Effects of the macromolecular pool are usually neglected in T1
mapping using the variable flip angle (VFA)
method. To demonstrate the influence of magnetization transfer (MT) on
the estimated T1, VFA experiments
were performed using sinc and rect pulses of different pulse lengths (0.5 ms ≤ TRF ≤ 2.0 ms). Substantial variations in T1 (11-21 %) were observed. Longer rect pulses yielded lower T1 values
than those obtained by inversion recovery. This can be explained by varying
saturation of macromolecules and inherent MT. A simplified model for the
influence of TRF on the T1
estimates is suggested for low-power rect pulses.
