Radiology - What is a Magnetic resonance imaging (MRI) scan?

Magnetic resonance imaging (MRI) is a type of scan that uses strong magnetic fields and radio waves to produce detailed images of the inside of the body.
An MRI scanner is a large tube that contains powerful magnets. You lie inside the tube during the scan.
An MRI scan can be used to examine almost any part of the body, including the:
- brain and spinal cord
- bones and joints
- breasts
- heart and blood vessels
- internal organs, such as the liver, womb or prostate gland
The results of an MRI scan can be used to help diagnose conditions, plan treatments and assess how effective previous treatment has been.

[@skybuck2000]

why do mri scan not scan the bottom nerves s2 to s5 ?!