Preclinical Demonstration of In-Vivo Vein Occlusion by Mechanical HIFU Without Contrast Agent Injection: Paving the Way for the Non-Invasive Treatment of Varicose Veins.

Objective: High-intensity focused ultrasound (HIFU) is an emerging non-invasive treatment for various pathologies, including in the field of vascular medicine. Clinical studies have demonstrated its efficacy for vascular occlusion through thermal effects. An interesting yet early-stage alternative is mechanical HIFU, where occlusion is achieved by cavitation initiated by the injection of microbubble contrast agents. Our study aims to demonstrate the feasibility of an innovative ultrasound-guided mechanical HIFU device for non-invasive in-vivo vein occlusion by cavitation without microbubble contrast agents.

Methods: A four piezoelectric ceramic device was developed and acoustically characterized. Erosion efficiency by cavitation was assessed on agar phantom models with cylindrical channels created to mimic veins. A preclinical feasibility demonstration was carried out in-vivo on a sheep model, targeting a collateral saphenous vein in the hind limb. Vein occlusion was investigated using ultrasound imaging during a 7-day follow-up and at the cellular level by histological analysis.

Results: A maximum negative pressure of -23 MPa was measured at the focal point of dimension 1.27 mm³ at -6 dB . In agar phantom models, a centrally applied HIFU treatment was sufficient to erode small veins, while an application at multiple points was needed for larger veins. In vivo, cavitation was triggered in a small-diameter vein, causing occlusion and preventing blood flow. Histology confirmed vein wall damage and occlusion.

Conclusion: Vein occlusion was successfully achieved in-vivo by cavitation using mechanical HIFU without microbubble contrast agents. This approach holds real potential for the non-invasive treatment of varicose veins, without the limitations of current techniques.