Assessing Exposures to Magnetic Resonance Imaging’s Complex Mixture of Magnetic Fields for In Vivo, In Vitro, and Epidemiologic Studies of Health Effects for Staff and Patients

Self Cite

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. Bioelectromagnetics. 40:3–15, 2019. © 2018 The Authors. Bioelectromagnetics Published by Wiley Periodicals, Inc.

Section: Introductionmentioning

confidence: 99%

EMF exposure variation among MRI sequences from pediatric examination protocols

Frankel

Mild

Olsrud

et al. 2018

Self Cite

“…Usually during clinical scanning, as many as 10 different sequences can be used to get the appropriate information. Based on our measurements, the peak values for the RF B 1 can reach several µT [Frankel et al, 2018;Frankel et al, 2019]. As the duty cycle in some sequences can be as low as a few percent, the short-term SAR value within each pulse can be rather high, in comparison with the time-averaged values of entire sequences.…”

Section: Exposure During An Mri Scanmentioning

confidence: 79%

“…We will here give a short introduction to the magnetic fields that are present in the MRI environment. For more detailed information, see, for instance, Kim and Kim [2017], Frankel et al [2018], andMcRobbie et al [2017]. There are also electric fields present in the MRI environment [Kangarlu et al, 2007;Park et al, 2015;Saniour et al, 2018].…”

Section: Exposure During An Mri Scanmentioning

confidence: 99%

“…Each MRI scanner has numerous preprogrammed investigation protocols consisting of various sequences to optimize the imaging results for the clinical question under investigation. The SGF varies between MRI sequences, and some examples of waveforms of the applied current in the gradient coils are given by Frankel et al [2018].…”

Section: Exposure During An Mri Scanmentioning

confidence: 99%

“…The amount of RF energy deposited depends on the setting of the parameters for the sequence, such as the flip angle and number of scanned slices. Furthermore, the SAR value reported by the scanner is an estimate with some inaccuracy in it [Allison and Yanasak, 2015;Frankel et al, 2018].…”

Section: Exposure During An Mri Scanmentioning

confidence: 99%

See 2 more Smart Citations

Valid Exposure Protocols Needed in Magnetic Resonance Imaging Genotoxic Research

Wilén

Olsrud

Frankel

et al. 2020

Self Cite

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. © 2020 Bioelectromagnetics Society.

Static Magnetic Field (0.2–0.4 T) Stimulates the Self‐Renewal Ability of Osteosarcoma Stem Cells Through Autophagic Degradation of Ferritin

Zhao

Wang

et al. 2021

Static magnetic field (SMF) can alter cell fate decisions in many ways. However, the effects of SMF on cancer stem cells (CSCs) are little-known. In this particular study, we evaluate the biological effect of moderate-intensity SMF on osteosarcoma stem cells (OSCs) and try to clarify the underlying mechanisms of action. First, we demonstrated that prolonged exposure to SMF induced the proliferation and tumorsphere formation in K7M2 and MG63 OSCs. Moreover, SMF promoted the release of ferrous iron (Fe 2+ ) and provoked reactive oxygen species (ROS) in OSCs. Interestingly, SMF evidently triggered the autophagic degradation of ferritin, which is characterized by the activation of microtubule-associated protein 1 light chain 3 (LC3) and nuclear receptor coactivator 4 (NCOA4), and downregulation of ferritin heavy chain 1 (FTH1) in OSCs. Particularly, the colony-forming ability of K7M2 OSCs promoted by SMF was obviously abolished by using a small interfering RNA (siRNA) against NCOA4. Finally, treatment of the tumor-bearing mice with SMF did not affect the tumor volume or tumor mass, nor pulmonary metastasis of K7M2 OSCs, but the SMF-treated K7M2 OSCs caused a preference of pulmonary metastasis in a mouse model, which suggested that SMF might induce the metastatic characteristic of OSCs. Consequently, this paper demonstrates for the first time that the cumulative SMF exposure promoted the self-renewal ability of OSCs via autophagic degradation of ferritin, implying that ferritinophagy may be a potential molecular target for cancer. Bioelectromagnetics. 2021;42:371-383.