Magnetic resonance imaging (MRI) of the lumbar spine is a safe and painless test
that uses a magnetic field and radio waves to produce detailed pictures of the lumbar
spine (the bones, disks, and other structures in the lower back).
An MRI differs from a CAT scan (also called a CT scan or a computed axial tomography
scan) because it does not use radiation. An MRI scanner consists of a large doughnut-shaped
magnet that often has a tunnel in the center. Patients are placed on a table that
slides into the tunnel. Some centers have open MRI machines that have larger openings
and are helpful for patients with claustrophobia. MRI machines are located in hospitals
and radiology centers.
During the examination, radio waves manipulate the magnetic positions of the atoms
of the body, which are picked up by a powerful antenna and sent to a computer. The
computer performs millions of calculations used to create cross-sectional, black and
white images of the body. These images can be reconstructed into three-dimensional
(3-D) pictures of the scanned area. This helps to pinpoint problems in the lumbar
spine when the scan focuses on that area.
Why It's Done
MRI can detect a variety of conditions of the lumbar spine, including problems
with the bones (vertebrae), soft tissues (such as the spinal cord), nerves, and disks.
An MRI sometimes is performed to assess the anatomy of the lumbar spine, to help
plan surgery on the spine, or to monitor changes in the spine after an operation.
For example, it can find areas of the spine where the spinal canal (which contains
the spinal cord) is abnormally narrowed and might require surgery. It can assess the
disks to see whether they are bulging, ruptured, or pressing on the spinal cord or
MRI of the lumbar spine can be useful in evaluating symptoms such as lower back
pain, leg pain, numbness, tingling or weakness, or problems with bladder and bowel
control. It can also help to diagnose tumors, bleeding, swelling, developmental or
structural abnormalities, and infections or inflammatory conditions in the vertebrae
or surrounding tissues.
A lumbar spine MRI usually doesn't require any special preparation. However, the
technician will have your child remove any objects containing metal (such as eyeglasses
and jewelry) because they can produce a bright or blank spot on the diagnostic film
(but braces and dental fillings won't interfere with the scan). You'll also be asked
questions to make sure your child doesn't have any internal metal clips from previous
surgery or anything else that might cause a problem near a strong magnetic field.
Electronic devices aren't permitted in the MRI room.
To obtain the highest quality MRI results, your child will need to stay still during
the scan. For this reason, sedation may be required, especially for infants and young
kids, who are likely to have difficulty staying still for the test. If sedation is
needed, food and liquids will be stopped at a certain point before the MRI to allow
your child's stomach to empty. It's important to notify the MRI technician of any
illness, allergy, previous drug reactions, or pregnancy.
Sedation medications are usually given through an intravenous (IV) line (small
tube in a vein) to help a child stay asleep during the entire test. Sedation is also
helpful for kids who are claustrophobic. To relieve anxiety before and during the
test, some patients take an oral sedative on the way to the hospital or radiology
You can stay in the MRI room with your child until the test begins, and in some
centers you may be able to stay throughout the test. Otherwise, you'll join the technician
in an outer room or be asked to stay in a waiting room.
If you're nearby, you'll be able to watch through a large window and talk to your
child through an intercom during breaks between the scans. This can soothe your child
if he or she is awake in the MRI machine.
A lumbar spine MRI usually takes about 30-60 minutes to perform. Your child will
lie on the movable scanning table while the technologist places him or her into position.
A special plastic device called a coil may be placed around your child's head. The
table will slide into the tunnel and the technician will take images of the lumbar
spine. Each scan takes a few minutes.
As the exam proceeds, your child will hear repetitive sounds from the machine,
which are normal. Your child may be given headphones to listen to music or earplugs
to block the noise, and will have access to a call button in case he or she becomes
uneasy during the test. If sedated, your child will be monitored at all times and
will be connected to a machine that checks the heartbeat, breathing, and oxygen level.
Once the exam is over, the technician will help your child off the table; if sedation
was used, your child may be moved to a recovery area.
What to Expect
MRIs are painless. Your child may have to lie still on the MRI table for 30-60
minutes during this procedure, but there are brief breaks between each scan. If your
child feels cold lying on the MRI table, a blanket can be provided.
Unless sedation is used or you are told otherwise, your child can immediately return
to normal routine and diet. Most sedation will wear off within 1-2 hours.
Getting the Results
The MRI images will be looked at by a radiologist who's specially trained in interpreting
the scans. The radiologist will send a report to your doctor, who will discuss the
results with you and explain what they mean. In most cases, results can't be given
directly to the patient or family at the time of the test.
If the MRI was done on an emergency basis, the results can be made available quickly.
MRIs are safe and easy. No health risks have been associated with the magnetic
field or low-energy radio waves that are used for the test. The procedure can be repeated
without side effects.
If your child requires sedation, you may discuss the risks and benefits of sedation
with your provider.
Helping Your Child
You can help your child prepare for an MRI by explaining the test in simple terms
before the examination. Make sure you explain that the lower back will be examined
and that the equipment will probably make knocking and buzzing noises.
It may also help to remind your child that you'll be nearby during the entire test.
If your child is going to be awake for the test, be sure to explain the importance
of lying still. Your doctor may suggest that you and your child take a tour of the
MRI room before the test.
If You Have Questions
If you have questions about the MRI procedure, speak with your doctor. You can
also talk to the MRI technician before the exam.