Neuroscience Research Institute, Gachon University, Incheon 21988, Korea.
Department of Neuroscience, College of Medicine, Gachon University, Incheon 21565, Korea.
Sensors (Basel). 2022 Feb 15;22(4):1512. doi: 10.3390/s22041512.
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 (B-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 B-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 B-field sensitivity under unnormalized conditions, as well as by considering their B-field uniformity and RF safety under normalized conditions.
磁共振成像（MRI）系统必须通过日常和定期的性能评估进行定量评估。通常，1.5 至 7.0 T MRI 系统这些性能评估的参考或标准射频（RF）线圈是低通型鸟笼（LP-BC）RF 线圈。然而，由于 LP-BC RF 线圈的磁场（B 场）灵敏度相对较低，与其他类型的 BC RF 线圈相比，特别是在高于 3.0 T 的超高场（UHF）MRI 系统中，它们不适合用作参考 RF 线圈。在此，我们提出了一种混合式 BC（Hybrid-BC）RF 线圈，作为 UHF MRI 系统中具有改进 B 场灵敏度的参考 RF 线圈，并将其应用于 11.7 T MRI 系统。对 Hybrid-BC RF 线圈进行了电磁场（EM）分析，为其用作参考 RF 线圈提供了适当的尺寸。商用有限差分时域程序用于 EM 场模拟，并使用自制的分析程序进行分析。根据归一化条件下的 B 场灵敏度，以及归一化条件下的 B 场均匀性和 RF 安全性，提出了拟议的 Hybrid-BC RF 线圈作为参考 RF 线圈的最佳规格。
