Figure 2-26. Comparison of two-pulse and 12-pulse patterns.
b. When low-speed electrons strike the target in an x-ray tube, their energy is
converted into heat or into low-energy photons. Since a single-phase system produced
comparatively more low-energy electrons, it also produces a greater proportion of heat
and low-energy photons than a three- phase system.
(1) The average photon energy is less in a single-phase system. Low
energy photons are absorbed by filtration or by the patient. In either case, they usually
serve no useful purpose in diagnostic radiology since they do not reach the film to
contribute to the exposure. (With certain examinations, such as mammography, some
low energy photons are indeed useful since they contribute to this kind of exposure.
However, in this type of examination, special techniques and equipment are used to