Human: My doctor wants me to get an ultrasound. What is an ultrasound and what can it tell me? Assistant: 
An ultrasound is a diagnostic medical imaging technique that uses high-frequency sound waves to create images of structures within the body. It can be used to visualize internal organs, blood vessels, and tissues, as well as assess the size of a fetus during pregnancy. Ultrasounds are typically painless and noninvasive, although some may require the use of an injection or gel. The images produced by ultrasounds can provide valuable information about a patient’s health, including the presence of tumors, cysts, or other abnormalities.