Dual-Echo EPI sequence for integrated distortion correction in 3D time-resolved hyperpolarized 13C MRI
Dual-Echo EPI sequence for integrated distortion correction in 3D time-resolved hyperpolarized 13C MRI
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DOI：
10.1002/mrm.26698
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发表时间：
2018-02-01
影响因子：
3.3
通讯作者：
Cunningham, Charles H.
中科院分区：
文献类型：
--
作者：
Geraghty, Benjamin J.;Lau, Justin Y. C.;Cunningham, Charles H.
目的通过实现一种新的双回波三维回波平面成像序列和重建，在时间分辨、体积超极化的C-13代谢成像中提供内建的非共振校正。方法采用光谱-空间脉冲进行单共振激发，然后进行双回波三维回波平面成像，以5 x 5 x 5 mm(3)的名义分辨率提供x 8 x 6 cm(3)的覆盖。使用多回声H-1 EPI参考扫描对EPI失真的多个来源进行编码。从参考扫描计算的相位图与在双回波[1-C-13]丙酮酸盐图像中编码的整体C-13频偏相结合，以校正几何失真和改善空间配准。该方案在体模研究中得到了验证，并在体内采集了故意传输频率偏差的[1-C-13]丙酮酸和[1-C-13]乳酸大鼠的图像，以评估双回波3D EPI序列。在大鼠成像实验中，代谢肾信号与潜在的解剖结构之间观察到了密切的一致。与单回波采集相比，两个校正回波的相干相加可使信噪比提高约2。结论提出了一种新的用于超极化C-13成像综合失调校正的双回波三维EPI采集序列。在时间分辨代谢图谱方面，建议的序列提供了明显优于反激式EPI的优势。Magn Reson Med 79：643-653,2018。(C)2017国际医学磁共振学会。
PurposeTo provide built-in off-resonance correction in time-resolved, volumetric hyperpolarized C-13 metabolic imaging by implementing a novel dual-echo 3D echo-planar imaging (EPI) sequence and reconstruction.MethodsA spectral-spatial pulse for single-resonance excitation followed by a dual-echo 3D EPI readout was implemented to provide 64 x 8 x 6 cm(3) coverage at 5 x 5 x 5 mm(3) nominal resolution. Multiple sources of EPI distortions were encoded using a multi-echo H-1 EPI reference scan. Phase maps computed from the reference scans were combined with a bulk C-13 frequency offset encoded in the dual-echo [1-C-13]pyruvate images to correct geometric distortion and improve spatial registration. The proposed scheme was validated in a phantom study, and in vivo [1-C-13]pyruvate and [1-C-13]lactate rat images were acquired with intentional transmit frequency deviations to assess the dual-echo 3D EPI sequence.ResultsThe 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.ConclusionA novel dual-echo 3D EPI acquisition sequence for integrated off-resonance correction in hyperpolarized C-13 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. (c) 2017 International Society for Magnetic Resonance in Medicine.