Ultrasound can be used in medicine
Ultrasound can be used to investigate blood flow in organs, diagnose heart problems and check on fetal development. The examples below are two of the most common:
Breaking down kidney stones
Kidney stones are hard masses that can block the urinary tract, which can be very painful. An ultrasound beam concentrates high-energy waves at the kidney stone and turns it into sand-like particles. These particles then pass out of the body in the urine. It's a good method because the patient doesn't need surgery and it's relatively painless.
Pre-natal scanning of a fetus
Ultrasound waves can pass through the body, but whenever they reach a boundary between two different media (eg a fluid in the womb and the skin of the fetus) some of the wave is reflected back and detected. The exact timing and distribution of these echoes are processed by a computer to produce a video image of the fetus.
Medical imaging is full of compromises - Advantage
1) Ultrasound waves are non-ionising and therefore, safer than x-rays.
2) X-rays are ionising. They can cause cancer if you're exposed to too high a dose. They are definitely not safe to use on developing babies.
3) CT scans use a lot more x-ray radiation than standard x-ray photographs, so the patient is exposed to even more ionising radiation. Generally CT scans aren't taken unless they are really needed because of the increased radiation dose.
4) Ultrasound images are typically fuzzy - which can make it harder to diagnsoe some conditions using these images.
5) X-ray photographs produce clear images of bones and metal, but not much else.
6) CT scans produce detailed images and can be used to diagnose complicated illnesses, as the high resolution images can make it easier to work out the problem. High quality 3D images can also be used in the planning of complicated surgery.