An MRI, or Magnetic Resonance Imaging test, is done to see inside your body much like an x-ray, but with a few important differences. There are no x-rays or radioactive substances involved, no iodine contrast dyes, and it is not invasive (it doesn't "break" the skin). MRI also has the excellent quality of being painless. <g>
Because MRI can see through bone, it is especially useful for looking deep into the body. It can look beneath nerve coverings, see damage from a stroke, and probe blood vessels or the heart for disease. The radiologist examining the monitor image can program the computer to show cross-section slices of the image for a closer look. A new use for MRIs in heart disease testing is described later on this page.
While the patient lies inside a cylinder that contains a powerful electromagnet, technicians start radio waves that cause hydrogen atoms in the body to release energy. The magnet maps this activity from thousands of angles and sends the information to a computer, which produces a clear, high resolution picture of the scanned area. A radiologist then interprets the picture.
You're having the test because your doctor wants a look at some very high quality, custom made pictures of your heart, inside and out. He'll get them from an MRI.
After filling out the necessary paperwork, you will be sent to a dressing room with a clothes locker in it, to change. What you can wear during the test depends on what you are wearing when you show up. Jewelry, watches, coins, keys, credit cards and so on are not allowed in the MRI room. Such objects can stop radio frequency waves from getting into the body and cause distorted images. You'll have to leave these items in the locker during the test. Certain clothing - which contains metal zippers, rivets, wires, and belt buckles - are a no-no. These will have to stay in that locker and you'll have to wear a gown. (oh goodie!)
The MRI clinic has nursing, scan, control, computer, and reading rooms. You'll probably only see the scan room unless you need nursing care during or after the test. The MRI machine is in the scan room and it's a big sucker. The technicians operate the imager from the control room. The computer room is where the imaging hardware and computer are located. The last room is called the reading room. This room consists of large light boxes where a radiologist reads images, just like x-rays.
After changing clothes (if necessary) and entering the scan room, you should be asked some questions and have the test explained to you by a technician. Certain medical conditions, implanted devices and possible metal fragments under your skin don't get along well with this procedure. You'll be screened for these problems. If you have a "regular" pacemaker, you should not have an MRI because the pacemaker will not function in the MRI's magnetic field. New pacemakers may be okay but do not trust a technician on this. Find out from your doctor - or better yet your pacemaker's manufacturer - whether your pacer is safe for an MRI.
If you have metal filings, shrapnel, or metal-containing clips or pins in your body, you probably won't be imaged. These objects could be twisted inside your body by the magnetic field and injure you. If you ever worked with sheet metal, you must have x-rays to make sure you don't have small metal slivers under your skin. Most new surgical metal implants are made of a high quality stainless steel which is non-magnetic. You can be imaged with these, provided they are not in the anatomy being imaged.
One brand of ear implants cannot be safely scanned. One model penile implant is prohibited. Shrapnel near the heart is not safe. Brain aneurysm clips can become dislodged, causing fatal bleeding. Dental fillings and bridgework are okay. The tech will be asking you a lot of questions, but just answer them - there's a good reason for them all.
You should not wear a nitro patch on or near the area being imaged. It can cause a first or second degree burn. The following letter is taken from a Clinical Equipment Update from Picker Inc, a major MRI manufacturer:
"We are writing to warn you concerning MRI scanning of patients who are wearing a nitroglycerin transdermal delivery system (nitro patch). This type of device may contain metallic components that are susceptible to localized heating during an MRI scan, and thus cause patient burns....If a patient is wearing a nitro pad, the patient's physician should be consulted. The physician should be made aware that scanning with the nitro pad on may cause patient burns, and asked for instructions on how to proceed."
I include here a warning from Charlene, a Jon's Place reader. I have no confirmation of this but Charlene writes that
"A woman having an MRI at the same time I did had problems because she had recently applied antiperspirant and sunscreen. Both can contain metals (aluminum and titanium); So can foundation, lipsticks, rouges (all makeup, actually - not just eye makeup) and antiperspirants." End of Charlene's comment
You will be asked your height and weight. This information allows the pulse sequence to conform to the SAR (specific absorption rate) limits, protecting you from too much radiofrequency, which can cause burns. If you are extremely fat or just a very large person, you may not fit into a standard MRI machine and will not be able to take the test except on a new "open" MRI machine.
