RISK FACTORS FOR BREAST CANCER

• Age: the older you are, the higher the risk.

INTRO TO MAMMO • Family History: Mother, sister with breast cancer.
• Genetics: Presence of BRCA1 or BRCA2 gene
• Breast Architecture: Dense Breast tissue, obesity.
SOFT TISSUE RADIOGRAPHY • Menstruation: Onset before age 12 years
• only muscle and fat are imaged. • Menopause: Onset after age 55 years
• Example: MAMMOGRAPHY • Prolonged use of estrogen
• Late age at birth of first child or no children.
MAMMOGRAPHY • Previous Radiation therapy to the chest at an early age.
• is an x-ray imaging method used to examine the breast • Education: Risk increases with a higher level of education.
for the early detection of cancer and other breast diseases. • Socioeconomic: Risk increases with higher socioeconomic status.
It is used as both a diagnostic and screening tool. TYPES OF MAMMOGRAPHY
• Mammograms usually include 2 views of each breast taken
at different angles. The breasts are compressed with plastic 1. Screening Mammography – is performed in asymptomatic women with
paddles to optimize visualization of breast tissue and abnormalities. the use of a two-view protocol, usually medial lateral oblique and cranial-
• Regular mammograms can find breast cancer early, sometimes up caudal, to detect an unsuspected cancer.
to three years before it can be felt. 2. Diagnostic Mammography – is performed on patients with symptoms or
• As a distinctive type of radiographic examination, mammography elevated risk factors. Two or three views of the breast may be required.
was first attempted in the 1920s. AMERICAN CANCER SOCIETY
• Considered very safe and effective.
• recommends that women perform monthly breast self-examinations.
Breast Cancer • recommends annual breast examination by a physician and a baseline
• Second leading cause of death from cancer in mammogram.
women. BASELINE MAMMOGRAM
• Major risk factor: Female sex and advancing age
• Risk doubles with a first-degree relative with breast • first radiographic examination of the breasts and is usually obtained before
cancer age 40 years.
• 85% of cases are sporadic.
• 5-10% due to genetic mutation
• 1-8 women will develop breast cancer (vs men: lifetime risk is 1 in 1000)
 • Postmenopausal breasts are characterized by a degeneration of this fibro-glandular
tissue and an increase in adipose tissue. Adipose tissue appears dark on film with
higher OD and requires less radiation exposure.
BREAST ANATOMY
• The breast tissue most sensitive to cancer induction by radiation is glandular tissue.
• The anatomy of the breast and its tissue characteristics
make imaging difficult. Young breasts are dense and are more • X-ray mammography requires a low-kVp technique. As kVp is reduced, however, the
difficult to image because of glandular tissue. penetrability of the x-ray beam is reduced, which in turn requires an increase in mAs.
• Older breasts are more fatty and easier to image. If the kVp is too low, an inordinately high mAs value may be required, which could
be unacceptable because of the increased patient radiation dose. Technique factors
Normal breasts consist of three principal tissues:
of approximately 23 to 28 kVp are used as an effective compromise between the
1. Fibrous increasing dose at low kVp and reduced image quality at high kVp.
2. Glandular
THE MAMMOGRAPHIC IMAGING SYSTEM
3. Adipose (fat)
• X-ray mammography became clinically acceptable with the introduction of
molybdenum as the target and filter (1966) and the dedicated, single-emulsion,
screen-film image receptor (1972).
• By 1990, grid technique, emphasis on compression, high-frequency generators, and
automatic exposure control (AEC) raised mammography to the level of excellence in
breast imaging.

HIGH-VOLTAGE GENERATOR

• All mammography imaging systems incorporate high-frequency generators. Such a

generator accepts a single-phase input, which is rectified and capacitor-smoothed to
produce a direct current (DC) voltage waveform.
• This DC power is fed to an inverter circuit, which changes the power to a high
frequency (typically 5–10 kHz) that is then capacitor smoothed. The resulting voltage
ripple in the x-ray tube is approximately 1%—essentially constant potential.
• The screen-film radiographic appearance of glandular and • A maximum limit of 600 mAs is standard for preventing excessive patient radiation
connective tissue is one of high optical density (OD). dose.
 • Effective focal spots—0.3/0.1 mm— are obtained with an approximate
23-degree anode angle and a 6-degree x-ray tube tilt.

