could be used to approximate the exposure at arbitrary locations inside the scanner, with slight underestimation of gradient field metrics and large variability in some RF field metrics. With improvements in accuracy and efficiency, the method could become a useful exposure assessment tool for in vitro and in vivo research as well as clinical work on medical implant safety. Our search for suitable exposure metric proxies resulted in a limited selection with low correlation between proxies and their counterpart metrics, but, with further development, the proxy method has the potential to allow for much needed exposure classification relevant to large-scale epidemiological research.The work in this thesis has contributed to increased awareness of the unique MRI exposure environment, the characteristics of the magnetic fields involved, and the inherent exposure variability in MRI exams. The metrics and methods presented are specifically suited to exposure assessment of the unique MRI environment, and may contribute to improved research quality by allowing for meaningful comparisons between study results and for experimental conditions to be easily replicated in future studies.
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| 2. |
- Hansson, Boel, et al.
(författare)
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MR-safety: Evaluation of compliance with screening routines using a structured screening interview
- 2022
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Ingår i: Journal of Patient Safety and Risk Management. - : SAGE Publications. - 2516-0435 .- 2516-0443. ; 27:2, s. 76-82
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Tidskriftsartikel (refereegranskat)abstract
- Background Magnetic resonance (MR) safety procedures are designed to allow patients, research subjects and personnel to enter the MR-scanner room under controlled conditions and without the risk to be harmed during the examination. Ferromagnetic objects in the MR-environment or inside the human body represent the main safety risks potentially leading to human injuries. Screening for MR-safety risks with dedicated procedures is therefore mandatory. As human errors during the screening procedure might align and lead to an incident compliance is essential. Purpose To evaluate compliance with a documented structured MR-safety screening process. Method Written and signed MR-safety screening documentation collected at a national 7T MR facility during a four-year period was evaluated for compliance of trained personnel with multi-step MR-safety routines. We analysed whether examinations were performed or why they were not performed. Data analysis further included descriptive statistics of the study population (age, gender and patient or healthy volunteer status), identification of missing documents and omitted or incorrect answers, and whether these compliance shortcomings concerned predominantly administrative or MR-safety related issues. Results Documentation of the screening process in 1819 subjects was incomplete in 19% of subjects. The most common documentation shortcoming was omitted fields. Out of 478 omitted answer-fields in 307 subjects, 36% were of administrative nature and 64% related directly to MR-safety issues. Conclusion Compliance with MR-safety screening procedures cannot be taken for granted and deficiencies to comply with screening routines were revealed. Documentation shortcomings concerned both administrative and MR-safety related issues.
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| 3. |
- Hansson, Boel, et al.
(författare)
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Subjectively Reported Effects Experienced in an Actively Shielded 7T MRI: A Large-Scale Study.
- 2020
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Ingår i: Journal of magnetic resonance imaging : JMRI. - : Wiley. - 1522-2586 .- 1053-1807. ; 52:4, s. 1265-1276
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Tidskriftsartikel (refereegranskat)abstract
- Ultrahigh-field (UHF) MRI advances towards clinical use. Patient compliance is generally high, but few large-scale studies have investigated the effects experienced in 7T MRI systems, especially considering peripheral nerve stimulation (PNS) and caregiving.To evaluate the quantity, the intensity, and subjective experiences from short-term effects, focusing on the levels of comfort and compliance of subjects.Prospective.In all, 954 consecutive MRIs in 801 subjects for 3years.7T.After the 7T examination, a questionnaire was used to collect data.Descriptive statistics, Spearman's rank correlation, Mann-Whitney U-test, and t-test.The majority (63%) of subjects agreed that the MRI experience was comfortable and 93% would be willing to undergo future 7T MRI as a patient (5% undecided) and 82% for research purposes (12% undecided). The most common short-term effects experienced were dizziness (81%), inconsistent movement (68%), PNS (63%), headache (40%), nausea (32%), metallic taste (12%), and light flashes (8%). Of the subjects who reported having PNS (n = 603), 44% experienced PNS as "not uncomfortable at all," 45% as "little or very little uncomfortable," and 11% as "moderate to very much uncomfortable." Scanner room temperature was experienced more comfortable before (78%) than during (58%) examinations, and the noise level was acceptable by 90% of subjects. Anxiety before the examination was reported by 43%. Patients differed from healthy volunteers regarding an experience of headache, metallic taste, dizziness, or anxiety. Room for improvement was pointed out after 117 examinations concerning given information (n = 73), communication and sound system (n = 35), or nursing care (n = 15).Subjectively reported effects occur in actively shielded 7T MRI and include physiological responses and individual psychological issues. Although leaving room for improvement, few subjects experienced these effects being so uncomfortable that they would lead to aversion to future UHF examinations.1 TECHNICAL EFFICACY: Stage 5.
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| 4. |
- Hansson, Boel, et al.
(författare)
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Swedish national survey on MR safety compared with CT : a false sense of security?
- 2020
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Ingår i: European Radiology. - : Springer Science and Business Media LLC. - 0938-7994 .- 1432-1084. ; 30:4, s. 1918-1926
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: The objectives were to survey MR safety incidents in Sweden during a 12-month period, to assess severity scores, and to evaluate the confidence of MR personnel in incident-reporting mechanisms. Method: Data were collected within a web-based questionnaire on safety in clinical MR environments with CT for comparison. Data reported MR and CT safety incidents (human injury, material damage, and close calls), incident severity, and confidence of participants in incident-reporting systems. Results: The study population consisted of 529 eligible participants. Participants reported 200 MR and 156 CT safety incidents. Among MR incidents, 16% were given the highest potential severity score. More MR workers (73%) than CT workers (50%) were confident in being aware of any incident occurring at their workplace. However, 69% MR workers (83% for CT) were not aware of reported incidents at their hospitals. Conclusion: Safety incidents resulting in human injury, material damage, and close calls in clinical MR environments do occur. According to national risk assessment recommendations, risk level is high. Results indicated that MR personnel tend to a false sense of security, as a high proportion of staff members were sure that they would have been aware of any incident occurring in their own department, while in reality, incidents did occur without their knowledge. We conclude that false sense of security exists for MR. Key Points: • Safety incidents in clinical MR environments still result in human injury and material damage. • Severity level of MR incidents—assessed using Swedish national risk assessment recommendations—is high. • Confidence of MR personnel in incident-reporting mechanisms is high, but reflects a false sense of security, as a high proportion of staff is unaware of reported incidents in the same workplace.
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| 5. |
- Wilén, Jonna, et al.
(författare)
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Valid Exposure Protocols Needed in Magnetic Resonance Imaging Genotoxic Research
- 2020
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Ingår i: Bioelectromagnetics. - : WILEY. - 0197-8462 .- 1521-186X. ; 41:3, s. 247-257
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Tidskriftsartikel (refereegranskat)abstract
- Several in vitro and in vivo studies have investigated if a magnetic resonance imaging (MRI) examination can cause DNA damage in human blood cells. However, the electromagnetic field (EMF) exposure that the cells received in the MR scanner was not sufficiently described. The first studies looking into this could be regarded as hypothesis-generating studies. However, for further exploration into the role of MRI exposure on DNA integrity, the exposure itself cannot be ignored. The lack of sufficient method descriptions makes the early experiments difficult, if not impossible, to repeat. The golden rule in all experimental work is that a study should be repeatable by someone with the right knowledge and equipment, and this is simply not the case with many of the recent studies on MRI and genotoxicity. Here we discuss what is lacking in previous studies, and how we think the next generation of in vitro and in vivo studies on MRI and genotoxicity should be performed. Bioelectromagnetics.
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