Effect of blood vessel locations on high intensity focused ultrasound temperature field

Abstract

Objective To improve the safety and reliability in HIFU therapy, the effects of the vessel locations on the high intensity focused ultrasound temperature field were investigated. Methods The temperature distribution was obtained by combining the nonlinear acoustic propagation formula and the Pennes bio-heat transfer equation, as well as the finite difference time domain method. Results The HIFU temperature fields were almost unchangeable whether the vessels had perfusion or not. However, there was a significant reduction in the center temperature rise, while the vessel was located in the acoustic axis. If the distance between the vessel wall and the acoustic axis was leas than 3.0mm, the therapeutic focal region was no longer symmetric and the change in the peak temperature rise was negligible. Neither did the change in the temperature field if the distance was larger than 3.0 mm. Conclusion The effects of vessel perfusion on the HIFU temperature field may be ignored. When the vessel is located within the therapeutic region, the one with 2 mm diameter has a significant effect on the temperature rise of the endovascular and the surrounding tissues, leading to incomplete infarct of the tissues around the vessel. When the distance is leas than 3.0 mm, the vessel with 2 mm diameter might affect the distribution of temperature field. While the effect is negligible, if the distance is larger than 3.0 mm. Key words: High intensity focused ultrasound; Perfusion; Blood vessel locations; Temperature field