An Ultrasound Image-Based Dynamic Fusion Modeling Method for Predicting the Quantitative Impact of In Vivo Liver Motion on Intraoperative HIFU Therapies: Investigations in a Porcine Model.

Organ motion is a key component in the treatment of abdominal tumors by High Intensity Focused Ultrasound (HIFU), since it may influence the safety, efficacy and treatment time. Here we report the development in a porcine model of an Ultrasound (US) image-based dynamic fusion modeling method for predicting the effect of in vivo motion on intraoperative HIFU treatments performed in the liver in conjunction with surgery. A speckle tracking method was used on US images to quantify in vivo liver motions occurring intraoperatively during breathing and apnea. A fusion modeling of HIFU treatments was implemented by merging dynamic in vivo motion data in a numerical modeling of HIFU treatments. Two HIFU strategies were studied: a spherical focusing delivering 49 juxtapositions of 5-second HIFU exposures and a toroidal focusing using 1 single 40-second HIFU exposure. Liver motions during breathing were spatially homogenous and could be approximated to a rigid motion mainly encountered in the cranial-caudal direction (f = 0.20 Hz, magnitude > 13 mm). Elastic liver motions due to cardiovascular activity, although negligible, were detectable near millimeter-wide sus-hepatic veins (f = 0.96 Hz, magnitude 75%). Fusion modeling predictions were preliminarily validated in vivo and showed the potential of using a long-duration toroidal HIFU exposure to accelerate the ablation process during breathing (from 0.5 to 6 cm3 · min(-1)). To improve HIFU treatment control, dynamic fusion modeling may be interesting for assessing numerically focusing strategies and motion compensation techniques in more realistic conditions

Study of a fusion modeling method for US-guided intraoperative liver HIFU ablations performed during respiration in a pig model.

<p>Methodology for preliminary validation of fusion modeling <i>in vivo</i>.</p

HIFUture 2021: Programme de la 1ère édition. 17-18 Juin 2021, Lyon, France

HIFUture is a French Scientific Symposium whose 1st edition has been launched in 2021 to bring together clinicians, researchers, engineers and industrialists involved in the development of ultrasound treatments in France and abroad, with an eye to imagine today the ultrasound treatments of tomorrow. The first edition of the conference was organized in Lyon (France) on June 17-18, 2021 by the Laboratory of Therapeutic Applications of Ultrasound (LabTAU, INSERM, Univ Lyon) and the Hospices Civils de Lyon (HCL)

US-speckle tracking key parameters for <i>in vivo</i> liver motion detection in a porcine model.

<p><b>FOV</b>: Field Of View; <b>RR</b>: Reference Region; <b>SR</b>: Search Region; <b>SA</b>: Search Area; <b>ROI</b>: Region Of Interest; <b>CC</b>: Cranial-caudal direction; <b>AP</b>: Anterior-Posterior; <b>T</b>: Transverse</p><p>US-speckle tracking key parameters for <i>in vivo</i> liver motion detection in a porcine model.</p

Fusion modeling of HIFU treatment versus experimental <i>in vivo</i> HIFU in a porcine model.

<p>Post-treatment fusion modeling merged real <i>in vivo</i> liver motion acquired intraoperatively during HIFU treatments (US speckle tracking) and numerical data from the BHTE solving program. Example with the spherical HIFU focusing strategy studied: <i>in vivo</i> HIFU ablations were generated with a juxtaposition of 7x7 lesions during breathing (total exposure time: 8 minutes, P_ac = 30 W). The HIFU lesion was stretched along the motion direction (cranial-caudal) and individual cigar-shaped type lesions were not juxtaposed homogenously. View of the anterior surface of the liver <b>(a)</b><i>in vivo</i> result (Day 0); <b>(b)</b> fusion modeling result.</p

Modeling of the effects of liver respiratory motion on the creation of a large single HIFU lesion generated with a toroidal transducer.

<p>From left to right: 3D view of the equivalent time at 43°C corresponding to the HIFU lesion; 2D view of the lesion in the cranial-caudal plane; 2D view of the lesion in the transverse plane; 2D view of the lesion in the coronal plane. <b>(a)</b> Control lesion (no liver motion); <b>(b)</b> example of a single lesion generated in presence of liver motion (amplitude of 14 mm in the cranial caudal direction and of 1.5 mm in the tissue depth direction); <b>(c)</b> corresponding under- and overtreatment caused by liver respiratory motion, respectively represented by negative and positive thermal dose differences (cool and hot color scales).</p

Preliminary <i>in vivo</i> validation of fusion modeling in a porcine model for 2 ultrasound focusing strategies: toroidal and spherical HIFU.

<p>Post-treatment fusion modeling merged real <i>in vivo</i> liver motions acquired intraoperatively during HIFU treatments and realistic geometries of sus hepatic veins. Macroscopic analyses were performed on liver tissue samples removed 14 days after HIFU sessions. <b>(a to b)</b> Spherical focusing: 2 examples of <i>in vivo</i> HIFU ablations generated with a juxtaposition of 7x7 lesions during breathing (total exposure time: 8 minutes, P_ac = 30 W); <b>(a)</b> in moving homogeneous liver tissues; <b>(b)</b> in moving liver tissues in presence of a sus-hepatic vein. <b>(c to e)</b> Toroidal focusing: 3 examples of <i>in vivo</i> HIFU ablations generated with one single exposure during breathing (total exposure time: 40 seconds, P_ac = 50 W); <b>(c)</b> in stationary homogeneous liver tissues (40-second apnea); <b>(d)</b> in moving homogeneous liver tissues; <b>(e)</b> in moving liver tissues in presence of a sus-hepatic vein.</p

Liver tissue physiological parameters used during numerical modeling of HIFU treatments.

<p>Liver tissue physiological parameters used during numerical modeling of HIFU treatments.</p

Liver motion effects on HIFU treatment key parameters.

<p>Lesions performed with spherical and toroidal HIFU exposure sequences in liver.</p

Quantitative impact of <i>in vivo</i> tissue motion on 2 different HIFU focusing strategies.

<p><b>(a)</b> A spherical HIFU focusing: 7 x7 millimetric cigar-shaped lesions; Pac = 30W, HIFU sequence: 5s ON / 5s OFF, total treatment time = 8 min; <b>(b)</b> a toroidal HIFU focusing: 1 single centimetric lesion, Pac = 50W, HIFU sequence: 40s ON, total treatment time = 40 s; <b>(c)</b> Schematic illustrating the different volume measurements performed for quantifying the effect of tissue motions on HIFU lesions, with V being the volume of the Control lesion (without motion), V’ the volume of lesion when induced in moving tissues, VUt the volumetric undertreatment and VOt the Volumetric Overtreatment.</p