Repeatability of Myelin and Myelin Water Quantification Using Short-TR Adiabatic Inversion-Recovery Sequences

Myelin and myelin water (MW) behavior is becoming increasingly relevant in their role in neurodegenerative diseases. Myelin proton fraction (MPF) and myelin water fraction (MWF) measured with short-TR adiabatic inversion-recovery (STAIR) sequences are potential biomarkers of myelin and MW, respectively, but their repeatabilities are unknown. This study aims to evaluate the repeatability of MPF and MWF measured with the STAIR ultrashort echo time (STAIR-UTE) and STAIR short echo time (STAIR-STE) sequences, respectively. 10 volunteers were scanned three times on different days using the same protocol, including 3D STAIR-UTE for myelin mapping and STAIR-STE for myelin water mapping on the same 3 T clinical scanner. The repeatability of each biomarker was analyzed by scan-rescan correlation, Bland-Altman analyses, intraclass correlation coefficients (ICC), and coefficients of variation. There was no bias or significant difference between the three scans for MPF and MWF. Strong repeatability and intrareader/interreader agreement were demonstrated between repeated MPF and MWF measurements on each subject's scans. Strong repeatability was demonstrated for two myelin imaging biomarkers, MPF and MWF, highlighting the utility of STAIR sequences for reliable myelin mapping and potential applications in neuroinflammatory and neurodegenerative diseases.