3D in vivo brain elasticity mapping in small animals using ultrasound

Supersonic Shear Imaging (SSI) 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 SSI scan in the sagittal plane of the brain, a 3D elasticity map is reconstructed. A good correlation between the elasticity map and anatomy is observed. The values of dynamic modulus lie between 1 and 16 kPa and grey matter appears softer than white matter. The propagation of shear waves is found to be anisotropic in the cortex, which could be a consequence of the fiber orientation. Moreover, the good temporal resolution of this technique allows a dynamic estimation of brain elasticity within one single cardiac cycle. In the cortex, it is shown that the passage of the arterial pulse do not transiently modify elasticity. Next experiments will focus on applying this new technique in small animal models of neurological pathologies to estimate the effect of damaged tissues on elasticity.