P0-5 An In Vivo Tumor-Mimic Model for Evaluating the Accuracy of HIFU Treatments: Preclinical Studies

Abstract

The purpose of this preclinical study was to use an in vivo tumor-mimic model on pig liver for evaluating the accuracy of large HIFU ablations as required for Human treatments. Tumor-mimics were created in in vivo porcine livers by injecting a 1 cc warm mixture of agarose, cellulose, glycerol and methylene blue, which formed 1 cm hyperechoic discrete lesions on sonograms. Three studies were conducted: (i) in vitro experiments were carried out to study the acoustical proprieties of the tumor-mimics. (ii) in vivo experiments were conducted in 10 pigs to evaluate the tolerance of the tumor-mimics and the evolution of their dimensions at mid-term (30 days). (iii) in vivo ultrasound-guided HIFU ablations have been performed in 10 pigs to demonstrate the feasibility of treating accurately a predetermined zone. Thereby, elementary lesions at 10 mm from the tumor-mimic were created. In addition, HIFU ablations were performed by juxtaposing single lesions to surround tumormimics with an average margin of 2 mm in all directions. It has been shown that the acoustical properties of tumor-mimics made them visible on sonograms and did not modify the shape and dimensions of HIFU lesions. The local and biological tolerances of tumor-mimics were excellent. Tumor-mimics were measured on sonogram with reproducible dimensions (average diameter at D0: 9.7 ± 1.0 mm (range 5.6-12.0 mm)), similar to those measured on the sample removed after surgery (average diameter at D0: 10.1 ± 0.7 mm (range 6.3-11.5 mm)). HIFU ablations at 10 mm from the tumor-mimics were measured on the sample at 11.3 ± 1.0 mm (range 8.0-14.0 mm), this is a 13% difference. In addition, it has been showed that 90% of the margins established with juxtaposed HIFU ablations were upper than 2 mm. Therefore this tumormimic can be used to learn HIFU ablation before starting clinical studies especially when the ultrasound device is to be used manually as the one presented in this study.