c. Structural Variations. Structural variations result in the breasts being
classified as virginal, adult (mature), lactating, menopausal, or atrophic.
(1) The virginal breast. The virginal breast appears relatively dense on a
mammogram because it consists mainly of fibrous and glandular (fibroglandular) tissue.
Minimal subcutaneous fatty tissue is present which accounts for the radiolucent margin.
(2) The mature breast. The mature breast usually has the widest variation
in appearance on a mammogram. The reason is that there is a somewhat equal
balance between fibroglandular and fatty tissue. The mature breast can be considered
average in terms of density.
(3) The lactating breast. The glandular tissue proliferates and becomes
engorged with milk secretion during and after pregnancy. During the period, the
glandular tissue compresses the fibrous tissue and causes an increase in both size and
density of the breast. The breast is denser during the lactation period than it is at any
other stage. Following the lactation period, however, density decreases when the need
for fluid is gone and both the lobes and ducts decrease in size. At the time, fatty tissue
begins to develop and fills the space formed by expansion.
(4) The menopausal breast. As a woman approaches and passes through
the age of menopause, commonly called "change of life," the structure of the breast is
again modified. Hormonal stimulation of the glandular tissue progressively decreases,
which results in a gradual loss of both glandular and fibrous tissue. These tissues are
replaced, in part, by fatty tissue, the breast becomes softer, and there is less
(5) The atrophic breast. As the menopausal stage progresses, fatty tissue
continues to replace fibroglandular tissue until the breast is comprised solely of fatty
tissue. When this transition is complete, the breast is referred to as being atrophic.
There are two important factors to consider when selecting the focal spot to be
used in mammography. The first, and perhaps most important, consideration is the
capacity of the tube to withstand the heat generated in a single exposure. Naturally, a
large focal spot can tolerate higher exposures than a small one. Consequently, when
high exposure factors are used, it may be necessary to use a large focal spot.
However, if the exposure factors are low enough to permit the use of a small focal spot,
then it should be used. Remember, a smaller focal spot gives better detail, and detail
on a mammogram is extremely important.