An MRI uses strong magnets to take amazingly detailed pictures of the inside of your body.
The structure of your bones is always changing with new bone tissue being laid down and old bone tissue being resorbed by your body.
The traditional MRI, although capable of producing more detailed images than an X-ray or CT scan, does have some drawbacks. You have to lie very still for a long time in a narrow tunnel-like space inside the MRI machine to obtain proper images.
Neck or low back pain that radiates into your arms or legs is often a sign of impingement or pinching of a nerve as it emerges from your spinal cord. An MRI may be able help identify structural lesions that may be pressing against the nerve so the problem can be corrected before permanent nerve damage occurs.
A concussion is a blow to the head or any other part of the body that causes a shaking or a twisting injury to the brain. It can be called a functional injury of the brain as it changes how the brain functions, but generally doesn't change how the brain appears. A CAT scan can help identify a structural injury to the brain, but not so much functional injuries. The reason why a CAT scan may be ordered is when an individual does not seem to be getting better after a concussive injury.