Ultrasound uses high-frequency sound waves to obtain real-time images of the body. Not only can this evaluate abdominal and pelvic organs, joints, tendons, and ligaments, ultrasound can also evaluate the movement of structures given real-time image acquisition and evaluation. Ultrasound is a radiation-free imaging modality. This allows it to be the standard for obstetrical imaging and specific imaging of newborns, such as the fetal brain or spinal cord. Ultrasound can also be used to guide certain interventional procedures.