Aetna Intelihealth
Aetna: Inteli Health: Ultrasound
This overview of ultrasound medical procedures describes their uses, preparation, risks, and the like.
Khan Academy
Khan Academy: Doppler Effect in Living Tissue
Read a passage about the doppler effect in living tissue and answer the follow-up questions.
WebMD
Medicine Net: Ultrasound
This site from MedicineNet.com gives an Ultrasound description, why they're performed, risks, and patient preparation. A thoughrough explanation of the process is provided.