MRI Scans

[guardian5]

what happens when one has a scan

[Hamish]

During an MRI scan the patient is placed in a magnetic feild, this causes the centres of hydrogen atoms in the water in the body to line up with the feild. Low energy radion waves are passed through the body, these flip the hydrogen atoms about and the radio waves are absorbed, this absorption is detected and processed to give a signal. The signal depends on the frequency of the radio waves and the environment the water is in (ie. water in bone will look a little different to water in the brain or liver) and the amount. This information is then converted into a picture. If you want a more detailed description let me know how much physics you know and I'll see if I can improve on this explanation. All the best, Hamish

[guardian5]

Many thanks very helpful.

[firefly]

Is an MRI scan the same as a CAT/CT scan? This provides X-Ray like images at different horizontal or vertical layers.

[Hamish]

No a CT scan works by looking at how X-Rays pass through soft tissue vs hard - its good for bones, MRI looks at water environments and is good for soft tissue. MRI can also be used in may other ways to get more detailed information. CT and MRI are completely different techniques and work in very different ways.