Fast magnetization transfer saturation imaging of the brain using MP2RAGE T₁ mapping

Purpose Magnetization transfer saturation (MT sat ) mapping is commonly used to examine the macromolecular content of brain tissue. This study compared variable flip angle (VFA) T 1 mapping against compressed‐sensing MP2RAGE (csMP2RAGE) T 1 mapping for accelerating MT sat imaging. Methods VFA, MP2RAGE, and csMP2RAGE were compared against inversion‐recovery T 1 in an aqueous phantom at 3 T. The same 1‐mm VFA, MP2RAGE, and csMP2RAGE protocols were acquired in 4 healthy subjects to compare T 1 and MT sat . Bloch‐McConnell simulations were used to investigate differences between the phantom and in vivo T 1 results. Ten healthy controls were imaged twice with the csMP2RAGE MT sat protocol to quantify repeatability. Results The MP2RAGE and csMP2RAGE protocols were 13.7% and 32.4% faster than the VFA protocol, respectively. At these scan times, all approaches provided strong repeatability and accurate T 1 times (< 5% difference) in the phantom, but T 1 accuracy was more impacted by T 2 for VFA than for MP2RAGE. In vivo, VFA estimated longer T 1 times than MP2RAGE and csMP2RAGE. Simulations suggest that the differences in the T 1 measured using VFA, MP2RAGE, and inversion recovery could be explained by the magnetization‐transfer effects. In the test–retest experiment, we found that the csMP2RAGE has a minimum detectable change of 2.3% for T 1 mapping and 7.8% for MT sat imaging. Conclusions We demonstrated that MP2RAGE can be used in place of VFA T 1 mapping in an MT sat protocol. Furthermore, a shorter scan time and high repeatability can be achieved using the csMP2RAGE sequence.