Ultrasound Thermal Ablation in a Tumor-Mimic Pig Liver Model.

In a large number of applications, high intensity focused ultrasound (HIFU) treatments are guided using ultrasound imaging. The purpose of this study was to use an in vivo tumor-mimic model for guiding HIFU ablation in the liver. Tumor-mimics were created in in vivo porcine livers by injecting a mixture of agarose, cellulose, glycerol and methylene blue, which formed 1 cm hyperechoic discrete lesions on sonograms. In vivo experiments were then conducted in 10 pigs for 30 days. Four tumor-mimics were created in each animal using an open approach to evaluate if they are well tolerated. Lesions were characterized sonographically, examined pathologically and using histopathologic analysis with reproducible dimensions (0.92 ± 0.25 cm3) and similar to those measured on the sample removed during surgery. The mean difference between macroscopic measurements and ultrasound measurements is 0.19 ± 0.06 cm3 for 1 cm3 injections. Target creation took a few minutes per tumor-mimic and 80% of injections were successful. Ablations in normal liver tissue and in tumor-mimic were performed in vitro on 20 samples using a HIFU probe (working frequency: 3 MHz) with an integrated ultrasound imaging probe (working frequency: 7.5 MHz). Ablation sizes were not significantly different for controls and tumor-mimics. The agarose-based tissue-mimic creates realistic sonographic targets in vivo and in vitro for learning ultrasound-guided open HIFU ablation in an in vivo model. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]