The research project Echobrain aims to innovate in transcranial ultrasound (US) imaging. Indeed, brain echography could be much more accessible than the current used techniques Xrays or Magnetic Resonance Imaging (MRI) but remains challenging due to strong attenuation and aberration of the US beam when crossing the skull bone. The quality of transcranial echography can be significantly increased provided that skull distortions can be accounted for at the emission, to focus the beam inside the brain, and at the reception, during the image formation process. These distortions can be experimentally measured, but need an invasive procedure generally using probes located inside the area to image. Models of US wave propagation, using a description of the morphology of the skull obtained by MRI or X-rays can also be used to predict these aberration corrections in a non-invasive way.
For the past two decades, CEA-LIST has been developing the Non Destructive Testing (NDT) expertise platform CIVA, including simulation and advanced imaging tools for phasedarray ultrasonic techniques. In particular, the Total Focusing Method and the Plane Wave Imaging have significantly improved NDT imaging in complex configurations, including strong attenuating media. These methods are based on the asymptotic pencil method, to simulate the propagation of elastodynamic waves in complex structures, considering refractions and reflections, with and without mode conversion, at the different interfaces. The global objective of EchoBrain is to adapt these imaging tools to compensate for the effects of aberration of the skull and significantly improve the quality of brain echography. The corollary of this approach is that we have a precise knowledge of the acoustic properties of the patient’s skull in front of the imaging probe.
The first step will be dedicated to the evaluation of the elastodynamic field propagation model of the CIVA platform by comparison with US measurement through ex vivo human skulls. The actual description of each human skull, derived from CT imaging, will be provided as input to the simulation. In the second step, the direct model thus validated will be used for the optimisation of the transcranial imagery by compensation of the aberration’s effects of the skull. Several procedures will be investigated.
From a scientific point of view, this project will provide a method to exhibit a simplified propagation model that suffices in order to obtain satisfactory correction of skull. From a technological point of view, it will contribute to the development of new US scanners dedicated to brain imaging based on programmable multichannel electronics. From a medical stand point, virtually all brain diseases could benefit from this improvement (stroke imaging at the early stage, cavitation activity monitoring, Doppler imaging, elastography of brain tumors or other lesions, intracranial pressure monitoring) The societal impact could therefore be significant.