| Mammography
What is Mammography? Back to Top
Mammography is a specific
type of imaging that uses a low-dose x-ray system for examining 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.
What are some common uses of the procedure? Back to Top
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.
How should I prepare for a mammogram? Back to Top
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 mammogram
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 Mammography equipment look like? Back to Top
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? Back to Top
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? Back to Top
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
image receptor behind the plate, thus exposing the film or digital
receptor.
- You will be asked to change positions
slightly between images. The routine views are a top-to-bottom view and
an oblique 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? Back to Top
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? Back to Top
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? Back to Top
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
0.7 mSv, which is about the same as the average person receives from
background radiation in three months. Federal mammography guidelines
require that each unit be checked by a medical physicist every year to
ensure 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. Five percent to 15 percent of screening mammograms
require more testing such as additional mammograms or ultrasound. Most
of these tests turn out to be normal. If there is an abnormal finding a
follow-up or biopsy may have to be performed. Most of the biopsies
confirm that no cancer was present. It is estimated that a woman who
has yearly mammograms between ages 40 and 49 has about a 30 percent
chance of having a false-positive mammogram at some point in that
decade and about a 7 percent 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? Back to Top
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. Back to Top |
