BONE
SCAN
Test
Overview
Nuclear
scanning tests use a special camera to take pictures
of certain tissues in the body after a radioactive
tracer accumulates in the tissues to make them visible.
Each type of tissue that may be scanned uses a different
radioactive compound as a tracer. The tracer remains
in the body temporarily before it is eliminated as
waste, usually in the urine or stool.
For
a bone scan, the tracer (radioactive technetium disphosphonate)
is injected into a vein in the arm. The tracer then
travels through the blood stream and into the bones.
Areas of rapid bone growth of repair absorb increased
amounts of the tracer show up as bright or "hot"
sports in the pictures. Hot spots may indicate the
presence of a tumor, a fracture, or an infection.
Areas where little or no tracer is absorbed appear
as dark or "cold" spots, which may indicate
a lack of blood supply to the bone or the presence
of a certain types of cancer.
Bone
scans are used to evaluate damage to the bones, to
detect cancer that has spread to the bones, and to
monitor conditions that can affect the bones. A bone
scan can often detect a problem months earlier than
a regular X-ray test.
This
test may be done on the entire body or just a part
of it.
Why
it is Done
A
bone scan is done to :
- Determine
whether a cancer from another area (such as the
breast, lung, kidney, thyroid gland or prostate
gland) has spread (metastasized) to the bone.
- Help
diagnose the cause of unexplained bone pain.
- Help
diagnose broken bones not clearly evident on X-ray
- Detect
damage to the bones caused by infection or other
conditions.
How
to Prepare
Before
the bone scan, tell your doctor if :
- You
might be pregnant.
- You
are breast-feeding.
- Within
the past 4 days, you have had an X-ray test using
barium contrast material or have taken a medication
that contains bismuth. Barium and bismuth can interfere
with test results.
You
usually have to wait 1 to 3 hours after the radioactive
tracer is injected before your bone scan is done.
Therefore, you may want to bring some reading materials
or items for another project to pass the time during
this waiting period. For some types of bone scans,
pictures are taken during the tracer injection, immediately
afterward, and then 3 to 5 hours after the injection.
No
other special preparations are needed before having
a bone scan.
You should empty your bladder just before the test
begins.
How
it is Done
A
bone scan is usually done by a radiology or nuclear
medicine technologist. The resulting pictures are
usually interpreted by a doctor who specializes in
evaluation nuclear scanning tests (radiologist or
nuclear medicine physician).
You
will need to remove any jewelry that might interfere
with the scan. You may need to take off all or most
of your clothes, depending on which area is being
examined. You will be given a cloth or paper covering
to use during the test.
The
technologist cleans the site on you arm where the
radioactive tracer will be injected. An elastic band
is then wrapped around your upper arm to temporarily
stop the flow of the blood through the veins in your
arm. This makes it easier put the needle into a vein
properly because the veins below the band get larger
and do not collapse easily. A small amount of the
radioactive tracer is then injected, usually into
a vein on the inside of your elbow.
It
takes 1 to 3 hours for the tracer to distribute throughout
your body. During this time you may be asked to drink
4 to 6 glasses of water to help eliminate any of the
radioactive substance that does not collect in your
bones. Just before the scan begins, you will usually
be asked to empty your bladder to prevent any radioactive
urine from blocking the view of your pelvic bones
during the scan.
During
the scan, you will lie on your back on a table and
the scanning camera will be positioned closely above
you. It may move slowly above and around your body,
scanning for radiation released by the tracer and
producing pictures of the tracer's distribution in
your bones. The camera does not produce any radiation,
so you are not exposed to any additional radiation
while the scan is being done. You may be asked to
move into different positions so the area of interest
can be viewed from other angles. You need to lie very
still during each scan to avoid blurring the pictures.
The
scan takes about an hour.
How
it feels
You
may feel nothing at all from the needle puncture when
the tracer is injected, or you may feel a brief sting
or pinch as the needle goes through the skin. Otherwise,
a bone scan is painless. You may find it uncomfortable
to remain still in different positions during the
scan. Ask for a pillow or blanket to make yourself
as comfortable as possible before the scan begins.
Risks
There
is always a slight risk of damage to cells or tissue
from being exposed to any radiation, including the
low level of radiation released by the radioactive
tracer used for this test. However, if this test is
really needed, the risk of damage from the tracer
is usually very low compared with the potential benefits
of the test. Most of the tracer will be eliminated
from your body within a day. Allergic reactions to
the tracer are very rare.
Occasionally,
some soreness or swelling may develop at the site
where the radioactive tracer was injected. These symptoms
can usually be relieved by applying moist, warm compresses
to your arm.
Results
The
results of a bone scan are usually available within
2 days.
Bone
Scan
Normal : The radioactive tracer is evenly distributed
among the bones. No areas of abnormally high or low
accumulation are seen.
Abnormal
: The tracer may accumulate in certain areas of
the bone, indicating one or more hot sports. Hot spots
may be caused by a fracture that is healing, bone
cancer, a bone infection (osteomyelitis), arthritis,
or a disease of abnormal bone metabolism (such as
Paget's disease).
Certain areas of the bone may lack the presence of
radioactive tracer, indicating one or more cold spots.
Cold spots may be caused by a certain type of cancer
(such as multiple myeloma) or lack of blood supply
to the bone (bone infarction).
What
affects the test
- A
bone scan is not usually done for a pregnant woman
because the radiation could damage the developing
fetus.
- Barium
and bismuth can interfere with test results. If
a bone scan is needed, it should be done before
any tests that use barium (such as a barium enema).
- The
results of a bone scan may not be accurate if the
person cannot remain still during the test.
- A
full bladder can block the view of the pelvic blocks.
What
to think about
- A
bone scan does not distinguish between normal and
abnormal bone growth. Therefore, bone scan results
must be interpreted along with the results of X-ray
tests. In addition, other tests (such as magnetic
resonance imaging, MRI) may also be needed to further
evaluate abnormal bone scan results. For more information,
see the following medical tests :
-
Chest X-ray
- Extremity X-ray
- Spinal X-ray
- Magnetic Resonance imaging (MRI) of the Body
- Magnetic Resonance imaging (MRI) of the spine
- A
woman who is breast -feeding and has a bone scan
should ask her doctor whether she needs to wait
for a period of time before she resumes breast-feeding
her child.
