3D ultrasound is a medical ultrasound technique used during pregnancy, providing three dimensional images of the fetus. Often these images are captured rapidly and animated to produce a "4D ultrasound".
3D ultrasound works similarly to the traditional ultrasound except that the ultrasound waves are directed from multiple angles. The waves are reflected back and captured and together provide enough information to construct a 3-dimensional image in much the same way as 3D movies. 3D Ultrasound was first developed by Olaf von Ramm and Stephen Smith at Duke University in 1987.
The 3D/4D ultrasound imaging should utilize ultrasound energy subject to the same limits as conventional (2D) ultrasound to create the 3D images.
Medical ultrasonography uses ultrasound (high-frequency sound waves) to visualize soft tissue structures in the body in real time.
No ionizing radiation is involved, but the quality of the images obtained using ultrasound is highly dependent on the skill of the person (ultrasonographer) performing the exam. Ultrasound is also limited by its inability to image through air (lungs, bowel loops) or bone. The use of ultrasound in medical imaging has developed mostly within the last 30 years. The first ultrasound images were static and two dimensional (2D), but with modern-day ultrasonography 3D reconstructions can be observed in real-time; effectively becoming 4D.