Physio-fUS: a tissue-motion based method for heart and breathing rate assessment in neurofunctional ultrasound imaging.

BACKGROUND

Recent studies have shown growing evidence that brain function is closely synchronised with global physiological parameters. Heart rate is linked to various cognitive processes and a strong correlation between neuronal activity and breathing has been demonstrated. These findings highlight the significance of monitoring these key physiological parameters during neuroimaging as they provide valuable insights into the overall brain function. Today, in neuroimaging, assessing these parameters requires additional cumbersome devices or implanted electrodes. Here we demonstrate that ultrasonic neurofunctional imaging data alone is sufficient to extract these parameters.

METHODS

In this work, we performed ultrafast ultrasound imaging in male rodents and human neonates, and we extracted heart and breathing rates from local tissue motion assessed by raw ultrasound data processing. Such "Physio-fUS" automatically selects two specific and optimal brain regions with pulsatile tissue signals to monitor such parameters.

FINDINGS

We validated the correspondence of these periodic signals with heart and breathing rates assessed using gold-standard electrodes in anaesthetised rodents. We extracted heart and breathing rates in sleeping rats and heart rate in rats moving freely in an arena. We also validated Physio-fUS imaging in sleeping human newborns using conventional ECG.

INTERPRETATION

We show the potential of fUS imaging as an integrative tool for simultaneously monitoring physiological parameters during neurofunctional imaging. Beyond the technological improvement, it could enhance our understanding of the link between breathing, heart rate and neurovascular activity in preclinical research and clinical functional ultrasound imaging.

FUNDING

This study was supported by the European Research Council under the European Union's Seventh Framework Program (FP/2007-2013)/ERC Grant Agreement n°311025 and by the Fondation Bettencourt-Schueller under the program "Physics for Medicine".