Figure 7 –

Introducing a limit on the Maxwell index reduces the efficiency of the diffusion encoding and the penalty depends on the timing asymmetry. The left plot shows that the impact on efficiency is independent of the Maxwell index for m below approximately 1000 (mT/m)²ms. The absolute and relative impact on the encoding duration (c_abs & c_rel) is stated for the experiment setup used in the practical experiments (δ₁ = δ₂ + 8 ms) at m = 100 (mT/m)²ms. For completeness, the same penalty is 3.6 ms or 7.9 % (data not shown), for STE when constraining the gradient waveform within a cube with sides of length 2×75 mT/m (max-norm optimization⁵) and disallowing arbitrary waveform rotation. The right plot shows that the efficiency depends heavily on the encoding time asymmetry of the sequence. As expected, equal gradient duration on either side of the refocusing pulse yields the highest efficiency.