Neuroimaging modalities such as functional MRI (fMRI) are invaluable for understanding brain function, but the large cost and size of MRI systems makes clinical use challenging, particularly for bedside brain imaging of vulnerable newborns. The development of portable systems for real-time monitoring of brain function in babies is of crucial importance.

With this aim, the researchers - from Institut Langevin and Robert Debré University Hospital - are investigating the use of functional ultrasound imaging to monitor brain activity in newborns. The approach is based on ultrafast ultrasound imaging, which achieves more than 10,000 ultrasound frames per second and, in ultrafast Doppler mode, can map subtle changes in blood flow inside small brain vessels correlated with electronic signals of neural activity.

The researchers demonstrated the feasibility of this approach by combining ultrafast Doppler imaging of the brain microvasculature with continuous video-electroencephalography (EEG) recordings. They designed a flexible, non-invasive headmount to fix a lightweight (40 g) ultrasound probe to the baby's head, while surface EEG electrodes simultaneously recorded electrical activity in both brain hemispheres.

In tests on six healthy napping newborns, the probe measurements could distinguish between quiet and active sleep (two sleep states defined by EEG recordings). The authors note that all recordings were performed at the bedside without any sedative drugs, and that they did not observe adverse events or visible discomfort in the babies.

Next, the team performed multichannel continuous video-EEG and ultrafast Doppler brain imaging in two infants with drug-resistant seizure disorders. This enabled them to detect waves of neurovascular changes spreading throughout the babies' cortexes and trace the brain regions where the seizures originated. Such insight into infant brain activity could potentially help in the development of therapies for neurological disorders.

"The data presented here demonstrate that real-time functional ultrasound imaging is feasible and safe in neonates at the bedside," the authors write. "Functional ultrasound imaging in newborns could become a useful neuroimaging modality that can be correlated temporally and spatially with EEG events. Its portability, low cost and usability might make it the standard choice for bedside functional imaging."