Comparison between transfrontal and axial three-dimensional ultrasound acquisition in the visualization of midline structures of the fetal brain

Abstract

Objective To compare the visualization of the midline structures of the fetal brain as well as visualization of the fastigium of the fourth ventricle and the primary and secondary vermian fissures obtained by three-dimensional (3D) multiplanar reconstruction of volumes acquired from the axial plane with transfrontal 3D acquisition. Study design A prospective observational study. Patients and methods A total of 127 patients with a normal fetal anomaly scan between 18 and 24 weeks participated in this study. Fetal brain volumes for the multiplanar evaluation were obtained with the transcerebellar plane as the initial plane of acquisition, with the incident ultrasound beam making an angle of about 45° with the cerebral midline. For the transfrontal acquisition, the plane of the midsagittal fetal facial profile was obtained with the ultrasound beam aligned with the frontal suture so as to utilize the metopic suture as an acoustic window. Results The acquisition of the fetal brain in the axial plane was successful in 122 cases (96.1%), whereas the transfrontal acquisition was successful in 106 cases (83.4%), with a statistically significant difference between the two methods (P=0.002). Visualization of the median plane of the fetal brain by 3D multiplanar reconstruction was adequate in 99 out of the 122 (81.1%) volumes, whereas 94 out of the 106 (88.7%) transfrontal acquisitions resulted in adequate midline images; the difference between the two acquisition methods was not statistically significant (P=0.12). There was no statistically significant difference between the two acquisition methods in the visualization of the fastigium of the fourth ventricle or the primary and secondary vermian fissures, which were adequately visualized in 58/122 (47.5%) of the 3D multiplanar reconstructed images and in 62/106 (60.8%) of the transfrontally acquired volumes (P=0.09). Conclusion Images of the midsagittal plane of the fetal brain obtained by 3D multiplanar reconstruction of volumes acquired from axial plane are easier to acquire than the 3D transfrontal approach and result in comparable image quality, with adequate visualization of the cerebral midline as well as the main landmarks of the cerebellar vermis.