Magnetic resonance imaging (MRI) uses radio frequency waves and a strong magnetic field rather than x-rays to provide remarkably clear and detailed pictures. MRI is especially good for imaging soft tissues of the body, including the brain, nerves, muscle and solid organs. MRI is excellent for identifying normal and abnormal structures in the joints. Because MRI can give such detailed pictures of soft-tissue structures near and around bones, it is the most sensitive exam for spinal and joint problems. In addition, MRI of the heart, aorta, coronary arteries and blood vessels is a fast, noninvasive tool for diagnosing coronary artery, aortic and heart problems. MRI is growing in popularity as an adjunct to traditional mammography in the early detection of breast cancer.
- Images of the soft-tissue structures of the body—such as the heart, lungs, liver and other organs—are clearer and more detailed than with other imaging methods.
- MRI can help physicians evaluate the function as well as the structure of many organs.
- MRI contrast material is less likely to produce an allergic reaction than the iodine-based materials used for conventional x-rays and CT scanning.
- MRI enables the detection of abnormalities that might be obscured by bone with other imaging methods.
- Exposure to radiation is avoided.
- An undetected metal implant may be affected by the strong magnetic field.
- MRI is generally avoided in the first 12 weeks of pregnancy. Doctors usually use other methods of imaging, such as ultrasound, on pregnant women unless there is a strong medical reason to use MRI.
How should I prepare for the procedure?
You will need to complete a detailed screening sheet, on which you will be asked whether or not you have any metal or other devices implanted in your body. If you have any concerns or questions about the procedure, please ask the technologist before you enter the room. We also will be happy to answer your questions by telephone at any time before your appointment. The technologist should know about any such item and also whether you have ever had a bullet in your body, or whether you ever worked with metals, if you have any aneurysm clips or cardiac pacing devices. If there is any question, an x-ray can be taken to detect metal objects. You will be asked to remove hairpins, jewelry, eyeglasses, hearing aids and any dental work that can be taken out. Some wigs contain metal and must be removed. Red dyes used in tattoos and permanent eyeliner may contain metallic iron. You should report any drug allergies to the Technologist and should mention if there’s any possibility that you might be pregnant. Some patients who undergo MRI in an enclosed unit may feel confined or claustrophobic. If necessary, you may take a sedative upon your arrival in the facility.
Since you will be positioned within a large, very strong magnet, you must remove all loose metal objects. Doing so is important for your safety as well as that of our staff, and for proper functioning of the equipment. You may be asked to change into a gown unless you are wearing clothing that is metal-free.
Please let us know if you have any of the following:
- Cardiac Pacemaker
- Artificial heart valve prosthesis
- Eye Implants or metal ear implants
- Any metal implants activated electronically, magnetically, or mechanically
- Aneurysm clips
- Copper 7 IUD
- Penile implant
- Shrapnel or non-removed bullet
- Any metal puncture(s) or fragment(s) in the eye
You can eat lightly before the exam (unless told differently). Medications may be taken as usual.
How is the procedure performed?
During an MRI scan, you will lie comfortably on your back on a table that is moved inside a large magnet. A piece of equipment called a “coil,” which sends and receives the radio frequency waves used in this technology, will be placed around the area being examined. During the scan, as with all MRI exams, you will hear various noises, ranging from a buzzing to a loud knocking. You will be given earplugs to diminish the noise. You may notice a warm feeling in the area under examination; this is normal but if it bothers you the technologist should be notified immediately.
Several sequences or sets of images will be taken. Each sequence will last from one to 10 minutes, and the technologist will inform you before the scanning noise begins. Depending on how many images are needed, the exam will generally take 15-30 minutes. You must lie very still during each sequence, in order to produce clear, diagnostic images. The patient is able to communicate with the technologist at any time using an intercom. Also, if a child is being examined, a parent may stay in the room.
Depending on your symptoms or prior medical history you may be given an intravenous contrast medium for your scan. A small needle connected to an intravenous line is placed in an arm or hand vein. The technologist will explain this procedure to you if necessary. If a contrast injection is needed, there may be discomfort at the injection site and you may have a cool sensation at the site during the injection.
There are two types of MRI scans: Open MRI and Closed MRI. Many of our closed MRI machines today have a short bore, meaning they are smaller in size and less intimidating to patients who fear small areas. Our MRI technologists have great success working with minimally claustrophobic patients using the short bore MRI machines. The weight limit for our closed MRI is 350 lbs.
Open MRI machines are a great option for patients with claustrophobia, as there is a large portion of the scanner that is actually open. The magnet strength is not as strong as that of a closed MRI though (.3 Tesla magnet strength in an open MRI compared to 1.5 Tesla or 3Tesla magnet strength in our closed MRI machines), so the image quality is a less than that of a closed MRI. The weight limit for our Open MRI is 450 lbs., which is greater than the closed units.
What is breast MRI?
Breast MRI is a sophisticated technology that uses a computer, magnetic field and radio waves instead of x-rays to produce images of the soft tissues in the breast. This non-invasive procedure helps our physicians to better evaluate the breast. MRI is used in addition to, not instead of, a screening or diagnostic mammogram. When used in conjunction with screening and diagnostic mammography, it can provide valuable information for the detection and characterization of breast disease.
While an MRI is more likely to detect cancer than a mammogram, it may still miss some cancers that a mammogram would detect. MRI also has a higher false positive rate (where the test finds things that turn out to not be cancer), which would result in unneeded biopsies and other tests if performed on a large portion of women.
MRI is superior at demonstrating the size and extent of a breast tumor prior to surgery. In addition, it is beneficial for screening patients at particularly high risk for breast cancer due to genetic predisposition or strong family history, diagnosing breast implant rupture, staging breast cancer and planning treatment. MRI also plays an important role in post-surgical and post-radiation follow-up.
The injection of contrast material is necessary if the MRI is being performed for the diagnosis of breast cancer. It is sometimes not necessary if the sole intent of the study is to evaluate silicone breast implants. You will be asked to lie very still, relax and breathe normally. The MRI scan will only take 15-20 minutes. There are typically no side effects during or after MRI, so you can resume normal activities as soon as your exam is over.
It is very important that any prior breast films (mammograms, ultrasound or MRI) be made available to the radiologist for comparison during the interpretation of your MRI scan. If you have had these at a different facility, please bring them with you on the day of your appointment. After the MRI is read, those films will be returned to the patient so that they can return them to the facility where they originated.
What is MR angiography?
MR angiography (MRA) is an MRI study of the blood vessels. It utilizes MR technology to detect, diagnose and guide the treatment of heart disorders, stroke and blood vessel diseases. MRA provides detailed images of blood vessels, most often without intravenous contrast medium. Common uses are for the evaluation of the aorta, the carotid arteries, the renal arteries and extremity vessels.