Lack of mutagenic and co-mutagenic effects of magnetic fields during magnetic resonance imaging

Effects of Static and Low-Frequency Magnetic Fields on Gene Expression

Substantial research over the past two decades has established that magnetic fields affect fundamental cellular processes, including gene expression. However, since biological cells and subcellular components exhibit diamagnetic behavior and are therefore subjected to very small magnetic forces that cannot directly compete with the viscoelastic and bioelectric intracellular forces responsible for cellular machinery functions, it becomes challenging to understand cell-magnetic field interactions and to reveal the mechanisms through which these interactions differentially influence gene expression in cells. The limited understanding of the molecular mechanisms underlying biomagnetic effects has hindered progress in developing effective therapeutic applications of magnetic fields. This review examines the expanding body of literature on genetic events during static and low-frequency magnetic field exposure, focusing particularly on how changes in gene expression interact with cellular machinery. To address this, we conducted a systematic review utilizing extensive search strategies across multiple databases. We explore the intracellular mechanisms through which transcription functions may be modified by a magnetic field in contexts where other cellular signaling pathways are also activated by the field. This review summarizes key findings in the field, outlines the connections between magnetic fields and gene expression changes, identifies critical gaps in current knowledge, and proposes directions for future research. LEVEL OF EVIDENCE: NA TECHNICAL EFFICACY: Stage 4.

The Effect of Contrast Enhanced Abdominopelvic Magnetic Resonance Imaging on Expression and Methylation Level of ATM and AKT Genes

Objective

To evaluate the effect of contrast enhanced abdominopelvic magnetic resonance imaging (MRI), using a 3 Tesla scanner, on expression and methylation level of ATM and AKT genes in human peripheral blood lymphocytes.

Materials and Methods

In this prospective in vivo study, blood samples were obtained from 20 volunteer patients with mean age of 43 ± 8 years (range 32-68 years) before contrast enhanced MRI, 2 hours and 24 hours after contrast enhanced abdominopelvic 3 Tesla MRI. After separation of mononuclear cells from peripheral blood, using Ficoll-Hypaque, we analyzed gene expression changes of ATM and AKT genes 2 hours and 24 hours after MRI using quantitative reverse transcription polymerase chain reaction (qRT-PCR). We also evaluated methylation percentage of the above mentioned genes in before, 2 hours and 24 hours after MRI, using MethySYBR method.

Results

Fold change analysis, in comparison with the baseline, respectively showed 1.1 ± 0.7 and 0.8 ± 0.5 mean of gene expressions in 2 and 24 hours after MRI for ATM, while the results were 1.4 ± 0.6 and 1.4 ± 1 for AKT (P>0.05). Methylation of the ATM gene promoter were 8.8 ± 1.5%, 9 ± 0.6% and 9 ± 0.8% in before contrast enhanced MRI, 2 and 24 hours after contrast enhanced MRI, respectively (P>0.05). Methylation of AKT gene promoter in before contrast enhanced MRI, 2 hours and 24 hours after contrast enhanced MRI was 5.4 ± 2.5, 5 ± 3.2, 4.9 ± 2.9 respectively (P>0.05).

Conclusion

Contrast enhanced abdominopelvic MRI using 3 Tesla scanner apparently has no negative effect on the expression and promoter methylation level of ATM and AKT genes involved in the repair pathways of genome.

The genotoxic effects of contrast enhanced abdominopelvic 3-tesla magnetic resonance imaging on human circulating leucocytes

PURPOSE

To evaluate the effects of contrast enhanced abdominopelvic magnetic resonance imaging (MRI) on DNA damage.

METHODS

For this study, blood samples of 20 volunteers (15 women and 5 men) with mean age of 43 ± 8 years were assessed. The mean age of women was 41.4 ± 8.9 years and mean age of men was 48.5 ± 4.9 years (P = 0.14). Peripheral blood samples were collected before, 2 and 24 h after MRI in heparin and ethylenediaminetetraacetic acid (EDTA) containing tubes. Heparinized blood was cultured to assess the cytogenetic effects using cytokinesis blocked micronucleus (CBMN) assay. After isolation of mononuclear cells, alterations in genes involved in repair (CHEK2, p21) and apoptosis (BAX, BCL2) were analyzed using real-time polymerase chain reaction (qRT-PCR).

RESULTS

The mean number of MN in binucleated cells at before, 2 and 24 h after MRI were 17.9 ± 2.9, 18.1 ± 2.4 and 18.3 ± 2.6, respectively (p > 0.05). Results of gene expression according to fold change compared with the baseline were 1.2 ± 0.6 and 1.02 ± 0.5 at 2 and 24 h after MRI for CHEK2, and 1.3 ± 0.7 and 1.7 ± 0.7 for CDKN1A (p21); respectively (p > 0.05). Gene expression based on fold change compared with baseline were 0.9 ± 0.6 and 1.2 ± 0.8 at 2 and 24 h after MRI for BAX, and 1.05 ± 0.3 and 1.1 ± 0.7 for BCL2; respectively (p > 0.05).

