Department of Health Technology, Technical University of Denmark, Kongens Lyngby, Denmark.
MR Research Centre, Aarhus University, Aarhus, Denmark.
Magn Reson Med. 2019 Dec;82(6):2104-2117. doi: 10.1002/mrm.27892. Epub 2019 Jul 11.
To investigate auto- and pre-calibration coil profile estimation for parallel imaging reconstruction of hyperpolarized C MRI volumetric data.
Parallel imaging reconstruction was studied with 3 different approaches for coil profile estimation: auto-calibration, phantom calibration, and theoretic calibration. Acquisition was performed with a 3D stack-of-spirals sequence with spectral-spatial excitation and Cartesian undersampling. Parallel imaging reconstructions were done with conjugate gradient SENSE and 3D gridding with inhomogeneity correction. The approaches were compared in simulations with different SNR, through phantom experiments, and in an in vivo pig study focused on the kidneys. All imaging was done with a rigid home-built 12-channel C receive coil at 3T.
The phantom calibrated and theoretic approaches resulted in the best structural similarities in simulations and demonstrated higher image quality in the phantom experiments compared to the auto-calibrated approach. In vivo mapping of pyruvate uptake and lactate conversion improved for accelerated acquisitions because of a better temporal resolution. From a practical and image quality point of view, use of theoretic coil profiles led to improved results compared to the other approaches.
The success of the theoretic coil profile estimation demonstrates a negligible effect of load on sensitivity profiles at the carbon frequency at 3T. Through theoretic or phantom calibrated parallel imaging, accelerated 3D volumes could be reconstructed with sufficient sensitivity, temporal, and spatial resolution to map the metabolism of kidneys exemplifying abdominal organs. This approach overcomes a critical step in the clinical translation of parallel imaging in hyperpolarized C MR.
研究用于超极化 13 C MRI 容积数据并行成像重建的自动和预校准线圈轮廓估计。
使用 3 种不同的线圈轮廓估计方法（自动校准、体模校准和理论校准）研究并行成像重建：采用具有谱空激发和笛卡尔欠采样的 3D 螺旋堆叠序列进行采集。并行成像重建采用共轭梯度 SENSE 和具有不均匀性校正的 3D 网格进行。在不同 SNR 的模拟、体模实验和聚焦于肾脏的体内猪研究中比较了这些方法。所有成像均在 3T 刚性自制 12 通道 13 C 接收线圈上进行。
在模拟中，体模校准和理论方法导致结构相似度最佳，并在体模实验中表现出比自动校准方法更高的图像质量。由于时间分辨率提高，加速采集时丙酮酸摄取和乳酸转化的体内映射得到改善。从实用和图像质量的角度来看，与其他方法相比，使用理论线圈轮廓导致了更好的结果。
理论线圈轮廓估计的成功证明了在 3T 处碳频率下负载对灵敏度分布的影响可以忽略不计。通过理论或体模校准的并行成像，可以以足够的灵敏度、时间和空间分辨率重建加速的 3D 容积，以映射肾脏的代谢，这代表了腹部器官。这种方法克服了超极化 13 C MR 中并行成像临床转化的一个关键步骤。
