Dentomaxillofacial Radiology, Vol 21, Issue 2 73-76, Copyright © 1992 by British Institute of Radiology

ARTICLES

Effects of additional filtration on image quality in dental radiography: comparison of niobium with aluminium

D. McDonnell and C. Price
Faculty of Dentistry, University of British Columbia.

Niobium filtration was compared with additional aluminium filtration with respect to the image quality of dental radiographs. An aluminium phantom was constructed which produced densities similar to those found in periapical regions and in enamel. Eight beam qualities were investigated and objective evaluation of the films was made by 20 observers with respect to any effects on radiographic contrast and successful identification of a pattern of holes in the phantom. Radiographic contrast decreased linearly as the half-value layer increased (r2 = 0.960, P < 0.0005), confirming the negative relationship between contrast and half-value layer as previously shown. No specific effect of niobium filtration on radiographic contrast was demonstrated. The number of successful identifications decreased with increasing half-value layer. A regression analysis in the total and dark zones yielded r2 values of 0.937 and 0.943 (P < 0.0005). Similar analyses for both the light and overall zones showed weaker relationships (r2 = 0.734 and 0.742: P = 0.007 and 0.006 respectively). Niobium reduces successful identification to the same extent as equivalent aluminium filtration.