Effects of JPEG compression in quantitative digital radiographic subtraction of simulated bone loss

Abstract

In order to evaluate the effect of JPEG compression in quantitative digital radiographic subtraction, 12 periapical x-rays of the lower molar region were digitized at 300 dpi and 8 bits, duplicated and saved as two subsets of images labelled 'A' and 'B' using the JPEG level 12 format. Areas simulating bone loss (1%, 3% and 5%) were digitally demarcated in the 'B' subset of images. All the images were reproduced digitally and saved using JPEG 10, 8, 6 and 4 compressions. For each compression tested, image subtraction was pezformd and the mean density and standard deviation of the gray levels was measured. The quantitative digital radiographic subtraction, using the Image Tool software application, was not affected by compression JPEG level 10. Although levels 8 and 6 allow the detection of changes in density, they tend to result in overestimation of the bone loss.