Pushing MP2RAGE boundaries: Ultimate time-efficient parameterization combined with exhaustive T₁ synthetic contrasts

MP2RAGE parameter optimization is redefined to allow more time-efficient MR acquisitions, whereas the T₁ -based synthetic imaging framework is used to obtain on-demand T₁ -weighted contrasts. Our aim was to validate this concept on healthy volunteers and patients with multiple sclerosis, using plug-and-play parallel-transmission brain imaging at 7 T.

A "time-efficient" MP2RAGE sequence was designed with optimized parameters including TI and TR set as small as possible. Extended phase graph formalism was used to set flip-angle values to maximize the gray-to-white-matter contrast-to-noise ratio (CNR). Several synthetic contrasts (UNI, EDGE, FGATIR, FLAWS_MIN , FLAWS_HCO ) were generated online based on the acquired T₁ maps. Experimental validation was performed on 4 healthy volunteers at various spatial resolutions. Clinical applicability was evaluated on 6 patients with multiple sclerosis, scanned with both time-efficient and conventional MP2RAGE parameterizations.

The proposed time-efficient MP2RAGE protocols reduced acquisition time by 40%, 30%, and 19% for brain imaging at (1 mm)³ , (0.80 mm)³ and (0.65 mm)³ , respectively, when compared with conventional parameterizations. They also provided all synthetic contrasts and comparable contrast-to-noise ratio on UNI images. The flexibility in parameter selection allowed us to obtain a whole-brain (0.45 mm)³ acquisition in 19 min 56 s. On patients with multiple sclerosis, a (0.67 mm)³ time-efficient acquisition enhanced cortical lesion visualization compared with a conventional (0.80 mm)³ protocol, while decreasing the scan time by 15%.

The proposed optimization, associated with T₁ -based synthetic contrasts, enabled substantial decrease of the acquisition time or higher spatial resolution scans for a given time budget, while generating all typical brain contrasts derived from MP2RAGE.