Image contrast enhancement for film-based dental panoramic radiography

The dental panoramic radiography is one of dental imaging that used to visualize the entirety of the maxilla and mandible jaws on the one image planes. Although the direct digital panoramic radiography has been available, however film-based panoramic radiography is still used on the mostly dental clinic and laboratory in Indonesia. The quality of film-based image has significant limitation due to chemical processing and image enhancement cannot be done if required. Therefore, digitized film-based image to digital image was required to allow image enhancements in order to improve the interpretability quality of information in the image. Digitized film-based image is performed using a flatbed scanner on transmission and reflection mode. In this paper, the contrast quality of digital image that scanned using both mode is evaluated based on statistic image characteristic. The results showed that the quality of digitized image using transmission mode is better than using reflection mode. However, if direct digital imaging is used as a gold standard, image enhancement on digitized image is still required. Four methods, i.e. contrast stretching, HE, AHE, and CLAHE are used to attempt improve the quality digitized image. Evaluation of the preference image quality is performed based on objective criterion. The preference image quality for digitized panoramic image can be obtained by using image enhancement based on CLAHE-Rayleigh method, that indicated by the lowest value of mean, standard deviation, RMSE, and average difference and the higher value of NAE and SAE.