Magnetic Resonance Imaging (MRI) scans are one of the newer technologies that allow us to view the inner structures of the body. The scanners use extremely powerful magnetics that align the hydrogen proton spins, which are present in water and most tissue, and create signals that can be detected and interpreted by computers into pictures of the body and its contents.
There is no radiation used, just a powerful magnet that forms a detailed picture of the tissues in the body. The most common magnet used today is 1.5 Telsa, and that can give excellent detail of most body structures. However, the most sophisticated and experimental scanners are 5 times stronger and give us even more detailed information about the body.
MRI scans are used to give us detailed information about the tissues in the body. They are commonly used to study all of the following structures:
- The brain and nervous system
- The spine
It is a tool to give a physician more information to help define what is wrong and guide future treatment choices. Since it only shows the structures, it still requires a physician to examine a patient to determine if what is seen correlates to symptoms presented by the patient.
The risks of MRI scans are very low in general. Since there is no radiation, they are often considered completely safe without any side effects. MRI scans use very powerful magnets, therefore any magnetic metal can not be in close proximity of the scanner. Since the early 1990’s, all metal objects used for implants have usually been made to be compatible for a MRI. A few notable exceptions include:
- Most pacemakers
- Some ear implants
- Heart valves
- Implantable stimulators
If you have had surgery and an implant, notify the scanner personnel and they can check whether you may have problems. Other metal such as bullets or metal fragments near the eye (from metal grinding work) may also be an issue. The other main problem is if the noisy, closed space of the scanner can cause severe anxiety of people, preventing them from tolerating the scan, and support by the MRI staff or medication may help with the problem.
Preparing for a MRI Scan
There is very little preparation necessary for a MRI scan. Know if you have any metal in your body, so the scanner radiologist can determine if a scan can be performed, and leave all metal jewelry outside the scanner room when changing for the scan. A scan can often take an hour of time, and keeping still and relaxing during the scan will allow the best pictures to be obtained. The results will be given to the ordering physicians usually within a day, and they will help you interpret the results.
Read our previous article on the differences between MRI scans, CT scans, and X-rays.
Thomas Cohn, MD
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