Concepts in Magnetic Resonance Part B, Magnetic Resonance Engineering
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The “Loopole” Antenna: A Hybrid Coil Combining Loop and Electric Dipole Properties for Ultra-High-Field MRI

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Concepts in Magnetic Resonance Part B publishes research concerning the design and development of hardware and software employed in magnetic resonance techniques, including magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR).

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Concepts in Magnetic Resonance Part B maintains an Editorial Board of practicing researchers from around the world, to ensure manuscripts are handled by editors expert and up-to-date in the field of study.

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Research Article

The “Loopole” Antenna: A Hybrid Coil Combining Loop and Electric Dipole Properties for Ultra-High-Field MRI

Purpose. To revisit the “loopole,” an unusual coil topology whose unbalanced current distribution captures both loop and electric dipole properties, which can be advantageous in ultra-high-field MRI. Methods. Loopole coils were built by deliberately breaking the capacitor symmetry of traditional loop coils. The corresponding current distribution, transmit efficiency, and signal-to-noise ratio (SNR) were evaluated in simulation and experiments in comparison to those of loops and electric dipoles at 7 T (297 MHz). Results. The loopole coil exhibited a hybrid current pattern, comprising features of both loops and electric dipole current patterns. Depending on the orientation relative to B0, the loopole demonstrated significant performance boost in either the transmit efficiency or SNR at the center of a dielectric sample when compared to a traditional loop. Modest improvements were observed when compared to an electric dipole. Conclusion. The loopole can achieve high performance by supporting both divergence-free and curl-free current patterns, which are both significant contributors to the ultimate intrinsic performance at ultra-high field. While electric dipoles exhibit similar hybrid properties, loopoles maintain the engineering advantages of loops, such as geometric decoupling and reduced resonance frequency dependence on sample loading.

Review Article

Thermal Effects Associated with RF Exposures in Diagnostic MRI: Overview of Existing and Emerging Concepts of Protection

Apart from magnetic attraction risks, the primary biophysical concern associated with MRI is radiofrequency heating of the human body and associated discomfort, health deterioration, or potential burns. This paper reviews experimental data and numerical modeling of systemic (core and brain) temperature and local thermal effects associated with diagnostic MRI exposures at 1.5T (64 MHz) and 3.0T (128 MHz). Allowable temperatures and duration of systemic exposure are established based on knowledge of (short-term) human thermobiology. Longer term effects related to DNA damage or altered cellular pathways are not covered in this review. Updated limits are proposed for core temperature increase (≤1.3°C) and for Specific Absorption (<4 kJ/kg). The potential use of thermal dose (CEM43) for local thermal protection is described, and previously proposed exposure limit values are evaluated against available data from current MRI practice. Gaps in knowledge are identified, and recommendations for additional research are provided.

Research Article

Inherent Geometry Correction for Diffusion EPI Using the Reference Echoes as Navigators

Diffusion-weighted EPI has become an indispensable tool in body MRI. Geometric distortions due to field inhomogeneities are more prominent at large field–of–view and require correction for comparison with T2W TSE. Several known correction methods require acquisition of additional lengthy scans, which are difficult to apply in body imaging. We implement and evaluate a geometry correction method based on the already available non phase-encoded EPI reference data used for Nyquist ghost removal. The method is shown to provide accurate and robust global geometry correction in the absence of strong, local phase offsets. It does not require additional time for calibrations and is directly compatible with parallel imaging methods. The resulting images can serve as improved starting point for additional geometry correction methods relying on feature extraction and registration.

Concepts in Magnetic Resonance Part B, Magnetic Resonance Engineering
Publishing Collaboration
More info
Wiley Hindawi logo
 Journal metrics
Acceptance rate-
Submission to final decision-
Acceptance to publication-
CiteScore0.780
Impact Factor0.690
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