MRI stands for magnetic resonance imaging. MRI does not use radiation in any form to obtain its images. Any body structure can be scanned with MRI, but certain scans are only done on MRI units that have the software and hardware to achieve high quality images of those areas. MRI is a wonderful diagnostic tool that shows muscle, bone, ligaments, tendons, nerves, vessels, cartilage and any other body structure in high detail.
The MRI uses a strong magnetic field to align the hydrogen atoms in your body. The coil, which is over the part of your body being imaged, then uses radio frequency to knock those hydrogen atoms out of alignment. As they return to the magnetized state and realign with the magnet each hydrogen atom gives off a signal. Each different type of tissue has a different amount of time before that signal is released. The coil then reads all these signals and a computer configures them into a cross section representation of the tissues in the body part being imaged.
All metal will have to be removed before your MRI. In most cases you will be given a gown or scrubs to wear during this procedure. No metal may be taken into the room with the MRI unit without the MRI staff’s permission. It is important to note that the MRI machine is a large magnet that is always on. Before you are allowed to enter the MRI suite a thorough medical history will be obtained by the MRI staff. This is to ensure that it is safe for you to enter the magnetic field. Some surgically implanted items are not MRI compatible. This being said any patient with a pacemaker or defibulator should not have an MRI or be allowed into the MRI suite. If you have any surgically implanted devices it is of the utmost importance that you let the radiographer know before entering the MRI suite. If you were given an implant card with your surgical implanted device it is always beneficial to bring this card to your appointment, that way the MRI staff can check on the compatibility with that MRI unit.
After you have been cleared by the MRI staff and have changed into your scrubs, the MRI staff will take you to the MRI room. Before entering the room a hand held scanner will be used to scan your clothing for any left over metal. After clearance you will be lead into the MRI suite. The MRI unit will always be making noise but this noise will intensify greatly when a scan is in progress. The MRI staff will give you ear plugs or head phones to help protect your hearing and help with communication during your exam. You will also be given a squeeze ball that will help alert the MRI staff to any problems you may be having during the MRI. It is important to note that the MRI staff will always be watching you and will communicate with you throughout the exam.
After you receive your hearing protection you will be laid on the scan table and positioned in the way needed to best demonstrate the area of interest. A coil will be placed over that area and additional padding will be added to help suppress motion and add comfort. MRI is very motion sensitive so it is very important to hold as still as possible during your study the MRI staff will give you verbal instructions on this subject throughout your exam. Exams times can run from 30 minutes to several hours if multiple exams are ordered. Scans can take any where from one minute to 15 minutes depending on the area to be covered and the scan parameters needed.
Before each scan the table will advance to a point putting the region of interest in the center of the magnetic field. After the exam is completed the patient will be brought out of the MRI unit and the table will be lowered. It is always important to sit for a short period of time before attempting to stand due to disorientation from the magnetic field and lying for extended period of time. Some MRI exams will include a contrast injection and others will have a fasting prep for several hours before the exam so abdominal motion will be limited.
Contrast is used in MRI but usually only intravenously. This will be given half way through the exam so the radiologist will be able to see the region of interest both with and without contrast.
Gadolinium is the contrast used in MRI it will help highlight any structure getting blood flow.
It is very important to tell your radiographer if you have decreased renal function or suffer from diabetes as this can effect whether contrast will be administered or not. As with any medicine or substance injected or ingested there is a slight risk of allergic reaction to the MRI contrast and it is always important to let the MRI staff know about any difference or change in the way you feel.
Claustrophobia is a common problem for people getting an MRI exam. The MRI staff will due their best to make you as comfortable as possible for your scan and will always be watching you and communicating with you throughout the exam. Additionally, some patients go to open MRIs, which aren’t tubes like closed MRIs, but rather a top and a bottom of the machine which you slide between with open sides thus giving larger patients or patients with claustrophobia more space around them.
MRI results are interpreted by a radiologist who is a physician trained to supervise and interpret radiological examinations. The radiologist will analyze all images taken during your exam and send a signed report to the ordering physician. This will take 24 to 48 hour and additional copies can be sent upon request to primary care physicians or specialists. The ordering physician or your primary care physician will go over the results with you.