Beijing City Key Lab for Medical Physics and Engineering, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China.
Center for MRI Research, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.
Magn Reson Med. 2017 Nov;78(5):1711-1723. doi: 10.1002/mrm.26559. Epub 2016 Nov 25.
To develop a novel analytical method for quantification of chemical exchange saturation transfer (CEST) in the transient state. The proposed method aims to reduce the effects of non-chemical-exchange (non-CE) parameters on the CEST signal, emphasizing the effect of chemical exchange.
The difference in the longitudinal relaxation rate in the rotating frame ( ΔR1ρ) was calculated based on perturbation of the Z-value by R1ρ, and a saturation-pulse-amplitude-compensated exchange-dependent relaxation rate (SPACER) was determined with a high-exchange-rate approximation. In both phantom and human subject experiments, MTRasym (representative of the traditional CEST index), ΔR1ρ, and SPACER were measured, evaluated, and compared by altering the non-CE parameters in a transient-state continuous-wave CEST sequence.
In line with the theoretical expectation, our experimental data demonstrate that the effects of the non-CE parameters can be more effectively reduced using the proposed indices ( ΔR1ρ and SPACER) than using the traditional CEST index ( MTRasym).
The proposed method allows for the chemical exchange weight to be better emphasized in the transient-state CEST signal, which is beneficial, in practice, for quantifying the CEST signal. Magn Reson Med 78:1711-1723, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
开发一种新的分析方法，用于在瞬态状态下定量化学交换饱和转移（CEST）。该方法旨在减少非化学交换（非 CE）参数对 CEST 信号的影响，强调化学交换的效果。
根据 R1ρ对 Z 值的扰动用公式计算出在旋转框架中的纵向弛豫率差异（ΔR1ρ），并采用高交换率近似法确定饱和脉冲幅度补偿交换相关弛豫率（SPACER）。在体模和人体受试者实验中，通过改变瞬态连续波 CEST 序列中的非 CE 参数来测量、评估和比较 MTRasym（传统 CEST 指数）、ΔR1ρ和 SPACER。
与理论预期一致，我们的实验数据表明，与传统 CEST 指数（MTRasym）相比，使用所提出的指数（ΔR1ρ和 SPACER）可以更有效地减少非 CE 参数的影响。
该方法可使瞬态 CEST 信号中化学交换权重得到更好的强调，这在定量 CEST 信号方面具有实际意义。磁共振医学 78:1711-1723, 2017。© 2016 国际磁共振学会。
