Research on Thermal Dosage for High Intensity Focused Ultrasound in Bovine Liver Based on the Magnetic Resonance Thermometry

Abstract

Discussing the relationships between the simulated threshold thermal dose of coagulation and coagulation on the histological slides based on the magnetic resonance (MR) thermometry. The MR imaging guided HIFU system was used, the parameters of therapeutic transducer were: frequency-1 MHz, diameter-150 mm, focal length-150 mm. Sonications were delivered in fresh bovine liver tissue in vitro at a fixed depth of 20 mm and at varying powers. Temperature-sensitive MR images obtained during the sonications were used to estimate the temperature and the thermal dosage of each voxel in the target region was calculated. The thermal dosage of each voxel can be compared with the reference threshold thermal dosage, so as to calculate the boundary and area of the coagulated tissue. After the exposure, the tissue was dissected along the maximal section of the coagulation necrosis, and the area of the biological focal region was measured. The results from this study showed that the occurrence of tissue damage correlated well with the equivalent thermal dose calculation based on the T-mapping of MRI, and they share the same variation tendency.