Signal-to-Noise Ratio and MR Tissue Parameters in Human Brain Imaging at 3, 7, and 9.4 Tesla Using Current Receive Coil Arrays
Signal-to-Noise Ratio and MR Tissue Parameters in Human Brain Imaging at 3, 7, and 9.4 Tesla Using Current Receive Coil Arrays
复制标题
DOI：
10.1002/mrm.25677
复制
发表时间：
2016-02-01
影响因子：
3.3
通讯作者：
Scheffler, Klaus
中科院分区：
文献类型：
--
作者：
Pohmann, Rolf;Speck, Oliver;Scheffler, Klaus
目的：弛豫时间，发射均匀性，信噪比（SNR）和平行成像g-因子在人脑中测定在3 T，7 T和9.4T，使用标准，紧配合线圈arrays.Methods：相同的人类受试者进行扫描，在所有三个场强，使用相同的序列参数和类似的31或32通道接收线圈阵列。使用多副本方法确定三维（3D）梯度回波图像的SNR，并使用测量的翻转角和T-2* 分布以及白色物质的T-1进行校正，以获得固有SNR。结果：与预期的一样，随着磁场的增加，T-1值增加，T-2* 降低，B-1均匀性恶化。在整个大脑范围内，SNR随场强的增加呈明显的超线性增加，从3 T到7 T增加3.10+/-0.20倍，从7 T到9.4T增加1.76+/-0.13倍。g因子没有显示出预期的降低，表明线圈design.Conclusion的主导作用：在标准实验条件下，SNR随着场强的增加而超线性增加（SNR类似于B-0（1.65））。为了充分利用这种增益，必须克服B1均匀性的恶化和T-2* 的降低。(C)2015 Wiley Periodicals，Inc.
Purpose: Relaxation times, transmit homogeneity, signal-to-noise ratio (SNR) and parallel imaging g-factor were determined in the human brain at 3T, 7T, and 9.4T, using standard, tight-fitting coil arrays.Methods: The same human subjects were scanned at all three field strengths, using identical sequence parameters and similar 31- or 32-channel receive coil arrays. The SNR of three-dimensional (3D) gradient echo images was determined using a multiple replica approach and corrected with measured flip angle and T-2* distributions and the T-1 of white matter to obtain the intrinsic SNR. The g-factor maps were derived from 3D gradient echo images with several GRAPPA accelerations.Results: As expected, T-1 values increased, T-2* decreased and the B-1-homogeneity deteriorated with increasing field. The SNR showed a distinctly supralinear increase with field strength by a factor of 3.10+/-0.20 from 3T to 7T, and 1.76+/-0.13 from 7T to 9.4T over the entire cerebrum. The g-factors did not show the expected decrease, indicating a dominating role of coil design.Conclusion: In standard experimental conditions, SNR increased supralinearly with field strength (SNR similar to B-0(1.65)). To take full advantage of this gain, the deteriorating B1-homogeneity and the decreasing T-2* have to be overcome. (C) 2015 Wiley Periodicals, Inc.