Fast and Accurate Multi-Channel B1+ Mapping Based on the TIAMO Technique for 7T UHF Body MRI
Fast and Accurate Multi-Channel B1+ Mapping Based on the TIAMO Technique for 7T UHF Body MRI
复制标题
DOI：
10.1002/mrm.26925
复制
发表时间：
2018-05-01
影响因子：
3.3
通讯作者：
Orzada, Stephan
中科院分区：
文献类型：
--
作者：
Brunheim, Sascha;Gratz, Marcel;Orzada, Stephan
目的：当前通过多通道射频（RF）匀场来缓解超磁场（UHF）MRI中发射场B-1（+）不均匀性的方法依赖于准确的B-1（+）标测。当许多RF通道必须被标测用于体内身体MRI时，这可能是耗时的，其中B-1标测图应该理想地在单次屏气内被采集。因此，一个新的B-1（+）映射技术（B1 TIAMO）的性能进行了验证对一个既定的方法（DREAM）在体模测量的圆柱形头部体模与8通道发射/接收（Tx/Rx）阵列。此外，在大型体模中进行32通道Tx/Rx远程阵列的测量，并根据发射RF场分布的模拟验证垂直条B-1（+）垂直条标测图的可靠性。结果：对于头部体模（8通道Tx/Rx线圈），B1 TIAMO、直接DREAM测量和模拟数据之间的单个垂直条B-1（+）垂直条比较显示出良好的一致性，差异为10-19%。结论：B1 TIAMO能够在7 T UHF MRI条件下，在16 s的屏气时间内获得32个准确的单通道B-1（+）标测图，用于大视场人体成像。(C)2017年国际医学磁共振学会。
Purpose: Current methods for mitigation of transmit field B-1(+) inhomogeneities at ultrahigh field (UHF) MRI by multi-channel radiofrequency (RF) shimming rely on accurate B-1(+) mapping. This can be time consuming when many RF channels have to be mapped for in vivo body MRI, where the B-1 maps should ideally be acquired within a single breath-hold. Therefore, a new B-1(+) mapping technique (B1TIAMO) is proposed.Methods: The performance of this technique is validated against an established method (DREAM) in phantom measurements for a cylindrical head phantom with an 8-channel transmit/receive (Tx/Rx) array. Furthermore, measurements for a 32-channel Tx/Rx remote array are conducted in a large body phantom and the vertical bar B-1(+)vertical bar map reliability is validated against simulations of the transmit RF field distribution. Finally, in vivo results of this new mapping technique for human abdomen are presented.Results: For the head phantom (8-channel Tx/Rx coil), the single vertical bar B-1(+)vertical bar comparison between B1TIAMO, the direct DREAM measurements, and simulation data showed good agreement with 10-19% difference. For the large body phantom (32-channel Tx/Rx coil), B1TIAMO matched the RF field simulations well.Conclusion: The results demonstrate the potential to acquire 32 accurate single-channel B-1(+) maps for large field-of-view body imaging within only a single breath-hold of 16 s at 7T UHF MRI. (C) 2017 International Society for Magnetic Resonance in Medicine.