Department of Diagnostic Radiology, The University of Hong Kong, Hong Kong, China.
Department of Diagnostic Radiology, The University of Hong Kong, Hong Kong, China.
Magn Reson Imaging. 2022 Sep;91:69-80. doi: 10.1016/j.mri.2022.05.015. Epub 2022 May 26.
To develop a motion-resolved and free-breathing liver magnetic resonance fingerprinting (MRF) protocol.
The deformation maps were obtained from the first singular image of MRF data. The reconstruction method enforced the consistency of the MRF data with the deformation maps by adding the deformation maps to the encoding matrix. A sliding window reconstruction was inherently assumed, with a window size of 60 repetition times (TRs) and a step size of 30 TRs. L1 wavelet regularization was applied to reduce the undersampling artifact. MRF was tested on four healthy volunteers with parameters: 13 s/slice, 0.39 s/frame, and 33 time frames/slice.
For measuring the accuracy of the deformation map, the typical normalized root mean square error (NRMSE) of the first singular image after motion correction was 0.19. In the sagittal scan, the liver T1 and T2 were 808.7±96.8 ms and 52.7±11.6 ms, respectively. They agreed with our previously reported values, i.e., T1 = 759 ms and T2 = 51 ms at 3 T, using free-breathing liver MRF. Compared to breath-hold MRF, the NRMSEs for T1 and T2 maps (without considering vessel pixels) from the proposed method were 0.13 and 0.18, respectively.
We demonstrated a motion-resolved MRF with a nominal frame rate of 2.5 Hz for free-breathing liver imaging.
开发一种运动分辨且自由呼吸的肝脏磁共振指纹成像（MRF）协议。
变形图是从 MRF 数据的第一奇异图像中获得的。重建方法通过将变形图添加到编码矩阵中，强制 MRF 数据与变形图保持一致。固有地假设采用滑动窗口重建，窗口大小为 60 个重复时间（TR），步长为 30 TR。应用 L1 小波正则化以减少欠采样伪影。在 4 名健康志愿者上测试 MRF 参数：13 s/slice、0.39 s/frame 和 33 个时间帧/slice。
为了测量变形图的准确性，运动校正后的第一奇异图像的典型归一化均方根误差（NRMSE）为 0.19。在矢状扫描中，肝脏 T1 和 T2 分别为 808.7±96.8 ms 和 52.7±11.6 ms，与我们之前在 3 T 下使用自由呼吸肝脏 MRF 报告的 T1 = 759 ms 和 T2 = 51 ms 一致。与屏气 MRF 相比，该方法得到的 T1 和 T2 图（不考虑血管像素）的 NRMSE 分别为 0.13 和 0.18。
我们展示了一种用于自由呼吸肝脏成像的具有名义帧率为 2.5 Hz 的运动分辨 MRF。
