Simultaneous T<sub>1</sub> and T<sub>2</sub> Mapping in the Brain With QuantoRAGE: An MP2RAGE Variant Using T<sub>2</sub>-Prepared Inversion.
Authors
Affiliations (16)
Affiliations (16)
- Swiss Innovation Hub, Siemens Healthineers International AG, Lausanne, Switzerland.
- LTS5, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
- Department of Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland.
- Laboratory of Computational Neuroscience, School of Computer and Communication Sciences and School of Life Sciences, EPFL, Lausanne, Switzerland.
- Laboratory of Sensory Processing, School of Life Sciences, EFPL, Lausanne, Switzerland.
- Donders Institute for Brain Cognition and Behaviour, Radboud University, Nijmegen, the Netherlands.
- Translational Imaging Center, Swiss Institute for Translational and Entrepreneurial Medicine, Bern, Switzerland.
- Department of Diagnostic, Interventional and Pediatric Radiology (DIPR), University Hospital Bern, Bern, Switzerland.
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland.
- Magnetic Resonance Methodology, Institute of Diagnostic and Interventional Neuroradiology, University Hospital Bern, Bern, Switzerland.
- Support Center for Advanced Neuroimaging, Institute of Diagnostic and Interventional Neuroradiology, University Hospital Bern, Bern, Switzerland.
- Laboratory of Magnetic Resonance Imaging Systems and Methods, EPFL, Lausanne, Switzerland.
- CIBM Center for Biomedical Imaging (CIBM), Lausanne, Switzerland.
- Research & Clinical Translation, Magnetic Resonance, Siemens Healthineers AG, Erlangen, Germany.
- Siemens Healthineers AG, Erlangen, Germany.
- Swiss Innovation Hub, Siemens Healthineers International AG, Bern, Switzerland.
Abstract
To develop and validate a repeatable and reproducible approach, QuantoRAGE, for simultaneous whole-brain T<sub>1</sub> and T<sub>2</sub> mapping using adiabatic magnetization preparation. QuantoRAGE is a 3D FLASH-based sequence using an adiabatic T<sub>2</sub>-prepared inversion followed by two readout blocks. Sequence repetitions with different preparation durations and inversion times provide T<sub>1</sub>- and T<sub>2</sub>-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 T<sub>1</sub> and multi-echo spin-echo T<sub>2</sub> 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, T<sub>1</sub> and T<sub>2</sub> phantom quantification agreed with nominal values (T<sub>1</sub>: r = 0.98, T<sub>2</sub>: r = 0.99). In eight healthy volunteers, high repeatability (bias ± SD, T<sub>1</sub>: 14.1 ± 30.2 ms, T<sub>2</sub>: 1.2 ± 1.7 ms) and reproducibility (T<sub>1</sub>: 18.9 ± 32.6 ms, T<sub>2</sub>: 1.1 ± 2.1 ms) were observed across brain regions, with T<sub>1</sub> estimates comparable to reference methods (r = 0.96, slope = 0.74), and T<sub>2</sub> 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 T<sub>1</sub> and T<sub>2</sub> maps at 0.8-mm isotropic resolution. QuantoRAGE enabled reproducible simultaneous T<sub>1</sub> and T<sub>2</sub> mapping at 3 T, providing an efficient framework for longitudinal and cross-sectional quantitative MRI studies and showed feasibility at 7 T.