a. Density equalization filters may be made up of the following materials:
(4) Opaque plastic paste-like mixture (commercially available) that is
especially suited for this purpose.
Barium sulfate-impregnated paste.
b. Density equalization filters are usually made up in characteristically sloped or
wedge-like forms by modeling if a paste-like substance is used or by grinding if a
metallic substance is used.
c. Density equalization filters should be built to fit a particular type of
examination. For example, a filter made of brass with a heel thickness of approximately
1/8-inch may be practical for making placentograms, but unsatisfactory for making full-
length venograms of the lower extremities.
d. These filters should be fabricated in such a way as not to cause the
superimposition of distracting densities over any part of the resulting image pattern.
1-19. WHERE DENSITY EQUALIZATION FILTERS MAY BE INTRODUCED
Density equalization filters may be introduced into the x-ray beam at the level of
the filter slot near the x-ray tube housing where the normal complement of filters is
usually located or at the level of the exit portal of the beam-restricting device or they
may be interposed between the part and the film. The normal equivalent of filtration is
always retained where any type of density equalization filter is used. In every case, the
filter is an addition to the normal filter system.
1-20. BASIC PRINCIPLES
a. The density equalization filter (figure 1-8) must be oriented in the path of the
x-ray beam in such a way that its "heel" (thicker-edge) portion is toward the thinner or
less-dense portions of the part or area to be radiographed.
b. Whenever a density equalization filter is introduced into the path of the x-ray
beam, the exposure factors should be adjusted to deliver sufficient x-ray intensity to
achieve optimum visualization over the thickest and densest portions of the part or area