A T1-independent sequence enables accurate quantitative proton density mapping from standard MRI protocols in human brain

Motivation: Quantitative Proton Density (qPD) mapping can track Multiple Sclerosis (MS) progression, but current methods are limited by inaccurate cerebrospinal fluid (CSF) T1 values in standard protocols. Goal(s): To develop accurate CSF-referenced water content mapping from standard brain MRI by implementing a T1-independent sequence. Approach: A rapid T1-independent Echo Planar Imaging sequence was added to standard 3T MRI protocols. Correction factors for PD maps were developed from Multi-Echo Gradient Echo and Turbo Spin Echo sequences. Results: Accurate qPD mapping was enabled by correcting suppressed CSF values, confirmed through phantom studies and testing in MS and healthy subjects. Impact: A rapid (20 s) T1-independent MRI sequence allows quantification of accurate CSF-referenced brain water content when combined with common protocols, enabling an additional quantitative parameter for examining MS disease progression.