NHS Choices Medical Reference
During an MRI scan you may have to remain motionless for up to an hour, which can be difficult. However, most MRI scans only last between 15 and 30 minutes.
MRI scanners can be very noisy, although you will be given headphones to block out the noise and in many cases will be able to listen to music.
Depending on the part of the body being scanned, your head may need to be inside the MRI scanner tube, and for some people this may feel claustrophobic.
MRI scanners can be affected by movement, which makes them unsuitable for investigating problems such as mouth tumours, because coughing or swallowing can make the scan less clear.
Bone and calcium do not show up on an MRI scan. This means that tissue calcification, a feature of a number of diseases such as osteoporosis, cannot be detected using MRI scanning.
Tissue: Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.