4-42. TECHNICAL FACTORS AND PROCEDURE
a. General. The vital principle of soft-tissue radiography is that full advantage is
taken of all factors that contribute to the optimum differentiation of soft-tissue details.
(1) The technique must be selective. For a specific body of soft tissue to be
x-rayed, all the associated technical variables should be "correct" for only that particular
part under examination. The part or area of interest must be definitely circumscribed as
to zone, extent, thickness, and density. It is impractical to attempt to combine structures
of varying thickness and densities on the same radiograph with the part that is the focal
point of diagnostic interest.
(2) The soft-tissue part must be adequately penetrated. The main objective
is to produce differentiation of details within the soft-tissue structure and not merely the
semblance of an outline. The practical kVp range is from 40 to 70, but each case must
be judged on the thickness and density of the part. Use the lowest kVp necessary for
(3) The radiograph should exhibit relatively high (short-scale) contrast
graduated over the entire image pattern. The emphasis on short-scale contrast should
be solely for the purpose of causing the finer image details to be demonstrated clearly.
A radiograph presenting a chalky appearance, areas devoid of silver, or areas of
excessively dense silver deposits is of little or no diagnostic value.
b. Factors. To obtain the quality of radiographic contrast suitable for soft-tissue
radiography, the following factors must receive consideration.
(1) A relatively high mAs ratio with as low a kVp as is consistent with
adequate penetration for the particular soft-tissue structure under examination should
(2) Non-screen film in a cardboard holder is useful when referring to the
detail factor and the exposure latitude involved. However, the use of intensifying
screens aids in obtaining contrast and reduces the exposure time. The use of a
cassette with a single screen (back) may prove especially advantageous at the very low
kVp ranges where the front screen might absorb too much of the remnant radiation. In
the majority of cases, however, satisfactory results can be obtained by the use of
(3) Best results are achieved when filtration of the primary x-ray beam is at
a minimum, especially if the tissue thickness is very small.
(4) Beam-restricting devices are especially useful because they limit the
amount of irradiation to the part, with consequent lessening of fogging SR.