In 4D ultrasound fetal scanning, however, instead of the sound waves being sent straight down and
reflected back, they are sent at different angles. The returning echoes are processed by a sophisticated
computer program resulting in a reconstructed three-dimensional volume image of the fetus's surface or
internal organs, in much the same way as a CT scan machine constructs a CT scan image from multiple x-
4D ultrasound is a medical ultrasound technique, often used in obstetric ultrasonography (during
pregnancy), providing three-dimensional images of the fetus.
There are several different scanning modes in medical and obstetric ultrasound. The standard common
obstetric diagnostic mode is 2D scanning.