Theoretical and experimental study on temperature elevation behind ribs caused by weakly focused ultrasound.

Temperature distribution in tissues behind ribs produced by weakly focused ultrasound had been calculated using Pennes bioheat equation and the validity of the theoretical model was experimentally confirmed in vitro using porcine live. We found that the position of the maximum temperature in tissue is strongly influenced by the distance between the transducer and ribs, while the gap between ribs is the determining factor for the maximum achievable temperature. Within the focal length, when the distance between the transducer and ribs increases, the maximum temperature increases and its position shifts away from the transducer. The rib width has little effect on the position of the maximum temperature but affects the achievable peak temperature. Our results provide useful information for treating liver cancers using ultrasound induced hyperthermia.