Dataset Information

Evaluation of specific absorption rate as a dosimetric quantity for electromagnetic fields bioeffects.

ABSTRACT:

Purpose

To evaluate SAR as a dosimetric quantity for EMF bioeffects, and identify ways for increasing the precision in EMF dosimetry and bioactivity assessment.

Methods

We discuss the interaction of man-made electromagnetic waves with biological matter and calculate the energy transferred to a single free ion within a cell. We analyze the physics and biology of SAR and evaluate the methods of its estimation. We discuss the experimentally observed non-linearity between electromagnetic exposure and biological effect.

Results

WE FIND THAT: a) The energy absorbed by living matter during exposure to environmentally accounted EMFs is normally well below the thermal level. b) All existing methods for SAR estimation, especially those based upon tissue conductivity and internal electric field, have serious deficiencies. c) The only method to estimate SAR without large error is by measuring temperature increases within biological tissue, which normally are negligible for environmental EMF intensities, and thus cannot be measured.

Conclusions

SAR actually refers to thermal effects, while the vast majority of the recorded biological effects from man-made non-ionizing environmental radiation are non-thermal. Even if SAR could be accurately estimated for a whole tissue, organ, or body, the biological/health effect is determined by tiny amounts of energy/power absorbed by specific biomolecules, which cannot be calculated. Moreover, it depends upon field parameters not taken into account in SAR calculation. Thus, SAR should not be used as the primary dosimetric quantity, but used only as a complementary measure, always reporting the estimating method and the corresponding error. Radiation/field intensity along with additional physical parameters (such as frequency, modulation etc) which can be directly and in any case more accurately measured on the surface of biological tissues, should constitute the primary measure for EMF exposures, in spite of similar uncertainty to predict the biological effect due to non-linearity.

SUBMITTER: Panagopoulos DJ

PROVIDER: S-EPMC3672148 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Publications

Evaluation of specific absorption rate as a dosimetric quantity for electromagnetic fields bioeffects.

Panagopoulos Dimitris J DJ Johansson Olle O Carlo George L GL

PloS one 20130604 6

<h4>Purpose</h4>To evaluate SAR as a dosimetric quantity for EMF bioeffects, and identify ways for increasing the precision in EMF dosimetry and bioactivity assessment.<h4>Methods</h4>We discuss the interaction of man-made electromagnetic waves with biological matter and calculate the energy transferred to a single free ion within a cell. We analyze the physics and biology of SAR and evaluate the methods of its estimation. We discuss the experimentally observed non-linearity between electromagne ...[more]

PMID: 23750202

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Project description:BackgroundMRI exams for patients with MR-conditional active implantable medical devices (AIMDs) are contraindicated unless specific conditions are met. This limits the maximum specific absorption rate (SAR, W/kg). Currently, there is no general framework to guide meeting a lower SAR limit.PurposeTo design and evaluate a workflow for modifying MRI protocols to whole-body SAR (WB-SAR ≤0.1 W/kg) and local-head SAR (LH-SAR ≤0.3 W/kg) limits while mitigating the impact on image quality and exam time.Study typeProspective.PopulationTwenty healthy volunteers on head (n = 5), C-spine (n = 5), T-spine (n = 5), and L-spine (n = 5) with IRB consent.AssessmentVendor-provided head, C-spine, T-spine, and L-spine protocols (SARRT ) were modified to meet both low SAR targets (SARLOW ) using the proposed workflow. in vitro SNR and CNR were evaluated with a T1 -T2 phantom. in vivo image quality and clinical acceptability were scored using a 5-point Likert scale for two blinded readers.Field strength/sequences1.5T/spin-echoes, gradient-echoes.Statistical analysisIn vitro SNR and CNR values were evaluated with a repeated measures general linear model. in vivo image quality and clinical acceptability were evaluated using a generalized estimating equation analysis (GEE). The two reader's level of agreement was analyzed using Cohen's kappa statistical analysis.ResultsUsing the workflow, SAR limits were met.Lh-sar0.12 ± 0.02 W/kg, median (SD) values for LH-SAR were 0.12 (0.02) W/kg and WB-SAR: 0.09 (0.01) W/kg. Examination time did not increase ≤2x the initial time. SARRT SNR values were higher and significantly different than SARLOW (P < 0.05). However, no significant difference was observed between the CNR values (value = 0.21). Median (IQR) CNR values were 14.2 (25.0) vs. 15.1 (9.2) for head, 12.1 (16.9) vs. 25.3 (14.2) for C-spine, 81.6 (70.1) vs. 71.0 (26.6) for T-spine, and 51.4 (52.6) vs. 37.7 (27.3) for L-spine. Image quality scores were not significantly different between SARRT and SARLOW (median [SD] scores were 4.0 [0.01] vs. 4.3 [0.2], P > 0.05).Data conclusionThe proposed workflow provides guidance for modifying routine MRI exams to achieve low SAR limits. This can benefit patients referred for an MRI exam with low SAR MR-conditional AIMDs.Level of evidence1 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2020;52:91-102.

Dataset Information

Evaluation of specific absorption rate as a dosimetric quantity for electromagnetic fields bioeffects.

Purpose

Methods

Results

Conclusions

Publications

Evaluation of specific absorption rate as a dosimetric quantity for electromagnetic fields bioeffects.

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