Will the MR
imaging examination hurt?
No, MR imaging itself should cause no
pain. MR imaging requires that the patient remain still during the examination. For some
patients, keeping still for some time may be slightly uncomfortable. Sometimes patients
may feel warmth in the area being imaged, this is normal. However, if this warmth becomes
irritating or excessive, the patient should notify the imaging technologist as soon as
possible.
MR imaging examinations which require
the patient to receive Gadolinium contrast may cause slight, temporary discomfort while
the intravenous needle is placed (see below section "do I need an injection").
How long
will the MR examination take?
Most MRI centers offer a wide array of
Magnetic Resonance (MR) imaging examinations. Depending on the type of exam you will
receive, the length of the actual procedure will typically last between 15 minutes and 45
minutes. A few involved MRI examinations take longer than 45 minutes. Also, some MR exams
require the patient to hold their breath several times. This helps to eliminate blurring
from the images, which can be caused by breathing or other patient motion. Please discuss
specific questions about the duration of your MR imaging examination with the MR
technologist before your exam.
Why
does the MR system make the knocking sound during the exam?
The tapping or knocking noise heard
during the MR exam is created when "gradient coils" are switched on and off to
measure the MR signal reflecting back out of the patient's body. Depending on the type of
study being performed, the knocking may be loud enough to require ear plugs or head phones
for the patient. Please discuss this with the technologist before your examination. During
the MR examination, the technologist and patient may usually communicate at any time via
intercom or a type of call button.
The gradient coil is one of several
internal parts of the MR system that you cannot see. The gradient coil is made up of
loops of wire which are embedded in a hard plastic tube. During the scanning process an
electric current is switched on and off through the gradient coil approximately every few
milliseconds. Because the switching is so rapid, the wires vibrate within the hard plastic
and cause the knocking sound. This knocking is not harmful but the sound can be irritating
to some patients. You will here different knocking sounds during the MR exam, this means
that different types of "MR sequences" are being run to acquire different views
and images of your body.
Why may I
need to have an x-ray image before my MR imaging exam?
MR imaging involves the use of a
strong magnetic field. This magnetic field pulls on many metal objects. Thus, for safety
reasons, the MR staff must determine if you unknowingly have metal in your body. Some
patients may have small pieces of metal in their eyes, a metal implant, a prosthetic
device that may contain metal, surgical clips or other implanted objects that may be
susceptible to the magnetic field. After asking you a few questions, x-ray imaging may be
necessary to screen for metallic items prior to the MR examination.
Will
the MR imaging affect the fillings in my teeth?
No, MR imaging will not cause
fillings in your teeth, if in proper condition, to dislodge or come out. The metal in most
fillings is not affected by the MR system's magnetic field. However, the fillings may
cause some distortion of the images if you are having a scan of your neck, brain or facial
area.
Can I have an
MR exam if I have braces on my teeth?
Patients with braces may receive an MR
imaging examination. However, if you have braces and need MR imaging of your brain or
facial area, the MR system may have difficulty "tuning" to your body. The MR
tuning process is similar to tuning a radio to a specific frequency or radio station. This
tuning process can be "confused" if the patient has metal in his or her body,
particularly if the metal is in the area being imaged. Unfortunately, there is no way to
know in advance how much distortion from braces may result on MR images of the head, face
or upper neck.
Do I have
to go all the way inside the MR scanner tunnel?
Yes, however, only the portion of
the body that is being imaged must be positioned in the middle (end to end and side to
side) of the MR system's tunnel or "all the way inside." For example, if a head
study is being performed, the patients head must be positioned in the middle of the
tunnel. For knee studies, the knee is positioned in the middle of the tunnel with the
patients head facing the open end or possibly outside of the open end of the scanner
(depending on the length of the magnet tunnel and the height of the patient). So-called
"Open MR" systems do not have a tunnel design and may be more comfortable for
some patients. Most MR systems use the cylindrical tunnel design; however, recent versions
of the cylindrical MR systems have tunnels that are shorter, more open, and more comfortable than
systems designed and manufactured previously.
