MRI is one of the best-known medical imaging investigations in existence, which over the years has helped to correctly diagnose a significant number of patients. A guide to this procedure can help you better understand the mechanics of how it works, in case you or someone you care about is about to have an MRI.
The magnetic resonance imaging (MRI) machine is a cylinder-shaped tube that creates a strong magnetic field around the person inside. The device’s scanner will periodically send magnetic fields as well as pulses of radio waves to the patient.
The regular alignment of the hydrogen atoms in the body is thus disrupted as a result of the coupling between the magnetic field and the radio frequency. Meanwhile, a computer collects the radio signals emitted by the nuclei. Atoms then begin to return to their normal location and the radio signals are analyzed by the computer. The results are displayed as clear images of the area of the body that has been investigated.
Thus, the two-dimensional (2D) or three-dimensional (3D) image of the structures or organs being analyzed is created based on the activity of hydrogen atoms.
Who can NOT have an MRI
- Patients who have metal joint prostheses;
- Those with artificial heart valves;
- People with an implantable cardioverter defibrillator;
- Those with pacemakers;
- People who have metal clips;
- Patients with cochlear implants;
- Those with bullets, shrapnel or any other type of metal fragment in their bodies.
When is the use of contrast agents recommended?
In many cases, the investigation is possible without the use of contrast material, but there are circumstances in which the radiologist may use this material to visualize a particular element in detail.
This requirement depends on the patient’s pathology. It is up to the doctor to decide whether or not to inject the contrast material. Most often this choice is made after the specialist views the preliminary images that were taken without contrast. Gadolinium is used to increase the contrast of the final image, thereby drawing attention to particular organs, blood vessels or tissues. Variations in contrast might shed light on the existence of a disease or lesion. In most cases, people have no problems tolerating this product, but you may experience mild allergic responses such as hives.
What conditions does MRI investigation detect?
- Brain conditions such as strokes or tumors;
- Spinal conditions such as herniated discs, spinal or spinal cord pathologies;
- Musculoskeletal conditions such as arthritis, ligament or meniscus tears.
Preparing for the MRI exam
In the most common cases, your doctor will advise you to refrain from eating for up to three hours before the investigation, but the recommendation will vary depending on the nature of the examination you are having. If no other suggestions are offered, then you can continue with your normal activities, and if you are following a specific treatment, you will be able to continue taking your medication as instructed. If you have any pre-existing medical conditions or have had surgery in recent months, be sure to let your doctor know about these details and follow the advice he or she gives you.
To get a clearer picture of the organs during the investigation, your specialist may need to give you a contrast dye by mouth or inject it intravenously.
Keep in mind that before you enter the magnet room, you will need to remove all jewelry, watches, glasses, hair clips or any other objects that may contain metal such as pens, keys, coins, hearing aids or piercings.
