What is an MRI Scan?
Magnetic resonance imaging (MRI) uses magnetism 20,000 times stronger than the Earth’s magnetic field to produce remarkably clear and detailed images of your head, spine, knee, shoulder or other parts of your body. This procedure is painless and does not use radiation like an x-ray.
In addition to a strong magnet, an MRI scanner machine also has a radio transmitter and receiver. These components together obtain information from your body by using pulses of radio waves to align all the water molecules in the part of the body being scanned into one dimension. Once the radio waves are turned off, the molecules flip back to their rotation and are picked up by a sensor which delivers the scanned body part as an image.
What Does an MRI Scan Show?
MRI produces soft tissue images and is used to distinguish normal, healthy tissue from any abnormal tissue that may be present.
MRI scans can be taken over time to show the change in progression of a condition and the effect it has on the body part being scanned. Depending on what information your doctor needs, the MRI scan may require the use of a contrast agent given by IV to assist in seeing certain structures in your body.
There is little preparation for a MRI exam but be mindful of the following:
- Continue taking your daily medications as normal unless instructed otherwise.
- During the scheduling process, you will be informed if there are dietary requirements for your exam, but dietary restrictions are rare.
- Since the MRI uses a very strong magnet, there is no metal allowed near the scanner. If your clothes have metal fasteners or metallic design you will be asked to change into a hospital gown or a scrub top and pants.
- It is very important to review the list of common conditions that could make the procedure unsafe for you.
- All jewelry and metal must be removed before the procedure as the magnet could heat up that metal during the scan and cause injury.
- Please bring a list of your current medications and their dosage with you to the scan.
- If you are claustrophobic, your doctor may prescribe oral medication that you can bring to take at your MRI appointment.
- Please arrive 30 minutes prior to your exam to check in so a board-certified MRI technologist can review your MRI safety screening form and discuss any safety considerations and questions that you may have concerning the exam.
- Please inform technician if you have any type of implants
What Can I Expect During my MRI Exam?
During the exam you will hear loud intermittent knocking noises and you will be provided with ear plugs or headphones so that you can listen to music or talk radio. The technologist will be in contact with you both visually and verbally during the entire exam. You will be provided with a call button that can notify the technologist if you need their assistance immediately during the exam.
How Long Does an MRI Take?
MRI procedure times will vary but the average is 30-45 minutes per body part. You will be required to lie very still during the exam.
MRI Scan Patient Safety Precautions
Because of the strong magnetic field used during the exam, certain conditions may prevent you from having an MRI procedure or require modifications for the examination. It is important to carefully review the list below to make sure it is safe for you to receive an MRI. When scheduling your appointment and prior to your exam, please alert our staff and technologist to the following conditions that may apply to you:
- High blood pressure
- History of cancer
- Ever had an injury where a piece of metal got in your eyes
- Pierced body parts (other than earrings) or recent tattoos, including tattooed makeup
- History of renal or liver disease, or currently in renal dialysis
- Dentures, partials, braces or retainer
- Internal Cardiac Defibrillator
- Implanted drug infusion device (i.e., insulin pump)
- Please inform technician if you have any type of implant
- Exposure of metal fragments to your eye/eye implant/eyelid spring
- Artificial heart valve
- Aneurysm clips
- Cochlear implants
- Metallic implants or prosthesis
- Artificial joint, plate or screws
- Coil, catheter or vascular stent or stent grafts
- Shrapnel, bullet wounds or other metal fragments
- Diaphragm, IUD or penile implant
- Tissue expander (breast)
- Electrical stimulator for nerves or bone (TENS unit)
- Medication patch (any kind)
Please remove the following before your MRI scan:
- Body piercing/jewelry
- Medication patches
- Hearing aids
- Removable drug infusion devices
- Metal retainer
What to Expect After an MRI Scan
We suggest moving carefully and slowly when your MRI is complete, as sudden movement after lying flat for the time of the procedure may cause you to feel lightheaded or dizzy. This may be especially true if you took sedatives before the procedure. If sedatives were taken, avoid driving until their effects cease.
Are there side effects from an MRI scan?
Some MRI procedures use contrast dye, which can cause allergic reactions in some persons, such as swelling, rash, itching, or difficulty breathing. Therefore, if dye is used, our staff may monitor you after the procedure to watch for any reactions.
Additional special care after an MRI is typically not required, but your physician may provide you with additional instructions after the procedure specific to your situation.
When can I expect my results?
After the MRI is completed, a radiologist will review the scan and provide the results to the ordering physician. The timeline for these results will depend on the urgency of the situation and the radiologist's capacity.
How will I know if another MRI is needed?
The ordering physician will communicate with the patient if another MRI is needed for any reason.
CAT Scan vs. MRI
The main difference between a CAT scan and an MRI is the technology used to create the pictures.
A CAT scan uses x-rays that scan the body in an arc to produce a picture from many different angles (think slices of bread in a loaf). Physicians can then view each picture out of the arc to review to help diagnose and treat. An MRI uses a magnetic field 20,000 times stronger than the Earth’s magnetic field to produce images of the body’s internal structures and organs. The magnetic field uses pulses of radio waves to align the water molecules into one dimension. When the radio waves are turned off, the molecules flip back to their original rotation and are picked up by a sensor which delivers the scanned body part as an image.