4. A new approach for reproducible water fraction and T1 mapping across different qMRI protocols

COEX 

Quantitative MRI (qMRI) is highly valuable method to estimate the human brain microstructural changes during aging and disease. An important goal of qMRI field is to provide reliable multi-parametric brain maps¹, with T1 map being commonly used. Two main acquisition approaches to quantify T1 on clinical scanners are variable flip angle (VFA) and Magnetization Prepared with 2 Rapid Gradient Echoes (MP2RAGE), yet the agreement between these approaches was not determined. A potential benefit of VFA is that it also allows the extraction of proton density (PD) map², which is not often explicitly extracted using the MP2RAGE formalism or mentioned in the original publications^3,4. In the brain, normalized PD is used to estimate the water fraction (WF). In this work, we first examined the agreement between the T1 maps obtained from these two approaches. Second, we presented a pipeline to obtain PD and WF maps from the MP2RAGE protocol that agree well with the VFA's maps. Hence, this work obtains an additional qMRI map for the MP2RAGE approach which is in agreement with the VFA approach.