Yen Y-F, Kohler S J, Chen A P, Tropp J, Bok R, Wolber J, Albers M J, Gram K A, Zierhut M L, Park I, Zhang V, Hu S, Nelson S J, Vigneron D B, Kurhanewicz J, Dirven H A A M, Hurd R E
GE Healthcare Global Applied Sciences Laboratory, Menlo Park, CA 94025, USA.
Magn Reson Med. 2009 Jul;62(1):1-10. doi: 10.1002/mrm.21987.
One of the challenges of optimizing signal-to-noise ratio (SNR) and image quality in (13)C metabolic imaging using hyperpolarized (13)C-pyruvate is associated with the different MR signal time-courses for pyruvate and its metabolic products, lactate and alanine. The impact of the acquisition time window, variation of flip angles, and order of phase encoding on SNR and image quality were evaluated in mathematical simulations and rat experiments, based on multishot fast chemical shift imaging (CSI) and three-dimensional echo-planar spectroscopic imaging (3DEPSI) sequences. The image timing was set to coincide with the peak production of lactate. The strategy of combining variable flip angles and centric phase encoding (cPE) improved image quality while retaining good SNR. In addition, two aspects of EPSI sampling strategies were explored: waveform design (flyback vs. symmetric EPSI) and spectral bandwidth (BW = 500 Hz vs. 267 Hz). Both symmetric EPSI and reduced BW trended toward increased SNR. The imaging strategies reported here can serve as guidance to other multishot spectroscopic imaging protocols for (13)C metabolic imaging applications.
在使用超极化（13）C-丙酮酸进行（13）C代谢成像时，优化信噪比（SNR）和图像质量面临的挑战之一与丙酮酸及其代谢产物乳酸和丙氨酸不同的磁共振信号时间进程有关。基于多激发快速化学位移成像（CSI）和三维回波平面光谱成像（3DEPSI）序列，在数学模拟和大鼠实验中评估了采集时间窗、翻转角变化和相位编码顺序对SNR和图像质量的影响。图像采集时间设置为与乳酸的峰值产生时间一致。结合可变翻转角和中心相位编码（cPE）的策略在保持良好SNR的同时提高了图像质量。此外，还探讨了EPSI采样策略的两个方面：波形设计（回扫式EPSI与对称EPSI）和光谱带宽（BW = 500 Hz与267 Hz）。对称EPSI和降低的BW都有使SNR增加的趋势。本文报道的成像策略可为其他用于（13）C代谢成像应用的多激发光谱成像协议提供指导。
