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Mammography
What is Mammography?
Mammography is a specific type of imaging that
uses a low-dose x-ray system for examination
of the breasts. The images of the breasts can
be viewed on film at a view box or as soft copy
on a digital mammography work station. Most medical
experts agree that successful treatment of breast
cancer often is linked to early diagnosis. Mammography
plays a central part in early detection of breast
cancers because it can show changes in the breast
up to two years before a patient or physician
can feel them. Current guidelines from the U.S.
Department of Health and Human Services (HHS),
the American Cancer Society (ACS), the American
Medical Association (AMA) and the American College
of Radiology (ACR) recommend screening mammography
every year for women, beginning at age 40.
The National Cancer Institute (NCI) adds that
women who have had breast cancer and those who
are at increased risk due to a genetic history
of breast cancer should seek expert medical advice
about whether they should begin screening before
age 40 and about the frequency of screening.
See the Breast
Cancer page for information about
breast cancer therapy.
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What are some common uses of the procedure?
Mammography is used to aid in the diagnosis of
breast diseases in women. Screening
mammography can assist your physician in
the detection of disease even if you have no
complaints or symptoms.
Initial mammographic images themselves are not
always enough to determine the existence of a
benign or
malignant disease
with certainty. If a finding or spot seems suspicious,
your radiologist may
recommend further diagnostic studies.
Diagnostic mammography is used to evaluate a patient
with abnormal clinical findings, such as a breast
lump or lumps, that have been found by the woman
or her doctor. Diagnostic mammography may also
be done after an abnormal screening mammography
in order to determine the cause of the area of
concern on the screening exam.
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How should I prepare for a mammogram?
Before scheduling a mammogram, the ACS and
other specialty organizations recommend that
you discuss any new findings or problems
in your breasts with your doctor. In addition,
inform your doctor of any prior surgeries,
hormone use, and family or personal history
of breast cancer.
Do not schedule your mammogram for the week
before your period if your breasts are usually
tender during this time. The best time is
one week following your period. Always inform
your doctor or x-ray technologist if
there is any possibility that you are pregnant.
The ACS also recommends you:
- Do not wear deodorant,
talcum powder, or lotion under your
arms or on your breasts on the day
of the exam. These can appear on
the x-ray film
as calcium spots.
- Describe any breast
symptoms or problems to the technologist performing
the exam.
- If possible, obtain
prior mammograms and make them available
to the radiologist at
the time of the current exam.
- Ask when your results
will be available; do not assume
the results are normal if you do
not hear from your doctor or the
mammography facility.
In addition, before the examination, you will
be asked to remove all jewelry and clothing
above the waist and you will be given a gown
or loose-fitting material that opens in the
front.
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What
does the Mammography equipment look like?
A mammography unit is a rectangular box that
houses the tube in which x-rays are produced.
The unit is dedicated equipment because it
is used exclusively for x-ray exam of the
breast, with special accessories that allow
only the breast to be exposed to the x-rays.
Attached to the unit is a device that holds
and compresses the breast and positions it
so images can be obtained at different angles.
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How does the procedure work?
The
breast is exposed to a small dose of radiation to
produce an image of internal breast tissue.
The image of the breast is produced as a
result of some of the x-rays being
absorbed (attenuation)
while others pass through the breast to expose
either a film (conventional mammography)
or digital image receptor (digital mammography).
The exposed film is either placed in a developing
machine—producing images much like
the negatives from a 35mm camera—or
images are digitally stored on computer.
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How is the procedure performed?
During
mammography, a specially qualified radiologic
technologist will
position you to image your breast. The breast
is first placed on a special platform and
compressed with a paddle (often made of clear
Plexiglas or other plastic).
Breast compression is necessary in order to:
- Even out the breast
thickness so that all of the tissue
can be visualized;
- Spread out the
tissue so that small abnormalities
won't be obscured by overlying breast
tissue;
- Allow the use of
a lower x-ray dose since a thinner
amount of breast tissue is being
imaged;
- Hold the breast
still in order to eliminate blurring
of the image caused by motion;
- Reduce x-ray scatter
to increase sharpness of picture.
