MRI Scans
Introduction
In magnetic resonance imaging (MRI), magnetic waves (rather than x-rays)
stimulate tissues of the hip to produce signals. These signals are picked up
by a scanner and analysed by a computer to create a series of
cross-sectional views of the hip. An MRI is particularly helpful in
detecting damage, disease, or inflammation of soft tissues, such as
ligaments and muscles.
A typical MRI machine looks like a large,
hollow tube with a table at its centre. The machine is usually located in a
room of its own, with the controls behind a window off to the side. The
procedure is extremely safe, but requires you to remain motionless for a
long time (usually 10 to 45 minutes).
People who cannot
tolerate confined spaces sometimes find a standard tunnel-like MRI machine
upsetting. Some newer models, however, have a more “open” design: The
scanner itself is overhead, but there are no walls on either side of the
table to make you feel closed in.
An MRI is painless. It usually does
not require an injection with special dyes. However, you cannot have an MRI
if you have anything magnetic in your body, including metal pins, clips, or
plates. You also can’t have this type of scan if you have a pacemaker.
Getting Ready for the Scan
Some patients do need dye injected to improve the clarity of the images. If
that is the case, do not eat or drink anything for 4 to 8 hours before the
test.
Even if you are not being injected with dye, cut back on
caffeine before the exam. You will not be able to get to the bathroom during
the scan.
Since you are not allowed to wear any metal during the
scan, leave your watch and other jewellry at home.
If you cannot
stand cramped spaces, your doctor can prescribe medicine to help you relax
during the scan.
If you are not pregnant, tell your doctor. An MRI
should not harm the baby, but the doctor still needs to be aware of your
condition.
Many MRI machines tend to be noisy. Ask about earplugs or
headphones to block out the sound.
During the Scan
After putting on a gown, you will lie down on the scanner’s table. The table will then slide into the machine. Typically, you will hear knocking sounds when the procedure is going on. Despite the loud noise, the technician operating the machine in the other room can hear you, if you need to talk to him.
After the Scan
If you were given medicine to relax during the test, have someone drive you
home afterwards. Otherwise you can drive home yourself.
Your doctor
will review the pictures and call you with the results, or review the
results with you at your next office visit.
Frequently Asked Questions
Are MRI examinations ever painful?
The magnetic waves used to make the MRI images will not cause any pain.
Occasionally they make the imaged area feel warm, but this is usually not
uncomfortable. If it does cause discomfort, let the technician know.
Will I need to be placed all of the way inside the tunnel?
The area to be studied needs to be positioned in the middle of the tunnel. For a picture of the hip, you’ll therefore need to be entirely inside the tunnel.
Is it alright to have someone with me during the examination?
MRI centers have different rules concerning the presence of a friend or
relative. You will need to ask the technician about this. If it is alright
for someone to stay with you, make sure that the individual has no metal in
or on his body. Your companion should also leave credit cards outside the
room, since the magnetic field of the MRI will erase the magnetic strips on
the cards.
Why is it important to remove all metal objects prior to the examination?
The MRI produces a strong magnetic field that can displace metallic objects and disrupt the action of metallic implants. People with pacemakers and implanted brain aneurysm clips should not even enter the room during an MRI exam. Likewise, individuals with certain types of artificial heart valves or ear implants should not have an MRI. Most metal dental fillings are not affected by the magnetic field of an MRI, so they are not likely to be dislodged.
When may I talk during the examination?
While the MRI is producing the loud knocking noise, images are being taken and recorded. It is alright to talk when the knocking has stopped. You may communicate with the technician through an intercom.
Why is an injection sometimes needed prior to the examination?
To improve the accuracy of the images, a substance called gadolinium is occasionally injected into the joint to be imaged, or into a vein. The gadolinium makes easier to see the smaller structures in the joint and increasing the accuracy of the examination.
Why is it sometimes necessary to repeat some of the images taken during an examination?
You need to keep extremely still during the examination. If the area being
imaged moves while the machine is making its knocking noise, the picture
will be blurry and the scan will need to be repeated.
Is a referral needed for an MRI examination?
Yes, your doctor will need to write a prescription for the examination.
Related site pages |
| www.hip-replacement.org.uk |
| www.hip-surgery.org.uk |
| www.hip-resurfacing.zimmer.co.uk |
| www.arthritis-1.org.uk |
