A finite element simulation of High Intensity Focused Ultrasound with polyacrylamide as coupling material for acoustic hemostasis

Abstract

High Intensity Focused Ultrasound (HIFU) has emerged as an interesting technology for different medical treatments such as thermal ablation, hyperthermia, and bleeding control (hemostasis). Bleeding control requires a coupling material to deliver the ultrasonic energy provided by the focalized transducer to the tissue to be treated; therefore, improvement in application methods and coupling materials of HIFU are necessary in hemostasis treatment. This paper describes a finite element simulation model of polyacrylamide (PAA) and low density polyethylene (LDP) as coupling materials between the transducer/tissue interface. Both materials were selected due to their acoustic properties, biocompatibility, hardness and durability. The modeled geometry represents a PAA-filled cone made of LDP which works as a coupling material between HIFU transducer and treatment zone. The simulated model comprises a 1.965 MHz concave transducer which was previously characterized within water. Results of time dependent simulations considering PAA and LDP as coupling materials showed an intensity of 3000 W/cm2 at the focal zone of treated tissue which achieved a temperature increase above 62°C on treatment tissue after 1 s. Ultrasound hemostasis could be obtained due to the thermal and mechanical effects. Finite element modeling is a helpful method to simulate HIFU propagation waves and heating on homogenous medium.