CONCLUSION

Contrast enhanced abdominopelvic MRI showed no adverse effect on DNA in terms of MN formation and alterations in expression levels of some genes involved in repair and apoptosis pathways.

Valid Exposure Protocols Needed in Magnetic Resonance Imaging Genotoxic Research

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.

Comments on potential health effects of MRI-induced DNA lesions: quality is more important to consider than quantity

Magnetic resonance imaging (MRI) is increasingly being used in cardiology to detect heart disease and guide therapy. It is mooted to be a safer alternative to imaging techniques, such as computed tomography (CT) or coronary angiographic imaging. However, there has recently been an increased interest in the potential long-term health risks of MRI, especially in the light of the controversy resulting from a small number of research studies reporting an increase in DNA damage following exposure, with calls to limit its use and avoid unnecessary examination, according to the precautionary principle. Overall the published data are somewhat limited and inconsistent; the ability of MRI to produce DNA lesions has yet to be robustly demonstrated and future experiments should be carefully designed to optimize sensitivity and benchmarked to validate and assess reproducibility. The majority of the current studies have focussed on the initial induction of DNA damage, and this has led to comparisons between the reported induction of γH2AX and implied double-strand break (DSB) yields produced following MRI with induction by imaging techniques using ionizing radiation. However, γH2AX is not only a marker of classical double-ended DSB, but also a marker of stalled replication forks and in certain circumstances stalled DNA transcription. Additionally, ionizing radiation is efficient at producing complex DNA damage, unique to ionizing radiation, with an associated reduction in repairability. Even if the fields associated with MRI are capable of producing DNA damage, the lesions produced will in general be simple, similar to those produced by endogenous processes. It is therefore inappropriate to try and infer cancer risk by simply comparing the yields of γH2AX foci or DNA lesions potentially produced by MRI to those produced by a given exposure of ionizing radiation, which will generally be more biologically effective and have a greater probability of leading to long-term health effects. As a result, it is important to concentrate on more relevant downstream end points (e.g. chromosome aberration production), along with potential mechanisms by which MRI may lead to DNA lesions. This could potentially involve a perturbation in homeostasis of oxidative stress, modifying the background rate of endogenous DNA damage induction. In summary, what the field needs at the moment is more research and less fear mongering.

Magnetic resonance imaging (MRI): A review of genetic damage investigations

Magnetic resonance imaging (MRI) is a powerful, non-invasive diagnostic medical imaging technique widely used to acquire detailed information about anatomy and function of different organs in the body, in both health and disease. It utilizes electromagnetic fields of three different frequency bands: static magnetic field (SMF), time-varying gradient magnetic fields (GMF) in the kHz range and pulsed radiofrequency fields (RF) in the MHz range. There have been some investigations examining the extent of genetic damage following exposure of bacterial and human cells to all three frequency bands of electromagnetic fields, as used during MRI: the rationale for these studies is the well documented evidence of positive correlation between significantly increased genetic damage and carcinogenesis. Overall, the published data were not sufficiently informative and useful because of the small sample size, inappropriate comparison of experimental groups, etc. Besides, when an increased damage was observed in MRI-exposed cells, the fate of such lesions was not further explored from multiple 'down-stream' events. This review provides: (i) information on the basic principles used in MRI technology, (ii) detailed experimental protocols, results and critical comments on the genetic damage investigations thus far conducted using MRI equipment and, (iii) a discussion on several gaps in knowledge in the current scientific literature on MRI. Comprehensive, international, multi-centered collaborative studies, using a common and widely used MRI exposure protocol (cardiac or brain scan) incorporating several genetic/epigenetic damage end-points as well as epidemiological investigations, in large number of individuals/patients are warranted to reduce and perhaps, eliminate uncertainties raised in genetic damage investigations in cells exposed in vitro and in vivo to MRI.

Bioeffects of static magnetic fields: oxidative stress, genotoxic effects, and cancer studies

The interaction of static magnetic fields (SMFs) with living organisms is a rapidly growing field of investigation. The magnetic fields (MFs) effect observed with radical pair recombination is one of the well-known mechanisms by which MFs interact with biological systems. Exposure to SMF can increase the activity, concentration, and life time of paramagnetic free radicals, which might cause oxidative stress, genetic mutation, and/or apoptosis. Current evidence suggests that cell proliferation can be influenced by a treatment with both SMFs and anticancer drugs. It has been recently found that SMFs can enhance the anticancer effect of chemotherapeutic drugs; this may provide a new strategy for cancer therapy. This review focuses on our own data and other data from the literature of SMFs bioeffects. Three main areas of investigation have been covered: free radical generation and oxidative stress, apoptosis and genotoxicity, and cancer. After an introduction on SMF classification and medical applications, the basic phenomena to understand the bioeffects are described. The scientific literature is summarized, integrated, and critically analyzed with the help of authoritative reviews by recognized experts; international safety guidelines are also cited.

