ABSTRACT
BACKGROUND: The liver is the most common organ injured in blunt abdominal trauma and makes up roughly 5% of all trauma admissions. Current treatments are invasive and resource-intensive, which may delay care. We aim to develop and validate a contrast-enhanced ultrasound (CEUS)guided noninvasive tool to treat liver lacerations at the bedside. METHODS: Two 1.8 MHz high-intensity focused ultrasound (HIFU) elements were coupled to a C1-6 diagnostic ultrasound probe and a Logiq E10 scanner (GE HealthCare) utilizing a custom enclosure for co-registered imaging and ablation. A phantom was created from polyacrylamide gel combined with thermochromic ink whose color changes above biological ablative temperatures (60 °C). The HIFU wave was focused approximately 0.5 cm below the surface utilizing a 50% duty cycle generating 11.9 MPa for 20, 30, 40, 50, and 60s. Experiments were repeated on ex vivo chicken livers in a water bath. Finally, the livers of 4 live swine underwent up to 6 CEUS-guided treatments using parameters optimized from in vitro work. RESULTS: Treatment of the phantom between 20-60s, produced ablation sizes from 0.016 to 0.4 cm 3 . The relationship between time and size was exponential (R 2 = 0.992). Ablation areas were also well visualized on with ultrasound imaging. The ex vivo liver ablation size at 20s was 0.37 cm 3 , at 30s was 0.66 cm 3 , and at 100 s was 5.0 cm 3 . For the in-vivo swine experiments, the average ablation area measured 2.0x0.75 cm with a maximum of 3.5x1.5 cm. CEUS was utilized with the contrast agent Definity (Lantheus) for identification of lacerations as well as immediate post operative evaluation of therapy. CONCLUSION: These experiments demonstrate the feasibility of CEUS guided transdermal HIFU ablation and the time-dependent size of ablation. This work warrants future investigations into using ultrasound to detect active bleeding and HIFU to coagulate grade III and IV liver laceration. STUDY TYPE: Therapeutic/care management.
