Department of Biomedical Engineering, School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK.
MR Research Collaborations, Siemens Healthcare Limited, Frimley, UK.
MAGMA. 2022 Oct;35(5):765-778. doi: 10.1007/s10334-021-00988-z. Epub 2022 Jan 8.
Neonatal brain and cardiac imaging would benefit from the increased signal-to-noise ratio levels at 7 T compared to lower field. Optimal performance might be achieved using purpose designed RF coil arrays. In this study, we introduce an 8-channel dipole array and investigate, using simulations, its RF performances for neonatal applications at 7 T.
The 8-channel dipole array was designed and evaluated for neonatal brain/cardiac configurations in terms of SAR efficiency (ratio between transmit-field and maximum specific-absorption-rate level) using adjusted dielectric properties for neonate. A birdcage coil operating in circularly polarized mode was simulated for comparison. Validation of the simulation model was performed on phantom for the coil array.
The 8-channel dipole array demonstrated up to 46% higher SAR efficiency levels compared to the birdcage coil in neonatal configurations, as the specific-absorption-rate levels were alleviated. An averaged normalized root-mean-square-error of 6.7% was found between measured and simulated transmit field maps on phantom.
The 8-channel dipole array design integrated for neonatal brain and cardiac MR was successfully demonstrated, in simulation with coverage of the baby and increased SAR efficiency levels compared to the birdcage. We conclude that the 8Tx-dipole array promises safe operating procedures for MR imaging of neonatal brain and heart at 7 T.
与较低场强相比，7T 场强下的信噪比水平提高将使新生儿脑部和心脏成像受益。最佳性能可能通过专门设计的射频线圈阵列来实现。在这项研究中，我们引入了一个 8 通道偶极子阵列，并使用模拟技术研究了其在 7T 下用于新生儿应用的射频性能。
根据新生儿的介电特性对 8 通道偶极子阵列进行了设计和评估，以获得用于新生儿脑部/心脏配置的 SAR 效率（发射场与最大比吸收率之比）。为了进行比较，还模拟了一个工作在圆极化模式的鸟笼线圈。对线圈阵列的模拟模型进行了体模验证。
与新生儿配置中的鸟笼线圈相比，8 通道偶极子阵列的 SAR 效率水平高达 46%，因为特定吸收率水平得到了缓解。在体模上，测量的和模拟的发射场图之间的平均归一化均方根误差为 6.7%。
为新生儿脑部和心脏磁共振成像集成设计的 8 通道偶极子阵列在模拟中得到了成功演示，与鸟笼相比，该阵列覆盖了婴儿，并提高了 SAR 效率水平。我们得出结论，8Tx-偶极子阵列有望在 7T 下实现新生儿脑部和心脏磁共振成像的安全操作程序。
