Magnetic resonance imaging (MRI) is an imaging scan that uses magnetic fields, radio waves and a computer to create pictures that are cross-sections of organs and other body structures. This procedure is based on the fact that the water content and magnetic properties of each body part are different. That is why the signal each body part gives off distinguishes it from every other part. The MRI is designed to read each signal and create an image from it.
How is an Image Created by an MRI?
An MRI exam can provide more detailed images of the interior of organs, tissues, etc. that are not possible using other types of scanners. In some instances, patients are given a contrast agent through an intravenous line inserted into the hand or arm. This is a magnetically active material that intensifies the clarity of the internal structures.
The majority of MRI devices use an electric current that is sent through coiled wires, which produces a temporary magnetic field surrounding the patient’s body. Radio waves are then sent/ received by a transmitter/receiver inside the machine, and the signals create digital images of the area being scanned.
These images are evaluated for clarity on a computer monitor as they are being produced. They can also be transmitted electronically, printed, or copied to a CD.
What are the Benefits Associated with this Type of Diagnostic Tool?
There are several important advantages this kind of imaging scan provides that other scans do not:
- It is a non-invasive technique that does not use ionizing radiation.
- The images it creates of organs like the heart and the liver are more likely to identify disease than other imaging scans in some cases.
- It has been shown to be a valuable tool in diagnosing a wide spectrum of medical conditions.
- The type of contrast agent used in MRIs is less likely to create an allergic reaction than the kind used for x-rays and CT scans.
What are the Risks?
According to the Food and Drug Administration (FDA), there are no known harmful side-effects from temporary exposure to the magnetic field used by MRI scanners. However, the agency has created the following list of safety concerns to consider before undergoing an MRI scan:
- The magnet may cause pacemakers, artificial limbs, and other implanted medical devices that contain metal to malfunction or heat up during the exam.
- Any loose metal object may cause damage or injury if it gets pulled toward the magnet.
- If a contrast agent is used, there is a slight risk of an allergic reaction. MRI contrast agents can cause problems in patients with significant kidney disease.
- Dyes from tattoos or tattooed eyeliner can cause skin or eye irritation.
- Medication patches can cause a skin burn.
- The wire leads used to monitor an electrocardiogram (ECG) trace or respiration during a scan must be placed carefully to avoid causing a skin burn.
- Prolonged exposure to radio waves during the scan could lead to slight warming of the body.