Magnetic Resonance Imaging (MRI)
Magnetic resonance imaging (MRI) is an imaging procedure utilizing strong magnetic fields and radio waves to produce cross-sectional images of organs and internal structures in the body. Each cross-section represents a “slice” of the part of the body being imaged. When viewed together these images provide a comprehensive view of the area imaged, with greater clarity and more detail than conventional X-ray images. MRI provides different or complementary information about structures in the body than the information that can be obtained using ultrasound or computed tomography (CT).
Doctors use MRI scans of internal organs, bones, soft tissue, and blood vessels to detect brain and nervous system disorders; problems affecting tendons, cartilage, ligaments, and bone marrow; inflammatory bowel disease and other gastrointestinal disease; and heart problems, such as congenital heart disease. In addition it is often used to diagnose cancer and monitor response to therapies for cancer and other conditions.
A form of MRI called magnetic resonance angiography (MRA) is an MRI that focuses on blood vessels and blood flow. MRA is most commonly used to identify aneurysms and blockages of blood vessels in the head, neck, chest, abdomen, or extremities.
An MRI system includes a scanner shaped like a donut and a motorized table that slides in and out of the opening in the scanner. The scanning process entails applying strong magnetic fields to the area being scanned and detecting how the area looked appears with the magnetic waves. Because different normal tissue types have different appearance with the magnetic field (for example bones, cartilage, tendons, ligaments, brain, spinal cord, heart, lungs, liver, uterus, prostate gland), a highly detailed anatomical map of the area being evaluated can be constructed from the information obtained. In addition, diseased tissue has different characteristics from normal tissue with the magnetic field, allowing identification and display in great detail of any abnormal tissue within the anatomical map created. Computer reconstructions allow this anatomical detail to be viewed in numerous ways, for example as three-dimensional images or as "slices", to allow for diagnosis, treatment, and follow-up for change. These images are essential to the health care team as they coordinate care.
For some MRI exams we will give intravenous contrast ("dye") to amplify the visibility of normal organs and to differentiate better between normal and abnormal anatomical details.
How do I prepare for the test?
On the day of the test you should wear comfortable clothes, and we may ask you to change into a gown when you arrive at the exam site. Do not wear eye makeup and leave metallic accessories like jewelry and watches at home.
If you will be sedated or receive a contrast material for the MRI, we will give you more specific instructions when you schedule the exam.
Please let us know about allergies you may have to contrast agents.
What will happen during the test?
If your doctor has requested that you have an MRI with contrast, we will first insert an IV, usually into your arm. We will then take you to the MRI exam room and position you on the MRI table. Usually you will lie on your back, although for some scans you may have to lie on your stomach or side. Once you are positioned the table will slide into the scanner, and a red light may shine on your body momentarily to ensure that you are properly positioned. MRI scanners make loud buzzing and clicking sounds, so we will give you ear plugs to make you more comfortable. The MRI technologist will leave the room to perform the scan, but he/she will be able to see, hear, and speak with you at all times.
The MRI scan can take from 15 minutes to one hour, most commonly 20-30 minutes.
Are there any risks?
MRI does not use ionizing radiation, the type of radiation used in x-rays and CT scans, and there are no known harmful side effects associated with temporary exposure to the magnetic field used by MRI scanners. There is a slight risk that you will develop an allergic reaction to the contrast agent.
After the test
After the exam you can immediately resume your normal activities. A radiologist will analyze the MRI images and will share the results with the doctor who requested the exam. Your doctor will then discuss the results with you.