Rapid and accurate T₂ mapping from multi-spin-echo data using bloch-simulation-based reconstruction

Purpose: Quantitative T₂-relaxation-based contrast has the potential to provide valuable clinical information. Practical T₂-mapping, however, is impaired either by prohibitively long acquisition times or by contamination of fast multiecho protocols by stimulated and indirect echoes. This work presents a novel postprocessing approach aiming to overcome the common penalties associated with multiecho protocols, and enabling rapid and accurate mapping of T₂ relaxation values. Methods: Bloch simulations are used to estimate the actual echo-modulation curve (EMC) in a multi-spin-echo experiment. Simulations are repeated for a range of T₂ values and transmit field scales, yielding a database of simulated EMCs, which is then used to identify the T₂ value whose EMC most closely matches the experimentally measured data at each voxel. Results: T₂ maps of both phantom and in vivo scans were successfully reconstructed, closely matching maps produced from single spin-echo data. Results were consistent over the physiological range of T₂ values and across different experimental settings. Conclusion: The proposed technique allows accurate T₂ mapping in clinically feasible scan times, free of user- and scanner-dependent variations, while providing a comprehensive framework that can be extended to model other parameters (e.g., T₁, B₁⁺, B₀, diffusion) and support arbitrary acquisition schemes.