Figure 2.

Conventional (A) and rotary echo (B) composite pulses for T1ρ relaxation measurements and the magnetization path during on-resonance spin locking pulse. Magnetization flipped at an angle α with the y-axis (grey) nutates about the ω₁ or y-axis and at τ/2 accumulates a phase ω_eff τ/2 (black). While the traditional pulse sequence continues accumulating phase in the same direction (white), the rotary echo returns the magnetization back to its initial position (grey).