High-Intensity Focused Ultrasound Using a Toroidal Transducer as an Adjuvant Treatment for Placenta Accreta: A Preliminary Ex Vivo Study

Abstract

BackgroundPlacenta accreta is an abnormal invasion of the placenta within the myometrium, which has increasing rate and could result in maternal mortality or morbidity. The objective of this study was to evaluate the feasibility of treating placenta accreta with high-intensity focused ultrasound (HIFU) using an ex vivo model. Material and methodsA toroidal HIFU transducer working at 2.5 MHz with an integrated ultrasound-imaging probe was used. Ex vivo experiments were performed in eight human placentae (from 39 to 40 weeks) within a configuration that mimicked clinical conditions as closely as possible. The fetal side of the placenta was placed in contact with the sterile envelope that covered the HIFU device to simulate the uterine serosa. HIFU lesions were studied on sonograms and macroscopically. ResultsIn total, 19 single HIFU lesions were created with the same exposure parameters for all of the lesions. The exposure time was 75 s. The acoustic power was 90 W. HIFU lesions were created at different distances (2, 6, 7 and 8 mm) from the uterine serosa by adjusting the thickness of the coupling water and thus, the distance between the HIFU emitters and placental tissues. All of the lesions were homogeneous and approximately spherical in shape. The two diameters of the HIFU lesions were on average 14.6±2.1 mm and 14.1±2.3 mm. Lesions were immediately visible on sonograms after each HIFU exposure as a hyperechoic region. The distance between the surface of the placenta and HIFU lesion as measured on ultrasound images was closely correlated with the same distance that was measured on gross pathology (r=0.89, p<0.05). ConclusionsThis study demonstrates that HIFU may be an interesting option for adjuvant treatment during a cesarean of placenta accreta. These results must be validated under real clinical conditions.