What is an MRI?
Magnetic resonance imaging (MRI) uses a powerful magnetic field, radio frequency pulses, and a computer to produce detailed pictures of organs, soft tissues, bone, and virtually all other internal body structures.
Unlike CT scans and X-rays, MRI does not use radiation. Rather, it utilizes a powerful magnet which aligns hydrogen atoms from water molecules in the body in such a way that it produces a magnetic field in the body which can be detected by the scanner. Radio frequency, also known as resonance, is used to slightly alter the alignment to compose more detailed information.
An MRI can capture different information about the body than other imaging techniques, including X-ray, ultrasound, or CT scan. It is especially useful for obtaining images with detailed contrast between the soft tissues of the body.
How to prepare
- You will be given a gown to wear during the procedure. You may be able to wear your own clothing if it is loose-fitting with no metal such as rivets, buttons, or zippers.
- Metal objects can affect an MRI. Jewelry, eyeglasses, dentures, and hairpins will need to be removed before the exam, and you may also be asked to remove hearing aids and removable dental work. Let your doctor know ahead of time if you have a pacemaker, artificial limb, any metal pins, plates, heart valves, or other metal implants of any kind, as these may pose a risk during the exam.
- Be sure your doctor is aware of any recent illnesses or other medical conditions; if you have a history of heart disease, asthma, diabetes, kidney disease or thyroid problems; or if there is a possibility that you may be pregnant.
- Let your doctor know if you become very nervous in confined spaces. If possible, an open MRI will be ordered, or you may be sedated for the exam. If you are to be sedated, arrange for transportation home from the exam.
What to expect
Depending on the type of exam, a special dye may be injected through an IV to make certain internal organs or systems of the body show up more clearly in the pictures. You may experience a warm sensation in the body when the dye is administered.
When the scan begins, you will be lying on a narrow examination table. The technologist will help position you, and straps and pillows may be used to help you maintain the correct position throughout the exam. You will need to maintain the same position throughout the exam, but the technologist will tell you when you can relax, and when you need to be especially still.
The exam table will move into position inside the magnet. Depending on the machine, it may look like a short tunnel, or it may have a partial circle opening. The table will move and stop several times during the exam. You may hear a thumping or tapping sound during the exam. The exam will generally take 15 to 45 minutes, but it can sometimes take much longer. Your doctor will tell you what to expect before the exam is ordered.
After your MRI
When the MRI is complete, the technologist will review the images to verify that they are of high enough quality for accurate interpretation. The images will then be reviewed by a doctor, and you will hear back about the results within several days.
If you are not sedated, no recovery time is generally needed after an MRI, and you will be able to drive yourself home, or even back to work immediately after your appointment.
Risks or side effects
There are no known lasting side effects from the magnet or radio frequencies of the MRI machine. However, the powerful magnet does pose a risk to patients with pacemakers, or any kind of metal in the body.
If your MRI calls for use of a contrast dye, there is a small risk of allergic reaction or inflammation caused by the dye.
Types of MRI
Listed below are some of the types of MRI offered at Community Hospital.