| 1. |
- Frankel, Jennifer, et al.
(författare)
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EMF exposure variation among MRI sequences from pediatric examination protocols
- 2019
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Ingår i: Bioelectromagnetics. - : Wiley-Blackwell. - 0197-8462 .- 1521-186X. ; 40:1, s. 3-15
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic resonance imaging (MRI) exposure environment is unique due to the mixture and intensity of magnetic fields involved. Current safety regulations are based on well-known acute effects of heating and neuroexcitation while the scientific grounds for possible long-term effects from MRI exposure are lacking. Epidemiological research requires careful exposure characterization, and as a first step toward improved exposure assessment we set out to characterize the MRI-patient exposure environment. Seven MRI sequences were run on a 3-Tesla scanner while the radiofrequency and gradient magnetic fields were measured inside the scanner bore. The sequences were compared in terms of 14 different exposure parameters. To study within-sequence variability, we varied sequence settings such as flip angle and slice thickness one at a time, to determine if they had any impact on exposure endpoints. There were significant differences between two or more sequences for all fourteen exposure parameters. Within-sequence differences were up to 60% of the corresponding between-sequence differences, and a 5-8 fold exposure increase was caused by variations in flip angle, slice spacing, and field of view. MRI exposure is therefore not only sequence-specific but also patient- and examination occurrence-specific, a complexity that requires careful consideration for an MRI exposure assessment in epidemiological studies to be meaningful.
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| 2. |
- Hansson, Boel, et al.
(författare)
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Short-term effects experienced during examinations in an actively shielded 7T MR.
- 2019
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Ingår i: Bioelectromagnetics. - : Wiley. - 1521-186X .- 0197-8462. ; 40:4, s. 234-249
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to evaluate occurrence and strength of short-term effects experienced by study participants in an actively shielded (AS) 7 tesla (7T) magnetic resonance (MR) scanner, to compare results with earlier reports on passively shielded (PS) 7T MR scanners, and to outline possible healthcare strategies to improve patient compliance. Study participants (n=124) completed a web-based questionnaire directly after being examined in an AS 7T MR (n=154 examinations). Most frequently experienced short-term effects were dizziness (84%) and inconsistent movement (70%), especially while moving into or out of the magnet. Peripheral nerve stimulation (PNS)-twitching-was experienced in 67% of research examinations and showed a dependence between strength of twitches and recorded predicted PNS values. Of the participants, 74% experienced noise levels as acceptable and the majority experienced body and room temperature as comfortable. Of the study participants, 95% felt well-informed and felt they had had good contact with the staff before the examination. Willingness to undergo a future 7T examination was high (>90%). Our study concludes short-term effects are often experienced during examinations in an AS 7T MR, leaving room for improvement in nursing care strategies to increase patient compliance. Bioelectromagnetics. 2019;9999:XX-XX. © 2019 The Authors. Bioelectromagnetics Published by Wiley Periodicals, Inc.
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