Fig 1. T_1ρ pulse sequence designed for use in humans using breath-hold and electrocardiogram (ECG)-triggering.

The pulse sequence is synchronized to the R-wave using a MRI- compatible vector ECG. The spin lock pulse cluster shown here is a spin lock, spin echo (90_x-SL_y-180_+y-SL_-y-90_-x), consisting of a pair of continuous RF spin locking pulses with opposite phase ±y to refocus magnetization in a heterogeneous B₁ magnetic field and a refocusing pulse to refocus B₀. TSL is total spin lock time. After the T_1ρ pulse cluster, a crusher gradient is delivered to eliminate remaining transverse signal and then a second magnetization preparation period employing a bSSFP flip angle ramp to stabilize the transverse magnetization prior to spatial encoding. The readout sequence employed is a single-shot bSSFP.