Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA.
High Field MR Center, Center for Medical Physics and Biomedical Engineering, Medical University, Vienna, Austria.
Magn Reson Med. 2023 Dec;90(6):2592-2607. doi: 10.1002/mrm.29798. Epub 2023 Aug 15.
A 128-channel receive-only array for brain imaging at 7 T was simulated, designed, constructed, and tested within a high-performance head gradient designed for high-resolution functional imaging.
The coil used a tight-fitting helmet geometry populated with 128 loop elements and preamplifiers to fit into a 39 cm diameter space inside a built-in gradient. The signal-to-noise ratio (SNR) and parallel imaging performance (1/g) were measured in vivo and simulated using electromagnetic modeling. The histogram of 1/g factors was analyzed to assess the range of performance. The array's performance was compared to the industry-standard 32-channel receive array and a 64-channel research array.
It was possible to construct the 128-channel array with body noise-dominated loops producing an average noise correlation of 5.4%. Measurements showed increased sensitivity compared with the 32-channel and 64-channel array through a combination of higher intrinsic SNR and g-factor improvements. For unaccelerated imaging, the 128-channel array showed SNR gains of 17.6% and 9.3% compared to the 32-channel and 64-channel array, respectively, at the center of the brain and 42% and 18% higher SNR in the peripheral brain regions including the cortex. For R = 5 accelerated imaging, these gains were 44.2% and 24.3% at the brain center and 86.7% and 48.7% in the cortex. The 1/g-factor histograms show both an improved mean and a tighter distribution by increasing the channel count, with both effects becoming more pronounced at higher accelerations.
The experimental results confirm that increasing the channel count to 128 channels is beneficial for 7T brain imaging, both for increasing SNR in peripheral brain regions and for accelerated imaging.
在专为高分辨率功能成像设计的高性能头部梯度内，模拟、设计、构建和测试了一种用于 7T 脑成像的 128 通道接收仅阵列。
该线圈采用紧密贴合的头盔几何形状，填充有 128 个环形元件和前置放大器，以适合内置梯度内 39 厘米直径的空间。使用电磁建模在体内测量了信号噪声比 (SNR) 和并行成像性能 (1/g)，并进行了模拟。分析了 1/g 因子的直方图，以评估性能范围。将该阵列的性能与行业标准的 32 通道接收阵列和 64 通道研究阵列进行了比较。
可以使用以体噪声为主的环路构建 128 通道阵列，其平均噪声相关系数为 5.4%。测量结果显示，与 32 通道和 64 通道阵列相比，该阵列通过提高固有 SNR 和 g 因子的改进，提高了灵敏度。对于未加速成像，与 32 通道和 64 通道阵列相比，在大脑中心，128 通道阵列分别获得了 17.6%和 9.3%的 SNR 增益，在大脑外围区域（包括皮质）中，128 通道阵列的 SNR 增益分别为 42%和 18%。对于 R = 5 加速成像，在大脑中心的增益分别为 44.2%和 24.3%，在皮质中的增益分别为 86.7%和 48.7%。1/g 因子直方图显示，随着通道数的增加，不仅平均 SNR 得到提高，而且分布更加紧凑，这两种效应在更高的加速度下更加明显。
实验结果证实，增加通道数到 128 个通道对于 7T 脑成像有益，既可以提高外围脑区的 SNR，也可以提高加速成像的性能。
