Center for Magnetic Resonance Research (CMRR), University of Minnesota, Minneapolis, Minnesota.
Lifeservices, LLC, Minnesota.
Magn Reson Med. 2019 Jul;82(1):495-509. doi: 10.1002/mrm.27695. Epub 2019 Feb 25.
PURPOSE: Despite the clear synergy between high channel counts in a receive array and magnetic fields ≥ 7 Tesla, to date such systems have been restricted to a maximum of 32 channels. Here, we examine SNR gains at 7 Tesla in unaccelerated and accelerated images with a 64-receive channel (64Rx) RF coil. METHODS: A 64Rx coil was built using circular loops tiled in 2 separable sections of a close-fitting form; custom designed preamplifier boards were integrated into each coil element. A 16-channel transmitter arranged in 2 rows along the z-axis was employed. The performance of the 64Rx array was experimentally compared to that of an industry-standard 32-channel receive (32Rx) array for SNR in unaccelerated images and for noise amplification under parallel imaging. RESULTS: SNR gains were observed in the periphery but not in the center of the brain in unaccelerated imaging compared to the 32Rx coil. With either 1D or 2D undersampling of k-space, or with slice acceleration together with 1D undersampling of k-space, significant reductions in g-factor noise were observed throughout the brain, yielding effective gains in SNR in the entire brain compared to the 32Rx coil. Task-based FMRI data with 12-fold 2D (slice and phase-encode) acceleration yielded excellent quality functional maps with the 64Rx coil but was significantly beyond the capabilities of the 32Rx coil. CONCLUSION: The results confirm the expectations from modeling studies and demonstrate that whole-brain studies with up to 16-fold, 2D acceleration would be feasible with the 64Rx coil.
目的:尽管在接收阵列中具有高通道数和磁场≥7 特斯拉之间存在明显的协同作用,但迄今为止,此类系统的通道数最多限制为 32 个。在这里,我们在未加速和加速图像中检查了 7T 时的 SNR 增益,使用的是 64 个接收通道(64Rx)RF 线圈。
方法:使用紧密贴合的 2 个可分离部分中的圆形环路构建了 64Rx 线圈;将定制设计的前置放大器板集成到每个线圈元件中。采用沿 z 轴排列的 2 排 16 通道发射器。实验比较了 64Rx 阵列与行业标准的 32 通道接收(32Rx)阵列的性能,以比较未加速图像中的 SNR 和并行成像下的噪声放大。
结果:与 32Rx 线圈相比,在未加速成像中,在大脑的外围观察到 SNR 增益,但在大脑中心没有观察到。在 k 空间的 1D 或 2D 欠采样,或与切片加速一起进行 1D k 空间欠采样的情况下,在整个大脑中观察到 g 因子噪声的显著降低,与 32Rx 线圈相比,整个大脑中的 SNR 得到了有效提高。使用 12 倍 2D(切片和相位编码)加速的基于任务的 fMRI 数据,使用 64Rx 线圈产生了具有出色质量的功能图,但这远远超出了 32Rx 线圈的能力。
结论:这些结果证实了模型研究的预期,并表明使用 64Rx 线圈可以实现多达 16 倍、2D 加速的全脑研究。
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