AUTHOR=Madsen Signe Sloth , Lindberg Ulrich , Asghar Sohail , Olsen Karsten Skovgaard , Møller Kirsten , Larsson Henrik Bo Wiberg , Vestergaard Mark Bitsch 

TITLE=Reproducibility of cerebral blood flow, oxygen metabolism, and lactate and N-acetyl-aspartate concentrations measured using magnetic resonance imaging and spectroscopy

JOURNAL=Frontiers in Physiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2023.1213352

DOI=10.3389/fphys.2023.1213352

ISSN=1664-042X

ABSTRACT=<p>In humans, resting cerebral perfusion, oxygen consumption and energy metabolism demonstrate large intersubject variation regardless of methodology. Whether a similar large variation is also present longitudinally in individual subjects is much less studied, but knowing the time variance in reproducibility is important when designing and interpreting longitudinal follow-up studies examining brain physiology. Therefore, we examined the reproducibility of cerebral blood flow (CBF), global cerebral metabolic rate of oxygen (CMRO<sub>2</sub>), global arteriovenous oxygen saturation difference (A-V.O<sub>2</sub>), and cerebral lactate and N-acetyl-aspartate (NAA) concentrations measured using magnetic resonance imaging (MRI) and spectroscopy (MRS) techniques through repeated measurements at 6 h, 24 h, 7 days and several weeks after initial baseline measurements in young healthy adults (<italic>N</italic> = 26, 13 females, age range 18–35 years). Using this setup, we calculated the correlation, limit of agreement (LoA) and within-subject coefficient of variation (CoV<sub>WS</sub>) between baseline values and the subsequent repeated measurements to examine the longitudinal variation in individual cerebral physiology. CBF and CMRO<sub>2</sub> correlated significantly between baseline and all subsequent measurements. The strength of the correlations (R<sup>2</sup>) and reproducibility metrics (LoA and CoV<sub>WS</sub>) demonstrated the best reproducibility for the within-day measurements and generally declined with longer time between measurements. Cerebral lactate and NAA concentrations also correlated significantly for all measurements, except between baseline and the 7-day measurement for lactate. Similar to CBF and CMRO<sub>2</sub>, lactate and NAA demonstrated the best reproducibility for within-day repeated measurements. The gradual decline in reproducibility over time should be considered when designing and interpreting studies on brain physiology, for example, in the evaluation of treatment efficacy.</p>