Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China.
MR Collaboration, Siemens Healthcare Ltd., Shanghai, China.
Magn Reson Med. 2023 Mar;89(3):922-936. doi: 10.1002/mrm.29480. Epub 2022 Nov 6.
To develop an auto-calibrated technique by joint K-space and Image-space Parallel Imaging (KIPI) for accelerated CEST acquisition.
The KIPI method selects a calibration frame with a low acceleration factor (AF) and auto-calibration signals (ACS) acquired, from which the coil sensitivity profiles and artifact correction maps are calculated after restoring the k-space by GRAPPA. Then the other frames with high AF and without ACS can be reconstructed by SENSE and artifact suppression. The signal leakage due to the T -decay filtering in k-space compromises the SENSE reconstruction, which can be corrected by the artifact suppression algorithm of KIPI. The 2D and 3D imaging experiments were done on the phantom, healthy volunteer, and brain tumor patient with a 3T scanner.
The proposed KIPI method was evaluated by retrospectively undersampled data with variable AFs and compared against existing parallel imaging methods (SENSE/auto, GRAPPA, and ESPIRiT). KIPI enabled CEST frames with random AFs to achieve similar image quality, eliminated the strong aliasing artifacts, and generated significantly smaller errors than the other methods (p < 0.01). The KIPI method permitted an AF up to 12-fold in both phase-encoding and slice-encoding directions for 3D CEST source images, achieving an overall 8.2-fold speedup in scan time.
KIPI is a novel auto-calibrated parallel imaging method that enables variable AFs for different CEST frames, achieves a significant reduction in scan time, and does not compromise the accuracy of CEST maps.
开发一种自动校准技术，通过联合 K 空间和图像空间并行成像（KIPI）实现 CEST 加速采集。
KIPI 方法选择具有低加速因子（AF）的校准帧和自动校准信号（ACS）进行采集，从这些信号中通过 GRAPPA 恢复 K 空间后，计算线圈灵敏度分布和伪影校正图。然后，其他具有高 AF 且没有 ACS 的帧可以通过 SENSE 和伪影抑制进行重建。由于 K 空间中的 T -衰减滤波导致的信号泄漏会影响 SENSE 重建，这可以通过 KIPI 的伪影抑制算法进行校正。在 3T 扫描仪上对 phantom、健康志愿者和脑肿瘤患者进行了 2D 和 3D 成像实验。
通过回顾性欠采样数据评估了所提出的 KIPI 方法，该方法具有可变的 AF，并与现有的并行成像方法（SENSE/auto、GRAPPA 和 ESPIRiT）进行了比较。KIPI 使得具有随机 AF 的 CEST 帧能够实现相似的图像质量，消除了强烈的混叠伪影，并产生了比其他方法更小的误差（p < 0.01）。KIPI 方法允许在相位编码和切片编码方向上的 AF 最高达到 12 倍，实现了 3D CEST 源图像总体 8.2 倍的扫描时间加速。
KIPI 是一种新颖的自动校准并行成像方法，它能够为不同的 CEST 帧实现可变的 AF，显著减少扫描时间，同时不影响 CEST 图的准确性。
