A Patient's Guide to CAT Scans
What it is: The CAT scan is an X-ray test that is similar to both the
MRI and a regular X-ray, because it can show both bones and soft tissues. The
CAT scan uses X-rays that are interpreted by a powerful computer to create images
that appear as "slices" through the body. Today, using the computer software,
these slices can be combined by the computer to actually give a 3-D view of
the bones of the spine.
What the test shows: CAT scans are also able to produce X-ray "slices"
taken of the spine, so each section of the spine can be examined separately.
The CAT scan was developed before the MRI, and for several years, was used to
show the soft tissues of the spine. The pictures of the soft tissues produced
by a CAT scan are probably not as clear as the MRI. To make the soft tissues
easier to see, the CAT scan is often combined with a myelogram. For the myelogram,
dye is placed into the spinal sac to outline the nerves and spinal sac so they
show up clearly on the X-ray. Because the CAT scan uses X-rays, it shows the
bones of the body in great detail. It is the test of choice when looking at
fractures or damaged bones due to infection or cancer.
What the test does not show: A CAT scan without dye is not as good at
showing the discs and the nerves of the spine. The MRI is the best test to show
problems such as a herniated disc. The CAT scan does not show muscles or ligaments
How the test is done: As with an MRI, a CAT scan will require you to
lie on a table that slides into a scanner. The scanner is essentially an X-ray
tube that rotates in a circle taking many pictures. The procedure takes 30-60
minutes. You will have to lie very still for short periods as the scanner is
taking the pictures.
What risks the test has: The CAT scan uses X-rays (which use radiation).
In large doses, this can increase the risks of cancer. The vast majority of
patients who have a CAT scan will never get enough radiation to worry about
cancer. Only patients who must have multiple X-rays and CAT scans (hundreds)
over many years need worry about this risk. Children and young adults who plan
to have children should be protected from radiation exposure to the testicles
and ovaries. The radiation may damage the sperm and eggs. It is simple to protect
the area whenever possible by shielding it with a lead apron or blanket.
What the test costs: A CAT scan of the spine usually has two costs associated
with the test. The first cost is the fee for actually doing the test. This is
called the "technical fee". The second cost is the fee of having a specialist,
such as a radiologist, read and interpret the test. This is called the "professional
fee". You may get two bills for this test: one from the hospital or clinic where
you and the CAT scan done, and one from the specialist who read the test.
Copyright © 2003 DePuy Acromed.
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