Magnetic Resonance Imaging
MRI is a noninvasive procedure that uses no ionizing radiation. MR imaging 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. The images can then be examined on a computer monitor, printed or copied to CD. MRI does not use ionizing radiation (x-rays).
An MRI scan is often used for soft-tissue structures of the body—such as the heart, liver and many other organs— is more likely in some instances to identify and characterize abnormalities and focal lesions than other imaging methods. MRI enables the discovery of abnormalities that might be obscured by bone with other imaging methods and allows physicians to assess the biliary system noninvasively and without contrast injection.
What are the limitations of MRI of the Body?
High-quality images are assured only if you are able to remain perfectly still or hold your breath, if requested to do so, while the images are being recorded. If you are anxious, confused or in severe pain, you may find it difficult to lie still during imaging.
What does the equipment look like?
The traditional MRI unit is a large cylinder-shaped tube surrounded by a circular magnet. You will lie on a moveable examination table that slides into the center of the magnet.
Some MRI units, open on the sides ("low-strength" open MRI). These units are especially helpful for examining patients who are fearful of being in a closed space and for those who are very obese. But certain types of exams cannot be performed using open MRI.
How does the procedure work?
The procedure is performed by the patient positioned on the moveable examination table. Straps and bolsters may be used to help you stay still and maintain the correct position during imaging.
Small devices that contain coils capable of sending and receiving radio waves may be placed around or adjacent to the area of the body being studied.
You will be moved into the magnet of the MRI unit and the radiologist and technologist will leave the room while the MRI examination is performed.
If a contrast material is used during the examination, it will be injected into the intravenous line (IV) after an initial series of scans. Additional series of images will be taken during or following the injection.
When the examination is completed, you may be asked to wait until the technologist or radiologist checks the images in case additional images are needed.
Your intravenous line will be removed.
MRI exams generally include multiple runs (sequences), some of which may last several minutes.
MR spectroscopy, which provides additional information on the chemicals present in the body's cells, may also be performed during the MRI exam and may add approximately 15 minutes to the exam time
What will I experience during and after the procedure?
Most MRI exams are painless. It is normal for the area of your body being imaged to feel slightly warm
you will hear tapping or thumping sounds when the coils that generate the radiofrequency pulses are activated. The technologist will be able to see, hear and speak with you at all times using a two-way intercom.
You may be offered or you may request earplugs to reduce the noise of the MRI scanner, which produces loud thumping and humming noises during imaging. MRI scanners are air-conditioned and well-lit. Some scanners have music to help you pass the time.
When the contrast material is injected, it is normal to feel coolness and a flushing sensation for a minute or two.
Manufacturers of intravenous contrast indicate mothers should not breast feed their babies for 24–48 hours after contrast medium is given.
During MRI procedure
After you have removed all metal objects, our MRI Technologist will position you on the table of the scanner. Your head will be placed in a padded plastic cradle or on a pillow, and the table will slide into the scanner. An intercom system will allow you and the technologist to be able to communicate with one another at all times.
In order to obtain clear pictures, you will be asked to hold very still and relax. In some cases, you will be asked to hold your breath for up to 20 seconds. Any movement, especially of your head or back (even moving your jaw to talk) during the scan will blur and degrade the pictures. While the machine is taking your pictures, you will hear rapid, loud thumping noises coming from the scanner. During this time, you should breathe quietly and normally and refrain from any movement, coughing or wiggling. When the thumping noise stops, you must be still and maintain your position in the scanner. This noise comes from the gradient that allows the magnet to produce images. There will be multiple series of image acquisition, each with its own particular noises. The entire exam ordinarily takes between 30 and 60 minutes depending on exam type.
Who interprets the results and how do I get them?
A radiologist, a physician specifically trained to supervise and interpret radiology examinations, will analyze the images and send a signed report to your primary care or referring physician, who will share the results with you.
Why am I getting an MRI rather than x-ray or CT?
Detailed MR images allow physicians to better evaluate various parts of the body and determine the presence of certain diseases that may not be assessed adequately with other imaging methods such as x-ray, ultrasound, or CAT scan. It is important to note that MRI does not use x-rays.
If there's no radiation, why would I ever get a CT scan?
Obtaining MRI images takes much more time than a CT scan. Areas in the body that move in short periods of time, like your lungs or bowel, may not be ideal for MRI. Air doesn't contain a lot of protons and is largely invisible on MRI. Remember that lungs are mostly air.
Are there any needles? Why do I need contrast?
Depending on what information your doctor needs, the MRI scan may require the use of a contrast-agent given intravenously to assist in the visualization of certain anatomical structures in your body.
Do I need to be fasting?
If you are having a Cholangiogram (MRCP – Magnetic Resonance Cholangiopancreatography) or Liver study, you will have to fast for four hours prior to your exam. Other procedure doesn’t required fasting.
Items that need to be removed by patients before entering the MR system room include:
Purse, wallet, money clip, credit cards, cards with magnetic strips
Electronic devices such as beepers or cell phones
Metal jewelry, watches
Pens, paper clips, keys, coins
Hair barrettes, hairpins
Any article of clothing that has a metal zipper, buttons, snaps, hooks, underwires, or metal threads Shoes, belt buckles
Before the MRI procedure, you will be asked to fill out a screening form asking about anything that might create a health risk or interfere with imaging. You will also undergo an interview by a technologist to ensure that you understand the questions on the form. Even if you have undergone an MRI procedure before at this or another facility, you will still be asked to complete an MRI screening form.
Examples of items or things that may create a health hazard or other problem during an MRI exam include:
Implantable cardioverter defibrillator (ICD)
Implanted drug infusion device
Foreign metal objects, especially if in or near the eye
Shrapnel or bullet wounds
Permanent cosmetics or tattoos
Dentures/teeth with magnetic keepers
Other implants that involve magnets
Medication patch (i.e., transdermal patch) that contains metal foil
Check with the MRI technologist if you have questions or concerns about any implanted object or health condition that could impact the MRI procedure. This is particularly important if you have undergone surgery involving the brain, ear, eye, heart, or blood vessels.
Please indicate any possibility of pregnancy to your physician and the scheduling office when you book the appointment. Inform the MRI technologist as well when you arrive at the department.
How will I know the results of my MRI?
After your MRI completed our radiologists will read the images and dictate a report that will be sent to your referring physician, who will contact you with the results.
Sample of MRI procedures
All neuro cases for adult and pediatric MRI, MRA head and whole spine, orbits, neck MRA, MRA head.
Body cases MRI and MRA abdomens, MRCP, pelvis studies.
MRI for Upper and lower extremities.
MRA for upper and lower extremities.
Advanced technology; MR Spectroscopy, functional MRI (Tractography).
Cardiac MRI, fetal MRI.