Effects of Large Blood Vessel Locations during High Intensity Focused Ultrasound Therapy for Hepatic Tumors: a finite element study.

High-Intensity Focused Ultrasound (HIFU) has become a viable alternative for treatment of primary and metastatic liver tumors. We evaluated the effects of presence of a large blood vessel and its distance to the tumor on lesion size during HIFU heating. A finite element method (FEM) was used to obtain the temperature distribution for a transfer equation based on large blood vessels convection effect. In 3-D FEM simulation, a 4-mm diameter, 10-mm height cylindrical tumor tissue was heated by different heating schemes with a large blood vessel (10-mm diameter) located at different positions nearby. The distance between the vessel and the tumor tissue varied from 1 mm to 3 mm. For HIFU therapy, the large blood vessel of different locations do not have significant effect on temperature distribution and thermal dose profile, when the heating duration is short (~2s) or the distance of the large blood vessel from the tumor is larger than 2 mm. The domain of thermal lesion can effectively cover the desired therapeutic region with short ultrasound exposure duration (~2s).