Introduction
Magnetic resonance imaging (MRI) is a medical imaging technique that uses strong magnetic fields and radio waves to generate detailed images of the inside of the human body. An MRI scan is a common procedure that is generally very safe. However, there are some important safety considerations for patients undergoing an MRI scan.
The magnetic field in an MRI scanner is extremely powerful—up to 30,000 times stronger than the Earth's magnetic field. This field, along with the radiofrequency pulses used to create the images, can interact with items containing ferromagnetic metals. Patients must be screened to ensure there are no unsafe materials or implants in or on their bodies before entering the MRI suite.
Beyond monitoring for metal objects, patients should also be prepared for the experience of being inside the MRI scanner. For some, the small enclosed tunnel can cause anxiety and claustrophobia. The loud noises during the scan can also be startling if patients are not prepared. Understanding what to expect during the procedure can help patients remain calm and still, which is important for producing clear images.
Overall, MRI scans are very safe as long as proper precautions are taken. Being aware of the potential risks and knowing what to expect can help patients feel at ease when undergoing an MRI. This allows patients to benefit from this valuable diagnostic imaging technique.
Screening for MRI Safety
Before undergoing an MRI scan, patients will be screened to ensure it is safe for them to enter the MRI room. This screening process typically involves answering questions about:
Implants or medical devices in the body. Patients may be asked if they have pacemakers, infusion pumps, nerve stimulators, artificial joints, metal fragments in the body, cochlear implants, stents, shunts, clips, or anything electronic implanted. MRI scans can interact with these devices and cause problems.
Tattoos or permanent makeup. Certain inks contain metal and may heat up during an MRI. The location and date of tattoos is noted.
Pregnancy status. MRI scans are not recommended for pregnant women during the first trimester unless medically necessary.
Medications. Some medications contain metals that can interact with the MRI machine.
Medical conditions like sickle cell anemia or kidney disease. The strong MRI magnets can affect some medical conditions.
Previous surgeries or foreign objects. If there is shrapnel, bullet fragments, or metal implants from previous surgeries in the body, the MRI technician needs to know.
Claustrophobia or anxiety. Patients who feel anxious in enclosed spaces can be given medication to help them relax during the scan.
In addition to the screening questions, patients may undergo additional safety checks right before the scan. Implanted devices like pacemakers are scanned using a metal detector. Some facilities will ask patients to change into hospital scrubs to ensure there is no metal on their person. Knowing what to expect during the screening process can help patients feel at ease and ensure a safe MRI procedure.
Claustrophobia
Some patients experience claustrophobia during an MRI. Being in the MRI scanner involves lying still for an extended period in an enclosed space. This can trigger anxiety and panic in those predisposed to claustrophobia.
There are several techniques patients can use to cope with claustrophobic feelings during the scan:
Arrive early to acclimate to the MRI suite environment. Meet the technologist beforehand and understand the MRI process. This reduces fear of the unknown.
Practice relaxation techniques like deep breathing exercises or guided imagery. Listen to calming music during the scan via provided headphones.
Take anti-anxiety medication prior to the MRI if prescribed. This can reduce claustrophobic symptoms.
Use eye masks to block vision of the inside of the scanner. Looking out the opening of the scanner can also help.
Take breaks during longer scans. Technologists can pause the scan if patients need a moment.
Use handheld panic buttons that allow patients to immediately communicate with technologists when distressed.
If claustrophobia cannot be overcome, open MRI scanners are available at some facilities. Open MRIs have larger openings and provide more space around the patient's body. However, open MRIs may have lower image quality compared to closed tunnel scanners. Patients should discuss open MRI availability with their doctor if standard MRIs induce severe anxiety. Addressing claustrophobia concerns beforehand allows patients to undergo MRIs safely and comfortably.
MRI Noise
The loud noises that occur during an MRI scan can be alarming if you're not prepared for them. The MRI machine produces knocking and beeping sounds at noise levels of up to 110 decibels. That's roughly the noise level of a rock concert, so it's important to protect your hearing during the scan.
