Traditionally fetal ultrasounds are 2D, providing a two-dimensional image. These images are made up of image slices of which only one at a time is visible and creates a flat looking image. A 2D fetal ultrasound can display up to 100 images per second.
Recently, three-dimensional fetal ultrasounds have become more and more common. The 3D fetal ultrasound takes thousands of slices and digitally stores and shades them to emulate a more life-like image of the baby.
A four-dimensional fetal ultrasound simply means that the images can be seen in real time, allowing for the study of fetal behavior.
This technique estimates the average velocity of flow within a vessel by color coding the information. The direction of blood flow is assigned the color red or blue, indicating flow toward or away from the ultrasound transducer.
A form of ultrasound that can detect and measure blood flow.
Creating an image of the developing fetus within the uterus by means of measuring the vibrations returned when a device emits high-frequency sound waves.
An instrument that converts electrical energy into mechanical energy. A transducer can also act as a transmitter and receiver of ultrasound information.
A technique in which sound waves are sent out by an ultrasound probe that has been inserted in the vagina. The waves go through the vaginal wall and bounce off the ovaries, and a computer uses the ultrasound echoes to create a picture (a sonogram).
Sources: www.ob-ultrasound.net, www.medicinenet.com/prenatal_ultrasound/glossary.htm and www.fetaldopplerfacts.org.