Wilman A H, Allen P S
Department of Physics, University of Alberta, Edmonton, Canada.
J Magn Reson B. 1995 Apr;107(1):25-33. doi: 10.1006/jmrb.1995.1054.
The response of the strongly coupled AB system of citrate to the STEAM and PRESS spatial localization sequences is developed analytically and then verified experimentally at 2.35 T. At this field strength, the response predicted by the complete strong-coupling calculation is shown to differ greatly from that of the simpler weak-coupling approximation. It is shown that the strong-coupling effects induce a significant field-strength dependence in the time-dependent modulations of the response to either sequence. These effects are illustrated for the STEAM and PRESS responses at field strengths of 1.5, 2.35, and 4.7 T. Independent of the chosen sequence, the increase in the signal-to-noise (S/N) of the frequency response with increasing field strength is shown to be significantly less for the citrate system than for uncoupled spins. The factors which weaken the S/N dependence of the citrate AB signal with increasing field strength are quantified and discussed.
对柠檬酸盐的强耦合AB系统对STEAM和PRESS空间定位序列的响应进行了解析推导，然后在2.35 T下进行了实验验证。在该场强下，完整强耦合计算预测的响应与更简单的弱耦合近似的响应有很大差异。结果表明，强耦合效应在对任一序列响应的时间调制中引起了显著的场强依赖性。在1.5、2.35和4.7 T场强下，针对STEAM和PRESS响应说明了这些效应。与所选序列无关，柠檬酸盐系统频率响应的信噪比（S/N）随场强增加的增幅明显小于未耦合自旋的情况。对随场强增加而削弱柠檬酸盐AB信号S/N依赖性的因素进行了量化和讨论。