The technologist will go behind a glass shield
while making the x-ray exposure, which will
send a beam of x-rays through the breast
to the film behind the plate, thus exposing
the film.
You will be asked to change positions slightly
between images. The routine views are a top-to-bottom
view and a side view. The process is repeated
for the other breast.
The examination process should take about
half an hour. When the mammography is completed
you will be asked to wait until the technologist
examines the images to determine if more
are needed.
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What will I experience during the procedure?
You will feel pressure on the breast as it
is squeezed by the compressor. Some women
with sensitive breasts may experience discomfort.
If this is the case, schedule the procedure
when your breasts are least tender. The technologist will
apply compression in gradations. Be sure
to inform the technologist if pain occurs
as compression is increased. If discomfort
is significant, less compression will be
used.
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Who interprets the results and how do I get
them?
A radiologist,
who is a physician experienced in mammography
and other x-ray examinations, will analyze
the images, describe any abnormalities, and
suggest a likely diagnosis. The report will
be dictated by the radiologist, and then
sent to your referring physician. You will
also be notified of the results by the mammography
facility. This notification is usually sent
a few days after the official report goes
to your doctor. New technology also allows
for distribution of diagnostic reports and
referral images over the Internet at some
facilities.
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What are the benefits vs. risks?
Benefits
- Imaging
of the breast improves
a physician's ability
to detect small tumors.
When cancers are
small, the woman
has more treatment
options, and a cure
is more likely.
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- The
use of screening
mammography increases
the detection of
small abnormal tissue
growths confined
to the milk ducts
in the breast, called
ductal carcinoma
in situ (DCIS).
These early tumors
cannot harm patients
if they are removed
at this stage and
mammography is the
only proven method
to reliably detect
these tumors.
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Risks
- The
effective radiation
dose from a mammogram
is about 0.7
mSv, which is
about the same
as the average
person receives
from background
radiation in
three months.
The Federal mammography
guidelines require
that each unit
be checked by
a medical physicist
each year to
insure that the
unit operates
correctly. See
the Safety page
for more information
about radiation
dose.
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- Women
should always
inform their
doctor or x-ray
technologist if
there is any
possibility that
they are pregnant.
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- False
Positive Mammograms.
Five to 10 percent
of screening
mammogram results
are abnormal
and require more
testing (more
mammograms, fine
needle aspiration,
ultrasound or
biopsy),
and most of the
follow-up tests
confirm that
no cancer was
present. It is
estimated that
a woman who has
yearly mammograms
between ages
40 and 49 would
have about a
30 percent chance
of having a false-positive
mammogram at
some point in
that decade,
and about a 7
to 8 percent
chance of having
a breast biopsy
within the 10-year
period. The estimate
for false-positive
mammograms is
about 25 percent
for women ages
50 or older.
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What are the limitations of Mammography?
Interpretations of mammograms can be difficult
because a normal breast can appear differently
for each woman. Also, the appearance
of an image may be compromised if there
is powder or salve on the breasts or
if you have undergone breast surgery.
Because some breast cancers are hard
to visualize, a radiologist may
want to compare the image to views from
previous examinations. Not all cancers
of the breast can be seen on mammography.
Breast implants can also impede accurate
mammogram readings because both silicone
and saline implants are not transparent
on x-rays and
can block a clear view of the tissues
behind them, especially if the implant
has been placed in front of, rather than
beneath, the chest muscles. But the NCI
says that experienced technologists and
radiologists know how to carefully compress
the breasts to improve the view without
rupturing the implant. When making an
appointment for a mammogram, women with
implants should ask if the facility uses
special techniques designed to accommodate
them. Before the mammogram is taken,
they should make sure the technologist
is experienced in performing mammography
on patients with breast implants.
The American College of Radiology
has a program of accrediting qualifying
diagnostic radiology sites for mammography,
MRI and ultrasound.
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