Bi-phase age-related brain gray matter magnetic resonance T1ρ relaxation time change in adults.

OBJECTIVES: To investigate normative value and age-related change of brain magnetic resonance T1ρ relaxation at 1.5T. METHODS: This study was approved by the local ethical committee with participants' written consent obtained. There were 42 adults healthy volunteers, including 20 males (age: 41±16 (mean±standard deviation) years, range: 22-68years,) and 22 females (age: 39±15years, range: 21-62years). MRI was performed at 1.5T using 3D fluid suppressed turbo spin echo sequence. Regions-of-interests (ROIs) were obtained by atlas-based tissue segmentation and T1ρ was calculated by fitting the mean value to mono-exponential model. Correlation between T1ρ relaxation of brain gray matter regions and age was investigated. RESULTS: A regional difference among individual gray matter areas was noted; the highest values were observed in the hippocampus (98.37±5.37ms, median: 97.88ms) and amygdala (94.95±4.34ms, median: 94.73ms), while the lowest values were observed in the pallidum (83.81±5.49ms, median: 83.77ms) and putamen (83.93±4.76ms, median: 83.99ms). Gray matter T1ρ values decreased slowly (mean slope: -0.256) and significantly (p<0.05) with age in gray matter for subjects younger than 40years old, while for subjects older than 40years old there was no apparent correlation between T1ρ relaxation and age. Global white matter measured T1ρ value of 88.65±3.47ms (median: 87.86ms), and the correlation with age was not significant (p=0.18). CONCLUSION: Gray matter T1ρ relaxation demonstrates a bi-phase change with age in adults of 22-68years.