OC20.08: Non‐invasive high‐intensity focused ultrasound treatment for Twin–twin transfusion syndrome: preclinical application on a pregnant monkey model

The Twin–twin transfusion syndrome is the leading cause of death and disability for all twin pregnancies. The standard treatment for this condition is laser fetoscopy. The chances of survival for both twins after treatment are less than 60%, and this laser procedure exposes them to the risks of infection, rupture of the amniotic sac, and premature delivery. We propose an alternative to laser treatment using High-Intensity Focused Ultrasound (HIFU) technology, aiming to demonstrate its feasibility for in-vivo placental vessel occlusion in pregnant monkeys with twin-twin syndrome. Seven pregnant monkeys were included. The HIFU treatments were performed non-invasively using a toroidal transducer under general anesthesia. The underrated acoustic powers ranged from 95 to 110 watts. The HIFU treatment time was 25 seconds. A Caesarean section was performed immediately after treatment. An inspection of the surrounding organs was performed to eliminate any complication related to the treatment. HIFU lesions and were analysed using B-mode imaging, Doppler, macroscopically and histologically. The mean gestational age of monkeys was 77,8 ± 3,1 days at the day of treatment. 20 HIFU lesions were created. The average ultrasound lesion dimensions were 8,8 mm, 6,49mm and 12,3mm for the width, length and depth, respectively. The occlusion of targeted vessels was confirmed by Doppler and histological analyses. HIFU lesions were observed as a hypoechoic region in B-mode images. Macroscopic and histological analyses confirmed that HIFU lesions were homogeneous. For all experiments, there was no significant change in fetal or maternal parameters during or after HIFU exposure. No secondary fetal or maternal lesions were observed. HIFU treatment using a toroidal transducer could represent a future alternative by allowing non-invasive, safe and hyper-selective vascular obstruction of pathological placental anastomoses, mainly for the treatment of twin-twin-syndrome.