Do I
need a referral (prescription) to receive an MR examination?
Yes, your doctor must give you a
referral (prescription) in order for you to receive a Magnetic Resonance (MR) imaging
examination.
Can I move while
I am in the MR tunnel?
You should not move when you are inside
the tunnel and hear the knocking sound. For most MR exams, you may reposition your arms or
scratch your face or body in between image acquisition, when the knocking has stopped.
However, it is important that you not move the body part being imaged until the entire
exam is complete. Some MR exams of the chest and abdomen may require the patient to hold
their breath for a short period of time, for example, 10 to 25 seconds. This eliminates
blurring in the image caused by breathing or other patient motion.
Can I talk with
anyone during the scan?
You may talk to the technologists or
ask a question in between pictures image acquisition sequences when the knocking has
stopped. You will know when a picture is complete because the knocking and slight
vibration will stop.
Can I bring a
friend or a relative into the MR scan room with me?
Various MR centers may have different
procedures regarding this question (depending upon the type, strength and external
shielding of their magnet). All people entering the MR scan room should be checked for
metal in or on their body. This check may include the removal of keys, coins, jewelry,
watches, hairpins, hair clips, hearing aids, wallets, and credit cards or ID cards with
magnetic strips (since the strips magnetic coding can be erased by the magnetic field).
From a medical and safety standpoint, if your companion is checked and cleared to enter
the MR scan room, he or she may safely accompany you for the exam. Typically your
companion will be seated in a chair next to the MR scanner, or they may stand next to the
patient table during your exam.
Do I need
an injection of contrast for my MRI exam?
Not everyone needs an injection for MR
imaging. When an injection is needed, a pharmaceutical contrast agent called Gadolinium is
administered to the patient. This is only done when the radiologist and/or the referring
physician have determined that it is necessary for diagnostic purposes. Gadolinium
contrast is used to make specific organs, blood vessels or tissue types "stand
out" with more image contrast in the resulting picture. This highlights the structure
of the specific organs or vessel to better show the presence of disease or injury. The
referring doctor provides the MR imaging center with information about the patient's
medical condition and the goal of the MR imaging procedure being ordered (for example, to
diagnose cause of intense back pain). The decision to use or not to use an injection of
contrast (Gadolinium) is made based on this information and the body part being examined.
How is the
Gadolinium injection given for an MR imaging exam?
If an MR exam does require the use of a
Gadolinium injection, a small needle connected to an intravenous line is usually inserted
into the patient's arm or hand. A special saline solution is first dripped in to keep the
vein from clotting. Then typically, about two-thirds through the exam, a contrast agent
called "Gadolinium" will be administered through the intravenous line. At the
time of the injection, a patient may feel a cool sensation going up his or her arm. As
with anything taken into the body, there is a very slight chance of an allergic reaction..
For more information on contrast injections, please see the section on General Information About Contrast ("Dye") Used
in Medical Imaging Examinations.
If I'm nursing
an infant, can I breast feed after an injection of Gadolinium?
Typically, patients are instructed to
wait for 24 hours after receiving the Gadolinium injection before breast feeding again.
Patients may wish to pump breast milk prior to the MR exam and store it for use during
this 24-hour period. Always check with the radiologist and the imaging center for their
specific recommendations.
Can I have
an MR imaging exam if I am pregnant?
This question is difficult to answer
with a simple "yes" or "no." MRI (magnetic resonance
imaging) is considered a safe exam. However, conclusive information showing how safe MRI
is for pregnant women and the fetus is not yet available. MR imaging is generally not
performed on women in the first twelve weeks of pregnancy (first trimester).
Physicians typically do not perform MRI
on pregnant women unless there are strong medical indications. Depending on the condition,
there may be other exams available, such as ultrasound, to help diagnose a medical
condition.
If there is a strong medical reason for
an MRI, your physician may consult with a radiologist to determine if MRI is the best
course of action before proceeding. An abbreviated MRI exam may be performed, to reduce
the time in the magnetic field, based on the recommendation of the referring physician and
radiologist. Please consult with your physician for more specific information.
Updated: June 10, 2008
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