Deelchand Dinesh Kumar, Henry Pierre-Gilles, Marjańska Małgorzata
Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, Minneapolis, Minnesota, USA.
Magn Reson Med. 2015 Jan;73(1):13-20. doi: 10.1002/mrm.25088. Epub 2014 Jan 16.
To investigate the effect of Carr-Purcell (CP) pulse trains on transverse relaxation times, T2, of tissue water and metabolites (both noncoupled and J-coupled spins) in the rat brain at 9.4 Tesla (T) using LASER, CP-LASER, and T2ρ-LASER sequences.
Proton NMR spectra were measured in rat brain in vivo at 9.4T. Spectra were acquired at multiple echo times ranging from 18 to 402 ms. All spectra were analyzed using LCModel with simulated basis sets. Signals of metabolites as a function of echo time were fitted using a mono-exponential function to determine their T2 relaxation times.
Measured T2 s for tissue water and all metabolites were significantly longer with CP-LASER and T2ρ-LASER compared with LASER. The T2 increased by a factor of ∼ 1.3 for noncoupled and weakly coupled spins (e.g., N-acetylaspartate and total creatine) and by a factor of ∼ 2 (e.g., glutamine and taurine) to ∼ 4 (e.g., glutamate and myo-inositol) for strongly coupled spins.
Application of a CP pulse train results in a larger increase in T2 relaxation times for strongly coupled spins than for noncoupled (singlet) and weakly coupled spins. This needs to be taken into account when correcting for T2 relaxation in CP-like sequences such as LASER.
使用LASER、CP-LASER和T2ρ-LASER序列，研究 Carr-Purcell（CP）脉冲序列对9.4特斯拉（T）大鼠脑内组织水和代谢物（包括非耦合和J耦合自旋）横向弛豫时间T2的影响。
在9.4T下对大鼠脑进行体内质子核磁共振谱测量。在18至402毫秒的多个回波时间采集谱图。所有谱图均使用带有模拟基集的LCModel进行分析。代谢物信号作为回波时间的函数，使用单指数函数进行拟合，以确定其T2弛豫时间。
与LASER相比，CP-LASER和T2ρ-LASER测得的组织水和所有代谢物的T2明显更长。对于非耦合和弱耦合自旋（如N-乙酰天门冬氨酸和总肌酸），T2增加了约1.3倍；对于强耦合自旋，T2增加了约2倍（如谷氨酰胺和牛磺酸）至约4倍（如谷氨酸和肌醇）。
CP脉冲序列的应用导致强耦合自旋的T2弛豫时间增加幅度大于非耦合（单重态）和弱耦合自旋。在对LASER等类似CP序列中的T2弛豫进行校正时，需要考虑这一点。
