Many doctors order MRI scans for their patients. These scans are used for a variety of reasons, including imaging soft tissue throughout the body and staging and monitoring cancer. For every 1,000 people there are about 111 MRI exams performed per year.1 While preparing for an exam, many patients find themselves asking who can have an MRI.
Most people can, in fact, have an MRI. This is especially true since the introduction of wide (70 cm) bore MRI systems. Traditionally, MR scanners had a 60 cm bore, which caused some patients with wider girths to be unable to have an MRI. Many of these patients can now comfortably have an MR exam on a wide bore MRI. Additionally, the wide bore scanners allow a patient to have more head room, decreasing most patients' claustrophobia.
There are still people who are unable to have an MRI exam for a variety of reasons. Before an MRI, the technologist will typically ask a number of questions about possible permanent safety risks, including metal implants and tattoos that may prevent a patient from having an MRI scan. In some cases, patients may have to change their clothes in order to have an MRI, especially if they are wearing athleisure clothing which can sometimes cause burns.
Permanent safety risks
Pacemakers and Defibrillators
There are a number of metal objects that could be in a patient's body, such as a pacemaker or defibrillator.2 Such devices implanted in a patient can make a physician leery of performing MRI's. There are a number of different models and types of pacemakers and defibrillators, and older models could malfunction or heat up during an MRI.3 Pacemakers and defibrillators have metal leads that are implanted in the body and heart muscle and subjecting these leads to an MRI scanner's field could cause them to heat up against a patient's heart. The magnetic field from the MRI could cause an electric current within the lead which may cause the heart to beat abnormally. They can also distort the MR images around the device. Some of these devices are tested and labeled “MR Safe”, though it is rare for devices containing metal to be labeled as MR Safe. Some other newer devices are "MR Conditional", meaning that MRI scans with limitations may be possible. These limitations may be placed on magnet strength or radiofrequency levels. If it is unclear what the status is or if the device is “MR Unsafe”, doctors should avoid scanning the patient. Patients will need to inform their technologist of the exact model of their pacemaker in order for the exam to be as safe as possible. These devices will need to be fully tested and programmed to MRI-safe settings before entering the MRI room and tested again and returned to its original settings after the exam.4
Certain tattoo inks contain metals and, like implanted devices, can interfere with an MR exam. Most tattoo inks are safe in an MRI scanners, and it is rare to experience problems caused by a tattoo.5,6 However, patients with tattoos, including tattooed eyeliner, should still inform their technologist about their tattoos. The concern with tattoos, especially ones containing metal, results from a similar process as is caused by the leads in pacemakers and defibrillators. The magnetic field can cause an electrical current to build up in tattoos containing metal, which can result in a burning or itching sensation. Another phenomenon that overlaps between implanted metallic devices and metal-containing ink is the distortion of MR images. The metal causes a disruption in the magnetic field where the tattoo is and can cause distortion. However, most patients with tattoos are still recommended to have any MRI their physician orders.
Avoidable safety risks
Unlike permanent devices or tattoos, there are a number of different risks that are avoidable in the MR suite. These risks include makeup, piercings, jewelry and athleisure clothes, all of which could contain metal. Patients should tell their technologist if they are wearing any of these things. Athleisure, the fashion trend involving wearing athletic clothing in a non-athletic setting, has caused some avoidable issues for patients in MRI scanners.7,8 Patients are usually informed to wear comfortable loose fitting clothing before an exam, but may not realize the risk of wearing athleisure clothes, including yoga pants.9 The reason for this risk is that companies weave small threads of metal into their clothing, preventing bacteria from growing and thus limiting the sweaty smell. These fibers of metal cause the metal to heat up and can cause burns during an MRI. It is ultimately best to avoid clothes that are anti-microbial or anti-bacteria or clothes which contain spandex. However, often the patient may be asked to change into a hospital gown to avoid possible MR safety issues.
When a doctor decides they want a patient to have an MRI, they need to know the applicable risk factors. Patients should always tell their physician if they have a concern about the safety of an MRI and should especially tell their doctors about metal implants or tattoos. Pacemakers and defibrillators in particular can cause huge risks to a patients' health while in an MRI machine, though they may no longer prevent a patient from being scanned. MRI scanners can cause problems with the machines or excess heat in the body around the metal. Similarly, tattoos can potentially contain metal, which may heat up and burn the patient. Finally, wearing clothes which contain metal fibers can lead to burns as well and should be avoided on the day of the exam.
1. OECD. "Magnetic resonance imaging (MRI) exams (indicator)." OECD.org. 2019. Web. 3 January 2019. doi: 10.1787/1d89353f-en
2. "Who can have one: MRI scan." NHS.uk. 8 September 2018. Web. 28 December 2018.<https://www.nhs.uk/conditions/mri-scan/who-can-have-it/>.
3. "Are MRI Scans Safe If You Have a Pacemaker or Implanted Device?: What to know about cardiac implants and imaging tests." Clevelandclinic.org. 8 February 2017. Web. 3 January 2019. <https://health.clevelandclinic.org/are-mri-scans-safe-if-you-have-a-pacemaker-or-implanted-device/>.
4. "Magnetic Resonance Imaging in Patients with Implanted Cardiac Pacemakers and Defibrillators." HopkinsMedicine.org. Web. 3 January 2019. <https://www.hopkinsmedicine.org/heart_vascular_institute/conditions_treatments/treatments/mri_implanted_cardiac_pacemakers_difibrillators.html>.
5. Rose Eveleth. "Some Tattoo Inks Can Burn You During an MRI." Smithsonian.com. 6 March 2014. Web. 28 December 2018. <https://www.smithsonianmag.com/smart-news/some-tattoo-inks-can-burn-you-during-mri-180949995/>.
6. "Could Tattoos Complicate an MRI Scan?" Abingtonhealth.org. 1 September 2015. Web. 28 December 2018. <https://www.abingtonhealth.org/healthy-living/health-news/library/articles-related-to-general-health/could-tattoos-complicate-an-mri-scan/#.XCaePVxKg2w>.
7. Chris Melore. "People in Yoga Pants are Being Burned by MRIs, Doctors Say." Chicago.cbslocal.com. 9 May 2018. Web. 28 December 2018. <https://chicago.cbslocal.com/2018/05/09/mri-yoga-pants-burns-doctors/>.
8. Dennis Green. "Doctors are warning people not to wear Lululemon-like clothing during MRIs — here's why." BusinessInsider.com. 10 May 2018. Web. 28 December 2018. <https://www.businessinsider.com/lululemon-athleisure-burn-during-mri-doctors-warn-2018-5>.
9. "MRI Clothing Guidelines." bmap.ucla.edu. Web. 28 December 2018. <http://bmap.ucla.edu/docs/MRIClothingGuidelines.pdf>.