MRI facilities provide earplugs or headphones to help block the sound. Earplugs work fairly well at bringing the noise down to a more comfortable level. Some facilities also give out headphones that play music to drown out the banging from the machine.
Even with ear protection, the MRI noises can still sound incredibly loud as the machine cycles through the scan. The good news is the noise only lasts for a few seconds at a time in between pauses when no scanning is happening. Knowing what to expect with the noise can help you mentally prepare for the experience. Staying relaxed during the loud bursts can also help reduce any anxiety caused by the jarring sounds.
While the noise itself is harmless, it can certainly be unpleasant. Using the ear protection provided by your MRI technician is crucial. Let the technician know if the earplugs or headphones aren't blocking enough sound so they can provide better noise reduction. With proper protection, the loud noises shouldn't damage your hearing or prevent you from completing your MRI scan successfully.
Contrast Agents
Contrast agents, also called contrast media, are special dyes used to enhance the quality of MRI images. They function by altering the magnetic properties of nearby water molecules, providing a better signal on MRI scans.
There are different types of contrast agents available:
Gadolinium-based contrast agents are the most commonly used. They contain the metal gadolinium.
Iron oxide-based contrast agents contain iron particles.
Manganese-based contrast agents contain manganese.
Contrast agents are often administered intravenously through an IV line placed in the arm. They circulate through the bloodstream and may accumulate in certain tissues, allowing them to appear brighter on MRI images.
Most people tolerate contrast agents well. However, there are some risks and side effects to be aware of:
Allergic reactions may occur, including hives, swelling, low blood pressure, difficulty breathing, and anaphylaxis. Patients with allergies or asthma are at higher risk. Allergies to contrast agents are uncommon.
Nausea, vomiting, headaches, arm pain, and dizziness may occur. These tend to be mild and short-lived.
Rarely, contrast agents may cause kidney damage or a serious skin reaction called nephrogenic systemic fibrosis (NSF) in those with kidney impairment. Kidney function tests are done beforehand to assess risk.
Gadolinium deposits can remain in the body, particularly the brain. The clinical significance of this is still being investigated.
Breastfeeding may need to be avoided for a period of time after receiving a contrast agent.
Patients should tell their doctor about any prior reactions to contrast agents or history of allergies/asthma. The radiologist and MRI technologists are trained to monitor for reactions and manage any risks. Most people can safely receive contrast agents for improved MRI imaging when needed.
Pregnancy
Pregnancy requires special consideration when getting an MRI scan. The strong magnetic fields and radio waves used during an MRI do not appear to harm a developing fetus. However, as a precaution, MRI scans are generally avoided during the first trimester unless absolutely necessary.
During the second and third trimesters, MRIs are considered low risk for the fetus with a few precautions:
Let your doctor know if you are or could be pregnant before scheduling the MRI. Your doctor can determine if the benefits of getting the scan outweigh any potential risks.
MRI contrast agents are avoided unless critically important, as their effects on the fetus are uncertain.
The radiology staff takes measures to limit your exposure to the MRI's magnetic fields. This may include using a lower magnetic strength or scanning sequence. They also position you in the scanner to keep your belly farther from the magnetic coil.
MRI sounds can be very loud, so you are given earplugs or headphones to protect your baby's developing ears.
Overall, many pregnant women safely undergo MRIs when medically necessary. Discuss any concerns with your doctor and MRI technologist beforehand. They can ensure your pregnancy is handled with the utmost care.
Implants and Devices
Patients with metal implants, devices, or fragments in their bodies need to take extra precautions with MRI scans. The strong magnetic field used during an MRI can interact with metal objects and cause them to heat up, move, or malfunction. This could lead to serious injuries.
It's crucial to inform your MRI technologist about any implants or devices you may have. Common items that require screening include:
Pacemakers - The MRI magnetic field can disrupt a pacemaker's function. MRI scans are usually not performed on patients with pacemakers.
