Tokyo Medical and Dental University

The purpose of this study was to evaluate the efficacy of digital subtraction radiography using a direct digital imaging system in the follow-up study of endodonti-cally treated teeth. The RVG-S was used as a direct digital imaging system. The intraimage variation of the original RVG-S image caused by dark current and sen-sitivity variations among pixels was corrected by pixel-to-pixel. The interimage variation was further corrected using a copper step-wedge attached to the sensor. Standardized images were obtained from the same geometrical setup during the follow-up. Pixel values at the regions of interest positioned on the periapical le-sion increased after the endodontic treatment, and this change continued during the observation period up to 545 days. The subtraction method with direct digita