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
When you schedule your appointment, we will inform you about any specific
preparations depending upon the specific procedure your doctor has ordered.
Please contact the Scheduling Department at
949-764-5573 if you have any questions.
If you have a pacemaker (unless it is a MRI safe pacemaker), or breast
tissue expanders, please contact your physician as you are unable to have
an MRI procedure.
Because the MRI unit uses a very large, strong magnet, you will be asked
to remove and store jewelry, keys, wire-frame eyeglasses and any loose
metal objects. You may be asked to change into a gown unless you are wearing
clothing that is metal-free. Please wear comfortable clothing with no
metals, buttons or zippers. Preferably wear a sweat outfit or active wear.
You will need to complete a detailed screening sheet, on which you will
be asked whether or not you have any metal or other devices implanted
in your body that may interfere with the scan or cause injury to you.
If you have any concerns or questions about what expect of the procedure,
please ask the technologist before you enter the room. We also are happy
to answer your questions by telephone at any time before your appointment.
If you have hair extensions with metal clips, please remove them prior
to the MRI procedure.
Options exist for patients who suffer from claustrophobia or who are unable
to lie still for several minutes at a time. Because no radiation is involved,
a family member or friend can remain in the scan room with you to offer
comfort and support. Anyone who enters the scan room will need to be screened
by our staff.
A second option is taking anxiety-relieving medication such as Valium,
which your physician can prescribe for you. If you are planning on taking
anti-anxiety medication for this procedure, you must arrive 1 hour prior
to the procedure to sign your consent prior to taking your medication.
If you are already medicated, your consent will not be valid and your
procedure may need to be rescheduled. Also, be aware that you cannot drive
for several hours after you take this medication, so you will need to
arrange for transportation home. If you have a programmable shunt, you
will need to go to your physician’s office immediately after the
MRI to have it re-programmed. Please schedule this in advance with your
If you have a Vegus Nerve Stimulator, you can only have a MRI of the brain
and it must only be done at Hoag Hospital Newport or Hoag Hospital Irvine.
If your physician has ordered your MRI procedure with radiographic contrast:
You should inform your physician if you have any allergies. If you have
been told you are allergic to contrast or have ever had a reaction to
Iodine or any form of contrast media, your doctor may prescribe medications
to reduce the risk of an allergic reaction. A Radiology nurse should contact
you. If you have not been contacted by a Radiology nurse at least 24 hours
prior to your appointment, please contact the Imaging Scheduler immediately.
If you have diabetes, kidney problems, lupus, surgery on your kidneys or
multiple myeloma, you must have lab work that includes a BUN and Creatinine
performed within 30 days of your exam.
If you are over the age of 65 you must have lab work within 90 days of
your exam. This provides us with information regarding your current kidney
function. Please call your physician if you have not had this blood work.
If you are currently receiving Dialysis; please schedule your dialysis
to follow your procedure with Contrast or the following day. It is imperative
you have dialysis no later than the following day after you have received
contrast for your procedure.
We encourage you to hydrate with oral fluids at least 24 hours prior to
your study. You may have only clear liquids as well as your necessary
medications 2 hours before your exam.
You may receive additional specific instructions when you schedule your
appointment depending upon the type of procedure that will be performed.
Some types of scans require fasting beforehand.
Please complete, print out and bring with you the following forms to your
Locations where Hoag provides MRI services: