For this reason, the investigators propose to evaluate the interest of a new High Frequence Ultrasound Doppler (HFUD) (VEVO ®, Visualsonics, Toronto, Canada) in the surgical management of patients operated in an awake condition for a brain tumor. The ultra high frequency allows to reach a spatial resolution of 30 μm, 5 to 10 times better than MRI and conventional ultrasound. The Doppler mode allows the detection of microvascular flows of speeds less than 1 mm / second. The safety of this device is demonstrated and validated by CE marking (December 2015).