What is an MRI?
Magnetic Resonance Imaging (MRI) produces images of the body’s internal structures by passing radio waves through a powerful magnetic field. Differing frequencies of radio waves are produced by the different body structures, in return, these are mapped and converted into digital images by a computer. MRI is especially good for imaging soft tissues in the body, including the brain, nerves, muscles and organs.
Detailed MR images allow physicians to better evaluate various 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 To Expect
You will be lying on your back on a movable table that slides into the center of the MRI machine. The technologist may use straps or bolsters to help you stay still and maintain proper positioning during the examination. He or she may place a device called a coil around the part of the body being studied. This device sends and receives the radio waves which are used to generate the image.
The MRI scanner is noisy. You will be given a set of earplugs or headphones to wear during the examination to reduce the noise.
It is important that you follow the technologist's instructions. You will be asked to remain still multiple times throughout the examination while each sequence is being performed. Each sequence lasts between 2-10 minutes. If you are claustrophobic (have a fear of being closed-in), you may want to discuss the option of receiving sedation for the study with your physician prior to your appointment.
Some studies require the administration of contrast material into the vein. MRI contrast is called gadolinium and is different than the contrast administered for CT scans. A radiology technologist or nurse will place an intravenous line through which he or she will give the contrast.
Most MRI examinations last between 30 to 60 minutes.
How To Prepare
You will need to fill out a screening form before your appointment.
Before the scan, you will be asked to remove all jewelry and other metal items, including dental work, hearing aids, hair accessories.
Depending on the reason and area being scanned, you may be instructed to fast for several hours prior to the study.
Please inform the MRI technologist or radiologist before the examination if you have any of the following conditions:
Pacemaker or implanted defbrillator.
Any implanted electronic device, including joint prostheses, nerve stimulators, artificial heart valve, cochlear implant, etc.
Unable to lie still due to pain or involuntary movements.
Prior allergic reaction to intravenous contrast used for MRI (gadolinium).
History of kidney disease.
History of metal work or gunshot injury.
Tattoos or permanent makeup. Rarely, some dyes contain iron and may heat up during the study.