Figure 3.

ΔB₀ insensitive (A) and B₁ and ΔB₀ insensitive (B) composite pulses for T1ρ weighted imaging and the magnetization path during each sequence. In (A) magnetization is flipped along the y-axis (grey), where it nutates about the effective field (z′-axis) and at time τ/2 (black) is flipped 180° about the y-axis where it nutates around the effective field (z″-axis) back along the y-axis (grey). In (B) the magnetization follows a similar path, but with two differences: (1) the excitation flip angle does not need to be 90° and (2) B₁ insensitivity is maintained by flipping the magnetization along the −z-axis. While (B) is more robust than (A), an imperfect 180° flip can still produce artifacts.