Structures
that are dense (such as bone) will block most of the x-ray particles,
and will appear white. Metal and contrast media (special dye used to
highlight areas of the body) will also appear white. Structures
containing air will be black and muscle, fat, and fluid will appear as
shades of gray.
Radiography
The
test is performed in a hospital radiology department or in the health
care provider's office by an x-ray technologist. The positioning of the
patient, x-ray machine, and film depends on the type of study and area
of interest. Multiple individual views may be requested.
Much
like conventional photography, motion causes blurry images on
radiographs, and thus, patients may be asked to hold their breath or
not move during the brief exposure (about 1 second).
Inform the health care provider prior to the exam if you are pregnant, may be pregnant, or have an IUD inserted.
If
abdominal studies are planned and you have had a barium contrast study
(such as a barium enema, upper GI series, or barium swallow) or taken
medications containing bismuth (such as Pepto-Bismol) in the last 4
days, the test may be delayed until the contrast has fully passed.
You
will remove all jewelry and wear a hospital gown during the x-ray
examination because metal and certain clothing can obscure the images
and require repeat studies.
There is no discomfort from x-ray exposure. Patients may be asked to stay still in awkward positions for a short period of time.
During
a single radiograph, a small fraction of the x-rays pass right through
the body. The remaining photons are absorbed by tissues in the body.
The energy of the absorbed photons can break apart (ionize) compounds,
and this may cause cell damage. Most cell damage is soon repaired.
However, some is permanent.
For the exposures encountered in
conventional radiography, the risk of cancer or heritable defects (due
to damaged ovarian cells or sperm cells) is very low. Most experts feel
that this low risk is largely outweighed by the benefits of information
gained from appropriate imaging. X-rays are monitored and regulated to
provide the minimum amount of radiation exposure needed to produce the
image.
Young children and developing fetuses carried by pregnant
women are more sensitive to the risks of x-rays. Women should tell
health care providers about suspected pregnancy.
For additional
information regarding why the test is performed and normal and abnormal
results, please see the specific x-ray topics: