Functional brain MRI in patients complaining of electrohypersensitivity after long term exposure to electromagnetic fields.

9 septembre 2017 par maty185

MRIpublicdomainq-0000611xholoe

RESULTS:

All ten patients had abnormal functional MRI brain scans. The abnormality was often described as hyper connectivity of the anterior component of the default mode in the medial orbitofrontal area. Other abnormalities were usually found. Regular MRI studies of the brain were mostly unremarkable in these patients.

CONCLUSION:

We propose that functional MRI studies should become a diagnostic aid when evaluating a patient who claims electrohypersensitivity (EHS) and has otherwise normal studies. Interestingly, the differential diagnosis for the abnormalities seen on the fMRI includes head injury. It turns out that many of our patients indeed had a history of head injury which was then followed sometime later by the development of EHS. Many of our patients also had a history of exposure to potentially neurotoxic chemicals, especially mold. Head injury and neurotoxic chemical exposure may make a patient more vulnerable to develop EHS.

Source: https://www.ncbi.nlm.nih.gov/pubmed/28678737

The revised electromagnetic fields directive and worker exposure in environments with high magnetic flux densities.

https://www.ncbi.nlm.nih.gov/pubmed/24557933

One of the most noteworthy aspects of the new version of the directive is the exclusion of the limits of occupational exposure to electromagnetic fields in the clinical use of MRI. In exchange for this exception, physicians and experts in protection against non-ionizing radiation are asked to make additional efforts to train workers exposed to non-ionizing radiation and to establish mechanisms to guarantee the correct application of non-ionizing electromagnetic fields in patients, along similar lines to the principles of justification and optimization established for ionizing radiation. On the basis of the most recently published studies, this article reviews some safety-related aspects to take into account when examining patients with MRI with high magnetic fields.  https://www.ncbi.nlm.nih.gov/pubmed/24246885

Biological Effects and Safety in Magnetic Resonance Imaging: A Review

[…]the major application of high static MF is represented by Magnetic Resonance (MR), where a main magnet is used to generate a primary static field. Clinical imaging systems typically have field strengths up to 3T (1T = 10,000 Gauss, for reference the Earth’s magnetic field ≈ 0.5 Gauss)[…]

[…] Typical medical applications of IF comprise gradient fields which are superimposed upon the main static field in MR applications[…]

[…]RF electromagnetic fields for medical application have been introduced for therapeutic and diagnostic purposes. The first group comprises soft tissue healing appliances, cancer treatment with hyperthermia, and tissue heating [5] while the second are mainly RF fields associated to MR, necessary to generate a detectable MR signal [4].[…]

[…]During an MRI examination, three types of MF are employed to produce three dimensional images [4]: I) a high static MF, which generates a net magnetization vector in the human body, that is a measure of the proton density; II) a gradient MF (100 to 1,000 Hz), used to localize aligned protons inside the body, thus allowing spatial reconstruction of tissue sections into images; III) a RF electromagnetic wave (10 to 400 MHz), which energizes the magnetization vector allowing its detection by the MRI scanner, converting tissue properties into MR images. Different levels of contrast are based on the different magnetic properties and physical structure of the biological tissues (i.e. density of hydrogen atoms) [4].[…]

[…]To assess the potential dangerous biological effects associated with MRI environment and procedures, several studies have been conducted over the past thirty years, often producing controversial results.

Most of these studies are relative to the biological effects of a particular electromagnetic source utilized in MRI, while there is a lack of knowledge about the combination of three MF components. Thus, there is a need to integrate the current findings to better understand the interactions between EMF related to MRI and biological systems.[…]

[…]A recent paper of ICNIRP reviewed in vivo and in vitro studies carried out to detect biological responses to static MF in the range of milli T up to several T, in order to give new guidelines on limits of occupational exposures and exposure of general public [17]. The new proposed values are 2T for the occupational exposure of head and trunk, 8T for the occupational exposure of the limbs and, finally, 400mT for the general public exposure of any part of the body. These new guidelines do not apply to patients undergoing medical diagnosis or treatment: detailed considerations on the protection of patients are in preparation.[…]

[…]Cell growth, cell proliferation, cell cycle distribution pattern and apoptotic cell death seem not to be affected by an exposure up to four days at field strengths up to 10T [18], while an exposure of 10-17T for 30–60 minutes can reduce number and size, cells organization and vitality as observed in cultured mammalian cells [19]. A blood oxygenation dependent increase in blood viscosity due to an exposure of 1.5T was also observed in [20].

Genotoxic or carcinogenic effects have also been studied [21] and it was suggested that static MF might affect the process of cancer induction and/or progression by altering cellular responses to some known carcinogens (chemicals, radiation).[…]

[…]Neurobehavioral studies have shown a lack of effects on the normal activity of animals under exposure up to 1.5T, while exposures higher than 1.5T have led to adverse responses [23].

A change in Na+ or K+ ion channel conductivity produced by an exposure at 24T [24], and a reduction of visual evoked potential in the cat brain following an exposures to 120mT for 150s [25,26] were reported. It was suggested [27] that these effects result from the slow re-orientation of aligned groups of diamagnetic phospholipid molecules within the cell membrane.

Effects on cardiovascular function, including arterial blood pressure and peripheral blood flow, are less clearly established [22,28].[…]

[…]It is generally accepted that static fields below 1T are not genotoxic [30,31]. However, a recent study [32] reported significant, time and dose-dependent increases of the micronuclei frequency in mice exposed to static MFs of 2, 3 or 4.7T. Again, the general consensus is that there are insufficient studies to draw any conclusions relative to the genotoxicity or the carcinogenicity of static MF [33].[…]

[…]Studies on human volunteers exposed up to 8T, carried out to assess information about the relationship between exposure to high static MFs and human health, took into account as endpoints central and peripheral nervous activities, behavioural and cognitive functions, sensory perception, cardiac function, respiratory frequency, body temperature, but no conclusion could be drawn [15].

Temporary and dose-correlated vertigo and nausea in workers and patients exposed to static MFs higher than 2T have been found in several studies [34,35], while the correlation between the exposure and the metallic taste has not been confirmed [35]. No significant differences among several physiological parameters (heart rate, blood pressure, blood oxygenation, core temperature, ECG, respiratory rate) have been checked during the exposure at 8T, together with complete reversible tachycardia imputable to the stress correlated with the exam [34].

Finally, acute neurobehavioral effects, such as eye–hand coordination speed and visual and auditive working memory problems after exposure to static fields at 1.5 and 3T have been reported for health volunteers in [36].

A non statistically significant increase in the number of spontaneous abortion of MRI workers has been reported [37]. Different effects, such as fertility, length of gestation, birth weight, pregnancy outcome and offspring gender for pregnancies exposed to the MRI have also been reported [38], […]

[…]During an MRI examination, the gradient MF, which serves for the spatial localization in the image reconstruction process, is often switched on and off. For this reason, they are considered time varying MFs ranging between ELF and IF. Most of the available studies deal with possible association between residential ELF and cancer [33]. ELF MF has been classified in group 2B (“possibly carcinogenic to humans”), due to the possible association between residential MFs and childhood leukaemia [40]. Furthermore, a decreased survival of children with leukaemia after exposure to ELF magnetic fields has been observed [41], while no correlations have been established between ELF field exposure and breast cancer risk [42].

The time variation induces in the patient undergoing a MR scan, an electric field which could stimulate nerves and muscles, and could generate cardiac stimulation or even ventricular fibrillation. While the latter is a primary concern, being a life-threatening condition, possible peripheral nerve stimulation may cause discomfort and could not be tolerated by the subjects, thus interfering with the examination (e.g. due to patient movements) or would result in a request to stop the examination [43].

Due to technical difficulties for obtaining a reliable measure of induced electric currents, several works now are dealing with numerical simulations in human models [44].

In vitro effects

A significant increase of DNA strand breaks after ELF exposure was reported [45], while non-genotoxic mechanisms, such as stimulation of cell proliferation and apoptosis inhibition, can act as environmental agents for promoting cancer development [46]. An increase of micronucleus frequency in human fibroblasts exposed to a 50 Hz power line signal has been reported [47].

Mouse cell cultures exposed to gradient fields for hours did not show any effects with gradient fields of 25 mT/m in 300 ms [48]. Other studies [49,50] report no significant genotoxic effects as measured by sister chromatid exchange frequencies in human lymphocytes exposed to time varying fields of up to 220 μT, suggesting they are unlikely to act as carcinogens. Other studies report increased DNA synthesis in human fibroblast with exposure at 4 to 15 kHz [51], while fetal cell growth and cell cycle distribution of human lung fibroblasts exposed to gradient of 10mT/m are not affected [52]. These results provided no support for a teratogenic effect of this type of MF.

Detrimental effects of co-exposure to ELF and environmental carcinogens are reported, such as recombination of radical pairs alterations, indicating interactions among MF and chemical and/or physical agents [53]. This fact suggests that human population could be exposed to a variety of environmental insults which may not be genotoxic “per se”, but they may enhance the negative effects induced by other contaminants [2].[…]

[…]A 2000’s review [58] analyzed patient safety in time-varying gradient fields associated to a MR scan and concluded that cardiac stimulation is very unlikely in present-day systems, while at sufficient amplitudes, peripheral nerve stimulation is perceptible (tingling or tapping sensations) and can cause patient discomfort. Current safety standards have been developed by the International Electrotechnical Commission [59], establishing that the threshold for cardiac stimulation is largely above the value causing peripheral nerve stimulation, thus avoiding subjects’ ventricular fibrillation [60].

The use of MRI gradient MF represents a potential health risk beside peripheral nerve and cardiac stimulation to the patient. With the advent of the new generation of MR systems characterized by higher static MF and faster gradient fields, their effects on human health should be the object of further and properly designed studies.

[…]

[…]During an MRI scan, the patient is exposed to a time varying electromagnetic field in the RF range. It has been suggested that RF can induce effects via multiphoton absorption, i.e. through direct heating [61].

Thus, biological effects caused by RF field can be classified into two categories [62]:

  • – non thermal effects: due to direct interactions between MFs and tissues
  • – thermal effects: due to tissue heating caused by the induced electric currents

The non thermal effects have been less studied, however adverse effects mainly arise from a direct energy transfer from the field to the living system, which might be strongly non linear, and are dependent on the field frequency [63].

The temperature increase of the tissues due to the RF energy absorption, depends on parameters such as the electrical and geometrical tissue properties, the type of RF pulse used, its repetition time and the frequency of the radiation. The frequencies generally used in a MRI scanner are in the range at which high absorption occurs in the whole body [6]. Certain organs, such as the eyes and testes are, particularly sensitive to heating due to lack of perfusion, so the presence of “hot spots” at those sites can be very dangerous for the patient safety [64,65].

Moreover, tattoos and permanent cosmetics realized with iron oxide or other metal-based pigments, can cause reactions or adverse events (including first and second-degree burns) [6668].

The dosimetric parameter, normally used in safety standard and guidelines to quantify the energy absorption caused by RF, is the SAR [69]. During a MR scan the patient’s temperature is not easy to measure so SAR represents a convenient parameter to control any possible temperature increases. Generally, the MRI scanner software allows monitoring of the SAR for the whole body: these values have to be always below the limits values set by IEC standard [59] and must be recognizable by the software, so that if the SAR value exceeds the standard limits, the software stops the scanning process. The admitted SAR is usually 4 W/kg for a whole body scanner, calculated for a body temperature increase up to a 0.6 °C and a scanning period of 20–30 min [70,71].

It has been reported that, while average whole body SAR remains below the safety limits [72,73], hot spots could occur all the same making the automatic control system of the scanner not totally sufficient to assure patient safety.[…]

[…]There is a very wide body of literature regarding the possible induction of toxicity, genotoxicity, and transformation on mammalian cells in vitro due to high RF fields employed in cellular telephones (900-1,100 MHz) [74]. Although it is well known that the radiation energy from mobile phones is much lower than the energy necessary to break chemical bonds, several authors have reported DNA strand breaks, micronuclei induction and chromosomal aberrations [75] in human fibroblasts. Transient increase of DNA strand breaks in embryonic stem cell have also been reported [76].[…]

[…]Studies on effects due to RF at frequencies related to MR procedures are far less available.[…]

[…]Several studies have been carried out on animals to determine thermoregulatory reactions to tissue heating due to RF radiation at typical MR frequencies. These experiments demonstrated that RF exposure can cause a body temperature increase [63]. However, the results from animals cannot be extrapolated directly to humans since the pattern of the RF absorption strongly depends on the body size, the anatomical features and the sensitivity of the tissues [11].[…]

[…]Another study on volunteers [96] exposed to MR procedures with a high whole body SAR value (6 W/kg) monitored tympanic and skin temperature, heart rate, blood pressure, oxygen saturation and skin blood flow: statistically significant changes where found in some parameters such as skin blood flow, systolic blood pressure and heart rate, but all these changes were within acceptable safety levels.

A 2000’s review summarized physiological alterations in visual, auditory, endocrine, neural, cardiovascular, immune, reproductive, and developmental functions, under RF exposure: high levels of exposure were found to be related to an alteration of these functions [63].

Special attention was paid to over-heating of gonads [64] and eyes [65,97] for their reduced capabilities of heat dissipation thus becoming possible hot spots. In these experiments the observed temperature, however, was always below the recognized safety thresholds.

