Application of an integrated radio-frequency/shim coil technology for signal recovery in fMRI.
Application of an integrated radio-frequency/shim coil technology for signal recovery in fMRI.
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DOI：
10.1002/mrm.28925
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发表时间：
2021-12
影响因子：
3.3
通讯作者：
Truong TK
中科院分区：
文献类型：
--
作者：
Willey D;Darnell D;Song AW;Truong TK
常用于BOLD fMRI的回波EPI会因局部B 0不均匀性而导致失真和信号丢失。这种伪影不能用大多数扫描仪上可用的低阶球谐（SH）匀场线圈有效校正。集成的并行接收、激励和匀场（iPRES）线圈技术允许RF和直流电流在每个线圈元件上流动，从而实现一个线圈阵列的成像和局部B 0匀场。iPRES先前用于校正自旋回波EPI中的失真，并且在此进一步开发以还恢复梯度回波EPI中的信号损失。匀场优化中的成本函数通常使用表示B 0不均匀性的单个项，该成本函数被修改为包括表示信号损失的第二项，具有可调整的权重以优化失真校正和信号恢复之间的权衡。通过仿真和实验研究了该方法的匀场性能。与使用iPRES和原始成本函数的匀场或使用任一成本函数的二阶SH匀场相比，使用iPRES和所提出的成本函数的切片优化匀场大大减少了额叶和颞叶脑下部区域中的信号损失。在屏气fMRI实验中，Δ B 0和信号丢失均方根误差分别下降了-34.3%和-56.2%，而下额叶脑区的EPI信号强度和激活体素数量分别增加了60.3%和174.0%。iPRES可以恢复梯度回波EPI中的信号损失，这有望改善在遭受信号损失的大脑区域中的BOLD fMRI研究。
Gradient-echo EPI, which is typically used for BOLD fMRI, suffers from distortions and signal loss caused by localized B0 inhomogeneities. Such artifacts cannot be effectively corrected for with the low-order spherical harmonic (SH) shim coils available on most scanners. The integrated parallel reception, excitation, and shimming (iPRES) coil technology allows RF and direct currents to flow on each coil element, enabling imaging and localized B0 shimming with one coil array. iPRES was previously used to correct for distortions in spin-echo EPI and is further developed here to also recover signal loss in gradient-echo EPI. The cost function in the shim optimization, which typically uses a single term representing the B0 inhomogeneity, was modified to include a second term representing the signal loss, with an adjustable weight to optimize the trade-off between distortion correction and signal recovery. Simulations and experiments were performed to investigate the shimming performance. Slice-optimized shimming with iPRES and the proposed cost function substantially reduced the signal loss in the inferior frontal and temporal brain regions compared to shimming with iPRES and the original cost function or 2nd-order SH shimming with either cost function. In breath-holding fMRI experiments, the ΔB0 and signal loss root-mean-square errors decreased by −34.3% and −56.2%, whereas the EPI signal intensity and number of activated voxels increased by 60.3% and 174.0% in the inferior frontal brain region. iPRES can recover signal loss in gradient-echo EPI, which is expected to improve BOLD fMRI studies in brain regions suffering from signal loss.
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