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Introduction
Mammography
is a 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.
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, such as an MRI.
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.
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. 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.
 Mammography
Equipment
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.
The
Procedure
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 or images are digitally stored
on computer.
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; and
- 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 may be asked to wait
until the technologist examines the images to determine
if more are needed.
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.
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.
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.
Risks:
The effective radiation dose from a mammogram 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.
Women
should always inform their doctor or x-ray technologist
if there is any possibility that they are pregnant. 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 seven to eight 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.
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. |