Implanted cardioverter defibrillators (ICDs) - Like pacemakers, ICDs can malfunction around MRI magnets.
Neurostimulators - These devices treat conditions like chronic pain or epilepsy. The MRI can impact settings and operation.
Cochlear implants - Hearing loss devices with internal components may have MRI restrictions.
Metal implants - Joint replacements, metal pins, screws, plates, or stents can heat up and cause burns during MRIs. Newer models labeled "MR-safe" are less risky.
Insulin pumps or implanted drug infusion pumps - These will need to be turned off and removed beforehand due to risks from the magnets.
Intrauterine devices (IUDs) - There are mixed reports on risks for copper and hormonal IUDs. More research is still needed.
Discuss any implanted devices with your doctor and radiologist. They may request imaging records to verify the safety ratings. Some facilities can provide low-field or wide-bore MRIs as safer alternatives too. Being forthcoming allows the medical team to assess risks and proceed with proper precautions.
Tattoos and Cosmetics
Patients should be aware that certain inks used for tattoos and permanent makeup may contain traces of metal, which can interact with the strong MRI magnet. This can cause patients to feel a warm or stinging sensation during the MRI scan in areas where these tattoos are located. In some cases, the quality of the MRI image may also be affected.
To avoid potential issues, patients should inform the MRI technician about any tattoos or permanent makeup they have. The technician can then take extra precautions and make necessary adjustments to minimize any risks or imaging artifacts.
Some makeup products may also contain metals. Patients may be asked to remove eye makeup or other cosmetics before undergoing an MRI scan to prevent possible effects on imaging or patient discomfort.
By being aware of potential issues with tattoos and cosmetics ahead of time, patients can plan accordingly and take any recommended precautions. Clear communication with the MRI staff will allow for a smooth and safe scanning experience.
Patient Comfort
Going for an MRI scan can be an uncomfortable experience, but there are ways to help patients feel more at ease.
What to Wear
Patients will usually be asked to change into a hospital gown to avoid any metal that could be on their clothes interfering with the MRI machine. The gowns are designed to keep patients comfortable and preserve modesty.
If allowed, wearing loose, comfortable clothing without metal fasteners like sweatpants and a t-shirt can help patients feel more relaxed.
Socks can also be worn to keep feet warm during the scan.
Blankets
Blankets are often provided to help keep patients warm and comfortable during the MRI scan. The machine can feel cool, so having a blanket can improve the experience.
Music
Many MRI facilities now offer music that patients can listen to during their scan. This can help create a more soothing environment and distract from the noise of the machine.
Patients are encouraged to bring their own music on an MP3 player or CD if allowed to further customize their experience.
Earplugs are also provided to block noise, especially when patients prefer quiet.
Keeping patients informed and providing small comforts can go a long way in creating a better MRI experience. While MRIs can be intimidating, little things like blankets, music, and comfortable clothes can help patients feel more at ease.
Conclusion
Having an MRI scan can be a safe and comfortable experience if patients take some simple precautions. The main tips for MRI safety include:
Inform your doctor about any medical implants, devices, tattoos, or cosmetics. The MRI's strong magnets can interact with these.
Wear comfortable, metal-free clothing to your scan. You may be asked to change into a hospital gown.
Tell your doctor if you have any history of claustrophobia or anxiety. They can provide medication to help you relax.
Use earplugs or headphones to block out the loud noises during the scan.
Speak up about any discomfort you experience while inside the scanner. Technicians can provide cushions and adjustments.
Ask your doctor about MRI-safe contrast agents if they are recommended for your scan.
Expect the room to feel cool while you are inside the scanner. Request blankets if you get cold easily.
Follow all instructions from your doctor and MRI technician. Ask questions if you are unsure about anything.
By being informed and communicating with your medical team, patients can have a smooth MRI experience and get the most out of this valuable diagnostic imaging technique.
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