RF-EMF exposure of fetus and mother during magnetic resonance imaging.

Abstract

Magnetic resonance imaging (MRI) avoids risks of genetic damage but may be associated with excess heating of body tissues. To investigate the exposure to MRI radio-frequency (RF) electromagnetic fields (EMF), low-pass and high-pass birdcage coils were simulated and the whole-body pregnant woman model SILVY used to determine local and whole-body specific absorption rates (SAR) in mother and fetus. Resonant RF-EMF of MRI devices were investigated at 0.3, 1, 1.5, 2, 3 and 4 T. Results allow extrapolation also to higher fields. They showed that local SAR in mother's trunk reaches exposure limits first. However, data show that during abdominal MRI meeting exposure limits of the mother is not sufficient to protect the fetus if limits of the general populations are applied to it. In that case fetal whole-body SAR exceeds limits by 7.4-fold. It is up to the physician and/or the ethics commission to decide upon justification for abdominal MRI of pregnant women if limits are exceeded. The results indicate the need for specifically addressing fetal exposure to EMF and elaborating general recommendations by radiation protection bodies.

AI evidence extraction

Main findings

Simulations of low-pass and high-pass birdcage coils with a pregnant woman model across MRI field strengths (0.3, 1, 1.5, 2, 3 and 4 T) found that local SAR in the mother’s trunk reaches exposure limits first. The authors report that meeting maternal exposure limits during abdominal MRI may not be sufficient to protect the fetus when general-population limits are applied to the fetus; fetal whole-body SAR was reported to exceed limits by 7.4-fold.

Outcomes measured

• Local specific absorption rate (SAR) in mother
• Whole-body SAR in mother
• Whole-body SAR in fetus
• Exceedance of exposure limits during abdominal MRI

Limitations

• Computational simulation study (no direct measurements in humans reported in abstract)
• Exposure described by MRI field strengths (T) rather than RF frequency values in MHz
• Details of coil settings, imaging sequences, and assumptions for extrapolation to higher fields not provided in abstract
• No sample size applicable/reported for model-based analysis

Suggested hubs

• who-icnirp (0.6)
  Abstract discusses exceedance of exposure limits and calls for recommendations by radiation protection bodies.

{
    "study_type": "engineering",
    "exposure": {
        "band": "RF",
        "source": "magnetic resonance imaging (MRI)",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": "Pregnant woman and fetus (computational whole-body model SILVY)",
    "sample_size": null,
    "outcomes": [
        "Local specific absorption rate (SAR) in mother",
        "Whole-body SAR in mother",
        "Whole-body SAR in fetus",
        "Exceedance of exposure limits during abdominal MRI"
    ],
    "main_findings": "Simulations of low-pass and high-pass birdcage coils with a pregnant woman model across MRI field strengths (0.3, 1, 1.5, 2, 3 and 4 T) found that local SAR in the mother’s trunk reaches exposure limits first. The authors report that meeting maternal exposure limits during abdominal MRI may not be sufficient to protect the fetus when general-population limits are applied to the fetus; fetal whole-body SAR was reported to exceed limits by 7.4-fold.",
    "effect_direction": "harm",
    "limitations": [
        "Computational simulation study (no direct measurements in humans reported in abstract)",
        "Exposure described by MRI field strengths (T) rather than RF frequency values in MHz",
        "Details of coil settings, imaging sequences, and assumptions for extrapolation to higher fields not provided in abstract",
        "No sample size applicable/reported for model-based analysis"
    ],
    "evidence_strength": "low",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "MRI",
        "RF-EMF",
        "pregnancy",
        "fetus",
        "specific absorption rate",
        "SAR",
        "birdcage coil",
        "abdominal MRI",
        "exposure limits",
        "thermal heating"
    ],
    "suggested_hubs": [
        {
            "slug": "who-icnirp",
            "weight": 0.59999999999999997779553950749686919152736663818359375,
            "reason": "Abstract discusses exceedance of exposure limits and calls for recommendations by radiation protection bodies."
        }
    ]
}

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