Medical Physics, University of Wisconsin, Madison, Wisconsin, USA.
Radiology, University of Wisconsin, Madison, Wisconsin, USA.
Magn Reson Med. 2018 Apr;79(4):2183-2189. doi: 10.1002/mrm.26874. Epub 2017 Aug 22.
To develop a chemical shift encoding (CSE) approach for fluorine-19 MRI of perfluorocarbons in the presence of multiple known fluorinated chemical species.
A multi-echo CSE technique is applied for spectral separation of the perfluorocarbon perfluoro-15-crown-5-ether (PFCE) and isoflurane (ISO) based on their chemical shifts at 4.7 T. Cramér-Rao lower bound analysis is used to identify echo combinations with optimal signal-to-noise performance. Signal contributions are fit with a multispectral fluorine signal model using a non-linear least squares estimation reconstruction directly from k-space data. This CSE approach is tested in fluorine-19 phantoms and in a mouse with a 2D and 3D spoiled gradient-echo acquisition using multiple echo times determined from Cramér-Rao lower bound analysis.
Cramér-Rao lower bound analysis for PFCE and ISO separation shows signal-to-noise performance is maximized with a 0.33 ms echo separation. A linear behavior (R = 0.987) between PFCE signal and known relative PFCE volume is observed in CSE reconstructed images using a mixed PFCE/ISO phantom. Effective spatial and spectral separation of PFCE and ISO is shown in phantoms and in vivo.
Feasibility of a gradient-echo CSE acquisition and image reconstruction approach with optimized noise performance is demonstrated through fluorine-19 MRI of PFCE with effective removal of ISO signal contributions. Magn Reson Med 79:2183-2189, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
开发一种化学位移编码（CSE）方法，用于在存在多种已知氟化化学物质的情况下对全氟碳化合物进行氟-19 MRI。
在 4.7T 下，应用多回波 CSE 技术对全氟-15-冠-5-醚（PFCE）和异氟烷（ISO）进行光谱分离，基于它们的化学位移。Cramér-Rao 下限分析用于确定具有最佳信噪比性能的回波组合。使用非线性最小二乘估计重建，通过直接从 k 空间数据拟合多谱氟信号模型，对信号贡献进行拟合。该 CSE 方法在氟-19 体模和使用多个回波时间的 2D 和 3D 扰动脉冲梯度回波采集的小鼠中进行了测试，这些回波时间是根据 Cramér-Rao 下限分析确定的。
PFCE 和 ISO 分离的 Cramér-Rao 下限分析表明，回声分离为 0.33ms 时信噪比性能最佳。在使用混合 PFCE/ISO 体模的 CSE 重建图像中，观察到 PFCE 信号与已知相对 PFCE 体积之间存在线性关系（R=0.987）。在体模和体内均显示出 PFCE 和 ISO 的有效空间和光谱分离。
通过对 PFCE 的氟-19 MRI 显示出具有优化噪声性能的梯度回波 CSE 采集和图像重建方法的可行性，有效去除了 ISO 信号贡献。磁共振医学 79：2183-2189，2018。©2017 年国际磁共振学会。
