Test-retest reliability of cerebral blood flow for assessing brain activity in a single day

Motivation: Test-retest reliability of human activity in a single day has not yet been elucidated. Goal(s): To determine the reliability of ASL perfusion MRI within a single day and determine the diurnal impact on the test-retest reliability of fMRI. Approach: Participants were scanned at six time points in a day, during resting-state and Psychomotor Vigilance Test (PVT). Results: The study revealed a higher test-retest reliability for task-based CBF compared to resting-state, with a notable diurnal decline in reliability at 20:00, and showed a decline with time intervals. Impact: These findings underscore the importance of accounting for diurnal variations when designing functional MRI studies to ensure reliable and reproducible results, especially suggest avoiding nighttime data collection.