Abstract
Focused Ultrasound is the only truly transient, local and non-invasive technique able to induce safe Blood-Brain Barrier Opening (BBBO), technique used in Parkinson or Alzheimer diseases research. However, the presence of the skull in the path usually affects the focus characteristics (gain, beam width, shape and maxima location). In this work, transcranial acoustic wave propagation generated by a mono-element focused transducer has been modeled using 2D and 3D FDTD methods. Skull structure of the non-human primate under test can be compared in terms of density and sound speed with polymethylmethacrylate (PMMA) films. Then, focus aberration and the phenomena that cause it are characterized, providing a better control of the beam focus using the BBBO technique. Results show a frequency dependent with the thickness of the skull under the ultrasonic therapy. An initial shift of 6 mm is given for axial displacement in the 2D transcranial propagation. Moreover, if the skull geometry can be compared with the curvature radius of the transducer, displacements should be constant with angle independent, like those seeing in the homogenous flat films with the same thickness.
