Graham S J, Henkelman R M
Department of Medical Biophysics, University of Toronto, Sunnybrook Health Science Centre, Ontario, Canada.
J Magn Reson Imaging. 1997 Sep-Oct;7(5):903-12. doi: 10.1002/jmri.1880070520.
Using a two-pool exchange model of magnetization transfer (MT), numeric simulations were developed to predict the time dependence of longitudinal magnetization in both semisolid and liquid pools for arbitrary pulsed radiofrequency (RF) irradiation. Whereas RF excitation of the liquid pool was modeled using the time-dependent Bloch equations, RF saturation of the semisolid pool was described by a time-dependent rate proportional to both the absorption lineshape of the semisolid pool and the square of the RF pulse amplitude. Simulations show good agreement with experimental results for a 4% agar gel aqueous system in which the two-pool kinetics have been well studied previously. These simulations provide a method for interpreting pulsed MT effects, are easily extended to biologic tissues, and provide a basis for optimizing clinical imaging applications that exploit MT contrast.
使用双池交换磁化转移（MT）模型，进行了数值模拟，以预测任意脉冲射频（RF）照射下半固体池和液体池中纵向磁化强度的时间依赖性。液体池的RF激发使用随时间变化的布洛赫方程进行建模，半固体池的RF饱和则通过与半固体池吸收线形和RF脉冲幅度平方成正比的随时间变化的速率来描述。模拟结果与先前已对双池动力学进行深入研究的4%琼脂糖水凝胶系统的实验结果吻合良好。这些模拟提供了一种解释脉冲MT效应的方法，易于扩展到生物组织，并为优化利用MT对比的临床成像应用提供了基础。
