Reproducibility of brain hemodynamics and metabolism measurements using PET

Objectives Positron emission tomography (PET) using O15 tracers is commonly used to measure brain hemodynamic parameters such as cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral metabolic rate of oxygen (CMRO2). FDG PET is a widely accepted technique to measure the glucose metabolic rate. It is however unknown how reproducible these measurements are when measurements are made at different times during a day.

Methods Nine healthy participants underwent two PET sessions (evening and morning) and one MR session for the study. Each PET session includes two repeated sets of O15 PET scans for brain hemodynamics and one FDG PET for glucose metabolism. MR session includes T1-weighted anatomic images and time-of-flight MR angiography. All modalities were co-registered and transformed into a common space for quantitative analysis. Whole brain CBF, CBV, oxygen extraction fraction (OEF), CMRO2, and glucose metabolic rate (CMRglu) as well as oxygen-glucose index (OGI) were calculated based on the PET images. Quantification was achieved using image-derived arterial input function.

Results There is no evidence of significant changes in brain hemodynamic parameters and metabolic rate before and after a full night of sleep. Highly repeatable results were obtained between the repeated O15 scans, suggests reliability of the measurements.

Conclusions Highly reproducible brain hemodynamic and metabolic parameters were obtained using PET imaging. The difference in measurement time didn’t cause significant changes in global hemodynamic parameters and metabolic rates of the brain. Further investigation of regional measurement is ongoing.

Research Support P50AG005681, P20MH077967, P50NS00683

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