A new neuroimaging modality
In the quest for understanding the human mind, imaging of the human brain has proven invaluable. In the early 1990s, the advent of fMRI revolutionized the understanding of brain and paved the way for major discoveries of the last decades in neuroscience. It still progresses and remains the most popular “Gold Standard” imaging technique available today for deep brain imaging. However, our group demonstrated a new way to perform deep functional brain imaging based on ultrafast Ultrasound imaging (>1000 frames per second). This concept of ultrafast imaging based on plane wave transmissions was proposed by our group in 1996 at Langevin Institute and it is the core of fUltrasound imaging.
From ultrafast imaging…
This rupture is based on the concept of ultrafast ultrasonic scanners introduced by Langevin Institute. For an extended review on ultrafast Ultrasound, you can read the review article Ultrafast Imaging in biomedical ultrasound published in 2014. Such ultrafast scanners are able to produce thousands of ultrasonic images per second compared to the usual 50 frames per second in conventional ultrasound scanners. The key idea behind this revolution was to use plane wave transmissions instead of sequential focused beams transmissions. It was first applied to the field of Elastography and was then extended to Doppler ultrasound.
…to ultrasensitive doppler…
As seen in the video, in conventional doppler using focalization, only a few time samples are available for each pixel, whereas with ultrafast ultrasound imaging, all the field of view is recorded at once and for each pixel there are many time samples available which lead to a 100 fold increase in doppler sensitivity within the same acquisition time. More than a technology leap, this huge increase in sensitivity breaks a scientific barrier as it permits Ultrasound for the first time to map subtle hemodynamic changes in the brain vascularization without being restricted to large vessels.
and functional ultrasound
A first in vivo proof of concept was shown recently by imaging functional cerebral blow volume (CBV) changes in the cerebral microvascularization of the rat brain during whisker stimulation, thus leading to the concept of functional Ultrasound (fUS by analogy to fMRI). This technique was also applied in our seminal publication on fUS to brain activity imaging during epileptic seizures on anesthesized rats. The fUS method can image the blood moving at velocities higher than 4 mm/s (arterioles of ~10µm) with excellent spatial resolution (100×100×200 µm3) and sensitivity high enough to detect hemodynamic changes of only 2% without averaging over different trials. A technical review paper is available here.
Following these initial results, several other important papers were recently published demonstrating among others :
– the ability of fUltrasound to image vascular parameters such as arterial resistivity in clinics (Demene et al 2014)
Today, beyond this proof of concept, our objective is to introduce fUS as a full-fledged imaging modality of neuroscience.
Indeed, FUSIMAGINE will be dedicated to break some major barriers of neuroimaging :
- a unique real time, portable and high resolution functional neuro-imaging modality for awake and freely moving animals experiments in neuroscience research
- a unique clinical and portable (available in the patient room) functional neuro-imaging modality for newborns with unprecedented resolution
- a unique clinical functional neuroimaging modality during per-operative surgery without portability and electromagnetic compatibility constraints.