Robarts Research Institute, The University of Western Ontario, London, ON, Canada.
NMR Biomed. 2011 Aug;24(7):815-23. doi: 10.1002/nbm.1627. Epub 2010 Dec 8.
A 15-channel transmit-receive (transceive) radiofrequency (RF) coil was developed to image the human brain at 7 T. A hybrid decoupling scheme was implemented that used both capacitive decoupling and the partial geometric overlapping of adjacent coil elements. The decoupling scheme allowed coil elements to be arrayed along all three Cartesian axes; this facilitated shimming of the transmit field, B₁⁺, and parallel imaging acceleration along the longitudinal direction in addition to the standard transverse directions. Each channel was independently controlled during imaging using a 16-channel console and a 16 × 1-kW RF amplifier-matrix. The mean isolation between all combinations of coil elements was 18 ± 7 dB. After B₁⁺ shimming, the standard deviation of the transmit field uniformity was 11% in an axial plane and 32% over the entire brain superior to the mid-cerebellum. Transmit uniformity was sufficient to acquire fast spin echo images of this region of the brain with a single B₁⁺ shim solution. Signal-to-noise ratio (SNR) maps showed higher SNR in the periphery vs center of the brain, and higher SNR in the occipital and temporal lobes vs the frontal lobe. Parallel imaging acceleration in a rostral-caudal oblique plane was demonstrated. The implication of the number of channels in a transmit-receive coil was discussed: it was determined that improvements in SNR and B₁⁺ shimming can be expected when using more than 15 independently controlled transmit-receive channels.
开发了一种 15 通道发射-接收（收发）射频（RF）线圈，用于在 7T 下对人脑进行成像。实现了混合去耦方案，该方案同时使用电容去耦和相邻线圈元件的部分几何重叠。去耦方案允许线圈元件沿所有三个笛卡尔轴排列；这有助于对发射场、B₁⁺进行调谐，以及除标准横向方向外，还沿纵向进行并行成像加速。在成像过程中，每个通道都使用 16 通道控制台和 16×1kW RF 放大器矩阵独立控制。所有线圈元件组合之间的平均隔离度为 18±7dB。在 B₁⁺调谐后，在轴向平面中的发射场均匀性的标准偏差为 11%，在整个大脑中超过中脑的标准偏差为 32%。发射均匀性足以在单个 B₁⁺调谐解决方案下获取该大脑区域的快速自旋回波图像。信噪比（SNR）图显示，大脑外周的 SNR 高于中心，枕叶和颞叶的 SNR 高于额叶。在头侧-尾侧斜平面中展示了并行成像加速。讨论了收发线圈中通道数量的含义：当使用超过 15 个独立控制的收发通道时，可以预期 SNR 和 B₁⁺调谐的改善。
