731 - Contrast-enhanced Ultrasound Evaluation of Histotripsy Liver Tumor Ablation: A Case Series of Expected and Unexpected Findings

Learning Objectives:

1. Review the mechanism of action and clinical applications of histotripsy.


2. Demonstrate the added value of contrast-enhanced ultrasound in conjunction with histotripsy.


3. Discuss the complications of histotripsy for liver tumor ablation using select cases.

Background: Histotripsy is a non-invasive ablation modality that utilizes the cavitary effect of ultrasound to induce mechanical tissue disruption, offering precise ablation without thermal damage. First developed in 2004, recent clinical trials have demonstrated the safety of histotripsy for liver tumor ablation, leading to FDA approval in 2023 {1,2}. Histotripsy is now emerging as a viable option for patients with very early and early stage hepatocellular carcinoma when liver transplant or resection is not feasible {3}. Contrast-enhanced ultrasound (CEUS) is a dynamic imaging technique that utilizes microbubble-based contrast agents to assess tissue enhancement and washout kinetics. CEUS can be performed concurrently with histotripsy for enhanced tumor visualization to improve lesion targeting, ensure accurate ablation, and monitor for potential complications.

Clinical Findings/Procedure Details: Suspicious hepatic lesions exhibit characteristic imaging findings on CEUS that aid in targeting for accurate ablation. After histotripsy, the treated ablation target will undergo evolution from an acellular homogenate to avascular scar over the course of 1-2 months. Serial CEUS at regular intervals can monitor this progress, evaluating for complications and for residual or recurrent tumor. The most common complications of histotripsy are skin or body wall inflammation and portal vein thrombosis, both of which occur in 1-2% of cases and resolve without further complication within 30 days with conservative therapy {4}. The most commonly reported major complication is further progression of underlying liver disease although this finding is not directly attributable to the procedure itself.

Conclusion and/or Teaching Points: Histotripsy is a non-invasive ablation modality which is a safe and effective option for hepatic tumor ablation. Dynamic imaging with contrast-enhanced ultrasound is beneficial both for tumor targeting for accurate ablation as well as monitoring for complications. As the clinical applications of histotripsy evolve and adoption grows, CEUS should be embraced for periprocedural evaluation to optimize successful ablation and improve patient outcomes.