Table 1.
kmf WM | pm/pf WM | kmf GM | pm/pf GM | kmf Mus. | pm/pf Mus. | |
---|---|---|---|---|---|---|
Input parameters | 15 | 0.155 | 28 | 0.059 | 46 | 0.108 |
Parameters determined using data created using Bloch equations |
17.85 | 0.1364 | 30.15 | 0.0556 | 51.47 | 0.0972 |
Parameters determined using data created by nulling z- magnetization |
17.85 | 0.1367 | 30.15 | 0.0558 | 51.47 | 0.0974 |
The data is created by either integrating the coupled Bloch equations (the more realistic method) or by setting the z-magnetization of both pools to zero at the end of the FSE pulse train. Other parameters are td = 2s, R1m = 0.5 Hz, R2m = 100000 Hz, andR1f = 0.66 Hz, R2f = 25 Hz for white matter (WM), R1f = 0.52 Hz, R2f = 22 Hz for gray matter (GM), and R1f = 0.49 Hz, R2f = 33 Hz for muscle (M). Sequence parameters are as in Fig. 1. Note that deviations from zero z-magnetization after the FSE pulse train have only a minor effect on pm/pf and no effect on kmf. The difference between the fitted parameters and the input parameters is due nearly entirely to taking only a first order approximation in 1/kmf in Eqs. [4] and [10].