High Intensity Focused Ultrasound-Induced Ablation of the Intra-Abdominal Umbilical Vessels in a Rabbit Fetus: A...

To assess the efficacy of high intensity focused ultrasound (HIFU) to target and ablate the fetal intra-umbilical vessels and terminate fetal perfusion in a pregnant rabbit model.

Pregnant New Zealand white rabbits (gestational age: E25-27, n = 6 rabbits, n = 18 treated fetuses, n = 6 controls) underwent high-resolution MRI for fetal localization, orientation assessment, beam guidance, and treatment monitoring. Ultrafast ultrasound with power Doppler quantified cardiac output and placental perfusion pre- and post-treatment. HIFU (100-120Wac, 16-20s) induced thermal ablation; MR-thermometry monitored intraoperative temperature; histology confirmed ablation. Ultrafast ultrasound imaging and gross examination confirmed termination.

Target fetal livers (n = 18) reached a maximum temperature of $72°C\pm 8°C$ . Ultrafast ultrasound imaging confirmed the termination of target fetuses, verifying the treatment success in 11 fetuses. Successfully treated fetuses showed a 95% ± 7.4% decrease in cardiac output compared with 11% ± 4.6% decrease in controls, p = 0.022. Placental perfusion dropped 83% ± 10.0% in successfully treated fetuses compared with 16% ± 5.5% in control fetuses, p = 0.002. Overall, 83% (15/18) of targeted fetuses were terminated, with adjacent controls surviving. Thermal necrosis was present in all targeted livers.

MR-guided HIFU can effectively ablate fetal rabbit umbilical vessels to cause selective termination, modeling a non-invasive treatment for twin reversed arterial perfusion sequence.