Simultaneous T₁ and T₂ Mapping in the Brain With QuantoRAGE: An MP2RAGE Variant Using T₂-Prepared Inversion

To develop and validate a repeatable and reproducible approach, QuantoRAGE, for simultaneous whole-brain T₁ and T₂ mapping using adiabatic magnetization preparation.

QuantoRAGE is a 3D FLASH-based sequence using an adiabatic T₂-prepared inversion followed by two readout blocks. Sequence repetitions with different preparation durations and inversion times provide T₁- and T₂-weighted images. Quantitative parameters are voxel-wise estimated by matching signal evolutions to a dictionary generated from extended phase graph simulations. To accelerate the method, the protocol was optimized using Cramér-Rao lower bound analysis, and a neural-network was trained on sequence-specific dictionaries for fast matching. The optimized protocol was evaluated in phantom and healthy volunteers at 3 T and compared against reference MP2RAGE T₁ and multi-echo spin-echo T₂ measurements. In vivo repeatability and reproducibility were quantified using scan-rescan experiments. Feasibility of QuantoRAGE at 7 T was tested in vivo.

At 3 T, T₁ and T₂ phantom quantification agreed with nominal values (T₁: r = 0.98, T₂: r = 0.99). In eight healthy volunteers, high repeatability (bias ± SD, T₁: 14.1 ± 30.2 ms, T₂: 1.2 ± 1.7 ms) and reproducibility (T₁: 18.9 ± 32.6 ms, T₂: 1.1 ± 2.1 ms) were observed across brain regions, with T₁ estimates comparable to reference methods (r = 0.96, slope = 0.74), and T₂ underestimated (r = 0.79, slope = 0.44). Fast matching produced results consistent with dictionary-matching and significantly reduced parameter estimation time. At 7 T, the adiabatic preparation resulted in homogeneous T₁ and T₂ maps at 0.8-mm isotropic resolution.

QuantoRAGE enabled reproducible simultaneous T₁ and T₂ mapping at 3 T, providing an efficient framework for longitudinal and cross-sectional quantitative MRI studies and showed feasibility at 7 T.