Fig. 1
Diagrams of pulse sequences for relaxometry. They consist of a general scheme of sequence building blocks (SBBs). The individual types differ only in the preparation and evolution period. Acquisition parameters are summarized in Table 1. RF events are indicated as blue or orange rectangular boxes. For IR experiments (protocols 1 and 2), a rectangular or adiabatic pulse is utilized, while the magnetization is prepared by a composite MT pulse for transient MT experiments (protocol 3). Steady-state MT measurements (protocols 4–12) are performed using a saturation block (orange box), the details of which are shown in the enlarged insert on the right. It consists of \({{\varvec{N}}}_{\text{RF}}\) Gaussian-shaped, cosine-modulated pulses (second row of the insert) with pulse duration \({{\varvec{\tau}}}_{{\varvec{p}}}\) and inter-pulse delay \({{\varvec{\tau}}}_{{\varvec{s}}}\). Alternatively, off-resonance Gaussian pulses were also applied to acquire \({\varvec{z}}\)-spectra (first row of the insert). The brown trapezoids indicate crusher gradients. The four types of the GS-filters (protocols 13–16) are shown as a simplified block with indication of the different pulse phases of the final 90° pulse to obtain GS ‘up’ or GS ‘down’. Finally, IR experiments were combined with the MT-saturation block (protocols 17–22). Here, the MT-saturation train (orange box) was applied before the inversion pulse and (whenever feasible) also during the evolution period.
