Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland, Baltimore, Maryland, USA.
U.S. Food Drug Administration, Silver Spring, Maryland, USA.
Magn Reson Med. 2023 Nov;90(5):1932-1948. doi: 10.1002/mrm.29789. Epub 2023 Jul 13.
To improve the image reconstruction for prospective motion correction (PMC) of simultaneous multislice (SMS) EPI of the brain, an update of receiver phase and resampling of coil sensitivities are proposed and evaluated.
A camera-based system was used to track head motion (3 translations and 3 rotations) and dynamically update the scan position and orientation. We derived the change in receiver phase associated with a shifted field of view (FOV) and applied it in real-time to each k-space line of the EPI readout trains. Second, for the SMS reconstruction, we adapted resampled coil sensitivity profiles reflecting the movement of slices. Single-shot gradient-echo SMS-EPI scans were performed in phantoms and human subjects for validation.
Brain SMS-EPI scans in the presence of motion with PMC and no phase correction for scan plane shift showed noticeable artifacts. These artifacts were visually and quantitatively attenuated when corrections were enabled. Correcting misaligned coil sensitivity maps improved the temporal SNR (tSNR) of time series by 24% (p = 0.0007) for scans with large movements (up to ˜35 mm and 30°). Correcting the receiver phase improved the tSNR of a scan with minimal head movement by 50% from 50 to 75 for a United Kingdom biobank protocol.
Reconstruction-induced motion artifacts in single-shot SMS-EPI scans acquired with PMC can be removed by dynamically adjusting the receiver phase of each line across EPI readout trains and updating coil sensitivity profiles during reconstruction. The method may be a valuable tool for SMS-EPI scans in the presence of subject motion.
为了提高前瞻性运动校正（PMC）的脑同时多层（SMS）EPI 的图像重建，提出并评估了接收器相位的更新和线圈灵敏度的重采样。
使用基于相机的系统来跟踪头部运动（3 个平移和 3 个旋转），并动态更新扫描位置和方向。我们推导出与视场（FOV）偏移相关的接收器相位变化，并将其实时应用于 EPI 读出序列的每条 k 空间线。其次，对于 SMS 重建，我们采用了反映切片运动的重采样线圈灵敏度分布。在幻影和人体中进行了单次梯度回波 SMS-EPI 扫描以进行验证。
在存在运动的情况下进行大脑 SMS-EPI 扫描，并且没有对扫描平面偏移进行相位校正，显示出明显的伪影。当启用校正时，这些伪影在视觉上和定量上得到了减弱。校正未对准的线圈灵敏度图可以提高时间序列的时间 SNR（tSNR），对于大运动（高达约 35mm 和 30°）的扫描提高 24%（p=0.0007）。校正接收器相位可以将最小头部运动的扫描的 tSNR 从 50 提高到 75，对于英国生物库协议提高 50%。
在具有 PMC 的单次 SMS-EPI 扫描中，重建引起的运动伪影可以通过动态调整 EPI 读出序列中每条线的接收器相位以及在重建过程中更新线圈灵敏度分布来消除。该方法可能是在受试者运动时进行 SMS-EPI 扫描的有用工具。
