Influence of developer exhaustion on accuracy of quantitative digital subtraction radiography - An in vitro study

Objective. The aim of the study was to evaluate the influence of developer exhaustion on accuracy of quantitative digital subtraction radiography. Study design. Six objects, each incorporating a section of dry human mandible, were radiographed with 4 exposure times. Baseline films were processed in fresh solutions, whereas follow-up films were processed in fresh and in increasingly exhausted solutions (ie, 1, 2, and 3 weeks old). Bone loss and bone gain were computer simulated in 17 regions of interest on baseline radiographs. Area and volume of changes in mineralization were measured in subtracted images, obtained by subtraction of baseline from their corresponding follow-up radiographs. Friedman's 2-way analysis of variance by ranks and Wilcoxon signed-rank test were used for statistical analysis. Results. Because of exhausted developer, bone loss was relatively underestimated from 6.6% to 16.5% (P < .05), whereas bone gain was relatively overestimated from 9.7% to 16.7% (P < .05). Conclusions. This in vitro study demonstrates that films for quantitative digital subtraction radiography should be processed in fresh developer or error might be introduced.