FIG. 3.

IR-SPGR pulse sequence. This sequence consists of three main blocks. An RF pulse with angle β first inverts the magnetization. After observing an inversion evolution time TI, Q k-space encoding steps are acquired to capture the intended contrast. Parameters for the SPGR acquisition module include excitation angle θ, excitation time TE, and repetition time TR. In this work, the 3D stack-of-rings with spherical coverage is used for readout. Finally, a recovery delay period TD allows the magnetization to return to equilibrium before the next preparation segment. This whole prepare-acquire-recover loop is repeated P times such that P · Q equals the desired set of encoding steps.