MRI scanner

MRI (magnetic resonance imaging) scanners are used to scan the inside of the human body; mainly to observe tumours and other such objects hiding behind bones which cannot be easily observed through X-ray or CT scanners. MRI scanners use the phenomenon of nuclear magnetic resonance. In an MRI scanner, the human body is subjected to a very strong magnetic field and it is made to absorb and then radiate energy at the Larmor precession frequency of the hydrogen nuclei present in water. The intensity with which these radiations are emitted by the body are recorded by the MRI scanner which displays an image of the portion of the body under test on its monitor. The portions containing larger amount of water look darker on the screen as compared to those having little water. If different colours are assigned to different intensities, then a coloured picture can be obtained. Since water content in the bones and teeth etc. is very small, these parts of the body are nearly invisible and therefore it is very easy to see through the bones in the case of MRI scanners. This duality, along with a few others, makes MRI scanners very useful for medical science