Here's where we split the description for "old/closed" versus "new/open" MRI machines. First, the "old" or "closed" machines:
You will be imaged inside a long tubular "hole" in the machine, about 2 feet in diameter. Since your heart (chest) is being imaged, you will slide into the machine head first, with your feet outside the machine. If you are truly claustrophobic, you should insist on having this test done in a newer, "open" MRI machine. I am mildly claustrophobic but I had no problems except for the very first instant I opened my eyes inside the imager and realized I could barely move and that the "top" was only a few inches from my face. With my eyes closed (and prayers said), I quickly relaxed. I wound up going to sleep in the thing <g> but that's unusual.
There is an intercom built into the machine, so you and the technician can talk back and forth. If you don't say anything, every once in awhile they'll talk to you just to make sure you're okay, and to tell you how long there is to go. If you realize the tightness is too much for you at some point, they can slide you out anytime, so keep that in mind that you're not really "stuck."
Now, I gotta tell you, the imaging itself is loud! It will sound like someone is knocking hammers against the sides of this big metal machine you are inside. Not to fear - it's supposed to sound that way! The sounds are caused by the magnetic field gradients being turned on and off. Because of the volume, you'll be given foam ear plugs, which you roll between your fingers and stick into your ears. These plugs work really well. I worked 15 years in lumber mills and used similar ear protection all day long. Some clinics now give you headphones to wear with music instead.
You lie on the bed of the machine before being slid in and the tech puts an imaging coil around your chest. The tech will position your body so your heart is under 2 intersecting light beams that form a "bulls-eye." This spot will be advanced to the center of the magnet before the scan begins. This is called landmarking. You're now slid into the machine, during which you don't move at all. For the rest of the test, you must stay as still as possible.
Your MRI will last between 30 and 60 minutes. You will need to lie still for periods of 3 to 10 minutes at a time, while each series of images is collected. You can breathe freely during this time. You may be allowed to move slightly between scans, but not so much that your overall position changes. Aside from the noise, you really don't have a sense of anything being done, which I like in a test. <g>
At the end of the image-taking process, you will be slid out, your headphones or ear plugs removed, chest coil removed, and you'll slowly stretch to ease your stiff muscles. You're done, and can go back to the changing room and your locker to get dressed and head home.
A radiologist specially trained to interpret MRIs (he's also an MD) will read the images and send a report to your doctor. Sometimes the radiologist will want to take images or send them to another doctor for a second opinion. Your doctor will then get the report and share the results with you. This usually takes one one or two days, but if a consultation is needed, may take more.
I suggest getting a copy of both the films and the radiologist's interpretation if at all possible. That way, you always know where they are and what they really say.
"Open" machines are less confining, but with slightly lower picture quality because of lower magnetic field strengths. While quality of an MRI exam depends on a lot of factors, a standard (closed) high field magnet will perform better than a low or midfield open magnet, if everything else is the same. However, with image filtering, better coils, and state of the art software, a modern "open" magnet MRI gives good results.
Many open MRI units have a side chair, where a friend or loved one can sit to keep the patient company during the exam. It should also have a built-in intercom with a handheld button, so the patient can talk with the technician during the procedure. These open MRI systems provide techs nearly 360° access to patients. A mirror system allows the patient too see all around him. The wide patient table accommodates patients up to 400 pounds and is quiet, unlike traditional MRI systems.
So in an open machine you won't have all that noise, you won't feel claustrophobic, and you may be allowed to have company with you during the procedure. On the other hand, the quality of the images may not be quite as good. It depends on your doctor, the available facilities, the quality of images needed, and how claustrophobic you are, as to which machine is used.
As long as the precautions and rules outlined above are followed, no harmful effects are known from the radio waves used in an MRI. Most units monitor the amount of radio frequency energy used, called SAR, to prevent them from burning you.
