P3C-1 Modelling of In Vivo Liver Motion on HIFU Treatments: A Combined Method

Accurate HIFU treatments of abdominal tumors is difficult because of organs motions during breathing. Here we report that a combined method can be used for simulating HIFU lesion in the liver by considering effective in vivo motion. Sequences of ultrasound images were acquired in vivo during an open procedure on 4 pigs using a 2D ultrasound imaging probe working at a frequency of 12 MHz. Sequences were acquired during either breathing or apnea. Effects of real liver motions on a HIFU treatment were modeled on the basis of the combination of two techniques. An accurate ultrasound correlation-based method was used to estimate liver motion using speckle tracking. Effects of liver motion on HIFU lesions were observed by including these measured displacements in numerical simulations based on Bio Heat Transfer Equation. A first set of data was acquired on 2 pigs during breathing showed that the main movements were encountered in the cranial-caudal direction (f=0.2 MHz, average magnitude: 13.3 plusmn 1.1 mm (range 9.0 - 15.5)). A second set of data was acquired on 2 pigs during breathing and apnea in order to separate the motion due to cardiovascular activity only (f=0.96 MHz, magnitude < 0.5 mm). The results of simulated HIFU lesions considering real in vivo liver motion revealed that the lesions were significantly different in terms of size and homogeneity between control (no motion) and breathing samples. Therefore this study provides a useful and practical mean of determining the influence of effective 2D actual in vivo motions on HIFU treatments which can be applied to the liver or to any other moving organ.