To date there have been no epidemiological studies regarding RF fields associated with MR procedures. The ICNIRP therefore recommends epidemiological studies to be done on subjects with high levels of cumulative exposure or with particular conditions, like pregnant occupational workers. Because of the advent of new generation MRI scanners with higher MFs, there is an urgent need for monitoring workers [98].[…]

[…]Effects of combination of Static, Gradient and RF fields during MRI scan[…]

[…]Unluckily, very few works deal with the biological effects due to the simultaneous exposure to the three types of MF.[…]

[…]Recently, some biophysical properties of erythrocytes were analyzed in 25 patients during a MRI scan [104]. The results showed a significant decrease in red blood cells membrane permeability, membrane elasticity and erythrocytes sedimentation rate during MRI, but the removal of the MF resulted in a rapid return to the normal conditions.

In our work, the possibility that MRI tests could be associated to DNA damage was investigated by in vitro as well as in vivo experiments [2]. Experiments were carried out both in vitro, by exposing lymphocyte cultures from healthy subjects to MRI for different periods and different variable magnetic fields (MFs) obtaining dose-effect curves, and in vivo, analyzing lymphocyte cultures set up from individuals before and after cardiac MRI scan. Statistically significant induction of MN was found consistently both in vitro and in vivo experiments. A certain degree of repair of the genetic damage across time was also observed. This former result is quite relevant for patient’s safety: after 48 hrs, the MN numbers returned into control values, suggesting that two cell divisions are enough to eliminate all MN from the lymphocytes population. This short recovery time may be due to death of micronucleated cells or to their dilution in the pool of unaffected dividing cells. In the in vivo experiments we used a clinical protocol for cardiac examinations but we consider our results to have a general impact for all MR procedures.

The observed increase of the MN frequency, followed by a rapid return to normal values, although not confirmative of a hypothesis of risk for people undergoing MRI examinations, strongly suggests the need for further studies.[…]

[…]Our work [2] also pinpointed the relevance of (sub)chronical exposure: during the in vitro experiments we used control flasks located in the console room, and other flasks, named as “room controls”, located in the scanner room, around three meters far from the scanner bore. These flasks were exposed to 1 Gauss static MF and to negligible RF and gradients fields. Room control data showed no statistically significant differences, even though a weak increase was always observed (data not shown). This observation suggests a need of awareness on occupational risk assessment for MRI operators, but also for the general population that could be exposed to different environmental insults, not genotoxic “per se”, which may enhance the negative effects induced by other biological, chemical and/or physical agents.[…]

[…]While it is well established that ionizing radiations impose risks to human health and the environment, the available data on possible effects of MRI procedures relevant for patient and worker safety are not sufficient to draw any conclusions. For this reason, in 2003, the FDA declared “nonsignificant risk status” for MRI clinical systems generating static fields up to 8T [107].

To our knowledge, our work [2] has been the first, and up to now the only one, demonstrating any genotoxic effects induced by MRI scans. We concluded that better auditing rules and a more informed consent will reduce the number of inappropriate examinations, thus avoiding detrimental effects both for public health and environment, it being understood that MRI procedures are relative more safe than any other clinical test using ionizing radiations. Anyway, until a wider knowledge of the potential risk related to diagnostic MRI is available, a prudent attention should be adopted in order to avoid unnecessary examinations, according to the precautionary principle.[…]

Read all the paper at original SOURCE:   https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2705217

Experimental studies carried out on volunteers showed that short-term exposure to SMF induces a variety of acute effects: (i) vertigo, nausea and a metallic taste in the mouth occur during body or head movement with SMF in T range and may result in a possible negative influence on the performance of workers during critical procedures, (ii) changes in blood pressure and heart rate within the range of physiological variability occur for exposures to SMF up to 8 T (iii) induction of ectopic heart beats and increased likelihood of reversible arrhythmia (possibly leading to ventricular fibrillation) may occur in susceptible workers) (iv) a decrease of working memory and eye-hand coordination are dose-dependent for exposures to 1.5-3 T SMF and may affect the performance of workers executing intricate procedures. The limitations of the available studies, however, do not allow any firm conclusions to be drawn about the effects of SMF on the described endpoints. https://www.ncbi.nlm.nih.gov/pubmed/18254536

World Health Organization . Environmental Health Criteria 232. Static fields. World Health Organization; Geneva, Switzerland: 2006: 

http://www.who.int/peh-emf/publications/EHC_232_Static_Fields_full_document.pdf

 

Catégories

septembre 2017
D L M M J V S
« Août   Oct »
 12
3456789
10111213141516
17181920212223
24252627282930

Entrez votre adresse mail pour suivre ce blog et être notifié(e) par email des nouvelles publications.

Rejoignez 20 autres abonnés

Statistiques du blog

  • 27 603 hits
%d blogueurs aiment cette page :