Magnetic resonance imaging (MRI) is a minimally invasive way for doctors to examine high-resolution images of the inside of their patients' bodies.1
An MRI can play a key role in helping diagnose and stage cancer cases. Because an MRI does not use radiation, the test is safe for most patients. The results of the scan can help doctors look closely at areas of concern. An MRI is very detailed, and can allow doctors to look at individual cells for signs of cancer or pre-cancer tissue. It can even be used to determine whether cancer tissues have metastasized (spread to other parts of the body).
To generate detailed images of the inside of a patient's body, an MRI machine uses radio waves, powerful magnets, and a computer. The result of the scan is a series of images in the form of high-contrast slices—almost like a loaf of bread. So instead of looking at one area of a patient's body as a whole, a doctor can pick apart, isolate, and magnify the slices. An MRI is ideal for examining soft tissues, and can be more effective than related diagnostic tools, such as a CT scan, for detecting tissue abnormalities.1
How to Prepare for an MRI
When a doctor orders an MRI, the patient should receive detailed instructions from the imaging center. Any questions or concerns regarding the preparation process are best brought up before the procedure. For example, the effects of MRI on pregnant women are still not fully known, so a different imaging exam may be required, such as ultrasound or a CT scan. Patients should also let their doctor know if they have kidney or liver conditions, because issues with those organs may limit the imaging technologist's ability to inject contrast agents, which adds contrast to the MRI images and allow doctors to see higher levels of detail.
Because MRI uses magnetic waves, metal objects may be a safety hazard or affect the MRI results. Before having an MRI, a patient should disclose any metal devices in his or her body, such as:
- Metallic prostheses (such as an artificial heart, a hip, or a knee)
- A pacemaker
- Cochlear implants or other hearing aid devices
- Any other type of metal fragment (including shrapnel)
On the day of the procedure, patients will be asked to remove anything metal, such as jewelry and eyeglasses. The patient will then disrobe in private and put on a hospital gown. The room that contains the MRI machine will have a table that the patient lies on. This table slides into the MRI machine, which has a tube entrance. During the scan, the patient will hear loud noises coming from the equipment—this is perfectly natural, as an MRI can be noisy at times. The radiologist in attendance can provide ear plugs or headphones to block the noise at your request.
The MRI technologists will be in another room monitoring progress and are in constant contact throughout the procedure. MRIs are sensitive to motion, so patients must remain as still as possible to maximize the quality of the images. It's important to keep this in mind going into the MRI, as the procedure generally lasts about 45 minutes. If contrast dye is used, it will be delivered via an IV, typically inserted into the patient's upper arm. The contrast material is less likely to cause an allergic reaction than that used for CT scans.
Patients with concerns about discomfort, or a fear of enclosed spaces, may be prescribed a sedative or anti-anxiety medication before the procedure.2
What to Expect After an MRI
If a contrast dye is used, the health care professionals at the imaging facility will remove the IV before the patient leaves. Although allergic reactions to the contrast dye are very rare, if patients experience symptoms such as a rash, hives, or shortness of breath they should call their doctor or the imaging center immediately. In rare cases of a severe reaction, patients should go to the nearest ER facility. If sedative or anti-anxiety medications are used, the imaging facility may require that the patient be driven home by a friend or family member.3
An MRI is a low-impact, non-radiation, noninvasive imaging procedure that provides doctors with a close, layered look at a patient's affected area. The risks are minimal, and relate primarily to medications used for anxiety or IV contrast dyes. Knowing what to expect before, during, and after the procedure is key to a positive experience. Patients who can relax and remain still during an MRI will give their doctor the ability see concerning tissues at the cellular level. This level of detail is an essential part of the diagnosis, staging, and treatment processes.
- "MRI - Mayo Clinic." https://www.mayoclinic.org/tests-procedures/mri/about/pac-20384768.
- "How to Prepare for an MRI." https://radiology.ucsf.edu/patient-care/prepare/mri. Accessed August 8, 2018.
- "Preparing for an MRI." https://healthcare.utah.edu/radiology/preparing-appointment/mri.php. Accessed August 10, 2018.