Magnetic Resonance Imaging (MRI) is one of the most detailed imaging techniques available to health care professionals today. It also poses very little health risk because it does not depend on radiation, as does X-ray or computed tomography (CT) imaging. Instead, an MRI scan uses a strong magnetic field and radio waves to produce images. In some cases, an intravenous (IV) contrast is also used to improve the quality of images. Although the magnetic field generated for the procedure causes no tissue damage, and MRI is considered one of the safest diagnostic procedures available, certain conditions can pose a danger to patients undergoing an MRI scan.
The powerful magnetic field used in MRI attracts iron-containing objects and may cause them to move with great force. For this reason, patients are advised to remove all jewelry, clothing, and other items that may contain metal before entering the MRI area. These items could create a hazard during the procedure. Likewise, metal-containing objects implanted in the body can pose a danger because they may move or become heated during MRI. Consequently, the following conditions are often contraindications to MRI scanning:
- Implanted pacemaker or defibrillator: Until recently, MRI was contraindicated for all patients with implantable cardiac devices because the fields generated have the potential to damage components and interfere with functioning. New MRI-conditional pacemakers are now available, but MRI for patients with even these new devices should be undertaken only when deemed medically necessary and under strict guidelines.
- Ferromagnetic aneurysm clips may move or become dislodged under the force of the magnetic field.
- A cochlear implant can be damaged or create tissue damage in the presence of an MRI system. Strict protocols exist for cochlear implant patients in need of MRI.
- The electrodes used in deep brain stimulation may cause injury or suffer damage during MRI.
- Metallic foreign bodies: Shrapnel or other metallic objects in the body can be heated and/or moved by the magnetic field. Any such bodies must be evaluated to determine the risk of injury they pose during the procedure. This includes any minute metal chips or fragments that may have lodged in the eye as a result of welding, grinding, or any type of accident.
- Some varieties of ocular implants pose a risk of damage to the eye due to metallic components.
- A Swan-Ganz catheter may malfunction during MRI scanning.
Other conditions should be disclosed and evaluated but may not present contraindications for MRI. Discuss any of the concerns with your providers so that they can decide on the appropriate diagnostic testing.
- Pregnancy: Although ultrasound is the imaging method most commonly used during pregnancy, there are times when MRI images are preferable. Be sure that your health care providers know if you are pregnant so they can make fully informed decisions when advising you about your care. According to radiologyinfo.org, MRI has never been found to result in harm to a developing fetus.
- Drug infusion devices may malfunction during MRI. The details of your specific model will determine whether and how you can safely undergo MRI scanning.
- According to the FDA, some medication patches as well as wire electrocardiogram (ECG) leads may cause skin burns during MRI.
- Be sure your technologist is aware of any implants or prostheses that you may have.
In addition to the above-mentioned contraindications for MRI scanning, some conditions also contraindicate use of the gadolinium-based contrast agents often used to enhance imaging.
- Because the contrast agents cross the placenta during pregnancy, the American College of Radiology advises against use of these agents during pregnancy unless medically necessary and no suitable imaging alternative is available.
- Because a small amount of contrast agent will be found in breast milk, nursing women may be advised to discard breast milk for 24 hours following the procedure.
- A history of kidney disease, failure, or transplant may contraindicate the use of gadolinium-based contrast.
- Inform your health care provider if you have high blood pressure, diabetes, or vascular disease. These conditions may contraindicate the use of contrast agents.
At Iowa Radiology, your health and comfort are important to us. We always explain procedures before they are performed and answer any questions that arise. If you ever have any questions or concerns about a procedure scheduled at our office, please contact us.