What is MRI?
Common Uses | What Does the Equipment Look like? |
How Does the Procedure Work? | How is the Procedure Performed?
What Will I Experience During & After? | Who Interprets the Results?
What Are Benefits vs. Risks?
Magnetic resonance imaging (MRI) is a noninvasive, painless medical test that helps physicians diagnose and treat medical conditions.
MR imaging uses a powerful magnetic field, radio waves and a computer to produce detailed pictures of organs, soft tissues, bone and virtually all other internal body structures. MRI does not use ionizing radiation (x-rays).
Detailed MR images allow physicians to better evaluate parts of the body and certain diseases that may not be assessed adequately with other imaging methods such as x-ray, ultrasound or computed tomography (also called CT or CAT scanning).
What are some common uses of the procedure?
MR imaging of the body is performed to evaluate:
- organs of the chest, abdomen and pelvis—including the heart, lungs, liver, biliary tract, kidney, spleen, and pancreas. Spinal anatomy, nervous systm, major joints, Pelvic organs including the reproductive organs in the male (prostate and testicles) and the female (uterus and ovaries) pelvic and hip bones.
- blood vessels (MR Angiography).
Physicians use the MR examination to help diagnose or monitor treatment for conditions such as:
- lesions
- tumors
- coronary artery disease and heart problems including the aorta, coronary arteries and blood vessels, by examining the size and thickness of the chambers of the heart and the extent of damage caused by a heart attack or progressive heart disease.
- functional and anatomical abnormalities of the heart.
- arterial and venous vascular anomalies and diseases (e.g., atherosclerosis) of the chest, abdomen and pelvis (MR Angiography).
- biliary system conditions (MRCP).
- degenerative joint disorders
- spinal disk abnomalities
- infection
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What does the equipment look like?
The traditional MRI unit is a large cylinder-shaped tube surrounded by a circular magnet. You will lie on a moveable examination table that slides into the center of the magnet.
Some MRI units, called short-bore systems, are designed so that the magnet does not completely surround you; others are open on all sides (open MRI). These units are especially helpful for examining patients who are fearful of being in a closed space and those who are very obese.
The computer that processes the imaging information and monitor are located in a separate room.
How does the procedure work?
Unlike conventional x-ray examinations and computed tomography (CT) scans, MRI does not depend on radiation. Instead, radio waves are directed at protons, the nuclei of hydrogen atoms, in a strong magnetic field.
The magnetic field is produced by passing an electric current through wire coils in most MRI units. Other coils, located in the machine and in some cases, placed around the part of the body being imaged, send and receive radio waves. As you lie inside the MRI unit, radio waves are directed at the protons in the area of your body being studied. In the magnetic field, these protons change their position, producing signals that are detected by the coils.
A computer then processes the signals and generates a series of images each of which shows a thin slice of the body. The computer compiles the images into a three-dimensional representation of the body, which can be studied from many different angles on a computer monitor.
Because protons are most abundant in water molecules, MR images show differences in water content between various body tissues. As a result, MRI is especially suited to detecting disorders that increase fluid in diseased areas of the body, for example, areas affected by tumors, infection and inflammation. Overall, the differentiation of abnormal (diseased) tissue from normal tissues is significantly easier with MRI than with other imaging modalities such as x-ray, CT and ultrasound.
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How is the procedure performed?
MRI exams generally include multiple runs (sequences), some of which may last several minutes. When the examination is completed, you may be asked to wait until the technologist checks the images in case additional images are needed.
Music is available in the background or feel free to bring your favorite CD or reading material!
Small devices that contain coils capable of sending and receiving radio waves may be placed around or adjacent to the area of the body being studied. You will be positioned on the moveable examination table and will be moved into the magnet of the MRI unit and the technologist will leave the room while the MRI examination is performed. The technologist works from behind a control area and is able to see, hear and speak with you at all times.
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What will I experience during and after the procedure?
On very rare occasions some patients may find it uncomfortable to remain still during MR imaging and may experience a sense of being closed-in (claustrophobia). If you think you might be one of these patients, you should speak with your referring doctor to determine if they can arrange a sedation for you. We would like, however, to emphasize that fewer than one in 20 require it.
It is normal for the area of your body being imaged to feel slightly warm, but if it bothers you, notify the technologist. It is important that you remain perfectly still while the images are being recorded, which is typically only a few seconds to a few minutes at a time. You will know when images are being recorded because you will hear tapping or thumping sounds when the coils that create the magnetic field are turned on.
You will be alone in the exam room during the MR imaging, however, the technologist will be able to see, hear and speak with you at all times using a two-way intercom.
You may request earplugs to reduce the noise of the MRI scanner. MRI scanners are air-conditioned and well-lit.
If you have not been sedated, no recovery period is necessary. You may resume your usual activities and normal diet immediately after the exam. A few patients experience side effects from the contrast material, including nausea and local pain. Very rarely, patients are allergic to the contrast material and experience hives and itchy eyes.
It is recommended that nursing mothers not breastfeed for 36 to 48 hours after an MRI with a contrast material.
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Who interprets the results and how do I get them?
Your referring physician may request a specific radiologist. It they do not specifically request one we will refer your scans to a professional radiologist within our network. Our radiologists are specifically trained to supervise and interpret radiology examinations and will analyze the images and send a signed report to your primary care or referring physician, who will share the results with you.
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What are the benefits vs. risks?
Benefits
- MRI is a noninvasive imaging technique that does not involve exposure to radiation.
- MRI imaging of the soft-tissue structures of the body has a higher sensitivity to identify and characterize abnormalities and focal lesions than other imaging method. This detail makes MRI an invaluable tool in early diagnosis and evaluation of many conditions, includint tumors.
- MRI has proven valuable in diagnosing a broad range of conditions, including cancer, heart and vascular disease, and muscular and bone abnormalities.
- MRI can help physicians evaluate both the structure of an organ and how it is working.
- MRI enables the detection of abnormalities that might be obscured by bone with other imaging methods.
- MRI allows physicians to assess the biliary system non invasively and without contrast injection.
- The contrast material used in MRI exams is less likely to produce an allergic reaction than the iodine-based materials used for conventional x-rays and CT scanning.
- MRI provides a fast, noninvasive alternative to x-ray angiography for diagnosing problems of the heart and cardiovascular system.
Risks
- The MRI examination poses almost no risk to the average patient when appropriate safety guidelines are followed.
- There is a very slight risk of an allergic reaction if contrast material is injected. Such reactions usually are mild and easily controlled by medication. There also is a very small risk of skin infection at the site of injection. Nephrogenic systemic fibrosis is currently a recognized, but rare, complication of MRI believed to be caused by the injection of certain (but not all) MRI contrast material in patients with poor kidney function.
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