Ultrasound-Guided Gas Embolization Using A Single Linear Array Transducer

Transarterial chemoembolization is the first line therapy for patients with intermediate stage hepatocellular carcinoma, the third leading cause of cancer related deaths. This procedure is effective in extending patient survival but requires a complicated catheterization procedure and can induce off-target occlusion. Gas embolization has been proposed as an easily administered, more spatially selective alternative. Microbubbles produced in situ using acoustic droplet vaporization can accumulate and form occlusions within the tumor vasculature. While recent studies have demonstrated the efficacy of this method in mouse models, the focused ultrasound used for droplet vaporization has been manually guided, resulting in off-target hemorrhage. A more targeted yet similarly facile to administer insonation method will improve the clinical translatability of the proposed therapy. Here, we demonstrate the development of a custom ultrasound pulse sequence consisting of interleaved real-time imaging and droplet vaporization that operates on a single linear array transducer. GUI controls were developed to afford the user fine control over the localization of the focal spot. We first produced bubble clouds in fibrin gels seeded with droplets to demonstrate the accuracy of spatial control. Then, we successfully generated and tracked occlusions in real-time in a tumor model without the induction of off-target hemorrhage. These preliminary results indicate that gas embolization may serve as an easily administered ultrasound-guided and activated therapy.