A type of diagnostic test that creates images by bouncing high-frequency sound waves off of the organs and other structures in your body. The sound waves come from a device (transducer) that can be placed on top of your skin (external ultrasound) or inside an orifice (internal ultrasound) such as the vagina, rectum, or mouth/esophagus. The echoes differ depending upon the composition of the structure being evaluated.  For example, cancerous tissue will cause a different echo pattern than healthy tissue. A computer then turns the echo patterns into images. Generally, ultrasound texts are painless. If an internal ultrasound is done you may feel some pressure or minor discomfort. A typical ultrasound exam takes 30-60 minutes.  Preparation instructions will vary depending upon the part of the body being examined. Also called sonography and ultrasonography. Doppler ultrasound is used to see blood flowing through blood vessels. Echocardiograms are done to get images of the heart.