How does it work? of MRI scan

Health encyclopaedia - Alphabetical Topic List

| A |

| B |

| C |

| D |

| E |

| F |

| G |

| H |

| I |

| J |

| K |

| L |

| M |

| N |

| O |

| P |

| Q |

| R |

| S |

| T |

| U |

| V |

| W |

| X |

| Y |

Magnetic resonance imaging uses radio waves that are thousands of times stronger than the magnetic field of the earth to produce images. The human body is mainly composed of water molecules, which are constantly moving. When strong magnetic waves are sent through the body, these water molecules are forced into different positions. The way in which they move provides information about the density of the tissue.

Some of the bodyâ€™s tissues contain more water than others. This means that the molecules move in slightly different ways when a magnetic field is passed through them. When the radio transmitter is turned off, the molecules move back into their original position. As they do this, they send out radio waves of their own. The way in which they move provides information about the density of the tissue. These signals are picked up by a computer and turned into detailed pictures.

The tissues with the least water in (hydrogen atoms), such as bones, show up dark in the pictures. Fatty tissue that contains more water appears much brighter.