2D-Ultrasound imaging is a common diagnostic medical procedure that uses high-frequency sound waves to produce dynamic images (sonograms) of organs, tissues, or blood flow inside the body. Pre-natal ultrasound examinations are performed by trained professionals, such as sonographers, radiologists and obstetricians. The procedure involves using a transducer, which sends a stream of high-frequency sound waves into the body and detects their echoes as they bounce off internal structures. The sound waves are then converted to electric impulses, which are processed to form an image displayed on a computer monitor. In 3D imaging special software combines several 2D scans into a 3D image. By taking a sequence of 3D images a 4D video can be produced (the 4th dimension is time).(the 4th dimension is time).