Fast in vivo quantification of T1 and T2 MRI relaxation times in the myocardium based on inversion recovery SSFP with in vitro validation post Gd-based contrast administration

Balanced steady state free precession (bSSFP) sequences (also known by vendor-specific acronyms such as b-FFE, FIESTA or TrueFISP) have found widespread use in applications where rapid imaging is needed, in particular for cardiac imaging (1-3). An advantage of these sequences is their high signal-to-noise (SNR) efficiency. In contrast to conventional turbo spin-echo (TSE) sequences, the steady-state image contrast is not predominantly dominated by a single parameter such as proton density, T1 or T2 relaxation times; rather it is a function of proton density and the T2/T1 ratio. As a consequence, high signal is usually obtained from fluid compartments due to their relatively high T2 values (4). Steady state is reached after a certain transition period. Earlier implementations of this sequence achieved a smooth signal time course towards steady state by preparation of a radio frequency pulse (RF) of flip angle-α/2 at a time interval of half the repetition time (TR) prior to the first α pulse (5). This preparation only works for on-resonance spins. Current implementations use a series of preparation pulses for optimizing the transition to steady state (6)