Improved skull bone acoustic property homogenization for fast transcranial ultrasound simulations

Abstract Transcranial ultrasound simulations are crucial to optimize and secure ultrasound interventions in brain therapy, depending on the patient skull. When performing such simulations, accurate modeling of the skull is essential, although very challenging, because of the inter/intra sample property variability. Simulations based on semi-analytical methods require a homogeneous description of the skull. Averaging the acoustic property maps derived from the CT scan does not modify the focus shift, but it leads to an overestimation of the pressure field amplitude. The purpose of this work is to provide a homogenization method that compensates for this amplitude overestimation. First, the skull acoustic property maps are segmented into a three-layer medium to represent the different types of skull bone (cortical – trabecular – cortical). Then, equivalent properties are computed so as to minimize the time of flight and transmission coefficient errors between the three-layer medium and the one-layer equivalent medium. This method was validated using 3D simulations with CIVA Healthcare and k-Wave and has proven to be very efficient.