Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.
Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario, Canada.
Magn Reson Med. 2018 Feb;79(2):643-653. doi: 10.1002/mrm.26698. Epub 2017 Apr 10.
To provide built-in off-resonance correction in time-resolved, volumetric hyperpolarized C metabolic imaging by implementing a novel dual-echo 3D echo-planar imaging (EPI) sequence and reconstruction.
A spectral-spatial pulse for single-resonance excitation followed by a dual-echo 3D EPI readout was implemented to provide 64 × 8 × 6 cm coverage at 5 × 5 × 5 mm nominal resolution. Multiple sources of EPI distortions were encoded using a multi-echo H EPI reference scan. Phase maps computed from the reference scans were combined with a bulk C frequency offset encoded in the dual-echo [1- C]pyruvate images to correct geometric distortion and improve spatial registration. The proposed scheme was validated in a phantom study, and in vivo [1- C]pyruvate and [1- C]lactate rat images were acquired with intentional transmit frequency deviations to assess the dual-echo 3D EPI sequence.
The phantom study demonstrated improved spatial registration in off-resonance corrected images. Close agreement was observed between metabolic kidney signal and the underlying anatomy in rat imaging experiments. Relative to a single-echo acquisition, the coherent addition of the two corrected echoes provided the expected increase in signal-to-noise ratio by approximately 2.
A novel dual-echo 3D EPI acquisition sequence for integrated off-resonance correction in hyperpolarized C imaging was developed and demonstrated. The proposed sequence offers clear advantages over flyback EPI for time-resolved metabolic mapping. Magn Reson Med 79:643-653, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
通过实施新型的双回波 3D 回波平面成像（EPI）序列和重建，在时间分辨、容积超极化 C 代谢成象中提供内置的离共振校正。
实现了一个单共振激发的谱-空域脉冲，然后是双回波 3D EPI 读出，以在 5×5×5mm 的名义分辨率下提供 64×8×6cm 的覆盖。使用多回波 H EPI 参考扫描对 EPI 失真的多个源进行编码。从参考扫描计算出的相位图与双回波 [1- C]丙酮酸图像中编码的体 C 频率偏移相结合，以校正几何失真并改善空间配准。在一个体模研究中验证了所提出的方案，并在体内采集了 [1- C]丙酮酸和 [1- C]乳酸大鼠图像，有意地传送频率偏差，以评估双回波 3D EPI 序列。
体模研究表明，离共振校正后的图像具有更好的空间配准。在大鼠成像实验中，代谢性肾信号与底层解剖结构之间存在密切的一致性。与单回波采集相比，两个校正回波的相干相加预期增加了约 2 的信号噪声比。
为超极化 C 成像的集成离共振校正开发并演示了一种新的双回波 3D EPI 采集序列。与回扫 EPI 相比，所提出的序列在时间分辨代谢映射方面具有明显的优势。磁共振医学 79：643-653，2018。© 2017 国际磁共振学会。
