Soher Brian J, Pattany Pradip M, Matson Gerald B, Maudsley Andrew A
Department of Radiology, University of Miami School of Medicine, Miami, Florida, USA.
Magn Reson Med. 2005 Jun;53(6):1283-7. doi: 10.1002/mrm.20491.
A PRESS localization (1)H MRS acquisition sequence with a Carr-Purcell train of refocusing pulses (CP-PRESS) has been implemented using global refocusing "sandwich" pulses. The CP pulse train minimized the effects of J-coupled dephasing in metabolites with strongly coupled, multiplet resonance groups as demonstrated in both phantom data and in vivo single-voxel spectroscopy in normal volunteers. Metabolites with multiplet resonance patterns were maintained with greater signal to noise and a simpler resonance pattern at long echo times. T(2) decay times for metabolites with singlet and multiplet resonances were similar to published values, except for the NAA multiplet at 2.5 ppm, which had a significantly shorter T(2) value (147 ms) than that typically reported for the singlet at 2.01 ppm. Metabolite-nulled spectra were acquired in normal volunteers to evaluate the effects of CP-PRESS on baseline signal contributions from residual water, lipids, and macromolecules. The T(2) decay times in four baseline regions in data acquired with the CP-PRESS sequence showed longer decays than corresponding regions in metabolite-nulled spectra from a standard PRESS sequence, but were significantly diminished long before the metabolites of interest were gone. The spectral analysis for spectra with longer TE times also showed less variability due the higher metabolite SNR, simpler spectral patterns, and the decreased baseline contributions.
一种采用带有Carr-Purcell重聚焦脉冲序列（CP-PRESS）的预饱和定位（1）H磁共振波谱采集序列已通过全局重聚焦“三明治”脉冲得以实现。如在体模数据以及正常志愿者的体内单体素波谱分析中所证明的那样，CP脉冲序列将具有强耦合、多重峰共振基团的代谢物中J耦合去相位的影响降至最低。在长回波时间下，具有多重峰共振模式的代谢物能够保持更高的信噪比以及更简单的共振模式。具有单峰和多重峰共振的代谢物的T(2)衰减时间与已发表的值相似，但2.5 ppm处的NAA多重峰除外，其T(2)值（147毫秒）明显短于通常报道的2.01 ppm处单峰的T(2)值。在正常志愿者中采集了代谢物抑制波谱，以评估CP-PRESS对残留水、脂质和大分子的基线信号贡献的影响。用CP-PRESS序列采集的数据中四个基线区域的T(2)衰减时间比标准PRESS序列的代谢物抑制波谱中相应区域的衰减时间更长，但在感兴趣的代谢物消失之前很久就显著缩短了。对于具有更长回波时间的波谱进行的波谱分析还表明，由于代谢物的信噪比较高、波谱模式更简单以及基线贡献减少，其变异性也更小。
