What is an MRI?
What is an MRI?
MRI is the shortened name for magnetic resonance imaging. It uses a combination of radio waves and magnetic fields to allow a radiologist to view the internal body structure, and is usually considered to give a more complete picture than Xrays or ultrasounds, depending on what you’re looking for. The MRI machine is able to image a patient’s body in a way that can analyze different tissues within the body, and can provide two dimensional or three dimensional images. It is a noninvasive procedure.
The MRI machine itself is very large, most measuring seven feet high, seven feet wide, and ten feet long. There are some more recent models that are smaller and lighter. The magnet itself is a large cylinder. In its center, there is a movable platform that the patient lies on and which is slid in into and out of the magnet.
What will I experience?
The first experience you, the patient undergoing an MRI procedure, will have usually comes the night before the exam at most facilities (some places wait until the patient is checking into the office). You will receive a phone call from a receptionist asking some very particular questions. These questions are always the same, and are designed very specifically to make sure that no metal objects in or on your body are missed. You will be asked if you have a pacemaker, an aneurysm clip, any screws in your joints and bones, dental inplants. They will be asked about body piercings and tattoos, anything that you might not think to divulge. Most places will scan people with tattoos, but they like to know ahead of time, as some older tattoos may have some metal salts in the ink. Some patients have reported some mild discomfort or heating up of the tattoos.
The reason for this is that the magnet you are going to be lying inside is very, very strong. MRI magnets range from 5,000-20,000 gauss. To put this in perspective, the Earth’s magnetic field is only .5 gauss. The pull on anything metal is going to be very strong, and potentially dangerous.
An MRI tech told me that she had entered the MRI suite one day forgetting that she had a barrette in her hair. As soon as she opened to door of the suite, the barrette flew straight out of her hair and into the magnet. Fortunately, there was no patient inside, and she assured me that the techs are carefully screened before work each day when patients will be in the machine.
The questions you were asked on the telephone the night before will usually be asked a second time when you arrive at your appointment. After you have gone through all the things that may or may not be in or on your body, you are taken into a changing room where you remove all your clothing (you can keep your underwear, but the bra has to go- hooks) and get into the gorgeous gown. You will most likely be given pants, socks, and a robe as well, and the MRI suite is chilly. Most facilities give you a locker or a cubby for your clothes and belongings, and you are reminded to remove all jewelry. And there you will sit and wait for the technician. I have waited as little as five minutes and as long as forty-five. You may hear the loud repetitive “unnnnnhh unnnnnhh” of the machine scanning the patient ahead of you.
When they are ready for you, the tech will come and get you and lead you to the machine. You will be asked to lie down on the movable platform that is protruding from the magnet. Whether you will be placed on the platform head first or feet first will depend on the part of your body to be scanned. Most procedures are conducted with the patient lying head first into the magnet, as MRIs are commonly used to scan the brain or spinal cord, but foot or leg injuries of abnormalities are sometimes scanned. If this is the case with you, stop worrying. Your head and face, and most likely your entire torso will be outside the machine for the entire procedure.
Once you are lying on the platform, the tech will give you a blanket or anything else you need to keep you comfortable and able to lie still. You will be given headphones to allow you to hear the technician and to block out much of the noise of the machine. If your head or spine is being scanned, you will then have some cushions placed around your head, and your head will then be strapped into these cushions to help keep you from moving. You will then be handed a rubber bulb to hold onto during the test. You can squeeze this bulb if you need to be taken out of the machine for any reason.
Now is the time to close your eyes, unless you are incredibly comfortable in small spaces. It has been my experience through several MRIs that if you close your eyes before you are placed inside the machine it is much easier to convince yourself that you are somewhere else. Do not open them. If you do, it’s harder to undo the visual input to your brain and imagine that you are at the beach or in your bed. But if you keep them closed, it really is not as hard as you might think. I am not comfortable in closed spaces, particularly where my face is covered, but with a little imagination, I have made it through several full spine MRIs without having to squeeze that bulb.
Then you are slid into the magnet. How far you will be placed into the magnet, again, will depend on the part of your body in question. An MRI of the brain will usually only require that you to have your head and shoulders inside the magnet, and MRI of the entire spine will usually send you most or all of the way in. Should you choose to have your eyes open, what you will see is that you’re being slid into a tube that is narrow enough that the ceiling is just about two inches from your face and body.
While you are inside the magnet, the technician will talk to you to you through speakers in your headphones. He or she will tell you how long each sequence will take, so you can prepare your self, and keep you posted about the progress of the MRI.
You will not be removed from the tube unless your MRI requires the use of contrast (dye that in injected into your blood stream which allows certain tissues, blood, or irregularities to be more apparent in the image). If this is the case, you will be brought back out of the magnet about half way through your test. The contrast will be injected by the tech, you’ll get a chance to open your eyes and take a little break, and then you’ll be reloaded into the machine, and the same process will begin again.
And that’s it. The noise is annoying, but most places now pipe music into your headphones which helps a lot. Some let you bring your own CDs to play.
How can I lie in that small tube without freaking out?
You best friend during an MRI scan is your imagination. Just breathe deeply, and send your mind away. Keep your eyes gently closed, and try to think of it as your time to relax. It easier than you might believe possible because they keep you warm and bundled up, which has a calming effect on the sensory system. Occupational therapists have used heavy blankets with hypersensitive patients for years because of the calming effects of deep pressure. This will help you. Oddly, the noise of the machine is helpful as well. It is loud and grating, but it is consistent and repetitive, and, much like a metronome, can be helpful in calming the system and allowing the mind to meditate or wander elsewhere.
Just remember, the bulb in your hand can be squeezed at any time. Usually reminding yourself of that will ease the need to squeeze it. You can get out at anytime, so why not try a minute more and see if you can re-center yourself. For me, this thought has been particularly helpful during moments of anxiety or claustrophobia.
The MRI is truly a miracle of science and is a device that had been considered impossible until its inception. It will do wonders for diagnosing problems or ruling out disease, and if one has been ordered for you, drink some tea, take a walk, remove your earrings, and then keep your eyes closed and your mind moving.
Can everyone have an MRI?
There are some people who should not or can not have an MRI. If you are more than mildly claustrophobic, your primary care physician might prescribe a sedative for you, which will usually help. If you are severely claustrophobic, however, an MRI may not be possible for you. Talk to your doctor about the possibility of finding an “open” MRI. They exist, but are rare, and the quality of the pictures can be lower. Also, people who have any of the previously mentioned implants or devices may be unable to undergo an MRI scan, as may be people who are too large to fit into the machine.
