A brain MRI (also known as a head MRI) allows a radiologist to examine not only the brain itself but also the bones of the skull, the optic and cranial nerves, the blood vessels connected to the brain, the muscles, fat, and connective tissue in the head, and the structures of the inner ear. As a result, a brain MRI can help identify a host of issues, including structural abnormalities, inflammation, masses, fluid leakage, or damage to nerve fibers. In this article, we’ll examine why your doctor might order a brain MRI, how it’s done, and what it can reveal.
Why do doctors order brain MRI?
There are several reasons a doctor might order a brain MRI. It can be used to identify tumors, chronic conditions like multiple sclerosis, eye or inner ear disorders, developmental irregularities, or glandular disorders. It can also help doctors determine the cause of seizures as well as the presence of vascular problems, infection, or hydrocephalus. Your doctor might order this test to investigate a wide range of symptoms, including
- Neurological symptoms like chronic headaches, seizures, vertigo, or changes in thinking or behavior
- Hearing or vision issues that don’t have an identifiable cause
- Hormonal imbalances
- Extreme fatigue or weakness
MRI has the advantage of allowing doctors to visualize parts of the body that are otherwise obstructed by bone. Additionally, because MRI produces clearer, more detailed images than other methods, it’s extremely valuable in detecting and diagnosing problems early—before they become more advanced and more difficult to treat. In fact, a brain MRI can often detect a stroke within as little as 30 minutes of onset.
How is brain MRI performed?
Unlike CT scans, which use X-rays, MRI uses a powerful magnet and radio waves to influence the alignment of protons in the body. It then uses a computer to translate the changes that occur into highly detailed images of the body’s internal structures. As a safety measure, patients are asked to change into a gown and remove all clothing and accessories that contain metal, such as hairpins, jewelry, and metal fasteners, before entering the exam room.
For a head MRI, the patient is positioned face up on the scanning table, and the technologist places a helmet-like device on the patient’s head. The table then slides into the machine. As the machine operates, it makes a loud tapping noise. The technologist can see and hear the patient throughout the procedure, which typically takes up to 45 minutes.
What is the MRI machine like?
When choosing an imaging facility, find out what types of machines they use. Closed-bore MRI can cause some patients to feel claustrophobic. While open-bore machines can alleviate this problem, they can’t produce the same image quality as closed-bore units. Wide-bore machines, however, offer the best of both worlds. Wide-bore MRI uses a wider opening than traditional MRI machines while delivering the same image quality as closed-bore MRI. Patients who suffer from more extreme claustrophobia, however, may wish to talk with their referring providers about prescribing a sedative to help them complete the procedure.
What if my doctor ordered an MRI with contrast?
In some cases, gadolinium contrast is used to enhance image quality. Contrast is often used to better visualize blood vessels and tumors and to diagnose stroke, infection, multiple sclerosis, and dementia. If contrast is ordered for your MRI exam, the technologist will inject it into a vein in your hand or arm before images are taken. This is a different type of contrast than that used for CT exams, and it’s less likely to cause allergic reaction.
While gadolinium is considered safe, all drugs come with potential side effects. A small percentage of patients experience nausea and/or vomiting in response to the contrast dye. While rare, allergic reactions have been reported to cause hives, itchiness, and respiratory and cardiac symptoms. In patients with decreased kidney function, older formulations of gadolinium contrast carry the risk of nephrogenic systemic fibrosis, a rare and serious condition that causes the thickening of skin, organs, and other tissues. Newer formulations, however, are generally considered safe for patients with kidney disease. In recent years, researchers have discovered residual gadolinium in the brains and tissues of patients long after its use. Specific risks have not been correlated with gadolinium retention, but researchers continue to investigate this phenomenon.
What else should I know about MRI?
Because of the powerful magnet used in MRI exams, the procedure is contraindicated for some patients with implanted medical devices or embedded metal, such as shrapnel, in the body. Be sure your referring doctor and imaging center know about any such foreign bodies that may interfere with an MRI exam. Additionally, some tattoo inks contain magnetic pigments that are affected by MRI magnets, which occasionally results in pulling or burning sensations in the skin. However, most tattooed patients do not experience problems, and researchers have determined the risk of this type of side effect to be very small. If you notice discomfort during the procedure, let your technologist know.
If your doctor has ordered a brain MRI, they have determined that the benefit of the medical information it can provide outweighs any risks involved. If you have questions or concerns about this test, please discuss them with your referring doctor and/or your imaging provider.
Iowa Radiology is a trusted provider of imaging services in central Iowa, offering MRI, CT, ultrasound, X-ray, DEXA scanning, and more. Browse our blog and our library of free resources to learn more about modern imaging exams, important health topics, and the specific services we provide.
Blomqvist L, Nordberg GF, Nurchi VM, Aaseth JO. Gadolinium in Medical Imaging—Usefulness, Toxic Reactions and Possible Countermeasures—A Review. Biomolecules. 2022; 12(6):742. https://dx.doi.org/10.3390/biom12060742. Accessed April 24, 2023.
Chebib F. MRI: Is gadolinium safe for people with kidney problems? MayoClinic.org. Published September 29, 2022. Accessed April 24, 2023. https://www.mayoclinic.org/diseases-conditions/chronic-kidney-disease/expert-answers/gadolinium/faq-20057772.
Preidt R. Tattooed and Need MRI? What You Need to Know. Published February 13, 2019. Accessed April 24, 2023. https://www.webmd.com/a-to-z-guides/news/20190213/tattooed-and-need-mri-what-you-need-to-know.
Radiological Society of North America. Head MR. Radiologyinfo.org. Reviewed February 28, 2021. Accessed April 24, 2023. https://www.radiologyinfo.org/en/info/headmr.