An unknown test can lead to unease. Before you get an MRI, learn what to expect from your scan to calm your concerns.
by The Iowa Clinic on Wednesday, December 19, 2018
When your doctor orders an MRI, it leaves you with many questions. But there’s really just one question that you — and your doctor — want to answer: “What’s wrong with me?” MRI scans provide detailed images of your body so your doctor has the information to answer that core question.
You won’t know the answer until your MRI results are back and examined by a radiologist. But the rest of your concerns can be addressed before your appointment. So here are answers to the most common questions asked by patients at The Iowa Clinic to help calm your nerves about getting an MRI.
What is an MRI?
Magnetic resonance imaging — or as everyone knows it, MRI — is just another diagnostic tool used to see what’s going on with you. An MRI machine is a large piece of medical equipment that takes pictures of your body’s internal structures. It doesn’t use radiation like an X-ray or CT scan, instead using magnets, radio waves and a computer to create detailed diagnostic images.
An MRI takes slices from various angles — each one about a quarter-inch thick. The radio waves pass through a powerful magnetic field at different frequencies to produce each different slice of the body on a scan. Several images are taken at a time in sequences, with each sequence lasting up to 10 minutes. The computer then takes all these sequences and maps them into a seamless image.
What shows up on an MRI?
Almost everything. Your body is mostly made of water. And the hydrogen atoms in H2O are magnetic. So in essence, an MRI machine measures the water content in your soft tissue, like the brain, nerves, muscles and organs.
Your body tissue shows up in varying degrees of light and dark — depending on the fat and water content — which a radiologist can examine to see if your tissue is healthy. Air and hard bone don’t send out MRI signals, so they appear black on the image. But even in those black areas, radiologists can determine whether everything looks normal.
When do you need to get one?
When your doctor needs more info than an X-ray or CT scan can provide, they order an MRI. It produces high-resolution images of your insides, which makes it helpful in diagnosing a variety of problems in your organs, tissue and skeletal system. You may need an MRI to examine health problems in any part of the body:
- Head and neck – An MRI can detect brain tumors, traumatic brain injury, developmental anomalies, multiple sclerosis, stroke, dementia, infection and the causes of headaches.
- Arteries and veins – With the help of a contrast dye, an MRI can light up your blood vessels to see blockages, aneurysms, carotid artery disease and other malformations.
- Spine – MRI signals are sensitive to changes in your cartilage and bone structure, which helps in detecting injuries, disease, aging issues, herniated discs, pinched nerves, spinal tumors, spinal cord compression and fractures.
- Organs – An MRI can see differences in tissue to check the health of your breasts, liver, kidneys, ovaries, prostate, pancreas and other organs.
- Bones and joints – When an X-ray can’t provide a clear picture or diagnosis a problem, an MRI looks for injuries, fractures, bone infections, cancer and damage to joints.
What happens during an MRI?
For some people, the mere thought of entering a tube full of magnets brings on anxiety. But an MRI scan is actually comfortable — you’re just lying down on a table. The table just happens to move inside a large magnet! And some MRI machines are open to accommodate larger patients and those with claustrophobia.
Once you’re inside, a coil is placed around the area being examined to send the radio waves used to generate the MRI pictures. The coils can be a little noisy. They’re switched on and off rapidly during the scan, and the sounds can range from a light tapping to a loud knocking or thumping.
Don’t worry, though — it’s completely normal! The radiology technologist will let you know when the scan is about to begin so you can prepare yourself for the noise. And you can get earplugs to help reduce the machine’s noise or listen to music on the stereo system throughout your test.
How long does it take?
It depends on what’s being examined. A single sequence of images can take anywhere from one to 10 minutes and total scan times range from 20 to 50 minutes. You don’t have to lie perfectly still for nearly an hour though — just for each individual sequence so that the MRI machine can produce clear diagnostic images. The technologist will be in constant communication with you and will let you know when it’s okay to move or adjust your position.
Is there anything you need to do to prepare for an MRI?
Not much. An MRI uses a giant magnet, so you want to be metal-free. If you have any metal or devices implanted inside your body, they could interfere with the scan or cause injury. You’ll need to complete a detailed screening sheet to answer questions about any potential issues such as metal, pacemakers, artificial heart valves or other implants.
Just as you can’t have metal in your body, you can’t wear any on the outside either. That means no jewelry, glasses or clothing with zippers, snaps or other metal fasteners. Instead, wear loose, comfortable clothes or change into a hospital gown.
Some types of MRI scans — like anything requiring images of your abdomen or pelvis — require fasting for several hours beforehand so the scan can pick up your tissue and not your last meal. You’ll be told before your appointment if you need to avoid food and water before your test.
When do you get results?
As quickly as possible. A radiologist will promptly review your images and consult with the referring physician. Radiologists can identify a number of medical conditions in their early stages, helping increase your likelihood for recovery. Your doctor will go over the results with you, discuss a diagnosis and come up with a plan to treat your condition and get you back to better health.