Holograms to Focus Arbitrary Ultrasonic Fields through the Skull

The precise control of ultrasound focused into the central nervous system (CNS) is limited mainly by strong phase aberrations due to refraction and attenuation by the skull. This study proposes the use of acoustic holograms to correct these phase aberrations, and also to conform arbitrary acoustic images inside the brain corresponding to CNS structures, such as the hippocampus. Experiments using a skull phantom are in excellent agreement with theory and simulations. Ultrasonic focusing can be observed for various target structures simultaneously, using an inexpensive 3D-printed acoustic holographic lens. These results open paths to innovative biomedical ultrasound applications.