Magnetic Resonance Imaging (MRI) is a non-invasive medical imaging technique that uses a powerful magnetic field and radio waves to create detailed images of internal body structures. Healthcare providers use MRI to diagnose and monitor various medical conditions. While generally safe, patients should understand common sensations and potential concerns associated with an MRI scan.
Typical MRI Sensations
During an MRI scan, patients commonly experience specific sensations. Loud banging, knocking, or clicking noises originate from gradient coils rapidly switching electrical currents and vibrating within the strong magnetic field. Earplugs or headphones are provided to mitigate this noise.
A slight warming sensation is a normal physiological response from radiofrequency coils, mild and not a problem. Some individuals might also experience a mild, temporary tingling sensation, particularly in their extremities.
The enclosed nature of some MRI machines can lead to anxiety or claustrophobia. Strategies to manage this include open MRI designs or mild sedation. Communication with the technologist via an intercom and a call button also help patients feel more in control.
Magnetic Field Interactions
The powerful magnetic field generated by an MRI scanner poses specific considerations for metallic objects. Ferromagnetic items like jewelry, keys, and clothing with metal zippers can be strongly pulled into the machine, potentially causing injury to the patient or staff, or equipment damage. Patients must remove all such belongings before entering the MRI room. Even small metallic items on the skin, like body piercings, can heat up due to radiofrequency pulses, potentially causing thermal burns.
Internal medical devices or implants present a more complex set of considerations. Devices such as pacemakers, implantable cardioverter-defibrillators (ICDs), cochlear implants, neurostimulators, and certain aneurysm clips can malfunction, overheat, or move within the body.
A thorough screening process identifies any metallic objects or implants. Many modern implants are “MRI conditional,” meaning they can be safely scanned under specific conditions. However, older devices may still pose risks, so patients must inform staff about all implants. The strong magnetic field can also damage electronic items like credit cards and mobile phones, which should not be brought into the MRI suite.
Contrast Agent Concerns
In some MRI scans, a contrast agent is administered intravenously to enhance image clarity and provide additional diagnostic information. Gadolinium-Based Contrast Agents (GBCAs) are most commonly used, improving the visibility of internal structures like inflammation, tumors, and blood vessels. While generally safe, these agents can lead to specific side effects.
Mild reactions to GBCAs include hives, itching, nausea, or a headache. Some patients might also experience a temporary cold sensation at the injection site, dizziness, or a metallic taste. These reactions are short-lived, resolving within a few hours to a day.
More severe allergic reactions, such as anaphylaxis, are rare but can occur. Symptoms might include difficulty breathing, facial or throat swelling, or a significant drop in blood pressure. Nephrogenic Systemic Fibrosis (NSF), a rare fibrosing disorder affecting skin and internal organs, primarily in patients with severe kidney disease, is another concern. Kidney function is assessed before GBCA administration.
Gadolinium retention in the brain and other body tissues following GBCA administration has also been recognized. While small amounts of gadolinium can remain in the body for an extended period, the long-term clinical significance of this retention is still under investigation. Healthcare providers weigh the benefits against these potential concerns, using contrast only when medically necessary.
Recognizing Serious Symptoms
Knowing when to seek medical attention is important if unexpected symptoms arise during or after an MRI. During the scan, if a patient experiences acute pain, severe discomfort, difficulty breathing, or a sudden worsening of claustrophobia, they should immediately use the call button to alert the technologist.
After the scan, certain symptoms warrant prompt follow-up with a healthcare provider or emergency medical care. These include signs of a delayed allergic reaction, such as a worsening rash, persistent swelling, or continued difficulty breathing.
Other concerning symptoms include a severe or persistent headache, unusual or intense pain at the injection site, confusion, disorientation, or any new or worsening symptoms. Patients should communicate any pre-existing conditions, allergies, or concerns with their healthcare provider and MRI staff before the procedure to ensure safety.