In vivopreclinical evaluation of the accuracy of toroidal-shaped HIFU treatments using a tumor-mimic model

Abstract

The pig is an ideal animal model for preclinical evaluation of HIFU treatments, especially in the liver. However, there is no liver tumor model available for pigs. In this work, we propose to study an in vivo tumor-mimic model as a tool for evaluating if a sonographycally guided HIFU treatment, delivered by a toroidal-shaped device dedicated for the treatment of liver metastases, is correctly located in the liver. One centimeter tumor-mimics were created in liver tissues. These tumor-mimics were detectable on ultrasound imaging and on gross pathology. Two studies were carried out. First, an in vivo study of tolerance at mid-term (30 days, 10 pigs) revealed that tumor-mimics are suitable for studying HIFU treatments at a preclinical stage, since local and biological tolerances were excellent. The dimensions of the tumor-mimics were reproducible (diameter at day 0: 9.7 +/- 2.0 mm) and were the same as a function of time (p = 0.64). A second in vivo study was carried out in ten pigs. Tumor mimics were used as targets in liver tissues in order to determine if the HIFU treatment is correctly located in the liver. A procedure of extensive HIFU ablation using multiple HIFU lesions juxtaposed manually was then tested on eight tumor-mimics. In 88% of the cases (seven out of eight), tumor-mimics were treated with negative margins (>or=1 mm) in all directions. On average, negative margins measured 10.0 +/- 6.7 mm. These tumor-mimics constitute an excellent reference for studying in vivo the accuracy of HIFU therapy in the liver.

Design aspects of focal beams from high-intensity arrays

“…For spherical therapeutic arrays with a center hole to accommodate a separate imaging array, the near-field beam side lobes produced by such aperture voids, and the reduction in the total available focusing power are important design considerations [10], [27], [28]. …”

“…Currently, the field of therapeutic ultrasonic hyperthermia includes a very wide range of medical applications [3]. Strategies have been developed for the treatment of uterine fibroids [4], breast tumors [5], [6], prostatic hyperplasia [7], [8], thrombolysis [9], liver tumors [10], [11], and brain tumors [12]. Standard commercial imaging probes have been applied to guide ultrasound-based hyperthermia, and more recently, guidance has been built into the same probe [13], [14].…”

Assisted hepatic resection using a toroidal HIFU device: An in vivo comparative study in pig

“…1͑b͔͒ and could be accurately juxtaposed to enlarge the coagulative volume on predetermined regions of the liver. 36,38,39 These HIFU lesions are homogeneous, well defined within the parenchyma, and are not dependent on hepatic inflow occlusion ͓Fig. 1͑c͔͒, 41 which are interesting characteristics for performing large cauterization before hepatic transection.…”

“…It was previously shown that this HIFU prototype allowed the creation of large HIFU lesions in the liver and the accurate targeting of localized zones in the tissues. [35][36][37][38] At present, the aim is to verify whether the linear juxtaposition of multiple single lesions using this toroidal device permits to precoagulate the parenchyma on the line of resection and therefore improve vascular control to facilitate the surgical dissection. In a porcine model, the efficacy and usefulness of the HIFU method was compared to standard methods of resections with pedicle clamping and without clamping with regard to blood loss and dissection time during standardized major hepatic transaction.…”

Fusion modeling for predicting the impact of in-vivo liver motion on HIFU therapies

“…Acquisitions of ultrasound images of pig livers were performed with a 2D linear imaging probe working at the frequency of 12 MHz (Model 8805, B-K Medical, Denmark) during an in-vivo study on ultrasound-guided intraoperative liver HIFU treatments. This study involved HIFU exposures performed during an open procedure with an intraoperative HIFU system dedicated to liver metastases treatment [4,5]. Pigs were anaesthetized and mechanically ventilated.…”