MRI - Magnetic Resonance Imaging
MRI exams are performed using a powerful magnetic field and radio waves to produce detailed images of the anatomy. MRI does not use X-ray (ionizing radiation).
How does MRI work?
The human body is made up of millions of atoms. Normally, protons are oriented randomly. MRI equipment generates a powerful magnetic field, more than 10,000 times stronger than the earth's magnetic field. This magnetic field causes the protons to align in the same direction. Radio waves can slightly alter the proton's alignment in the magnetic field. When the radio waves stop, the protons realign in the magnetic field and release a radio wave that is detected and used to create an image, all without the patient feeling a thing.
Preparing for an MRI
Patients scheduled for an MRI at CMI should wear comfortable, loose-fitting clothing without metal zippers and snaps. You will also be asked to remove hairpins, jewelry, eyeglasses and hearing aids, and may be asked to change into scrubs or an examination gown. If you have a pacemaker, aneurysm clips, surgical clips, medical implants or other foreign objects in your body, the Technologist must be informed prior to the exam.
During an MRI
Before an MRI exam can be done, a patient MRI safety screening must be done. Because MRI uses a very strong magnetic field, magnetic materials that are in some patient's bodies may represent a danger to the patient and prohibit MRI imaging. This includes patients with cardiac pacing wires, brain aneurysm clips, pain electrodes, some heart valves, and other metal objects in the body.
You will be asked to lay flat on a movable table that is guided into the center of the MRI machine. During your time in the scanner you will be able to see out from the inner portion of the MRI, known as the "bore", and will be able to always communicate with the Technologist.
You will hear a thumping or knocking sound during the procedure but will not feel anything. We will provide you with headset and headphones may be offered so you can listen to music. It s is important that you remain completely still during your exam. Even the smallest movement can create blurred images, and occasionally our Technologist will ask you to hold your breath. If you are unable to hold still during your exam, please let our staff know and we will make every effort to help.
MRI with contrast
Some MRI procedures require a contrast agent (usually gadolinium) to be injected in your veins. This injection is done to differentiate the appearance of certain tissues or blood vessels. The contrast will be administered into an arm or hand vein with the use of a needle connected to an intravenous line. Contrast agents used for MRI are different from those used in X-rays or computed tomography (CT) scanning; they don't contain iodine and are less likely to cause an allergic reaction. The contrast agent is ultimately excreted in the urine. All contrast agents are approved by the Food and Drug Administration and are generally considered safe.
Patients having an MRI with contrast should inform the Technologist if they have allergies, are pregnant or breast-feeding, or if he or she has asthma, anemia or low blood pressure, epilepsy, heart disease, kidney disease, or sickle cell disease.
After an MRI
Once the MRI procedure is complete, a CMI Radiologist will review the detailed images, compare them to prior exams and a report will be delivered to the patient's physician.
How is MRI Used?
To detect subtle tissue abnormalities
Identify the type and extent of abnormalities - such as in musculoskeletal and nervous system disorder
It is the procedure of choice to detect sports injuries involving tendon and ligament damage
Identify brain and nervous system abnormalities