Three-dimensional volume-rendered imaging of embryonic brain vesicles using inversion mode

The purpose of this study was to present our first experience of normal embryonic brain vesicle shapes in the early first trimester of pregnancy, reconstructed by three-dimensional (3D) volume-rendered imaging using the inversion mode. Twenty-three women who were between 7.4 and 9.7 weeks of gestation were studied using 3D ultrasound with a mechanical 3.7-9.3 or 4.5-11.9 MHz 3D transvaginal probe. In order to clarify the anatomical correlation of the embryonic and fetal brain vesicles, the inversion mode was used. One patient who was at 7.4 weeks of gestation was excluded from the study because of the relative shallow scanning range of the 3D transvaginal transducer and very small embryonic brain structures. When viewed by means of transvaginal 3D volume-rendered imaging using the inversion mode, the brain vesicles were the most prominent structures at each week, and were clearly seen as multilobular consecutive structures. All embryos studied had five secondary brain vesicles. Moreover, the dramatic change of embryonic brain vesicle shapes with advancing gestation was noted during this period. Our results suggest that transvaginal 3D volume-rendered imaging using the inversion mode provides accurate visualization of embryonic brain vesicle structures in utero.