Magnetic resonance imaging is a non invasive (not requiring surgery) method of imaging the inside of the human body. The patient is placed inside a large superconducting electromagnet. The electromagnet produces very large magnetic fields – 40,000 times larger than the magnet produced by the Earth's magnetic field.
The human body is about 70% water by weight. Each water molecule contains one oxygen atom and two hydrogen atom. The nuclei or centers of the hydrogen atoms – each hydrogen nuclei is just a proton - are aligned by the magnetic field. A pulse of radio waves is sent through the body. Radio waves a very low energy and pose no threat to human health. Some of the radio waves are absorbed by the hydrogen nuclei. Soon after, these radio waves are re - emitted. The emitted waves are analysed by computer. Very good images are obtained, but each image is expensive.