Mapping fetal brain development in utero using magnetic resonance imaging: the Big Bang of brain mapping

The development of tools to construct and investigate probabilistic maps of the adult human brain from magnetic resonance imaging (MRI) has led to advances in both basic neuroscience and clinical diagnosis. These tools are increasingly being applied to brain development in adolescence and childhood, and even to neonatal and premature neonatal imaging. Even earlier in development, parallel advances in clinical fetal MRI have led to its growing use as a tool in challenging medical conditions. This has motivated new engineering developments encompassing optimal fast MRI scans and techniques derived from computer vision, the combination of which allows full 3D imaging of the moving fetal brain in utero without sedation. These promise to provide a new and unprecedented window into early human brain growth. This article reviews the developments that have led us to this point, examines the current state of the art in the fields of fast fetal imaging and motion correction, and describes the tools to analyze dynamically changing fetal brain structure. New methods to deal with developmental tissue segmentation and the construction of spatiotemporal atlases are examined, together with techniques to map fetal brain growth patterns.

Practice patterns in imaging of the pregnant patient with abdominal pain: a survey of academic centers

OBJECTIVE

The purpose of our study was to evaluate current practice patterns in the imaging of pregnant women with abdominal complaints.

MATERIALS AND METHODS

A survey was sent to the abdominal imaging division of 183 radiology residency programs in the United States. The survey asked for information regarding CT and MRI of abdominal complaints in pregnant patients.

RESULTS

Eighty-five surveys (46%) were returned. Sixty-three (74%) of 85 of respondents have a written departmental policy regarding imaging pregnant women. Eighty-two (96%) of 85 perform CT in pregnant women when benefits outweigh risks, with 58 (68%) obtaining written informed consent before CT examination. Eighty (94%) of 85 perform MRI in pregnant women, and 43 (51%) obtain written consent before MRI. Fifty-seven (67%) of 85 respondents do not administer gadolinium in pregnancy. In the setting of trauma, respondents choose CT over MRI for imaging in all three trimesters (75% vs 5%, 85% vs 5%, and 88% vs 4%). In the second and third trimesters, respondents prefer CT to MRI to evaluate for maternal renal calculus (35% vs 20% and 48% vs 18%, respectively), appendicitis (48% vs 38% and 58% vs 29%), and abscess (49% vs 41% and 58% vs 35%). However, MRI is preferred for imaging of appendicitis and abscesses in the first trimester (39% vs 32% and 46% vs 32%).

CONCLUSION

Most academic radiology departments have written policies regarding imaging of pregnant women. Academic radiologists prefer CT to MRI for imaging abdominal complaints in pregnant women, especially in the second and third trimesters.

Sectional anatomic and magnetic resonance imaging features of coelomic structures of loggerhead sea turtles

OBJECTIVE

To compare cross-sectional anatomic specimens with images obtained via magnetic resonance imaging (MRI) of the coelomic structures of loggerhead sea turtles (Caretta caretta).

ANIMALS

5 clinically normal live turtles and 5 dead turtles.

PROCEDURES

MRI was used to produce T1- and T2- weighted images of the turtles, which were compared with gross anatomic sections of 3 of the 5 dead turtles. The other 2 dead turtles received injection with latex and were dissected to provide additional cardiovascular anatomic data.

RESULTS

The general view on the 3 oriented planes provided good understanding of cross-sectional anatomic features. Likewise, major anatomic structures such as the esophagus, stomach, lungs, intestine (duodenum and colon), liver, gallbladder, spleen, kidneys, urinary bladder, heart, bronchi, and vessels could be clearly imaged. It was not possible to recognize the ureters or reproductive tract.

CONCLUSIONS AND CLINICAL RELEVANCE

By providing reference information for clinical use, MRI may be valuable for detailed assessment of the internal anatomic structures of loggerhead sea turtles. Drawbacks exist in association with anesthesia and the cost and availability of MRI, but the technique does provide excellent images of most internal organs. Information concerning structures such as the pancreas, ureters, intestinal segments (jejunum and ileum), and the reproductive tract is limited because of inconsistent visualization.

