Electromagnetic simulation of RF burn injuries occurring at skin-skin and skin-bore wall contact points in an MRI scanner with a birdcage coil

Tang, Minghui; Okamoto, Kiyoi; Haruyama, Takuya; Yamamoto, Toru

doi:10.1016/j.ejmp.2021.02.008

Cited by 9 publications

(13 citation statements)

References 39 publications

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“…An RF burn case of thumb-thigh loop posture indicates that the RF-induced heating of the skin-to-skin contact point is high and dependent on the shift distance. 30 This study does not, however, explain the mechanism of high RF-induced heating for the body-loop posture.…”

Section: Introductionmentioning

confidence: 76%

Body‐loop related MRI radiofrequency‐induced heating hazards: Observations, characterizations, and recommendations

Yang

Zheng

Wang

et al. 2021

Magnetic Resonance in Med

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To assess RF-induced heating hazards in 1.5T MR systems caused by body-loop postures. Methods: Twelve advanced high-resolution anatomically correct human body models with different body-loop postures are created based on poseable human adult male models. Numerical simulations are performed to assess the radiofrequency (RF)-induced heating of these 12 models at 11 landmarks. A customized phantom is developed to validate the numerical simulations and quantitatively analyze factors affecting the RF-induced heating, eg, the contact area, the loop size, and the loading position. The RF-induced heating inside three differently posed phantoms is measured. Results:The RF-induced heating from the body-loop postures can be up to 11 times higher than that from the original posture. The RF-induced heating increases with increasing body-loop size and decreasing contact area. The magnetic flux increases when the body-loop center and the RF coil isocenter are close to each other, leading to increased RF-induced heating. An air gap created in the body loop or generating a polarized magnetic field parallel to the body loop can reduce the heating by a factor of three at least. Experimental measurements are provided, validating the correctness of the numerical results. Conclusion: Safe patient posture during MR examinations is recommended with the use of insulation materials to prevent loop formation and consequently avoiding high RF-induced heating. If body loops cannot be avoided, the body loop should be placed outside the RF transmitting coil. In addition, linear polarization with magnetic fields parallel to the body loop can be used to circumvent high RF-induced heating.

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Section: Introductionmentioning

confidence: 76%

Body‐loop related MRI radiofrequency‐induced heating hazards: Observations, characterizations, and recommendations

Yang

Zheng

Wang

et al. 2021

Magnetic Resonance in Med

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“…Due to the physical aperture limitations of MRI, an individual with obesity may be uncomfortable or in pain with an increased feeling of being restricted or trapped that can contribute to, or exacerbate distress or claustrophobia [ 65 , 66 ]. Radiofrequency (RF) penetration and energy deposition are also major concerns when imaging larger patients within MRI [67] . The risk of heating body tissues is typically higher due to increased specific absorption rates (SAR) with potential thermoregulation implications.…”

Section: Magnetic Resonance Imaging (Mri)mentioning

confidence: 99%

“…The risk of heating body tissues is typically higher due to increased specific absorption rates (SAR) with potential thermoregulation implications. The risk of thermal burns is also increased because preventing conductive loops between limbs or insulating the patient from the side of the bore can be problematic as patient size increases [67] . Other significant challenges for this population include gradient strength, limited field of view, decreased SNR, reduced image resolution and an increase in artefacts such as annefact or aliasing artefact or reduced fat saturation [ 64 , 50 ].…”

Section: Magnetic Resonance Imaging (Mri)mentioning

confidence: 99%

“…70cm diameter bore scanners are now more readily available to accommodate larger body habitus (see Figure 5 ), however the field of view is typically smaller because a larger FOV is vulnerable to RF inhomogeneities and gradient non linearities [64] . • Open bore magnets may increase access for larger patients and also reduce skin to bore contact risks [67] .…”

Section: Magnetic Resonance Imaging (Mri)mentioning

confidence: 99%

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Imaging individuals with obesity

Nabasenja

Barry

Nelson

et al. 2022

Journal of Medical Imaging and Radiation Sciences

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“…In particular, an EM-field simulation is essential to more accurately predict the safety of RF coils as EM-fields play an important role in the generation of B 1 -fields and SAR distributions . Owing to these problems, various studies have been conducted with an aim to increase the uniformity of the B 1 -field [26][27][28][29][30][31][32][33][34][35][36][37] and to improve the sensitivity of the B 1 -field [38][39][40][41][42][43][44][45] along with RF safety [46][47][48][49][50][51][52][53][54][55][56][57].…”

Section: Introductionmentioning

confidence: 99%

A Preliminary Study for Reference RF Coil at 11.7 T MRI: Based on Electromagnetic Field Simulation of Hybrid-BC RF Coil According to Diameter and Length at 3.0, 7.0 and 11.7 T

Seo

Chung

2022

Sensors

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Magnetic resonance imaging (MRI) systems must undergo quantitative evaluation through daily and periodic performance assessments. In general, the reference or standard radiofrequency (RF) coils for these performance assessments of 1.5 to 7.0 T MRI systems have been low-pass-type birdcage (LP-BC) RF coils. However, LP-BC RF coils are inappropriate for use as reference RF coils because of their relatively lower magnetic field (B1-field) sensitivity than other types of BC RF coils, especially in ultrahigh-field (UHF) MRI systems above 3.0 T. Herein, we propose a hybrid-type BC (Hybrid-BC) RF coil as a reference RF coil with improved B1-field sensitivity in UHF MRI system and applied it to an 11.7 T MRI system. An electromagnetic field (EM-field) analysis on the Hybrid-BC RF coil was performed to provide the proper dimensions for its use as a reference RF coil. Commercial finite difference time-domain program was used in EM-field simulation, and home-made analysis programs were used in analysis. The optimal specifications of the proposed Hybrid-BC RF coils for them to qualify as reference RF coils are proposed based on their B1+-field sensitivity under unnormalized conditions, as well as by considering their B1+-field uniformity and RF safety under normalized conditions.

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Electromagnetic simulation of RF burn injuries occurring at skin-skin and skin-bore wall contact points in an MRI scanner with a birdcage coil

Cited by 9 publications

References 39 publications

Body‐loop related MRI radiofrequency‐induced heating hazards: Observations, characterizations, and recommendations

Body‐loop related MRI radiofrequency‐induced heating hazards: Observations, characterizations, and recommendations

Imaging individuals with obesity

A Preliminary Study for Reference RF Coil at 11.7 T MRI: Based on Electromagnetic Field Simulation of Hybrid-BC RF Coil According to Diameter and Length at 3.0, 7.0 and 11.7 T

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