Simultaneous T1 and T2 Mapping in the Brain With QuantoRAGE: An MP2RAGE Variant Using T2-Prepared Inversion.
Abstract
Purpose
To develop and validate a repeatable and reproducible approach, QuantoRAGE, for simultaneous whole-brain T1 and T2 mapping using adiabatic magnetization preparation.
Methods
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.
Results
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.
Conclusion
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.
