DIGITAL RADIOGRAPHIC IMAGE-BASED BONE LEVEL MEASUREMENTS - EFFECT OF FILM DENSITY

Previous studies have demonstrated that accurate alveolar bone-level m easurements can be made using digitally enhanced bitewing radiographs. In this study, we determined the effect of exposure variations on bon e-level measurement accuracy using digital radiographic images of dry skulls. 6 direct bone-level measurements on the mandibular 1st molars of dry skulls were established by consensus of 2 expert observers. 13 bitewing radiographs were taken on each side of 11 skulls, using a spe cially designed positioning device. Exposure settings of 70 kVp, 10 mA , and 24 impulses were empirically chosen as the baseline. Kilovoltage and impulses times were individually varied (50 to 100 kVp in 10 kV i ncrements and 15 to 48 impulses in 6 steps) to ensure a wide range of clinically relevant optical densities on the test images. The radiogra phs were digitized and alveolar bone level measurements, corresponding to those for skulls, were made on the images by 2 observers. Pearson product-moment coefficients between radiographs and criteria measureme nts were calculated. It was found that dry skull and digital bitewing radiographic measurements were highly correlated, within the limits of exposure parameter variations tested. Accurate measurements of alveol ar bone level are possible from bitewing radiographs taken within a wi de range of exposures, when digital image processing techniques are em ployed.