A novel MR-guided brain therapy device operating at 1 MHz has been designed and constructed. The system has been installed and tested in a clinical 1.5 T Philips Achieva MRI. Skull bone distortions induced on the ultrasonic beam are corrected using the concept of time reversal focusing. Prior to the treatment, a 3D CT scan of the patient head is performed and used as entry parameters for three-dimensional finite differences simulations that compute the propagation of the wave field through the human skull. The simulated phase distortions are then used as inputs for transcranial corrections. Temperature elevations during the treatment are imaged using MRI thermometry thus ensuring the control and safety of this therapeutic approach. First experiments are performed on four human cadavers and the promising results allow us to envision a first clinical investigation of this therapeutic approach in a near future. First targeted applications correspond to the non-invasive treatment of brain metastases and neurologic disorders such as the essential tremor. © 2010.