Acoustic field simulation for focused ultrasound on skull with craniotomy for drug delivery in rat brain

The drugs delivered in the central nervous system can be used for the treatment of Parkinson or Alzheimer by acting directly in the affected zones. The problem is that the Blood Brain Barrier (BBB), only allows the passage of certain substances to protect the brain. The focused ultrasound (FUS) with ultrasonic contrast agents (UCA), have demonstrated the reversible opening of the BBB. This paper presents the modeling of the acoustic field for a Focused Ultrasound transducer by finite element method (FEM), that allows evaluating a craniotomy with the less dimension to improve the propagation of ultrasonic waves without deforming the transducer's focus and cause minimal damage to the rat. For this work the head of a rat of 300 gr, following the dimensions and actual geometry of the murine models and a concave monoelemental transducer with a frequency of 2 MHz a focal length of 20 mm and a radius of 10 mm were taken as reference.