Cortex reorganization of Xenopus laevis eggs in strong static magnetic fields

Observations of magnetic field effects on biological systems have often been contradictory. For amphibian eggs, a review of the available literature suggests that part of the discrepancies might be resolved by considering a previously neglected parameter for morphological alterations induced by magnetic fields--the jelly layers that normally surround the egg and are often removed in laboratory studies for easier cell handling. To experimentally test this hypothesis, we observed the morphology of fertilizable Xenopus laevis eggs with and without jelly coat that were subjected to static magnetic fields of up to 9.4 T for different periods of time. A complex reorganization of cortical pigmentation was found in dejellied eggs as a function of the magnetic field and the field exposure time. Initial pigment rearrangements could be observed at about 0.5 T, and less than 3 T are required for the effects to fully develop within two hours. No effect was observed when the jelly layers of the eggs were left intact. These results suggest that the action of magnetic fields might involve cortical pigments or associated cytoskeletal structures normally held in place by the jelly layers and that the presence of the jelly layer should indeed be included in further studies of magnetic field effects in this system.

Genotoxicity evaluation of electromagnetic fields generated by 835-MHz mobile phone frequency band

It is still unclear whether the exposure to electromagnetic fields (EMFs) generated by mobile phone radiation is directly linked to cancer. We examined the biological effects of an EMF at 835 MHz, the most widely used communication frequency band in Korean CDMA mobile phone networks, on bacterial reverse mutation (Ames assay) and DNA stability (in vitro DNA degradation). In the Ames assay, tester strains alone or combined with positive mutagen were applied in an artificial mobile phone frequency EMF generator with continuous waveform at a specific absorption rate (SAR) of 4 W/kg for 48 h. In the presence of the 835-MHz EMF radiation, incubation with positive mutagen 4-nitroquinoline-1-oxide and cumene hydroxide further increased the mutation rate in Escherichia coli WP2 and TA102, respectively, while the contrary results in Salmonella typhimurium TA98 and TA1535 treated with 4-nitroquinoline-1-oxide and sodium azide, respectively, were shown as antimutagenic. However, these mutagenic or co-mutagenic effects of 835-MHz radiation were not significantly repeated in other relevant strains with same mutation type. In the DNA degradation test, the exposure to 835-MHz EMF did not change the rate of degradation observed using plasmid pBluescript SK(+) as an indicator. Thus, we suggest that 835-MHz EMF under the conditions of our study neither affected the reverse mutation frequency nor accelerated DNA degradation in vitro.

Safety of the magnetic field generated by a neuronal magnetic stimulator: evaluation of possible mutagenic effects

OBJECTIVE

The possible mutagenicity of a magnetic stimulus was checked using the Ames test with Salmonella typhimurium TA98 and TA100 as tester strains.

METHODS

Samples of these bacteria were exposed to a pulsed magnetic field, on the order of 1 T. The magnetic pulses were generated by a neuronal magnetic stimulator with a flat coil. The magnetic stimulus was a continuous sequence of slightly damped half sinusoids at a rate of 5 pulses/s. Exposure times were 2-5 and 15 min. Exposure position was such as to maximise the magnetic field and minimise the induced electric field. Room temperature was maintained at 28.5 +/- 0.5 degrees C and the temperature was measured inside the samples.

RESULTS

None of the exposure conditions showed any increase in mutation in either of the two bacterial strains.

CONCLUSIONS

These results are discussed in comparison with effects found in the literature. The magnetic stimulation used under the conditions of this study does not appear to have mutagenic effects. This does not apply to cases where both strong electric and magnetic fields are present.

Effect of N-acetylaspartic acid on the diffusion coefficient of water: a proton magnetic resonance phantom method for measurement of osmolyte-obligated water

N-acetyl-L-aspartic acid (NAA) is an amino acid present in the vertebrate brain that is synthesized and stored primarily in neurons, although it cannot be hydrolyzed in these cells. Nonetheless, neuronal NAA is dynamic and turns over more than once each day by cycling, via extracellular fluids (ECF), between neurons and catabolic compartments in oligodendrocytes. One important role of the NAA intercompartmental cycle appears to be osmoregulatory, and in this role it may be the primary mechanism for the removal of metabolic water, against a water gradient, from myelinated neurons. However, the number of water molecules that might be cotransported to ECF per NAA molecule released is as yet unclear. In this investigation, using a proton nuclear magnetic resonance method and diffusion measurements at two magnetic field strengths on water and NAA phantoms in vitro, the effect of NAA on the diffusion coefficient of water has been measured, and a ratio (K) of obligated water molecules per molecule of NAA has been determined. For NAA measured at 100mM and 3 Tesla K=24 and at 7 Tesla K=14. Based on these results, apparent K(NAA) varies inversely with field strength, and with a computed field strength factor of 2.55mmol water/unit Tesla, K(NAA) in the absence of any applied magnetic field strength would be 32.