Researchers at the Laboratory Physics for Medicine Paris (Inserm U1273/ESPCI Paris/PSL University/CNRS) have developed a new ultrasound imaging technique to record the vascular activity of the brain throughout its entire volume. The approach, which took nearly seven years to develop, could help advance the field of neuroscience research. It is detailed in Nature Methods.
The team, led by Mickael Tanter, began by imaging the brain activity of rodents using ultrasound functional imaging (fUS). This new ultrafast technique is 50 times more sensitive than standard ultrasound and is able to detect variations in cerebral blood flow linked to neuronal activity.
The researchers wanted to prove that the technique could be used to obtain dynamic and volumetric images of brain activity if extended to 4D (three spatial dimensions and one temporal dimension). To do this, they developed a prototype ultrafast ultrasound scanner equipped with a large number of electronic channels, capable of driving a prototype matrix ultrasound probe and acquiring images at more than 5000 volumes/second. They also developed ultrasonic emission sequencing (using spatiotemporal encoding methods) and innovative post-processing to compensate for the low sensitivity inherent in raster probes compared to conventional 2D ultrasonic imaging probes.
Tanter and colleagues say they have validated their study in experiments in rats in three experiments: complete brain imaging of multi-sensory stimuli; 3D functional connectivity imaging; and 4D monitoring of how epileptic seizures spread.
Functional ultrasound 4D imaging has tremendous potential for neuroscience research, as it allows for the first recording of brain vascular activity throughout the volume for studying whole-brain connection networks and monitoring transient brain events, they say.
One of the team’s goals is to apply 4D ultrasound functional imaging in the clinic, particularly in neonatology, where the technique could revolutionize new-born care through early diagnosis of neurodevelopmental disorders.
Read the research paper: 4D functional ultrasound imaging of whole-brain activity in rodents. Nature Methods 10.1038/s41592-019-0572-y. C. Rabut, M. Correia, V. Finel, S. Pezet, M. Pernot, T. Deffieux, M. Tanter.