Quasimonochromatic radiation for dental radiography

Because of the greater sensitivity of commonly used dental films near 40 kv and the inherently greater contrast between bone and other oral tissues that is achieved at lower energies than those conventionally used, a considerable reduction of radiation exposure can be obtained by the use of those quasimonochromatic photons whose energy lies between 30 and 40 kv. The simplest and clinically most efficacious and econimical method of obtaining this quasimonochromatic radiation using fixed-anode tubes involves the use of Ce, 0.008 inch in thickness, as a band-pass filter, with reduction of skin exposure by a third to a half. The considerable dose reduction achieved at an increased exposure time of only 1.2 seconds is significant in view of the fact that both a greater percentage as well as a greater number of people are receiving radiation for oral diagnosis every year. Since the quasimonochromatic rays produced are less energetic than much of the radiation in the unfiltered beam, the radiation doses from scattered radiation to skull, bone marrow, and gonads also are reduced. In addition, the softer photons result in less Compton scattering, reducing the fog and improving the diagnostic quality of the film. Quasimonochromatic radiation may also be used to enhance the contrast wherever iodine contrast medium is needed since iodine absorbs very strongly above its absorption edge near 33 kev, suggesting another use of this technique in the area of oral diagnosis.