TARGET COMPOSITION FILTRATION

• Mammographic x-ray tubes are manufactured with a tungsten • Dedicated mammography x-ray tubes have either a beryllium (Z = 4)
(W), molybdenum (Mo), or rhodium (Rh) target. window or a very thin borosilicate glass window.
• Tungsten L-shell x-rays are of no value in mammography because • Most mammography x-ray tubes have inherent filtration in the window of
their 12-keV energy is too low to penetrate the breast. approximately 0.1 mm Al equivalent.
• The x-rays most useful for enhancing differential absorption in breast • Under no circumstances is total beam filtration less than 0.5 mm Al
tissue and for maximizing radiographic contrast are those in the equivalent.
range of 17 to 24 keV. • If a tungsten target x-ray tube is used, it should have a molybdenum or
• Bremsstrahlung x-rays are produced more easily in target atoms with rhodium filter.
high Z than in target atoms with low Z. Molybdenum and rhodium • The purpose of each filter is to reduce the higher-energy bremsstrahlung
K-characteristic x-rays have energy corresponding to their respective x-rays.
K-shell electron binding energy. This is within the range of energy that is
most effective for breast imaging. • If a Mo target x-ray tube is used, then Mo filtration of 30 µm or Rh
• All currently manufactured mammographic imaging systems have filtration of 50 µm is recommended. These combinations provide the Mo
target–filter combinations of Mo–Mo. Many are also equipped characteristic x-rays for imaging along with the suppressed
with Mo–Rh and Rh–Rh bremsstrahlung x-ray emission spectrum.
• If a Rh target x-ray tube is used, it should be filtered with 25 µm Rh.
FOCAL-SPOT SIZE
-The use of Rh as a target or filter is designed for thicker, more dense
• The size of the focal spot is an important characteristic of mammography breasts. Regardless of x-ray tube target or filtration, the half-value layer is
x-ray tubes because of the higher demands for spatial resolution. Imaging of always very low.
microcalcifications requires small focal spots. HEEL EFFECT
• Mammography x-ray tubes usually have stated focal-spot sizes—large and
small of 0.3 mm and 0.1 mm. • The conic shape of the breast requires that the radiation intensity near
• A circular focal spot is preferred, but rectangular shapes are common. the chest wall must be higher than that to the nipple side to ensure near-
• To obtain such small focal-spot size and adequate x-ray intensity over the uniform exposure of the image receptor.
entire breast, manufacturers take advantage of the line-focus principle and • Source-to-image receptor distance (SID) of 60 to 80 cm, with the cathode
tilt the x-ray tube to the chest wall and the x-ray tube tilted.
• One consequence of the heel effect is variation in focal-spot size over the
image receptor. However, the use of long SID and vigorous compression
makes this change in effective focal-spot size clinically insignificant.
 Two types of AEC devices are used:

• ionization chamber
• Vigorous compression must be used in x-ray mammography. • solid-state diode.
✓ all tissue is brought closer to the image receptor.
MAGNIFICATION MAMMOGRAPHY
✓ focal-spot blur is reduced.
✓ reduces absorption blur and scatter radiation. • Magnification techniques are used frequently in mammography,
✓ immobilizes the breast and therefore reduces motion blur. producing images up to twice the normal size.
✓ spreads out the tissue and thus reduces superimposition of tissue structures. • Magnification mammography requires special equipment such as
✓ improved contrast and spatial resolution. microfocus x-ray tubes, adequate compression, and patient
✓ attain the best image quality. positioning devices.
✓ results in a lower patient radiation dose. • Effective focal-spot size should not exceed 0.1 mm.
• The purpose of magnification mammography is to investigate
GRIDS
small, suspicious lesions or microcalcifications seen on standard
• Grids are used routinely in mammography. mammograms.
• Most systems now have a moving grid with a ratio of 4:1 to 5:1 focused
• The most common anodes used for film/screen mammography
to the SID to increase image contrast. Grid frequencies of 40 lines/cm
are molybdenum, rhodium and tungsten.
for the moving grid are typical.
• The use of a 4:1 ratio grid approximately doubles the patient dose compared with • 2 TYPES OF COMPRESSION PADDLE:
non-grid contact mammography. However, the dose is still acceptably low,
and the improvement in contrast is significant. ▪ Full compression paddle- used to compress the
entire breast and should match the dimension of
• A unique grid that has been developed specifically for mammography is the
high-transmission cellular (HTC) grid. This grid has the clean-up characteristics of the image receptor.
a crossed grid in that it reduces scatter radiation in two directions rather than the ▪ Spot compression paddle- smaller in diameter
single direction of a parallel grid. The HTC grid has copper as grid strip material and (typically 5 cm) and are used to compress a
air for the interspace, and its physical dimensions result in a 3.8:1 grid ratio targeted region of interest of the breast.
AUTOMATIC EXPOSURE CONTROL

• Photo timers for mammography are designed to measure not only x-ray

intensity at the image receptor but also x-ray quality. These photo timers are called

AEC devices, and they are positioned after the image receptor to minimize the

object-to-image receptor distance (OID) and improve spatial resolution.