Day-to-day repeatability of total and regional cerebral blood flow

Background: Measuring cerebral blood flow (CBF) has been crucial in understanding brain function and health. Most studies use a resting CBF value for comparison when testing different experimental conditions on different days; however, it is unclear whether resting condition values can be repeated between days. This has important implications for intervention or mechanistic studies. We hypothesize that resting CBF will be repeatable across different days in a well-controlled setting using MRI based pseudo-continuous arterial spin labeling (pcASL). Methods: Seven subjects (1F, 6M) were studied on two separate occasions after abstaining from caffeine, NSAIDs and exercise for 24 hours, and fasting for 8 hours. The end tidal CO 2 had to be within 2mmHg between visits. Female subjects were on days 1-7 of their menstrual cycle and were not taking any hormonal contraception. CBF was quantified via MRI based pseudo-continuous Arterial Spin Labeling (pcASL) during both visits and expressed relative to gray and white matter (mL/min/100g). Data focuses on total grey matter, total white matter, and 8 emotional and memory regions. The repeatability of all CBF values was tested between both MRI visits using linear regression. Results: Scans were completed 113± 81 days apart. R2 values showed a weak effect size for grey matter (R2 =0.454) and a moderate effect size for white matter (R2 =0.527). When measuring for the 8 regions of the brain, there were no significant p-values, and weak R2 effect size for the accumbens (p=0.107, R2 =0.454), amygdala (p=0.204, R2 =0.299), anterior cingulate (p=0.092, R2 =0.463), caudate (p=0.122, R2 =0.409) hippocampus (p=0.175, R2 =0.332), and parahippocampus (p=0.183, R2 =0.323). In brain regions involved with memory, the entorhinal cortex indicated a R2 value of moderate effect size (p=0.068, R2 =0.519) t (p=0.068), as well as the precuneus (p=0.060, R2 =0.54) Conclusion: The results suggest that resting CBF demonstrates low repeatability between days. Noteworthy trends exist in the entorhinal cortex and precuneus, which both are involved in memory. These findings suggest that when comparing resting CBF, researchers may want to consider collecting new resting CBF measurements every time they are testing for reactivity since there might be variability in areas such as the accumbens, amygdala, anterior cingulate, caudate, hippocampus and parahippocampus. Funding: NIH R01 HL150361. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.