RF Exposure Assessment for Various Poses of Patient Assistant in Open MRI Environment

Hong, Seon-Eui; Oh, Sang Wook; Choi, Hyung‐Do

doi:10.3390/app11114967

Cited by 3 publications

(2 citation statements)

References 29 publications

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“…Even though the 7.0 T MRI has recently provided limited approval by the US FDA for use in head and extremities (arms and legs) imaging, whole body imaging is not permitted due to safety issues, including tissue heating, which occurs because UHF MRI requires a large amount of RF energy for human imaging [7]. Hence, RF safety studies have evaluated higher specific absorption rates (SAR), which indirectly measure tissue heating upon RF exposure [8][9][10][11][12][13][14][15], and research has focused on signal strength enhancement and SAR safety for RF coils used in 7.0 T MRI approved for clinical use. The required RF power to excite a spin system increases with the B 0 -field strength.…”

Section: Introductionmentioning

confidence: 99%

A Comparative Study of Birdcage RF Coil Configurations for Ultra-High Field Magnetic Resonance Imaging

Seo

Han

Chung

2022

Sensors

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Improvements in transmission and reception sensitivities of radiofrequency (RF) coils used in ultra-high field (UHF) magnetic resonance imaging (MRI) are needed to reduce specific absorption rates (SAR) and RF power deposition, albeit without applying high-power RF. Here, we propose a method to simultaneously improve transmission efficiency and reception sensitivity of a band-pass birdcage RF coil (BP-BC RF coil) by combining a multi-channel wireless RF element (MCWE) with a high permittivity material (HPM) in a 7.0 T MRI. Electromagnetic field (EM-field) simulations, performed using two types of phantoms, viz., a cylindrical phantom filled with oil and a human head model, were used to compare the effects of MCWE and HPM on BP-BC RF coils. EM-fields were calculated using the finite difference time-domain (FDTD) method and analyzed using Matlab software. Next, to improve RF transmission efficiency, we compared two HPM structures, namely, a hollow cylinder shape HPM (hcHPM) and segmented cylinder shape HPM (scHPM). The scHPM and MCWE model comprised 16 elements (16-rad BP-BC RF coil) and this coil configuration demonstrated superior RF transmission efficiency and reception sensitivity along with an acceptable SAR. We expect wider clinical application of this combination in 7.0 T MRIs, which were recently approved by the United States Food and Drug Administration.

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Section: Introductionmentioning

confidence: 99%

A Comparative Study of Birdcage RF Coil Configurations for Ultra-High Field Magnetic Resonance Imaging

Seo

Han

Chung

2022

Sensors

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“…Therefore, it is necessary to evaluate the RF energy exposure of patient assistants. A previous study [ 22 ] has shown that several variables can affect the distribution of SAR in a patient assistant, including distance from the head or body transmit RF coil and configuration of interventional treatments at 0.3 T in an open MRI system. In this study, we numerically investigated RF energy exposures of patient assistants using planar-shaped RF coil models, which are widely used to transmit RF coil type, particularly at 1.2 T in an open MRI system under various exposure conditions.…”

Section: Introductionmentioning

confidence: 99%

Proposed Safety Guidelines for Patient Assistants in an Open MRI Environment

Hong²,

Choi³

2022

IJERPH

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The wide-open side of an open magnetic resonance imaging (MRI) system allows a patient to easily contact the patient assistant during MRI scans. A wide-open-shaped magnet is highly effective when interventional procedures are necessary. Patient assistants can provide comfort by holding a part of the patient’s body. Because current regulations or guidelines are concerned with only patient radio frequency (RF) safety, investigations on the safety of patient assistants exposed to high-magnetic field MRI (up to 1.2 T) are required. In this study, five different poses of patient assistants were numerically simulated at a 1.2 T open MRI system to determine the impact of poses on the RF exposure level. The 10-g averaged specific absorption rate (SAR) levels were analyzed for the poses of each patient assistant wearing gloves. Compared with the patient, up to 29.8% of the patient SAR was observed in the patient assistant. When the patient assistant wore latex gloves, a 63.7% reduction in the 10-g averaged SAR level was observed, which could be a remedy to minimize possible RF hazards. To prevent possible RF hazards during MRI scans, certain clauses regarding the patient assistant’s poses or wearing gloves must be added to the existing MRI screening forms.

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A New Combination of Radio-Frequency Coil Configurations Using High-Permittivity Materials and Inductively Coupled Structures for Ultrahigh-Field Magnetic Resonance Imaging

Seo

et al. 2022

Sensors

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In ultrahigh-field (UHF) magnetic resonance imaging (MRI) system, the RF power required to excite the nuclei of the target object increases. As the strength of the main magnetic field ( field) increases, the improvement of the RF transmit field ( field) efficiency and receive field ( field) sensitivity of radio-frequency (RF) coils is essential to reduce their specific absorption rate and power deposition in UHF MRI. To address these problems, we previously proposed a method to simultaneously improve the field efficiency and field sensitivity of 16-leg bandpass birdcage RF coils (BP-BC RF coils) by combining a multichannel wireless RF element (MCWE) and segmented cylindrical high-permittivity material (scHPM) comprising 16 elements in 7.0 T MRI. In this work, we further improved the performance of transmit/receive RF coils. A new combination of RF coil with wireless element and HPM was proposed by comparing the BP-BC RF coil with the MCWE and the scHPM proposed in the previous study and the multichannel RF coils with a birdcage RF coil-type wireless element (BCWE) and the scHPM proposed in this study. The proposed 16-ch RF coils with the BCWE and scHPM provided excellent field efficiency and field sensitivity improvement.

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RF Exposure Assessment for Various Poses of Patient Assistant in Open MRI Environment

Cited by 3 publications

References 29 publications

A Comparative Study of Birdcage RF Coil Configurations for Ultra-High Field Magnetic Resonance Imaging

A Comparative Study of Birdcage RF Coil Configurations for Ultra-High Field Magnetic Resonance Imaging

Proposed Safety Guidelines for Patient Assistants in an Open MRI Environment

A New Combination of Radio-Frequency Coil Configurations Using High-Permittivity Materials and Inductively Coupled Structures for Ultrahigh-Field Magnetic Resonance Imaging

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