Mapping a reproducible water fraction and T₁ using MP2RAGE and variable flip angle quantitative MRI protocols

Purpose: Water fraction (WF) estimation, a form of quantitative MRI mapping, is typically performed using the variable flip angle (VFA) approach. In this study, WF estimation was extended to include the magnetization prepared with 2 rapid gradient echoes (MP2RAGE) protocol. The two methods were compared to assess the consistency of WF values across both acquisition strategies. Methods: WF and T₁ maps were calculated using both the VFA and MP2RAGE acquisition protocols. In vivo and phantom datasets were used to assess the comparability of WF estimation between the two methods. Repeatability and reproducibility were evaluated both within each acquisition approach and across the two protocols. Results: High agreement was observed between WF and T₁ maps derived from the VFA and MP2RAGE approaches. The extraction of WF maps from the MP2RAGE protocol was validated, and the consistency of WF estimation across both methods was confirmed. Conclusion: The findings support the use of WF alongside T₁ maps derived from both the VFA and MP2RAGE methods. The ability to obtain reliable WF estimates from either protocol expands the applicability of WF mapping across a broader range of imaging studies.