What is the difference between a MRI and a MRI with contrast?

An injection. Mri or magnetic resonance imaging uses a strong magnet to obtain detailed images of the body. The machine is shaped like a large donut. Sometimes contrast material or contrast dye is injected into a vein (usually in the arm) to see certain structures better.
Sensitivity. Contrast given during an MRI allows a radiologist to get more information in some cases. For example, in a patient who has had prior back surgery, an MRI of th spine given with contrast can allow the radiologist to distinguish between a recurrent disc herniation verses scar tisue and his can be difficult in an MRI done without contrast. Thank you.