Discomfort from lying in one position is often a problem when exams run for over 30 minutes. You usually have to keep all or part of your body still for the entire procedure. Claustrophobia, or that closed-in feeling, is a serious problem for about 5% of patients during a closed MRI. Even though many patients actually handle the magnet enclosure with little or no problem, most are anxious because of stories they have heard. It really ain't that bad, folks. I have had several closed MRIs, up to an hour long. Keep your eyes closed and you'll probably do fine.
Avoid clothing with metal. Don't wear jewelry or eye makeup. Watches, metal objects in your pockets, and credit cards with magnetic strips will not be permitted in the MRI room, so you might as well leave them at home. Don't wear clothes with metal parts, like metal zippers, rivets and such (Guys - wear button fly pants). Be sure to ask for a light blanket before being slid into the imager if you are cold blooded, and aren't we CHFers all cold blooded? <g> Be sure to go to the bathroom before the test, so you don't have to interrupt everything, and do not take your Lasix before this procedure.
Just in case the clinic you go to has a music system set up for the patient in the imager, bring along a favorite cassette tape and a CD (so you're covered regardless which kind of player they use), and ask the technician if you can listen to one of them during the procedure. It never hurts to ask, and will certainly help relieve any tension for you.
You may have some post-procedure pain from lying still for so long, so it might be a good idea to take some aspirin or Tylenol or something right before the test. (Coumadin users, do not take aspirin!) If you are having the procedure in a closed machine and you are claustrophobic, make sure your doctor knows in advance and that he tells the MRI personnel that you will need a sedative. Be sure the MRI staff is aware of your heart condition so they don't give you something that will depress your heart function too much. This is best planned ahead of time to avoid confusion.
Finally, if you have a lot of trouble lying flat due to shortness of breath from your heart failure, discuss this with your doctor well before the test date!
October, 1999 - A new type of stress test using MRI may offer a safer and easier way to diagnose heart disease. The new stress test, called fast cine MRI is a way to test for coronary artery disease in patients who have problems doing a standard stress tests. This may include those who are obese, have had heart surgery, or who have lung disease. However, the fast cine MRI stress test should not be used in patients with pacemakers, cochlear (ear) implants, metal clips or pins, or ICDs.
Standard stress tests, such as treadmill exercise tests, can measure how well a person's heart handles exertion. A thallium stress test uses a radioactive substance injected into the blood to show how well blood is flowing to the heart muscle. It is usually done in combination with an exercise stress test on a treadmill.
The fast cine MRI uses a new form of high-speed MRI to view the wall of the heart as it beats. The fast cine MRI is able to capture the heart's movement at almost the same time the heart is actually contracting and relaxing - almost "real time." Patients get an IV drug called dobutamine and are placed in the MRI machine. Dobutamine mimics the effects of exercise by increasing heart rate. It also causes cardiac ischemia - a reduction in the blood being supplied to your heart.
With the high-speed imaging, a doctor can see how well the left ventricular wall moves during physical stress. The fast cine MRI gets a nearly immediate image of the heart in motion.
Perhaps the best part of this new MRI use is that it can display heart function, structure, blood flow, and coronary arteries. It should provide everything needed in one package. The fast cine MRI stress test has advantages over other forms of stress testing. It doesn't require radioactive substances and it is 3D, so it gives a better view of what's happening inside the heart wall than standard stress tests. The MRI stress test takes about 35 minutes and is an accurate predictor of heart disease.
Jon's note: Dobutamine is a great way to ease severe CHF, but it can be a very unpleasant experience for many people, so please don't assume that the fast cine MRI is going to be an enjoyable experience!
All information on this site is opinion only. All concepts, explanations, trials, and studies have been re-written in plain English and may contain errors. I am not a doctor. Use the reference information at the end of each article to search MedLine for more complete and accurate information. All original copyrights apply. No information on this page should be used by any person to affect their medical, legal, educational, social, or psychological treatment in any way. I am not a doctor. This web site and all its pages, graphics, and content copyright © 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004 Jon C.