Journal of Dental Research, Vol 66, 1326-1330, Copyright © 1987 by International & American Associations for Dental Research Online Journals
Effects of rare-earth filters on patient exposure and image contrast
S. M. Mauriello, D. B. Washburn and S. R. Matteson
Minimizing patient exposure while maintaining a diagnostically acceptable
radiograph is a major goal in diagnostic radiography. Rare-earth filters
may be the means to achieve this goal due to their "band-pass effect". The
purpose of this study was to examine the image contrast effects and
exposure reductions for various thicknesses of aluminum, samarium,
gadolinium, gadolinium oxysulfide, and gadolinium oxysulfide added to 2.5
mm of aluminum. Trials were conducted on an intra-oral dental x-ray unit
(range, 65 to 90 kVp). When compared with conventional aluminum, all of the
rare-earth filters provided lower radiation exposures, with gadolinium in
the metallic or oxysulfide form providing the lowest exposures. Samarium,
at a thickness of 0.127 mm, yielded the highest image contrast. Gadolinium
or gadolinium oxysulfide added to 2.5 mm of aluminum resulted in a slight
loss of contrast when compared with conventional aluminum filtration. This
loss may not be clinically significant, and when coupled with the reduced
exposure afforded by these filters, they become viable as acceptable
alternatives to aluminum filtration.
