Mammography
Normal mammogram |
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.
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.
How should I prepare for the procedure?
Before scheduling a mammogram, you should 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.
Radiology Associates also recommends:
- 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.
What
does the 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.
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.
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 to 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.
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.
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.
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.
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 0.3 mSv,
which is about the same as the average person receives from
background radiation in one month. 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.
Women should always inform their doctor or x-ray technologist
if there is any possibility that they are pregnant.
False Positive Mammograms.
Between five and 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.
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.