In vivo brain elasticity mapping in small animals using ultrasound and its application to cerebral ischemia

Shear Wave Imaging (SWI) is an ultrasound based technique for elasticity imaging that has been successfully tested on several organs in the framework of cancer diagnosis. In this work, the potential of this technique to map brain elasticity in vivo on trepanned small animals is investigated. From a SWI scan of the rat brain, 3D elasticity maps are reconstructed reaching a spatial resolution of 800 μm. The dynamic modulus of the brain tissues exhibits values in the 1 to 16 kPa range and is quantified for different anatomical regions. The propagation of shear waves is found to be anisotropic, which could be a consequence of fiber orientation. Finally, the interest of brain elasticity mapping for the monitoring of brain ischemia is investigated on a rat model. Focal cerebral ischemia is shown to induce a dramatic decrease of elasticity in the lesion.