Dynamic range required for intra-oral radiographic systems

It has been reported that the CCD (charge-coupled device)-based intra-oral radiographic system has a narrow dynamic range of exposure. However, the required dynamic range depends on the contrast of the subject to be radiographed. We analyzed subject contrast in the maxillary molar region, which has the highest radiopacity, and determined the dynamic range required for intra-oral radiographic systems. Subjects were Japanese patients separated according to gender and further classified into 5 groups, according to age, 20-29, 30-39, 40-49, 50-59 and 60-69. In taking intra-oral radiographs of them for clinical purpose, a custom-made Copper (Cu) stepwedge was simultaneously exposed. Each radiograph was digitized. Cu equivalent value of the most radiopque part was obtained and the subject contrast was calculated. Maximal value of the mean subject contrast for all groups was used to determine the required dynamic range. In addition, the dynamic range of one CCD-based system was measured. Our results showed that males from the age of 20-29 had the highest radiopacity. Subject contrast was 1: 18.6±5.5. When one standard deviation is considered, the dynamic range required for intra-oral radiographic systems is approximately 1: 24. The dynamic range of the CCD-based system was 1: 14 and seemed insufficient to provide full utility for intra-oral radiography.[PUBLICATION ABSTRACT]